Volksamp Pass Aleph 30 Owner`s Manual
Contents
1. Volksamp Pass Aleph 30 Owner s Manual Dear Customer The Pass Aleph 30 is the first of the second generation of Aleph single ended Class A power amplifiers This design results from my commitment to create the best sounding product a simple circuit having the most natural characteristic The Pass Aleph 30 integrates power Mosfet devices and pure single ended Class A operation in a simple two gain stage topology with the sole purpose of recreating subjectively natural sound The Pass Aleph 30 is unique in a number of ways Most amplifiers on the market have between five and seven gain stages in series between the input and the output The Aleph 30 has but two and enjoys a very direct path from input to output further enhancing the purity of the circuit and the resulting sound The output stage of the Aleph 30 is a unique blend of traditional design and innovation addressing the unique requirements of loudspeakers Previous methods of loading the output stage have used networks consisting of resistors coils transformers and active current sources all of which offer an optimal load line based on a resistive load The Aleph 30 has a current source topology which optimizes performance for a wide range of impedance and reactance in the load improving all aspects of performance into real loudspeakers Pass Labs has US patent No 5710522 on this output stage topology The Aleph 30 is unique in that there are no adjustments of an2. Yet a third advantage tubes and Mosfets have over bipolar devices is their greater reliability at higher temperatures As noted single ended power amplifiers dissipate comparatively high wattages and run hot Bipolar devices are much more prone to failure at high temperatures In a decision between Triodes and Mosfets the Mosfet s advantage is in naturally operating at the voltages and currents we want to deliver to a loudspeaker Efforts to create a direct coupled single ended triode power amplifier have been severely limited by the high voltages and low plate currents that are the province of tubes The commercial offerings have not exceeded 8 watts or so in spite of hundreds of dissipated watts Transformer coupled single ended triode amplifiers are the alternative using very large gapped core transformers to avoid core saturation from the high DC current but they suffer the characteristic of such a loosely coupled transformer as well The promise of the transconductance characteristic in power amplifiers in providing the most realistic amplified representation of music is best fulfilled in Mosfet single ended Class A circuitry where it can be used very simply and biased very high The Pass Aleph 30 uses International Rectifier Hexfet Power Mosfets exclusively for all gain stages These Mosfets were chosen because they have the most ideal transfer curve for an asymmetric Class A design Made in the United States they have the highest qual
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4. Class A amplifiers on the market you might say opened a Pandora s box A very important consideration in attempting to create an amplifier with a natural characteristic is the selection of the gain devices A single ended Class A topology is appropriate and we want a characteristic where the positive amplitude is very very slightly greater than the negative For a current gain device that would mean gain that smoothly increases with current and for a tube or field effect device a transconductance that smoothly increases with current Triodes and Mosfets share a useful characteristic their transconductance tends to increase with current Bipolar power devices have a slight gain increase until they hit about an amp or so and then they decline at higher currents In general the use of bipolar in a single ended Class A circuit is a poor fit Another performance advantage shared by Tubes and Fets is the high performance they deliver in simple Class A circuits Bipolar designs on the market have between five and seven gain stages associated with the signal path but with tubes and Mosfets good objective specifications are achievable with only 2 or 3 gain devices in the signal path Readers of The Audio Amateur Magazine will be familiar with my Zen design which uses a Mosfet in a power amplifier which has only one gain stage and only one gain transistor Research continues at Pass Labs in improving the performance of very simple gain circuits
5. to the rest of the amplifier circuit We select the input devices as part of the complete amplifier swapping them in and out until the best performance is achieved Tweaking the input stage in this manner and with other adjustment techniques we have been able to significantly lower the noise floor and improve the power supply noise rejection of the amplifier Typically the Aleph 30 has about 6 dB greater dynamic range compared to the Aleph 3 We have increased the number of output power Mosfet devices from four per channel to six These are the same devices as the original Aleph 3 and are matched in the same manner taken from the same lot codes and matched to about 2 Vgs The greater number of devices lowers the distortion and improves the damping factor by about 5096 and also allows us to run the bias up a bit giving higher heat sink temperatures but with the same on chip temperatures The power supply has been improved with half again more power supply capacitors with twice the voltage ratings giving lower ESR figures Also the power supply incorporates much improved line noise filtering in both differential and common mode which filters out incoming noise and reduces noise emission by the amplifier One of the biggest differences in the Pass Aleph 30 is the type of chassis and heat sink used The Aleph 3 was machined entirely from aluminum extrusions stock While this resulted in a unique and very functional appearance it had several drawb
