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1. With short cables say less than 10 me ters symmetrical balanced transmis sion does not have any justification but marketing A given gear singing better in balanced mode only reveals poor de sign in some part of the circuit which can be partially masked by internal dis turbance cancellation Over longer lengths external distur bances like hum RFI and so forth take on a greater degree of importance The disturbances intensity can be fig ured out by computing the RMS signal to noise ratio in decibels A balanced high quality floating line can reach more than 120 dB of rejection or 120dB relative to the signal which represents one part per million 1 ppm a truly remarkable performance darTZeel NHB 108 model one Audiophile s technical manual In full balanced mode the result is far inferior and in practice is barely better than 60dB 0 1 This may seem small but just keep in mind that this implies component tolerances tighter than 0 5 a truly demanding task Professional consoles capable of such results are truly high end by their 6 figures price It is very important to point out that bal anced lines whatever they may be are not impedance matched This means that even though they are fairly immune to external disturbances they alter the musical signal proportionally to their length Just ask a sound engineer if he is happy to use a cable 100 meters long when 10 meters are plenty enough
2. In your darTZeel NHB 108 model one the power supplies are not really standard ones The amplifier is a true dual mono We apologize about stressing the word true but much too often this descrip tion is abused The darTZeel NHB 108 model one has 2 fully independent power supplies one for each channel The two channels are fully insulated from each other The crosstalk figure speaks for itself at more than 90dB separation across the entire audio spectrum Toroidal transformers each of 300VA are wound on 450VA cores Magnetic fields are thus reduced to the point that no core saturation can occur ensuring clear power output under any dynamic conditions without induced hysteresis distortion Cores are grain oriented and primaries are electrostatically shielded from the secondaries keeping RFI away The en tire units are impregnated in epoxy resin eliminating possible winding vibra tion As seen above the transformers are also suspended Their residual mechanical noise is so low that even in very quiet listening rooms you will not be disturbed anymore darTZeel NHB 108 model one Audiophile s technical manual Immediately after the rectifier bridges the DC sources are filtered by 6 paral leled 22mF capacitors for each rail totaling a whopping storage energy of 230 joules per channel Not so bad for a 100 watter The copper bus bars CNC machined in 5mm thick blocks connect the filtering capacitors le
3. Just ask him if high frequencies do not suffer from very great lengths of the order of 100 meters The 500 links used in the darTZeel NHB 108 model one and described hereunder behave differently 5 5 darT to Zeel 500 The darTZeel NHB 108 model one is equipped with 500 BNC connectors After a lot of research we concluded that the one and only means for transmitting an electrical musical signal with no al teration or losses over a long distance is impedance matched lines from end to end We have already mentioned that the darTZeel NHB 108 model one was thought up without any compromise in mind es pecially regarding its cost price We confirm this once again of course but the purpose here is just to say we pursued this quest of sound purity simply because no other amplifier could bring us what we were looking for So we designed the darTZeel NHB 108 model one As for electric transmission lines we didn t want to reinvent the already exist ing wheel Perfect impedance matched lines have been in use for almost a cen tury And so have coaxial cables Impedance matched links are utilized everywhere when high tech performance is needed Radio applications radar mi crowaves computers and all such preci Page 17 of 28 sion technologies use impedance matched links So why not audio The great advantage of impedance mat ched links is their virtual absence of losses whatever their length For those
4. vided the levels are not outrageously high Okay Now bring on the next suspect 5 1 3 Temporal Distortion In the seventies the famous Matti Otala highlighted a new kind of distortion not so easy to measure but clearly audible called Transient Intermodulation Distor tion TID also called TIM for Transient Inter Modulation TID occurs when the negative feedback NFB loop is in a state of overflow something that arises more often than you might think since the NFB correction always applies after the phenomenon to be corrected appears During these very short instants the amplifier can produce more than 100 THD and or IMD At darTZeel we prefer to call it Temporal Distortion or TD because this is obvi ously what it actually is It is one of our favorite subjects for discussion since it is here that we can find the key to the problem Since the CD came on the scene lots of water has flowed under bridges In the nineties a big bug reared its ugly head on the perfect sound for ever road Its name is Jitter and it is more scientifi cally speaking an uncertainty of chro nometer precision Jitter is nowadays well known and well explains why temporal errors even when small lead to amplitude distortion Effec tively a 0 or a 1 not arriving on time will be translated into output amplitude which will not be proportional to the in put amplitude of the signal We all know how jitter sound
5. It behaves like a bipolar transistor at its output while being driven like a FET at its input IGBTs are mostly used in power applica tions like inverters switching power supplies heart defibrillators and for some audio power amplifiers We do not have any preconceived notion about the use and more specifically the sound of IGBTs Results can vary with the samples used Their linearity is close to FETs which is alas not enough for us IGBT technology is by far the youngest and we lack time to fairly judge them as to their long term sound quality reliabil ity and availability So for now and maybe for still a little while we will probably not use them di rectly in audio applications darTZeel NHB 108 model one Audiophile s technical manual 5 2 2 FETs FET stands for Field Effect Transistor of which there are two main categories For small signals they are called as is FETs For power applications their most com mon name is MOSFET which stands for Metal Oxide Silicon Field Effect Tran sistor They behave similarly to FETs but their internal structure may vary FETs are being used more and more for several reasons including the most ob vious one It is commonly accepted that they per form very closely to vacuum tubes or electron tubes or valves Tube lovers generally like MOSFET amplifiers due to their similar behavior Here we are forced to say that we do not share this point
6. NHB 108 model one Audiophile s technical manual this sandwich minimizing the influence of electromagnetic fields Furthermore such an arrangement is of extreme rigidity ensuring exceptionally good mechanical coupling between the mother plate and heat sinks modules 4 2 Divide to conquer The inside of the darTZeel NHB 108 model one is divided into four distinct volumes The left and right channels are insulated from each other as are their respective power supplies This unprecedented con struction allows extremely low crosstalk behavior across the whole audio fre quency range You are either true dual mono or you are not The darTZeel NHB 108 model one definitely is The two front compartments are devoted to the power supplies and are them selves divided into a two storey struc ture The Crowbar elements and the soft start circuitry are located on the lower level while the suspended toroidal trans formers are fixed on the 6mm thick up per decks We insist on the fact that in the final as sembly process all parts are first care fully aligned before being tightly screwed together This additional precaution adds still more rigidity and the entire case then behaves as a single block As a free bonus the case is thus virtually dust proof 4 3 Eliminating vibrations The fastening of the power supply trans formers was carefully thought out as re gards noise reduction and trouble free life A specially d
7. costs 0 33 This means 160 after 30 years It is not too high a price to pay compared to changing the capacitors more frequently Bear in mind that producing new capacitors pollutes more than keeping them energized With all sonic benefits 9 2 Long term availability 9 2 1 Spare parts To own a darTZeel NHB 108 model one must not only give you musical pleasure darTZeel NHB 108 model one Audiophile s technical manual You must also benefit from a first class customer service whatever the problem encountered Whether it is a failed com ponent or a broken heat sink due to an unfortunate accident not dropped on your feet we hope all parts need to be available at anytime If as we think your machine only re quires maintenance every 30 or 40 years we will ensure that parts availabil ity will last far beyond that We at darTZeel always stock all non perishable components in sufficient quantity for very long term opera tion Semiconductors and passive components with no instable material inside are stoc ked and will be available at any time in brand new working condition As for electrolytic capacitors however their preservation is much more delicate when one tries to stock them for 30 or 40 years in brand new working condition their life span being limited even when not in use Fortunately we have chosen industrial models of the highest quality from one of the world s biggest and