6. acks First it was very expensive Also it allowed very limited space for access to input and output terminals on the rear of the amplifier and required the on off power switch to sit in the rear underneath the wiring It has been said that ownership of the original Alephs was proof of the owner s dedication to sound at the cost of convenience The Aleph 30 has a new more conventional chassis with heat sinks on the side a faceplate with a power switch and a regular sheet metal type chassis In addition to being more convenient this approach costs less and we have passed the difference on to the customer The final result is that the Aleph 30 performs better than the original Aleph 3 in all areas has the additional feature of balanced inputs and costs a lot less The Volksamp version of the Aleph 30 is produced under license from Nelson Pass and Pass Laboratories Inc and is distributed and serviced by Pass Labs Domestic Sales Inc and Pass Labs Foreign Sales Inc Thanks you for purchasing it Enjoy Nelson Pass nelson passlabs com Setup The amplifier has four sets of connections and one switch The first connection and switch is the AC line power system The amplifier s voltage and current rating are indicated on the bottom It will be either 240 volts 120 volts or 100 volts all with a SAG slow blow type fuse The frequency rating of the AC line source is 50 to 60 Hz Your amplifier is provided with a standard AC power
7. adjustments to the amplifier Values for biasing various components are taken from physical constants such as PN junctions and Zener voltages and through matching of Mosfet transistors The input Mosfets are matched in the working amplifier and the output Mosfets are in matched pairs within 1 volt although production tolerance is typically 01 volt The Vgs figures for the output devices are written on the top of the package of each For a 120 volts AC line the amplifier will draw about 2 amps RMS If you measure current draw with an averaging meter you will get a smaller number The amplifier is designed so that the heat sinks will operate approximately 25 degrees C above ambient for a typical temperature of 50 degrees C Temperature protection occurs at 75 degrees C The amplifier will not be damaged by driving a short circuit and it is probable that the only failures you will see will be random component failure VOLKSAMD Pass Labs Po Box 219 Foresthill CA 95631 tel 530 367 4935 fax 530 367 4984 www volksamp com www passlabs com OUTPUT MS ALEPH30 SIMPLIFIED Size Number FIGURE 1 Rev A Date 8 1 00 Drawn by PASS Filename 5 01 2007 106 Zup91d ZU oe ml ong PT SOA Q3HOIVN 1 65 dh g FANON mS ES STANNVHO HIO OL NOINWOO 3 8 ONY BIAPIO JSNVeL AM SOA Q3HOIVW 6 95 NANOHS THNNVHO INO ALIS NI Q3HOIVIW ZO LS O Hd3IV ay JA ME WHO ONY Y 0 163205 AN 96 L A P L 5 1663 TV
8. biased for ten times that amount will generally sound better than one biased for the few watts For this reason designs which operate in what has been referred to as pure Class A are preferred because their bias currents are much larger than the signal most of the time As mentioned preamp gain stages and the front ends of power amplifiers are routinely single ended pure Class A and because the signal levels are at small fractions of a watt the efficiency of the circuit is not important 4 Given the assumption that every process that we perform on the signal will be heard the finest amplifiers must employ those processes which are most natural There is one element in the chain which we cannot alter or improve upon and that is the air Air defines sound and serves as a natural benchmark Virtually all the amplifiers on the market are based on a push pull symmetry model The push pull symmetry topology has no particular basis in nature Is it valid to use air s characteristic as a model for designing an amplifier If you accept that all processing leaves its signature on the music the answer is yes One of the most interesting characteristics of air is its single ended nature Sound traveling through air is the result of the gas equation PV1 4 1 26 X 104 where P is pressure and V is volume and whose curve is illustrated in fig 1 The small nonlinearity which is the result of air s characteristic is not generally judged to be sig
9. cord which fits into the line receptacle located just below the power switch The amplifier is equipped for operation with an earth ground provided by the AC outlet Do not defeat this ground The chassis of the amplifier is connected directly to this earth ground and the audio circuit ground is connected to the chassis and earth through a power thermistor which gives a ground safety connection but helps avoid ground loops The second connection are the single ended inputs which occur through standard RCA connectors The input impedance of the amplifier is 47 K ohms and is DC coupled with no capacitors The third connection are the balanced inputs which occur through standard XLR connectors The balanced input impedance is 52 Kohms Input pin 1 of the XLR connector is input ground pin 2 is the positive input and pin 3 is the negative input As shipped there is a shorting jumper between pins 1 and 3 which is the configuration for single ended input This shorting jumper should be used when operating the amplifier with the RCA input otherwise you will not get the proper gain figure for the amplifier If you operate the amplifier with balanced inputs you will remove this jumper and we advise you to save it carefully for future use The fourth connection is the amplifier output connection Connect the 5 way output connectors to loudspeaker plus and ground using the cable of your choice The amplifier draws about 200 watts from the wall a
10. dual efforts and reflect a coherent underlying philosophy They make a subjective and an objective statement of quality which is meant to be appreciated It is essential that the circuitry of an audio component reflects a philosophy which address the subjective nature of its performance first and foremost Lacking an ability to completely characterize performance in an objective manner we should take a step back from the resulting waveform and take into account the process by which it has been achieved The history of what has been done to the music is important and must be considered a part of the result Everything that has been done to the signal is embedded in it however subtly Experience correlating what sounds good to knowledge of component design yields some general guidelines as to what will sound good and what will not 1 Simplicity and a minimum number of components is a key element and is well reflected in the quality of tube designs The fewer pieces in series with the signal path the better This often true even if adding just one more gain stage will improve the measured specs 2 The characteristic of gain devices and their specific use is important Individual variations in performance between like devices is important as are differences in topological usage All signal bearing devices contribute to the degradation but there are some different characteristics are worth attention Low order nonlinearities are largely additive
11. e simplified schematic of the amplifier Two p channel Mosfets form an input differential pair biased by a current source operating at about 20 ma The drain of the input Mosfet is attached to the gate of an n channel power Mosfet which forms the active output stage It is biased by a current source at slightly less than 2 amps The voltage rails of the supply are at 25 volts and each channel draws approximately 100 watts Figure 2 shows the actual schematic for the power supply and one channel F1 is a slow blow fuse set at 4 amps for 100 120 volt operation and 2 amps for 220 240 volt operation 51 is the power switch which has two sets of 25 amp contacts wire in parallel T1 is a thermostatic switch rated at 75 degrees Centigrade It is mounted to the rear heat sink TH1 is a power thermistor used to connect the circuit and chassis ground to the AC outlet ground It will normally operate at 5 ohms suppressing ground loops in the system but will drop to a low impedance if significant current is passed through it The power transformer drives a high current bridge and 120 000 uF of capacitance to form a plus and minus 25 volt supply Referring to the channel itself Q1 and Q2 form the differential input pair of Mosfets They are biased by the current source formed by Q3 Q3 is biased to about 25 ma by the reference Zener diode Z5 which sets about 5 volts across R11 Z1 Z4 protect the input from static spikes R2 3 4 5 6 7 f
12. ected from overheating by a 75 degree C thermostatic switch and from internal failure by a slow blow fuse The Pass Aleph 30 is warranted by Volksamp to meet performance specifications for 3 years from date of manufacture During that time Volksamp will provide free labor and parts at the manufacturing site The warranty does not include damage due to misuse or abuse or modified products and also does not include consequential damage SPECIFICATIONS Gain Freq Response Power Output Maximum Output Distortion 1KHz Input Impedance Damping factor Crosstalk Balanced Input Rejection Output Noise Random noise floor DC offset Power Consumption Temperature Dimensions Shipping Weight 20 dB balanced 26 dB single ended 0 5 dB 2 Hz 1 5 dB 100 KHz 30 watts ch 8 ohms 40 watts 4 ohms 25 volts 5 amps 0 2 30 watts 8 ohms 47 Kohm single ended 52 Kohm differential 100 80 dB 20 20 KHz 50 dB typical CMRR 500 uV unweighted 5 uV typical lt 100 mv 200 watts 25 degrees C above ambient 17 W x 15 5 D x 5 5 H 45 lb VOLKSAMD Pass Labs Po Box 219 Foresthill CA 95631 tel 530 367 4935 fax 530 367 4984 www volksamp com www passlabs com Pass Aleph 30 Service Information The Pass Aleph 30 has only two gain stages which are biased by current sources Because of the inherent simplicity of the circuit it is easy to understand and repair There are no adjustments Figure 1 shows th