8. metric system is not so bad especially when one wants to launch a probe to Mars But that s an other story Back to our story If a component life time is given for 10 years at 20 C it will only last one day if permanently exposed to 80 C This very same component will last for 40 years if ambient temperature is only 10 C This law does not take all parameters into account but it is close enough to reality to rely on it when designing elec tronic circuits We see then that while it is very impor tant to chose components designed to resist high temperatures it is always preferable to stop the problem at source by simply ensuring that components do not overheat In continuous round the clock domestic use but is this still domestic use provided you respect the location advice mentioned in the Owner s manual the darTZeel NHB 108 model one stabilizes at around 50 C on its heat sinks As bipolar transistors can work as high as 120 C the margin is comfortable here The internal temperature on the mother plate module is around 40 C At this crucial place are installed the very ex pensive filtering capacitors Do not be worried too much at 40 C 24 24 their estimated span life is 40 years Just imagine a poorer design we will not mention any name subject to an internal temperature of 60 C would im ply a change of capacitors every 2 anda half years Page 23 of 28 Furthermore in normal us
9. one Audiophile s technical manual 5 3 The circuit of darTZeel 5 3 1 Criteria of choice Simplicity The audio circuit of the darTZeel NHB 108 model one uses only 14 transistors in all including current sources Only three different bipolar transistor devices are used all of the same brand Purity The version A of the darTZeel NHB 108 model one takes unprecedented care of the precious musical signal No connector switch relay or fuse what soever is located in the signal path Even better we did not use any of these de vices except in the AC mains input No current limitation allowing unbeat able dynamic range when in cooperation with the single output pair devices No output DC voltage drift compensa tion offering a truly breathtaking sound from whispers to loud shouts Only a single small local symmetrical DC NBF leading to extremely wide bandwidth included in the very low fre quencies without addition of any multi polar phase shift The use of a very compact printed circuit board PCB reduces track lengths to the strict minimum Reliability The darTZeel NHB 108 model one does not use any exotic or esoteric compo nent Each element was chosen for its intrinsic sound qualities its long term availability and for its long life No com promise was conceded as to the build quality of any part or component Some of them were tested for 15 years in our lab before being selected 5 3
10. path not being of the very same length Much longer mean path length con siderably increasing the output im Page 21 of 28 pedance and hence the need for a greater NFB at output stage This also induces TD Much greater physical volume and area limiting the high frequency re sponse because of higher RFI sensi tivity And this list is unfortunately not exhaus tive Without special precautions the use of speakers with nominal impedance of 40 or less on a single output paired stage can cause excessive dissipated heat outside the safe working range of the output devices We gave great thought to this and finally came up with a solution allowing the use of 20 or even 10 loudspeakers if you can find some without loss of power or quality Power transformers have 4 identical sec ondary windings Depending on whether they are connected in series or parallel the result is a big voltage or a big cur rent For loads between 40 and 80 the cur rent remains fairly low around 7A RMS corresponding to about 200 watts under 40 but the voltage needed is relatively high in the region of 50 to 60 volts for delivering a comfortable 150 watts under 8Q Conversely 200 watts under 14 need an RMS current of 14 amperes but with only 14 volts RMS as an output voltage allowing power supply rails of about 25 to 30 volts By switching the secondary windings ac cordingly the power transfer is opti mized and t
11. result will be heard as if the flutes had some tremolo or vibrating behavior a very easily per ceived phenomenon And the combina tion s harmonics will add some warm ing factor or on the contrary some coldness or dryness to the perceived sound depending on how they will com bine together So you can see that IMD is even less easy to understand and quantify than THD And how can we appreciate IMD can we hear it at what level does it be come a nuisance Well the first thing we can admit is that it is not musical instruments that gener ate inter modulation effects but our own hearing brain included that is the cause Some acousticians say than our internal ear can produce inter modula tion artifacts at levels between 25 to 40 Of course the brain then does some necessary correction However this kind of correction cannot be compared with an electronic chain say the microphone and analysis system So we feel very uncomfortable about advancing any IMD value from external origin for which our ear is sensitive In practice it seems that IMD less than 2 Page 10 of 28 3 to 5 for THD is considered as not disturbing even not audible in a musical context judging by the Single Ended Triode aficionados or by all the psycho acoustical experiments conducted over the past few decades By way of conclusion it appears that IMD while perhaps more disturbing than THD remains practically harmless pro
12. utilizes twice the number of components implying a more complex signal path less reliability and furthermore espe cially in power amplifiers an output im pedance twice as high as with single Page 16 of 28 ended topology and requires a higher output stage NFB to compensate Now that you have read these simple but demonstrative explanations do the words full balanced still mean abso lute superior sound for you All this explains our choice for using as a matter of course transformers of the highest quality for our XLR inputs in the version B We said above that by very nature mu sic is part of a single end world More than 100 years ago designers chose floating balanced lines full balanced was not ready yet for long distance links for the sole purpose of minimizing external disturbances Electric signals were therefore transmit ted in a balanced way the equipment working in single ended mode The darTZeel NHB 108 model one version B offers this very same possibility to pro fessional users wanting to link their re mote consoles to the NHB 108 model one without having to use poor quality Balun DI devices Despite what all our esteemed competi tors might think we assert and corrobo rate that the one and only means of processing amplifying and broadcasting a musical signal without altering it even in the slightest is simply to use the sin gle ended mode But only in a special way though
13. 2 darTZeel schematics For the most curious readers we give hereunder the functional diagram of the darTZeel NHB 108 model one Connoisseurs will appreciate how simple it is so different from the common belief of bigger is better Page 13 of 28 For once we give the description in French which is after all the very origi nal text A translation can be provided on special request This schematic is multi patent protected a nm Description du circuit 3 tages en technologie discr te se d composent ainsi 1 tage tage d entr e Cet tage d pourvu de toute contre r action amplifie en courant le signal d entr e de telle sorte qu il ne subisse aucune charge susceptible de le d former La simplicit apparente de ce premier tage 1 seul transistor par polarit permet des vitesses de commutation tres lev es sans rotation de phase notable dans le spectre audio 2 me tage tage d amplification amplifie en ten sion le signal a la valeur nominale requise Cet tage comporte 2 demi contre r actions locales implant es de mani re sym trique Cette contre r action sym trique s effectue sur tout le spectre de fr quence y compris le courant continu afin d apporter une r ponse parfaite dans le grave La configuration de ce circuit permet une propaga tion de groupe homog ne sur tout le spectre audio grace a la faible valeur de la contre r action 3 m tage tage final d
14. EE E EEEE sets 16 5 5 dari to Zeel 50 Ova stk socio coc EE E EE EEE REE ETO EEE R 17 Onboard safety ent orii e EE EEE R EEEE EE Ea AE aletas isis 18 6 1 Crowbar ClUcUlt austin E E AA en E E AREE EE E EEEE Geel ES 18 6 1 1 Crowb ractivati d s Gnn aa aea e E ito 19 6 1 2 SS 19 6 2 SUPELVISION Sto al E ES 20 6 21 Current sensing ii E eee R leet ots 20 0 2 2 Foris eyes Only aora aa E wali E T ai Ai 20 Power supplies narenn nte A alia inh aia E AE me en E A E A AN NEE 20 7 1 From mains to loudspeakers ses 21 7 2 Voltage Of CUE A A AN asennad 21 7 3 Received id a iii Aa 22 The sound of darTZ06lreroiiis nepon iinan KE NEE AE NEEE AEAEE AE EA EEN 23 Rehabil yenan ra aie nanos E R ia Main en a e mme ent et aris 23 9 1 Quantified longevity resniem ritenere Ena Ee E EE ETE NEE eaa AEE EREA iris 23 9 2 Long terni avalabihityssss ss a iii 24 OD Lis Spare parts iii A 24 A AAA 24 MORA ZA RR 25 Keeping an open door uri 26 Special adj UStMent e tise tate neta a de Reta 26 12 1 Output DC voltage drift uni cd Patient tite 27 12 22 lt Monitorms circuit ll 28 123 Wersion But Rene dip tho ieee ee ads 28 12 4 Future development S oci e earn on ee EE en ici 28 darTZeel NHB 108 model one Audiophile s technical manual Page 3 of 28 darTZeel NHB 108 model one Audiophile s technical manual Page 4 of 28 darTZeel NHB 108 model one Audiophile s technical manual 1 Introduction Thank you for stud
15. K OF FIRE Page 19 of 28 6 2 Supervision system 6 2 1 Current sensing Most available amplifiers if not all use an output current limitation circuit pro tecting the output stages against any possible overload This current limitation generally takes the form of one or more transistors that will shunt the incoming signal to ground when the current has reached a defined value The current sensing is taken through one of the emitter resistors of the output stage Although very efficient this type of pro tection is unfortunately located in the very heart of the amplifier and cannot be kept apart from the signal path Other manufacturers in order to avoid such an intrusive protection circuitry just insert some fuses either in the rail supplies or even worse directly in series with the output speaker terminals Of course this solution is by far the least expensive but is sonically a true disas ter Any given fuse behaves as a non linear resistor Its resistance is substan tial and is thus not very compatible with high quality reproduction Last but not least fuses inserted in this way do not react quickly enough leading to dam aged components Purity As you might have guessed in the darTZeel NHB 108 model one we have used a somewhat different approach Rather than limiting the output current we far prefer to measure in real time the output power dissipation It is finally the output stage s tempera
16. ads together creating as it were a low impedance power supply on the spot The output transistors are lo cated only a few centimeters away from the power supply hence no problem in case of high current demand Our power supplies are filtered only avoiding any dynamic limitation for which regulated supplies are often re sponsible Fully regulated supplies have very low output impedance through high feedback regulation NFB everywhere When huge dynamic changes arise the NFB is in a state of overflow and the output impedance suddenly increases dramatically causing dynamic compres sion Does this remind you of some thing 7 2 Voltage or current For purity reasons invoked earlier the output stages of darTZeel NHB 108 model one only have a single bipolar pair of output transistors The vast majority of amplifiers of over 50wpc use paralleled transistors from 3 to 24 or even more pairs The purpose of this parallelism is to obtain a greater output current as required by low impedance loudspeakers This method is much cheaper than the solution used in the darTZeel NHB 108 model one power transistors being much less expensive than in the past But parallelism has numerous draw backs as follows The need to match components for even heat spreading The signal path is divided into multi ple parallel paths leading to TD Temporal Distortion by degradation of propagation time delay uniformity each
17. anual In the 70s and 80s here in Europe Japanese electronics were queens and kings of the market Very rare and above all virtually unknown was the real high end audio gear coming from USA or elsewhere The finish was already very good but the sound quality did not come up to scratch simply because it was not one of the original design goals Only a few companies were able to offer real breakthrough products Not all of them are still in business Alas The more the years passed the more our desire for designing a new machine became tangible In mid spring 1984 we produced a first digital power amplifier in a school lab as a diploma project Paradoxically the innovation here was not the fact that the amp was digital but that no feedback whatsoever was used The output stage was totally open loop The sonic result was so astounding that we immediately started the NHB project although its code name did not come until later The initial idea was to design a new very powerful digital amplifier totally open loop if possible with the purest sound reproduction we could attain without any other consideration especially the price factor The main problem at the time was that the technology did not yet offer the monochip solution so we had to build the circuit entirely in hybrid technology using mainly discrete devices The odd thing is that even in this early 21 cen tury we have still not surpassed the speed of
18. darTZeel NHB 108 model one Audiophile s technical manual darTZeel NHB 108 model one Audiophile s technical manual Page 2 of 28 PN 2 TABLE OF CONTENTS Introduction cin ais 5 MAA deco de a ee dsd da At 5 Genesis of NHB 108 conti iio tint diner de Rs ii 5 Cta A A A A A uli ue a ie 6 Structural aspect iii ns 6 4 1 TNE CASS modules ini ii nl io dira nee rs ruled 7 4 2 Divide LO COMU dns 7 4 3 Elhiinathno Vibrations sise ne A A RUES Pan deserves last roi 7 4 4 Everything 18 transparentsif tes sues dates Wace edie dn Me Ga ele RS Pie der hash anne 8 45 TO Totally Identified OBJECT renan n o totes RE End 8 The AUd1O electro iia isa 9 5 1 What is dista aa eS o as 9 5 11 Keeping im harmony se e e Sn e EE Aa E S E ne units 9 5 1 2 Inter Modulation Distortion ss 10 9 153 Temporal Dist rion s Essen nn nants a 11 5 2 What application tido oo 11 22 1 O A enr ae don nr e att Pan mg sepals omission ere tenta eines 12 52 2 ON 12 922 3 Y Et O lesbien Aandi th eaten pete 13 5 3 Thecircuto Carl Zee lito cional aves A E TEESE A E A SS 13 A Criteria Of Choice O E EE KE EE E E AE EN S 13 5 32 dart Zeel schematics ace 13 5 3 3 Component Layout ssie AS 14 5 4 Symmetrcally balance ro lost EE E 14 541 Fromithe Microph ne qmodonus lilas tn anne Mn ta urines 15 542 Torthe loudspeakers A 15 543 And into the airs iss rit retail 15 344 Viathe darlZeels esip ei E cud E E E
19. e say if you sometime power OFF your machine life span can be easily doubled or even quadrupled As soon as we realize that working tem perature is the most long lasting factor it becomes easier to choose components for their sonic attributes first Another factor even less known but very interesting is that of sustaining bias powering A given component being ac tive or passive lasts longer if some volt age however low it is remains applied to its terminals For electrolytic capaci tors this small polarizing voltage even keeps their internal electrolyte in perfect chemical working condition greatly re ducing the warming time usually needed with other gear All these reasons led us to keep the darTZeel NHB 108 model one powered at around 5 volts instead of 60 even when shut OFF by pressing the Power Nose Your amplifier is then always gen tly permanently energized extending even further its life span and attaining much more quickly the full performance the amplifier can deliver to your ears It is also the reason why you can still hear some music through the darTZeel NHB 108 model one even when it is powered OFF Incidentally the fact that the amp can sing with such a low voltage demonstrates how simple the audio cir cuit really is In case you are worried about this the power consumption of the power OFF mode is around 2 watts It represents around 5 33 per year assuming that a kilowatt hour
20. e channel concerned The principal advantage of such a Crow bar circuit is that it can be kept totally outside the audio signal path thus com pletely avoiding any influence on the music Its caveat The price Thyristors like those we use in the darTZeel NHB 108 model one can short peak currents of around 1 400 amperes They cannot be considered as being cheap parts 6 1 1 Crowbar activation In the Owner s manual we often men tion that the Crowbar can be triggered in cases where you have not followed the instructions for use To dissipate any remaining doubt from your mind we would like to mention hereunder the faulty conditions which will trig the Crowbar Using less than 4Q nominal loud speakers while the speaker s imped ance selector is on Hi position Short circuit at speaker terminals Output DC voltage drift greater than 2 volts at speaker terminals Powering ON the darTZeel NHB 108 model one while speakers are not hooked to the speaker terminals darTZeel NHB 108 model one Audiophile s technical manual 6 1 2 Crowbar cycle For those who want to know better when and how the Crowbar acts here are some further explanations When one of the following elements and or signals or a combination of them is detected namely An output DC voltage drift greater than 2 volts at speaker terminals A permanent output current greater than 5 amperes while the power supply impedance is o
21. e sortie d pourvu de toute contre r action Cet tage amplifie en courant le signal issu de l tage pr c dent permettant ainsi d alimenter un haut parleur Le courant de repos des transistors de sortie est ici d fini par une ten sion de jonction base metteur et non par un cou rant de polarisation Ce systeme limine le besoin d une r gulation thermique En effet lorsque les valeurs initiales ont t fix es tout chauffement des transistors de puissance entraine galement un chauffement des transistors drivers La tension VBE chute aussi bien dans les drivers que dans les l ments de puissance garantissant un quilibre thermique stable Ce montage permet galement des bandes passantes tres tendues sans d pha sage important The above description is an extract of the original patent text and is con densed to cover other applications even in the non audio field The darTZeel pre amplifier circuit is directly derived from the darTZeel NHB 108 model one schemat ics darTZeel NHB 108 model one Audiophile s technical manual If you have any specific questions about this circuit please do not hesitate to contact us at info dartzeel com 5 3 3 Component layout In analog especially in audio the layout of components is of paramount impor tance in the signature they can print onto the musical signal A transformer too close to input circuits or a power supply located too far from output de
22. ely used Un balanced links are very rare indeed The reason is very easy to understand Microphones generate very tiny electric signals and very long lengths of cable run from the studio to the mixing con sole In these conditions it is primordial darTZeel NHB 108 model one Audiophile s technical manual for the signal to be free of any hum and or noise Also in concert performances mixing consoles are generally located quite far from the stage and balanced lines are welcome A technical trick using that 3 ground wire also makes it possible to carry the phantom power supply feed ing electrostatic microphones So now you have understood that bal anced links are used especially in profes sional applications 5 4 2 To the loudspeakers Let us quit the studio and come back to the high end musical world Basing themselves on what they consider to be the real benchmark audio compa nies equip their flagship machines with the balanced lines described above us ing the well known XLR connectors Most of the time they offer fully bal anced topology from input to output claiming that the sound will remain unaf fected since it is immune to external dis turbances Technically speaking fully balanced to pology is relatively easy to achieve It suffices to double the entire electronics in a mirroring fashion assigning a new channel path for the inverted signal Of course this simplicity has a price