13. in quality bringing false warmth and coloration while abrupt high order nonlinearities are additive and subtractive adding harshness while losing information 3 Maximum intrinsic linearity is desired This is the performance of the gain stages before feedback is applied Experience suggests that feedback is a subtractive process it removes information from the signal In many older designs poor intrinsic linearity has been corrected out by large application of feedback resulting in loss of warmth space and detail High idle current or bias is very desirable as a means of maximizing linearity and gives an effect which is not only easily measured but easily demonstrated Take a Class A or other high bias amplifier and compare the sound with full bias and with bias reduced Bias adjustment is easily accomplished as virtually every amplifier has a bias adjustment pot but it should be done very carefully As an experiment it has the virtue of only changing the bias and the expectations of the experimenter As the bias is reduced the perception of stage depth and ambiance will generally decrease This perception of depth is influenced by the raw quantity of bias current If you continue to increase the bias current far beyond the operating point it appears that improvements are made with bias currents which are much greater than the signal level Typically the levels involved in most critical listening are only a few watts but an amplifier
14. ing on usage you will begin to have semiconductor and other failures between 10 and 50 years after date of manufacture Later the sun will cool to a white dwarf and after that the universe will experience heat death Pass Product Philosophy and Design Theory When started designing amplifiers 25 years ago solid state amplifiers had just achieved a firm grasp on the market Power and harmonic distortion numbers were king and the largest audio magazine said that amplifiers with the same specs sounded the same We have heard Triodes Pentodes Bipolar VFET Mosfet TFET valves IGBT Hybrids THD distortion IM distortion TIM distortion phase distortion quantization feedback nested feedback no feedback feed forward Stasis harmonic time alignment high slew Class AB Class A Pure Class A Class AA Class A AB Class D Class H Constant bias dynamic bias optical bias Real Life Bias Sustained Plateau Bias big supplies smart supplies regulated supplies separate supplies switching supplies dynamic headroom high current balanced inputs and balanced outputs Apart from digitally recorded source material things have not changed very much in twenty five years Solid state amplifiers still dominate the market the largest audio magazine still doesn t hear the difference and many audiophiles are still hanging on to their tubes Leaving aside the examples of marketing hype we have a large number of attempts to improve the sound
15. int There is only positive pressure more positive pressure and less positive pressure Push pull circuits give rise to odd ordered harmonics where the phase alignment reflects compression at both positive and negative peaks and crossover nonlinearity near the zero point Push pull operation in amplifiers is commonly portrayed by the analogy of a two man saw cutting down a tree Certainly if we are cutting down trees by hand we would opt for this method as it would be much more efficient As we are not cutting down trees much prefer the image of a violinist holding the bow at one end with one hand Only in this manner does the musician gain the degree of control and precision required to produce the range and subtlety required by music And so it is with single ended amplifiers Only one linear circuit topology delivers the appropriate characteristic and that is the single ended amplifier Single ended amplification only comes in pure Class A and is the least efficient form of power stage you can reasonably create typically idling at more than twice the rated output power under the best of conditions Single ended operation is not new It is routinely found in the low level circuitry of the finest preamplifying stages and in the front end circuits of the finest power amplifiers The first tube power amplifiers were single ended circuits using a single tube driving the primary of a transformer In 1977 designed and published in Audi
16. ity of power Mosfets we have tested to date We match output devices to within 296 The input devices are matched in circuit for lowest noise and distortion The smallest of these the input devices are capable of peak currents of 5 amps The largest are capable of peaks of 25 amps each and are run in parallel pairs The power Mosfets in the Pass Aleph 30 have chip temperatures ratings to 150 degrees Centigrade and we operate them at small fractions typically 2096 of their ratings For extended life we do not allow chip temperatures to exceed 85 degrees C Regardless of the type of gain device in systems where the utmost in natural reproduction is the goal simple single ended Class A circuits are the topologies of choice It is a very simple topology which is a key part of the sound quality Other solid state amplifier designs have five to seven gain stages in the signal path in order to get enough gain to use feedback to provide adequate performance In this amplifier we get greater linearity by providing much more bias through two gain stages a differential input stage and the output transistors SURPAT m OUIPUT SUPPLY Mosfets provide the widest bandwidth of solid state power devices however they were not chosen for this reason The design of the Aleph 30 does not seek to maximize the amplifier bandwidth as such The capacitances of the Mosfets provide a natural rolloff in conjunction with