23. ering a remarkably even surface and hardness Every item is CNC machined from the billet in order to ensure a very high den sity and outstanding rigidity thus con siderably lowering all unwanted reso nances The elements are finished in the three hard anodized darTZeel colors namely electric blue blazing red and gleaming yellow This unique finish gives to the darTZeel NHB 108 model one its inimitable appearance The three main elementary modules are the mother plate the transformer plat forms and the heat sinks They are tightly assembled together with non magnetic stainless steel screws Each basic module is first carefully hand assembled and individually tested Only then is it dated and signed before being fitted If you dismantle your darTZeel NHB 108 model one you will see that modules are not assembled in a hurry Some of them are installed with several weeks elapsing between construction and assembling In line with this non stress approach we take all the time necessary to achieve the best job we can If our tests show that a component is out of specification this can sometimes occur after its as sembling the entire module is disman tled checked and reassembled before being tested a second time The darTZeel NHB 108 model one housing features a 25mm false bottom sand wiched between the 6mm thick mother plate module and the 4mm thick bottom plate All cables and wires are routed in darTZeel
24. es Music is spread in wave form the latter being described by a physical law called wave propagation theory We will not enter into the details but mention just one crucial and essential point Acoustical waves do not move air When we read in some high end maga zine that such and such a flagship loud speaker can blow out a candle while re producing a trumpet or a saxophone this is just metaphorical The sound is produced by the vibration of air molecules step by step Yes you did read correctly It is vibration not movement If you know a friend who plays trumpet or saxophone just put your hand on the bell and you will only feel vibration not a single tiny puff of wind By the way you would never think about a piano being able to stir up air to produce wind would you These vibrations have a purely single ended behavior since they are produced around a point of equilibrium where vibrations are zero To cut a long story short we can say that the whole acoustical chain is single ended The only moment when the darTZeel NHB 108 model one Audiophile s technical manual acoustical signal could be balanced is when it travels into the electric wires In the air sound is unbalanced asymmet ric single ended as you prefer Why then this obsession to balance a naturally unbalanced signal Is it not against nature Furthermore where is the real advan tage in running the loudspeaker in bal anced
25. eveloped suspension ensures that even in case of failure the transformers will not fall off So in 40 or 50 years when the rubber absorbers have become perhaps worn out they will withstand their last trip to the factory for their replacement The same is true for the silentblocs used for suspending the lighter audio and monitoring circuits These various suspensions tuned on different resonance frequencies are coupled quite tightly to the chassis ab sorbing especially the medium and high Page 7 of 28 frequencies most important in terms of sound reproduction accuracy And while on this subject have you ever heard an amplifier singing This can oc cur when the transistors of the final stages and or the power transformers are not properly decoupled They start to vibrate at the excitation signal frequency in this case the music this vibration interfering with the electrical origin of the signal You can hear it if the amp is hooked to a dummy load since in normal use loudspeakers fortunately mask this disconcerting internal singing No such mechanical singing on the darTZeel NHB 108 model one The electric signal is transmitted stage to stage from input to output free from any mechani cal disturbance internal or external The darTZeel NHB 108 model one stands on 3 pads incorporating rubber inserts Oddly enough very few manufacturers rely on 3 legs instead of four We can recall that the Lunar E
26. han mentioned having less DC drift from cool to warm opera tion If so you can adjust these values a bit tighter Conversely it could arise that you may have to work closer to the critical 600mV say 590mV at cold start and 590mV at warm cruise for exam ple The final goal is only to maintain outputs within the voltage range mentioned above It is not necessary to symmetri cally adjust between cold and hot values The measured output DC drift does fluc tuate very slowly around the set value This is a normal behavior and cannot be interpreted as a failure If you are unable to find a tuning value between cold and warm points please check that the ambient room tempera ture does not vary over too wide a range If this is the case we strongly recommend using the darTZeel NHB 108 model one version B 12 2 Monitoring circuit The monitoring circuit also called super vision system includes a trimmer for clipping threshold adjustment We do not recommend altering the tuned value unless you happen to note that a mono input signal will trig both eyes with more than 0 8dB difference Please feel free to contact us in case of doubt On later machines bearing a serial num ber different to TZ UA1081 xxxX addi tional trimmers will be included on the PCB Do not alter these trimmers The war ranty could become totally void 12 3 Version B On the version B it is possible to disable the DC output drift compen
27. he power transistors in the output stage remain within their safe working range So we can only use one single output transistor pair per channel The signal path is shorter uniform and only passes though one silicon junction at a time Music is thus reproduced with unprece dented ease purity and fidelity simply impossible with more complex designs darTZeel NHB 108 model one Audiophile s technical manual 7 3 Received idea This chapter devoted to power supplies would not be complete without the fol lowing little addition small in size but of great significance It is usually admitted in the audio world particularly in the high end manufactur ers community that output current availability is of paramount importance to the point where one praises machines capable of outputting dozens or even hundreds of amperes What nonsense Until the contrary is proven as far as we know voltage and current are in a certain relationship as clearly stated by Mr Ohm s law It is of course the same equation just written in its 3 most usual forms Now let us take an ideal amplifier ca pable of delivering exactly 250 watts 8Q 500 watts 40 1000 watts 2Q and a whopping 2000 watts 10 The currents needed to deliver these abundant and generous powers are re spectively of 5 6A 11 2A 22 4A and 44 8A Yes we have to admit that the last fig ure is quite high So this amplifier can deliver roughly 45 amps u
28. imitations After several months of deep thinking circuit designing and circle squaring at tempts the project was revived in 1990 on brand new bases The gear would be fully analog moderately pow erful and as close as possible philoso phically speaking to the signal treat ment used in its digital ancestor Two new prototypes were built on the basis of existing designs even though heavily modified to suit our tastes they produced unexciting results Then we asked ourselves what is the point of pro ducing nice looking gear if the sonics bring nothing new under the sun In 1992 we decided to develop a revolu tionary design from scratch This ulti mate quest for ultimate sound lasted over 5 years with more disappointment than joy But the fun was always here Countless schematics were studied scru tinized and hooked together until we obtained in mid 1995 what we could darTZeel NHB 108 model one Audiophile s technical manual tained in mid 1995 what we could call the first theoretical design corresponding to our aims From 1995 to 1999 on that first elemen tary circuit basis dozens of different versions were simulated some of them being built and listened to By 11 November 1999 the definitive cir cuit was built and assembled This was the very first darTZeel machine the NHB 108 model zero The results sonically speaking were outstandingly better than expected It seems that this design
29. in fact double the price Finally the balanced signal is amplified and routed to the loudspeakers Come to think of it are loudspeakers balanced or not balanced That is the question 5 4 3 And into the air Once in the air the musical signal is traveling on its last trip before delicately tickling your eardrums How exactly does music propagate itself in the air Music is a matter of vibration and propagates in the shape of waves Any wave to be propagated needs a me dium No medium no wave no sound Just try playing trumpet on the Moon Not an easy task even if your name is Armstrong Page 15 of 28 What about radio waves What medium do they use in the vacuum of inter sidereal space Well write us and we will send you the Physicist manual as soon as we have got round to writing it As for acoustical waves it is a much eas ier phenomenon to describe and espe cially understand since it is part of our daily life The medium can be water in the case of mermaids singing er sorry when whales sing Or when more human technological things such as sonars hydrophones and the like generate and detect acoustical waves The medium can also be steel The hammer hitting the string in a piano generates a pulse which creates a propagating wave in the string making it vibrate Then this vibration will be trans mitted into the air Air this is the ultimate medium where man made music propagat
30. istinguish between a saxophone and a flute Did you know though that the level of these natural harmonics can easily reach 20 to 40 of the fundamental note de pending on the instrument played But do we Say that an instrument distorts 5 1 What is distortion In the audio world any signal change is called distortion A lot of different kinds of distortion exist but we mostly speak about Total Harmonic Distortion or THD THD is so well known that we more than often forget that other ones do ex ist Negative Feed Back NBF is a smart electronic trick used for diminishing or even eliminating all type of distortions and can be roughly described as follows At the amplifier input we put a signal having an inverse deformation from the one it naturally produces at its output So the new output signal will be puri fied since the 2 inverse deformations will cancel each other This is what the theory says Now let us see what actually happens in practice We will discuss only the best known distortions given that their be havior is simpler to explain 5 1 1 Keeping in harmony Let us take an amplifier especially de signed to produce exactly 1 of THD darTZeel NHB 108 model one Audiophile s technical manual Then let us feed it with a recorded musi cal instrument We shall suppose that this instrument is moderately rich har monically say around 20 Now let s be a bit optimistic and sup pose
31. lete machines sold ensuring another en tire electronic life to each darTZeel NHB 108 model one sold A number of electrolytic filtering capacitors equal to the number of darTZeel NHB 108 model one units sold and reaching their 25th working year All diagrams electronic and mechani cal drawings in paper and computer ized versions The entire and detailed list continu ously updated of components suppli ers CNC makers and all other com ponents involved in the darTZeel NHB 108 model one construction A complete computer system con tinuously updated allowing retrieval of the above mentioned data at any time A fully detailed manual explaining how to use and to work with all the above All these items have been put in a nitro gen filled container in a safe area In the improbable case of darTZeel s dis appearance or if we ourselves can no longer intervene you will be given a copy of these documents In such a Sad case our notary office will directly contact every owner with appro priate instructions Life is such a wonderful thing that we strongly hope that we will be able to serve you for many decades to come darTZeel NHB 108 model one Audiophile s technical manual 10 The next darTZeel Now that we are almost at the end of this manual we do think that you have a better idea about our philosophy We just hope that we have not fright ened you by our unusual way of thinking After a
32. ll if you proudly own one of our machines it is because you have trusted us We just say You were right Nevertheless do not believe that we set such a high level for the darTZeel NHB 108 model one that no one could ever im prove it Obviously we do not want nor even need to change our product line every year or even every 5 years but this does not mean that we will rest on our laurels The design of the darTZeel NHB 108 model one incorporates the best that this be ginning of the 21 century has to offer We sincerely think that at the time of going to press it is not possible to go much closer to the sonic truth than that which the darTZeel NHB 108 model one is already capable of providing As the years go by technology will re lentlessly improve We will endeavor to determine to what extent we can go even further Each time we can make a leap forward we will do so Every darTZeel NHB 108 model one can be easily upgraded at any time So when ever an improvement becomes available every customer can enjoy it at an attrac tive real world price At the time of writing we think that a significant update could take place every 3 years on average These updates will be of two different kinds Music Lover updates where sonic as pects only will be improved Audiophile updates where sonic and or technical improvements will be offered Of course every single owner will be kept informed about any significan
33. longest estab lished manufacturers We can bet that they will still be there in 100 years and that they will continue to offer equally outstanding capacitors or perhaps even better ones Furthermore darTZeel keeps permanently in touch with the industry with the aim of anticipating any shortage or ending of production as regards every component entering into the building of the darTZeel NHB 108 model one In the worst case perishable stock will be renewed ac cordingly in order to offer maximum availability at brand new specifications Our wish is to be capable of offering you true and full customer service for at least 120 years after your purchase date 9 2 2 Self preservation instinct One hundred and twenty Are they kid ding at darTZeel s Or are they just being pretentious Yes we only said that it is our wish But here again we have done our very best to make our wish a reality Page 24 of 28 In order to keep our word and offer full maintenance of your darTZeel NHB 108 model one we have stocked the following items 1 fully assembled darTZeel NHB 108 model one fully tested and in working condition powered OFF but main tained energized 1 darTZeel NHB 108 model one in the form of pre assembled and tested modules Spare parts representing 2 but a minimum of 5 complete sets of all mechanical and CNC machined com ponents A total number of transistors equal ing 120 of the number of comp
34. mode To our knowledge there is no balanced crossover in the market Has any manufacturer already told you that there is no such thing Okay now you ve been told 5 4 4 Via the darTZeel In the version B of the darTZeel NHB 108 model one we have also installed bal anced inputs Did we do this just in order to be with it First we want to stress that we use floating balanced inputs This means that rather than doubling the whole electron ics as seen above we use high quality input transformers Of course the use of transformers is much more expensive but the resulting performances are far superior Speaking of external disturbance immu nity transformers are much better than full balanced topology The common mode rejection this is the name given to that kind of immunity can be wait for it no less than five thousand times bet ter when using transformers instead of full balanced circuits Another unbeat able advantage is that they offer true electrical isolation called galvanic isola tion between the line and the gear providing outstanding safety in profes sional use Last but not least is the fact that all the above mentioned qualities are defined at the building stage mean ing that performances will not decrease over the years or even decades to come This is not by any means the case in full balanced versions In conclusion we cannot resist insisting on the fact that a full balanced solution
35. n Hi and output voltage swing is no greater than 60 VoltSp p permanent output current is greater than 12A peak transient output current greater than 25A and longer than 25ms Then the power thyristor paralleled with the total supply voltage is trigged i e put into conduction The huge abrupt short circuit current peaks to around 350 amperes for 6 5 ms completely releas ing the filtering capacitors storage en ergy through an appropriate custom designed choke absorber This sudden current rise at the trans former s secondary windings also implies a very high current at its primary wind ings proportional to the inverse ratio of the primary to secondary voltages This current is at least 20 times greater than the nominal value of the fuses The metal in the latter literally evaporates instantaneously against the glass enve lope as testified by the latter s black silver color While you are replacing the melted fuse with a new one the Crowbar circuit will have reset itself in the meantime and will now be ready to work again just in case It is important to note however that if a newly replaced fuse is blown at power ON you must follow the Owner s manual instructions that is to say un plug your darTZeel NHB 108 model one and contact our customer service at troubles dartzeel com Never ever replace faulty fuses by val ues different than those originally indi cated in the Owner s manual RIS
36. n right channel the trimmer is lo cated on PCB component side ori ented toward the inside of the ma chine A clockwise rotation induces a positive voltage shift When adjusting it is important to turn the trimmer s screw slowly Please allow 5 seconds at least after each tuning step to wait for the value to stabilize 3 Connect the DMM to the left output and open the glass cover DO NOT FORGET THAT THE AMPLI FIER 1S POWERED ON NEVER TOUCH THE COPPER BUS BARS WHICH ARE AT A POTENTIAL DIFFERENCE OF 115 VOLTS DC A SHORT CIRCUIT INDUCED BY THE SCREWDRIVER WILL PARTIALLY EVAPORATE THE BLADE BY IN STANTANEOUS MELTING OF THE METAL OF THE LATTER 4 Within the next 2 minutes set the DC voltage drift at 300mv 0 3V 5 Connect the DMM to the right output and perform within the next two minutes the same tuning as for left channel 6 Put back the glass cover without screwing it yet Wait for one hour 7 Then measure again the output volt ages They should be be tween 300mV and 400mV 8 Power the amplifier OFF and wait for one or two hours for total cooling down 9 Power the darTZeel NHB 108 model one ON again and recheck the outputs DC drift should not be greater than 500mV when ambient room tem perature is 22 C 10 If everything is okay you can screw on the cover glass Page 27 of 28 Voltage values are those obtained in av erage conditions It is possible that they vary much less t
37. nder 1Q Now say that you own speakers having an impedance of 69 much easier to drive than 10 How many amperes will this imposing amplifier deliver to your loudspeakers 45 amperes with a big smile Not at all Given Mr Ohm s law the amplifier will deliver at its best 333 watts say 7 45A under 44 7volts So you can see that in the real world you just need 7 5 amperes not 45 Let us confess that for 333 watts this is quite reasonable Do you now better understand why Lots of Amperes does not necessarily mean Superb Bass Page 22 of 28 8 The sound of darTZeel It is always hard to define objectively what we perceive subjectively isn t it How to enjoy an excellent glass of wine if not sharing it with friends We could say that the darTZeel NHB 108 model one offers an outstanding temporal linearity allowing true three dimensional re creation We also could say that the bass is deeper than the Mariana Trench with every nuance incredibly rendered We could add that voices are so sweet and timbres so accurate that you will turn your head believing that someone has just entered the room We could even conclude that no cymbals can be better reproduced than through our machine Instead we will just invite you to take a seat and listen to some good music After all if you read this manual you certainly already own a darTZeel NHB 108 model one and you know better than anyone what we are talki