17. nificant at normal sound levels and is comparable to the distortion numbers of fine amplifiers This distortion generally only becomes a concern in the throats of horns where the intense pressure levels are many times those at the mouth and where the harmonic component can reach several per cent 6 PRESSURE l bars 1 4 1 2 1 0 i 6 VOLUME M 1 Kg FIG 1 CHARACTERISTIC OF AIR Fig 1 shows the single ended nature of air Wecan push on it and raise the pressure an arbitrary amount but we cannot pull on it We can only let it relax and fill a space as it will the pressure will never go below 0 As we push on air the increase in pressure is greater than the corresponding decrease when we allow air to expand This means that for a given motion of a diaphragm acting on air the positive pressure perturbations will be slightly greater than the negative From this we see that air is phase sensitive As a result of its single ended nature the harmonic content of air is primarily 2nd order that is to say most of the distortion of a single tone is second harmonic The phase of this distortion reflects the higher positive pressure over the negative Air s transfer curve also shows also that it is monotonic which is to say its distortion products decrease smoothly as the acoustic level decreases This is an important element that has often been overlooked in audio design and is
18. o Magazine a single ended Class A amplifier using bipolar followers biased by a constant current source A considerable number of amateurs have built the device rated at 20 watts output and many have commented on its unique sonic signature Single ended Class A operation is generally less efficient than push pull Class A Single ended Class A amplifiers tend to be even bigger and more expensive than their push pull cousins but they have a more natural transfer curve The purity of Class A designs has been at issue in the last few years with pure Class A loosely defined as an idling heat dissipation of more than twice the maximum amplifier output For a 100 watt amplifier this would be 200 watts out of the wall at idle As the Pass Aleph 30 idles at four times its rated output think we can safely think of it as pure Designs that vary the bias against the musical signal will generally have bias currents at or below the signal level This is certainly an improvement from the viewpoint of energy efficiency but the sound reflects the lesser bias point authored the first patent on the dynamically biased Class A amplifier in 1974 however have not used the technique for the last 15 years The reason is that found the quality of sound associated with an efficient Class A operating mode inferior in depth and less liquid at high frequencies simply because it operates at reduced bias at low levels Given the plethora of cool running
19. of amplifiers each attempting to address a hypothesized flaw in the performance Audiophiles have voted on the various designs with their pocketbooks and products go down in history as classics or are forgotten The used market speaks eloquently Marantz 9 s command a high price while Dyna 120 s are largely unwanted So far there has been a failure in the attempt to use specifications to characterize the subtleties of sonic performance Amplifiers with similar measurements are not equal and products with higher power wider bandwidth and lower distortion do not necessarily sound better Historically that amplifier offering the most power or the lowest IM distortion or the lowest THD or the highest slew rate or the lowest noise has not become a classic or even been more than a modest success For a long time there has been faith in the technical community that eventually some objective analysis would reconcile critical listener s subjective experience with laboratory measurement Perhaps this will occur but in the meantime audiophiles largely reject bench specifications as an indicator of audio quality This is appropriate Appreciation of audio is a subjective human experience We should no more let numbers define audio quality than we would let chemical analysis be the arbiter of fine wines Measurements can provide a measure of insight but are no substitute for human judgment As in art classic audio components are the results of indivi
20. orm the input networks and feedback loops The output of the differential input paid drives the gates of output devices Q9 11 These parallel devices are matched as close as 01 volts however variations as high as 1 volts will not impede operation The voltage across R14 shows the drive voltage for the output stage and it should have 4 5 volts across it The output of the amplifier is taken from the drains of Q9 11 Q9 11 are provided a bias current by the current source circuitry of Q6 8 also matched N channel Mosfets Q6 8 are set at 2 amps DC by the network consisting of Q5 and the components surrounding it Q5 is biased by R17 and R18 in series A capacitor C9 is used to reduce supply noise R20 serves to sense the current running through Q6 and feeds that to the base of Q5 forming a loop that holds the output current at 2 amps The PN junction drop of Q5 forms the reference voltage for the system R19 is a fixed resistor which trims the DC current value R21 and C10 adjust the current against output current as sensed by the voltage across R34 Fig 3 and 4 shows the AC voltage wiring and component layout of the central power supply board This board holds the power supply components On Fig 3 you can see the wiring arrangements for the various AC line voltages 100 120 and 240 volts Fig 5 shows the component layout of the board assemblies forming the two channels left and right of the amplifier There are no