38. ng about So why do we need to produce any further advertising In fact just for the fun of it And music is fun too isn t it 9 Reliability 9 1 Quantified longevity How long does a darTZeel NHB 108 model one last Before first failure Well let s us try to see a bit more clearly and seek a better understanding of the different causes of failure Assuming that the first possible failure will be due to the weakest component we could be tempted to install only the longest lasting components Is the first criterion Purity compatible with Reliability If a component lasts twice as long as another but sounds twice as bad what would be the lesser evil Before giving a firm answer it is inter esting to ask ourselves what are the most influential parameters affecting the darTZeel NHB 108 model one Audiophile s technical manual life span of a given component Several studies show that one key factor is heat This might seem obvious and we have all experienced once in our life the con sequence of leaving our beloved CDs or cassettes for the most experienced of us under our car s rear window on a hot summer s day What is far less known is the mathemati cal relationship between expected life span and high temperature exposure Many studies have shown that for each 5 C increase lifespan is halved Sorry about not converting into Fahrenheit the law doesn t work out so easily Sometimes the
39. notes or more than this In theory we should hear 2 distinctive notes In theory only Well yes because in practice our hearing is not perfect Truly wonderful indeed but less than perfect Without entering into details we can nevertheless say that in fact we will not only hear 2 distinctive sounds but also combinations of those primary notes We beg musicians and music lovers to forgive us but for a while we need to replace notes by frequencies Not very darTZeel NHB 108 model one Audiophile s technical manual musical but much easier for the pur poses of our explanation If the first flute plays a 1 000 Hz tone and the second one a 2 500 Hz tone we will not only hear those two discrete tones but also the following combina tions 2 500 1 000 1 500 Hz also called the beating frequency and also the mirror ing part say 2 500 1 000 3 500 Hz Fortunately those combinations are of much less amplitude than the discrete notes themselves But that s not all We will also hear the harmonics of these combinations So frequencies of 1 500 3 000 4 500 Hz but also 3 500 7 000 and 10 500 Hz will be perceived Once again their level will be very low com pared to the 2 initial notes played It seems hardly believable but it is true In practice though this is far less embarrassing than you might think at first glance As said above the relative level of those ghosts is much lower than the basic notes The
40. of the ges ture Page 9 of 28 Some amplifiers available on the market claim extremely low THD figures at the very limit of instrumentation measure ment assuming this result necessarily leads to outstanding sound purity We take this with some caution since it re calls for us the 70 80 Japanese philoso phy by which performance implies quality We have to be fair by acknowl edging that such designs can be liked and even loved by audiophiles The world is big enough for multi musical tastes The idea is very nice indeed and we do admire such a philosophical approach even if it is not ours the problem is that those designs are highly sophisticated too much for our ears involving lots of added transistors op amps and higher than reasonable NFB leading finally to altered sound structure These electronics can be considered as very pure and detailed for the first listen ing hours or days but once noticed their sonic signature becomes harder and harder to bear So if THD does not seem to be a deter minant factor in the accuracy of the re produced sound we have to look else where 5 1 2 Inter Modulation Distortion Now let us listen to two flute players The flute is well known for its less rich than usual sound harmonically speak ing of course A kind of exception con firming the rule If each player produces a different sus tained note what will we hear One in termediary note two distinct
41. of view Not entirely at any rate It is true that the sound of MOSFETs tends to be soft and warm a bit like those found in tubes But their electrical behavior is not similar simply because they are not made of similar materials The only true similarity is that MOSFETs and FETs of course are voltage driven like tubes Apart from that they are in two different worlds vacuum for tube silicon for FETs Conduction in any type of transistor al ways acts in a solid here the metallic silicon hence their name of solid state devices In a vacuum tube electrons move in a vacuum Coming back to FETs what is their sound For most designs we would say that it is only a matter of taste We are convinced that one can design a stan dard good sounding machine in the 3 technologies mentioned above and even with the fourth tubes with virtually the same sound Obviously if you like music you defi nitely need a darTZeel NHB 108 model one Yet and contrary to common belief MOSFETs are less linear than bipolar transistors available today MOSFETs often need more sophisticated added Page 12 of 28 circuitry to make the best of their possi bilities and that means a longer and more complex signal path and hence a reduced resolution MOSFETs are also slower in absolute terms than bipolars and are much harder to drive in pulse mode Reproducing very fast transients requires a lot of instantaneous cur
42. of you who want to know eve rything about matching impedance in audio links do not hesitate to contact us at info dartzeel com Propagation time delay is preserved in DC up to several GHz in such lines and no other link from any make can claim this unless perfect impedance matching is achieved So the darTZeel NHB 108 model one is fit ted with such inputs here called Zeel 500 while the darTZeel preamplifier has 500 darT outputs These inputs outputs use 500 coaxial cables fitted on BNC connectors External disturbance immunity of a coax ial link depends on the cable itself It can vary from 50dB to 100dB or more the latter being greatly superior to the full balanced mode and all this please bear in mind without any sonic alteration You can use very affordable off the shelf RG58U cable and will be very surprised by the result Many shorter but much more expensive cables do not do better And when there is a big length increase there is no shadow of doubt darT to Zeel 50Q is simply unbeatable Trying and hearing is just believing The optional coaxial cable delivered with the darTZeel NHB 108 model one is fur thermore of the high end grade silver plated pure copper designed for hyper frequency applications You will at least discover what resolution really means As stated above one of the main advan tages of darT to Zeel links is that you can locate the power amplifier as far as you want from the p
43. reamplifier No more treble roll off harsh or fuzzy No more sluggish low end The theoretical length limit is infinite In practice we recommend not to use lengths greater than 10 kilometers we are not joking here for once This new way of linking is still in its in fancy as regards audio even if some of darTZeel NHB 108 model one Audiophile s technical manual our esteemed competitors disagree darTZeel will also offer in the near future for professional applications darT to Zeel floating balanced links Are you looking for darTZeel sound integrity in concerts and pro audio studios You can have it just for the asking 6 Onboard safety A power amplifier like the darTZeel NHB 108 model one cannot but offer the high est quality level when it comes to moni toring and protection Purity But we did not call this part of the darT Zeel NHB 108 model one the protection circuit by far preferring supervision system or monitoring circuit as you prefer Indeed this very sophisticated module is kept totally outside the signal path electrically and physically again so as not to disturb the delicate musical message Reliability The supervision system is based on a 100 analog design making it inde pendent from any problem or bug com ing from a microprocessor The vital passive components have been selected for their extremely long life greater than 40 years in continuous use Your loudspeake
44. rent drive not easy for the power supply to properly feed so temporal integrity could suffer 5 2 3 Bipolars These have been in existence for more than fifty years The industry knows them very well Today s bipolars are bet ter than ever Ultra linear and extremely fast they are perfectly suited for very high end audio applications Their excellent linearity makes it possible to minimize the number of peripheral components thus obtaining a straight forward signal path with many less su perfluous correction circuits In the darTZeel NHB 108 model one the audio signal travels through only 6 transistors from input to output maintaining low THD and IMD levels and without using any global NFB the output stage even operating in a totally open loop The slowest transistors used have a bandwidth of more than 30 MHz much higher than for a MOSFET This extreme intrinsic speed allows a total phase re spect across the whole audio range without any static or dynamic deforma tion In brief no Temporal Distortion In terms of music these breakthrough advantages bring you closer to the musi cians Now you can share the emotion of the violinist the fire of the conductor or the sweetness of the flutist Words are however not enough to de scribe what a single bipolar transistor pair is capable of The best is still to in vite your friends home making them understand share and believe your ears darTZeel NHB 108 model
45. rs and yourself can rest on both ears for quite a while 6 1 Crowbar circuit You will have read this odd name several times in the Owner s manual maybe without having a clue about what it really is This circuit has been well known for dec ades in industrial power electronics By power electronics we mean powers ranging from 50 to 200 kilowatts like in on line inverters used for mainframe computers or in hospital surgery white rooms On these powerful machines it is not al ways easy to suddenly cut off the power supply without causing electrical dam age Inductive loads can release huge energy transients which need to be properly directed Page 18 of 28 Generally the best solution is to insert a fuse rather a big one of its kind be tween the supplies and the loads In case of emergency you only need to short circuit the power at the load termi nals But this is easier said than done the sudden huge current peak gener ated well supported by the power in verter immediately melts the fuse shut ting the load down If the fuse is located at the input of the inverter the entire supply system will be stopped It is such a circuit that we have installed in the darTZeel NHB 108 model one When an anomaly or a faulty condition is de tected the Crowbar circuit consisting mainly of a power thyristor is activated The Crowbar shorts the power supply melting actually evaporating the mains fuse of th
46. s when not cured Thanks to or because of this famous jitter a truly digital calamity we can better understand that temporal distor tion will alter the precious and delicate darTZeel NHB 108 model one Audiophile s technical manual analog musical signal In the analog world though TD is more subtle and more difficult to treat and cure In the darTZeel NHB 108 model one every thing has been done to preserve the temporal integrity of the music There are two principal means for reduc ing or even eliminating TD The first is to use several small but local NFB loops instead of a bigger and slower global NFB loop This approach greatly improves signal transfer speed and propagation delay time The second is based on the principle that temporal error is equivalent to phase shift So if one can enlarge the frequency response by a factor of ten say 200 kHz phase shift will be also greatly re duced Ideally the best would be to apply both means described above The only prob lem is that they contradict each other High bandwidth generally requires higher global NFB while low NFB leads to poorer frequency response Here is where the darTZeel NHB 108 model one comes in the first very low NFB and high bandwidth power amplifier No global NFB is used and both 1 and 3 stages are even open loop So what about the frequency response Every thing is okay up to the Megahertz range 1 000 000 Hertz say fif
47. s frankly what you feel There are also a couple of technical ad vantages that glass has over metal Its crystalline inert structure combined with the rubber foam seal functions as an internal noise killer And contrary to metal glass is totally transparent to magnetic fields thus avoiding the inherent magnetic loop that metal would induce over the power sup ply transformers Last but not least the internal housing is much less polluted by magnetic ghosts 4 5 TIO Totally Identified Object It is however the final touch that makes this darTZeel NHB 108 model one now in stalled in your listening room your darTZeel NHB 108 model one We refer to the identification plate fully described in the Owner s manual Made from 24k gold plated brass it is a unique handmade piece just like the machine on to which it is affixed Your name is engraved in gold letters thus amalgamating the destiny of the darTZeel NHB 108 model one with your fu ture unforgettable musical moments We proudly congratulate you Page 8 of 28 5 The audio electronics Simplicity The whole darTZeel NHB 108 model one electronic concept could come down to this single word Simplicity does not mean simple how ever Purity Total cancellation or absence of har monic distortion does not mean purity alas You certainly know that most musical instruments are very rich harmonically speaking Thanks to these harmonics we can d
48. sation Likewise if you only use XLR floating balanced inputs it is possible to install jumpers in order to bypass the commu tating relays This would help improve the sound quality slightly darTZeel NHB 108 model one Audiophile s technical manual At the time of writing the additional cir cuit of the version B is not yet ready so we cannot describe this bypassing pro cedures in detail As soon as the optional version B circuit becomes available a new release of the present manual will be printed and sent to all darTZeel NHB 108 model one owners having either the A or B version 12 4 Future developments As and when further developments take place such as improvements updates modifications or simply some new ad vice this chapter will be supplemented Thank you very much for having read us through to the end Now you have earned a rest a quiet moment to listen to some nice music Page 28 of 28
49. ssary to produce any transient generated by instruments such as the piano or drums By using such a sophisticated supervi sion system a single output pair bipolar device can safely manage the demanding task ensuring the sonic purity laid down in the specifications 6 2 2 For its eyes only The monitoring circuit not only takes ex treme care of both your amplifier and loudspeakers It can also anticipate The darTZeel NHB 108 model one s eyes better described in the Owner s manual are also controlled by the monitoring circuit Apart from their we hope aesthetic appeal they warn you when limit condi tions occur With some experience you will be able to use them as a thermome ter Sorry this is a joke Page 20 of 28 7 Power supplies 7 1 From mains to loudspeakers More and more audio manufacturers are insisting on the quality of the power sup plies They are quite right After all the electric energy fed to your loudspeakers comes from the power sup ply and nowhere else The audio circuit itself is really just a sort of regulator for this energy The better the quality of the source en ergy the easier the task of modulating it into sound waves This modulation is truly the audio signal you listen to It is this same signal that will deliver the energy supply to your loudspeakers which in turn will excite the air molecules to vibration producing that magical feeling we audiophiles call music
50. t new de velopment concerning the darTZeel line Page 25 of 28 11 Keeping an open door Well now we have reached the end of the Audiophile s technical manual Is it too technical Not audiophile enough Please do not hesitate to tell us We will be pleased to read your com plaints and we will take them into ac count for future manuals Any suggestion or criticism concerning the darTZeel NHB 108 model one a particu lar manual or any other point can be emailed to info dartzeel com We wish you very long and happy hours of music listening with the world s first emotional amplifier One of our very first customers de scribed the darTZeel NHB 108 model one in such a way We have to admit that we fell in love with this description And now Music For darTZeel el Herv Del traz darTZeel NHB 108 model one Audiophile s technical manual Page 26 of 28 12 Special adjustments 12 1 Output DC voltage drift Caution The procedure described below can present some risk since the darTZeel NHB 108 model one must remain powered ON WE DECLINE ANY RESPONSIBILITY IN THE EVENT OF ELECTRIC SHOCK DUE TO INCORRECT MANIPULATION WARNING ONLY A QUALIFIED PER SON OR A TECHNICIAN CAN SAFELY PERFORM THIS ADJ USTMENT When darTZeel NHB 108 model one s eyes are blinking it means that an output DC voltage greater than 0 6 volt is present at the terminal speaker outputs An ad justment is then necessar
51. that the speakers we will use are truly perfect without a single trace of any distortion Well now let us try figure the THD we will have at the output of the amplifier We could be tempted to say 21 since 20 plus 1 makes 21 no Okay So then which golden ears could notice the THD difference between 20 and 21 Who could swear that the amplifier does add distortion In fact the distortion change is even less than this THD like most other non correlated physical phenomena does not increase in a linear fashion The total THD is equal to the square root of the sum of the squared individual THDs A little equation is even better than a less than clear definition THD HD HD HD In our particular case we only have 2 terms so the equation becomes 2 2 THD 100 eas satis 20 025 100 100 And now Who could distinguish between a 20 000 harmonically rich musical instrument and another one producing 20 025 Not us for sure And the very next note how rich is it And the next one Oh The song has al ready finished What sort of music was it Even though in reality THD is a bit more complicated than this we can still see that a posteriori it does not have the importance that was attached to it for decades quite the contrary If at darTZeel we could completely elimi nate THD while maintaining our 3 main criteria then maybe we would do so Maybe Just for the beauty
52. the terms balanced and symmetrical or un balanced and single ended In French these terms lead to even more confusion since both balanced and symmetrical are translated by sym trique So you will not feel less comfortable than our French speaking friends Feel free to contact us at info dartzeel com if you need explanations in greater depth It is absolutely fascinating to note that some technical choices only serve falla cious sales arguments and to our regret audio is no exception to the rule Most high end power amplifiers espe cially flagship models offer balanced inputs described as being the very best technically and sonically speaking As often as not there s no option as regards balanced inputs in fact there s nothing else For the darTZeel NHB 108 model one our approach has been almost the opposite To minimize the cost Could you even believe that Maybe the time has come to refresh our memory to some extent 5 4 1 From the microphone A balanced line is in fact a transmission line without reference to ground Imag ine that instead of transmitting the sig nal between one wire and ground we use two wires A 3 cable earmarked for ground is of course also present even though not necessary for the signal right now This transmission mode finally leads to external noise and disturbance cancella tion In pro audio engineering balanced lines are de rigueur and massiv
53. those old circuits Another problem then arose Our circuits were much more complex than a single modern IC and of course they were not very reliable either We especially en countered several performance consis tency problems from sample to sample and we gave up for a time Some years Page 5 of 28 later new ICs allowed further investiga tion and we built several prototypes We quickly noted however that digital had some limits when pushed hard We used a sample frequency of 500 kHz at the time corresponding to a theoreti cal bandwidth close to 250 kHz far higher than all competitors even in the analog domain But alas even with such a high sample frequency the actual measured bandwidth was strongly de pendant on the loudspeaker impedance Another problem jitter already well known in labs at the time was difficult to cure to say the least The signal to noise ratio was just above our minimum crite rion Since pure sound was the only goal then noise if at acceptable level could have been tolerated by us On the other hand interdependence between load imped ance and frequency response was not our cup of tea Not by a long chalk End of the digital trip It is interesting to note that several manufacturers offer digital amplifiers with greater or lesser success The theo retical limits remain the same even if better managed than in the 80s Analog fortunately does not have to cope with such l