21. reflected in the poor quality of early solid state amplifiers and D A and A D converters They are not monotonic the distortion increases as the level decreases The usual electrical picture of an audio signal is as an AC waveform without a DC component Audio is represented as alternating voltage and current where positive voltage and current alternates with negative in a reciprocal and symmetric fashion This fiction is convenient because it lends itself to the use of an energy efficient design for amplifier power stages known as push pull where a plus side of an amplifier alternates operation with a minus side Each side of a push pull amplifier handles the audio signal alternately the plus side supplying positive voltage and current to the loudspeaker and the minus side supplying negative voltage and current Problems with push pull amplifier designs associated with crossover distortion have been discussed elsewhere at length and one of the primary results is non monotonicity Class B and many AB designs have distortion products that dramatically increase with decreasing signal This is reduced greatly by Class A mode but crossover distortion remains as a lower order discontinuity in the transfer curve For reproducing music as naturally as possible push pull symmetric operation is not the best approach Air is not symmetric and does not have a push pull characteristic Sound in air is a perturbation around a positive pressure po
22. t all times and during idle operation nearly all of this energy will appear as heat on the heat sinks Good ventilation is vital to the proper operation of the amplifier It has been adjusted for optimal performance at room temperature but will work well between 50 and 90 degrees Fahrenheit 10 to 33 Celsius You should leave at least six inches clearance on the sides and top The amplifier should not be placed in a closed cabinet which does not have forced air ventilation This amplifier runs hot The heat sinks will warm up in about an hour to a temperature which will not be comfortable to touch for more than a moment or two which is 120 to 130 degrees Fahrenheit 50 to 55 degrees Celsius This is normal and there is a thermal shut off system which will shut down the amplifier at internal temperatures in excess of 160 deg F and 70 deg C It takes about an hour of warm up time to get the best performance out of the amplifier It will take that long to reach operating temperature and exhibit lowest distortion and noise This is not a subjective judgement but based on actual distortion and noise measurements Many customers have reported that longer warm up yields more improvement The amplifier does not require any maintenance While the design is conservative this is a hard running amplifier as single ended Class A operation is the least efficient operating mode In fifteen years the electrolytic power supply capacitors will get old Depend
23. the resistive impedances found in the circuit and the simplicity of the circuit allows for what is largely a single pole rolloff characteristic The slew rate of the amplifier is about 40 Volts uS load which is about 10 times faster than the fastest signal you will ever see and about 100 times faster than what you will be listening to In and of itself the slew rate is an unimportant factor when evaluating tube and simple Mosfet designs It becomes more important with complex circuit topologies where there is heavy dependence on feedback correction but even then its importance has been overstated The amplifier is powered by a toroidal transformer which charges 120 000 uF capacitance This unregulated supply feeds the output transistors only with a full power ripple of about 3 volt The power draw of this system is constant regardless of the music playing through the amplifier As such it does not depend on a high quality AC outlet or special power cords since the dynamic performance does not create a variation in AC line draw If the AC line is running low the output stage will bias to a higher current level by way of compensation The amplifier is stable into any load impedance or reactance including a direct The Aleph 30 is impervious to electrostatic shock at the input and dead shorts at the output You can safely plug and unplug inputs and outputs while the amplifier is running Do not try this with other products The Aleph 30 is prot
24. y kind in the circuitry There are no potentiometers to adjust The operating parameters of bias currents and DC offset and so on are defined by physical constants and will not go out of adjustment Most important the Aleph 30 brings improvement to the recreation of subjective sonic reality The amplifier delivers detail and subjective space rarely found in semiconductor circuits coupled with the authority and clarity rarely found in tube amplifiers The Pass Aleph 30 s ancestry lies in the highly praised Aleph 3 We have kept virtually all of the circuit design and choice of parts intact The amplifier uses exactly the same circuit topology except that a balanced XLR input has been provided in addition to the single ended RCA input of the Aleph 3 The balanced input circuitry is the same topology as the rest of the original Aleph series accomplishing true high performance balanced input without additional active components It has been improved however to offer a higher input impedance on the single ended input 47 Kohms The original Aleph 3 had a 23 Kohm input impedance and the other Aleph amplifiers had a 10 Kohm single ended input impedance The input devices are slightly better than the originals but significant improvement is to be found in the manner of matching the input devices Previously the input differential transistors were merely matched to each other but beginning with the Aleph 30 they are now matched both to each other and
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