54. ture that defines its working range An output device does not fail because the current is too high but simply because the temperature caused by this current rises too much So our monitoring circuit compares the instantaneous power dissipation with the value that the output stage can handle There is no thermal inertia here since we just measure the right thing at the right place A premiere in the audio field we can modestly say We then measure voltage and current passing through the output devices darTZeel NHB 108 model one Audiophile s technical manual Without adding any disturbance in the signal path Yes indeed As for measuring the voltage across the output devices it can be done quite eas ily without altering the signal Good news For the current however it s quite another story Keeping in mind not to harm the audio signal which is music after all we use a special Hall effect electromagnetic sen sor The speaker wire goes through it coupled magnetically This sophisticated current sensor has the enormous advantages of presenting an extremely light load in the region of 10 000Q compared to the 8 ohms of a speaker of not interrupting the signal path and of being truly linear from O Hz to more than 150kHz well above what is needed for music Its main drawback The price once again Simplicity To put it briefly the monitoring circuit allows unlimited peak currents for the time nece
55. ty times the audio range 5 2 What application field The electronic schematics of the darTZeel NHB 108 model one s audio circuit as we will soon see is astonishingly simple It s because the NHB 108 has high THD and IMD values would say our well meaning detractors If you have read us from the beginning you are now perfectly aware that har monics are not directly responsible for the sonic signature of an amplifier The apparent simplicity of our audio cir cuit has been effectively made possible through our choice of semiconductors technology Page 11 of 28 If the THD and IMD produced by the amplifier are kept low enough say lower than the audibility threshold then no further correction will be needed and the audio circuit can remain simple At the start of this new century 3 main technologies coexist in the construction of transistors these being in chronologi cal order Bipolar in the early 1950s Field effect in 1962 IGBT a mix of the previous two in the eighties At darTZeel we strongly believe in new technologies On the other hand we readily admit that nothing can replace experience So our winner is Bipolar technology 5 2 1 IGBTs For your own information we are ready to tell you an old secret What does the word transistor mean It comes quite simply from the contrac tion of transfer and resistor IGBT stands for Insulate Gate Bipolar Transistor
56. vices are just some examples among others These parameters are difficult to cope with particularly when cost considerations come into the picture The internal volume was exploited down to the last cubic centimeter Output power devices are located less than 10 centimeters from the huge crescent like bus bars All the energy coming from the capacitor reservoir can then effortlessly flow to the output bipolar transistors Also the Power Nose please read the Owner s manual for more about the ter minology we use does not directly switch the AC mains but drives static semiconductor relays This approach al lows freedom from any electromagnetic disturbance from AC and also to soft start the amplifier The switch is also subject to less wear since no spark can appear at its contacts extending its life span close to one million ON OFF opera tions We also placed inputs connectors very close to the entry PCB points altering as little as possible the still unamplified in coming music Dozens of other small things have been thought about and implemented We would need too much space to describe all of them furthermore such a descrip tion would be much too boring Please believe us we have done our best to look after the precious and delicate mu sical signal leaving as little as possible to chance Page 14 of 28 5 4 Symmetrically balanced The following could seem contradictory sometimes It is mainly due to
57. was the right one So much so that most of our test listen ers said that this product must be put into production even on a very small scale The darTZeel NHB 108 model one was born 3 Criteria Your darTZeel NHB 108 model one is not an ordinary machine and this is no doubt one of the reasons why you purchased it The entire concept is based on just three criteria Simplicity Purity Reliability These words can often be deceptive Easy to pronounce conjuring up ele gance and fascination they nevertheless constitute very tough technical chal lenges since their respective meanings are not at all easy to reconcile Nothing is eternal As for the darTZeel NHB 108 model one not enough time has yet elapsed for us to assert such a claim What we do assert is that everything has been taken into account so that you can benefit from your machine for a long time A very long time You will discover that more often than not simplicity means long lasting Sometimes it also means purity whether of sound or of form Welcome to darTZeel Page 6 of 28 4 Structural aspects It would be all too easy to compare the darTZeel NHB 108 model one and wrist watches both being made in Switzer land There are no springs cogwheels or hands in a NHB 108 model one Here eve rything is a tad bigger 4 1 The case modules The case of your machine is exclusively machined from AW 5754 ALMG3 alloy alu minum off
58. xplorer Module LEM also had three legs but that is another story after all Weighing around 30kg the darTZeel not the LEM needs to have a good stable base Those three pads are evenly lo cated around the horizontal center of gravity of the amplifier ensuring excel lent stability on virtually any surface The absorbing rubber pads dampen the lower frequencies thus forming the ideal complement to the suspensions de scribed earlier In the case where you would want to use 2 3 or even 4 stacked darTZeel NHB 108 model one units we have designed special pads of differ ent diameter to maintain the very same vibrational absorption behavior These pads are easy to install and can be pur chased separately 4 4 Everything is transparent The darTZeel NHB 108 model one cover is made of 8mm thick tempered bronze smoked glass It harmonizes magnifi cently with the colors of the housing and gives an inimitable touch The glass is held by a single central screw and rests on a foam rubber seal giving to the darTZeel NHB 108 model one darTZeel NHB 108 model one Audiophile s technical manual its dust proof quality Your machine will therefore remain as new for years to come The reason why we did not choose a metal cover is not so obvious as it might appear It is true that to look through the glass of the darTZeel NHB 108 model one is a pleasure for the eyes Look at those Moon crescent shaped bar busses and tell u
59. y Before doing any task it is important to ensure that Ambient room temperature is be tween 15 C and 35 C The darTZeel NHB 108 model one is properly vented as described in the Owner s manual The loudspeakers are connected to the speaker terminals The darTZeel NHB 108 model one has been in idle state for a minimum of 2 hours allowing an optimum distrib uted heat across the entire housing To make this adjustment you need the following tools A No 4 flat blade screwdriver for re moving the glass cover this tool is supplied as standard with the darT Zeel NHB 108 model one The 2 suction cups supplied with the darTZeel NHB 108 model one Please do not forget to slightly wet them to get firm vacuum on the glass A No O flat blade screwdriver for ad justing the 12 turn trimmer this tool is supplied as standard with the darTZeel NHB 108 model one A universal DMM Digital Multi Me ter not supplied Procedure 1 Using the DMM check that the DC output voltage is more than 0 6 darTZeel NHB 108 model one Audiophile s technical manual volt In practice the value is generally negative 2 Before opening the glass cover lo cate the trimmers using a pocket torch if need be the trimmers are close to the RCA input connectors On left channel the trimmer is lo cated on PCB solder side between PCB and heat sink A clockwise rota tion induces a negative voltage shift O
60. ying this manual demonstrating proof of your interest in the darTZeel NHB 108 model one First of all please do not think for a minute that we consider audiophiles dif ferently from music lovers We know perfectly well that audiophiles love music too and we are very happy with this It is however true that music lovers are generally less inclined to enjoy the tech nical and performance side of the music hence the existence of the Music lover s manual In the light of what follows you will bet ter understand why our technical choices during the design of the darTZeel NHB 108 model one led to what one could call a truly exceptional machine We trust that you will derive great pleas ure from reading this manual and that we succeed in communicating some of the burning passion that has been boiling inside us for more than 25 years Enjoy your reading 2 Genesis of NHB 108 The NHB Never Heard Before project began in summer 1984 Crazy about audio since childhood we gradually developed the idea of design ing a power amplifier Even though the NHB 108 model one is the fruit of a single man the moral financial and professional support from family and friends over all these years has played a huge part in this endeavor At the time it was only a dream and we are grateful to every gal and pal who has been involved in it and contributed to its achievement darTZeel NHB 108 model one Audiophile s technical m

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