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1. Skype ID phaedrusaudio We will diagnose the problem remotely and advise you of the warranty status If a repair or replacement is required we will issue a Return Merchandise Authorization RMA number and tell you where to send the unit to be repaired You MUST have an RMA number before you return the equipment to Phaedrus Audio Ltd s support service Be sure to write RMA number on outside of shipping box and to include your name address phone number a copy of original sales invoice and a detailed description of the problem Phaedrus Audio Ltd will not accept responsibility for loss or damage in shipping or for equipment returned without valid paperwork and or a valid RMA number Remember warranty is void if product serial numbers have been removed or altered or if the product has been damaged by abuse accident or unauthorized modification and or repair see Phaedrus Audio Ltd Limited Warranty for details There are no user serviceable parts inside PLEASE RETAIN Y OUR SALES RECEIPT IT IS YOUR PROOF OF PURCHASE COVERING Y OUR LIMITED WARRANTY LIMITED WARRANTY IS VOID WITHOUT SUCH PROOF OF PURCHASE Phaedrus Audio Ltd s Limited Warranty This limited warranty is valid only if you purchased the product from Phaedrus Audio Ltd of from a Phaedrus Audio authori zed dealer in the country of purchase a list of authorized dealers can be found on Phaedrus Audio website www phaedrus audio com or by contacting sales phaedrus audi o com Pha
2. these instruments need to be captured with microphones rather than applying a line level signal to the mixer However this is not always possible for a host of reasons including unacceptable spill from other sources feedback problems room resonance issues cabinet buzz inadequate microphone response and so on 12VAC only THRU a phaedrus el FLAT amp LIFT up to lift PHI DI Box 3 ALL TUBE CIRCUIT l INSTRUMENT LOUDSPEAKER OUTPUT manufactured in the UK by phaedrus IN In this situation it is useful to be able to DI not the output from the instrument but the signal which drives the loudspeaker This signal is not modified by the cabinet but it does have atleast the character of the amplifier its tonal modifications and distortion characteristics imprinted upon it The Phaedrus Audio PHI is able to provide this functionality However this loudspeaker signal is of a very much larger amplitude than this signal which leaves the instrument it has been amplified after all It is therefore necessary to attenuate this signal before presenting to the DI circuitry and this is exactly what is done when the LOUDSPEAKER INSTRUMENT switch is oap ca moved to the LOUDSPEAKER position loudspeaker output computer or recorder e The attenuation is 32dB YOU MUST SELECT THE LOUDSPE AKER POSITION OF THE LOUDSPE AKER INSTRU MENT SWITCH WHEN CONNECTING THE Phaedrus Audio PHI TO THE LOUDSPEAKER C
3. 1 C a am HPF me 4B ae OdB 4608 PHAB tube microphone preamp high pass filter rotary attenuator switch pad and gain switch 48V phantom power switch The Phaedrus Audio PHAB tube preamplifier is built around a modular amplifier with a fixed gain of 40dB with a switch available to raise this to approximately 46dB This amplifier is preceded by a rotary switched attenuator control offering attenuation of O to 30dB in steps of 6dB A further pad operated by a front panel switch is available to increase the attenuation to 40dB thereby matching the gain of the modular amplifier and reducing the overall unit gain of the equipment to unity These controls the input attenuator pad and the gain switch are used to set the overall preamplification level of the unit and feed a suitable electrical level to your downstream equipment see Operating level section for more information Normal operation should be to operate WITHOUT the 10dB pad engaged and with the preamplifier gain set to 40dB Only operate the pad switch when the signal from the microphone is too great for attenuation via the rotary attenuator control and only operate the 46dB gain switch when the signal from the microphone is too low even when the rotary attenuator is set to OdB HPF rumble filter By virtue of its very high quality input and output transformers and its minimalist wideband valve circuitry the pass band of the Phaedrus Audio PHAB pre
4. PHI REP Repair of a defective PHI DI box charged ata flat rate PHAB MISEAJ OUR Mise jour for PHAB preamp PHAME MISEAJOUR Mise jour for PHAME preamp PHI MISEAJ OUR Mise jour for PHI DI box PHAE EXTWARR Extends standard warranty see above by a further year A mise jour service includes a complete inspection re valve re tube and the implementation of any engineering updates as well as a re test to performance specification If extended warranty is ordered af ter the initial warranty has expired then the intervening period is charged without exception Please contact your dealer or Phaedrus Audio Ltd for current prices Warranty service conditions are subject to change without notice For the latest warranty terms and conditions and additional information regarding Phaedrus Audio Ltd limited warranty please see complete details online at www phaedrus audio com Chapter 3 Safety General Before using any piece of equipment manufactured by Phaedrus Audio Ltd be sure carefully to read the applicable items of these operating instructions and the safety suggestions Keep them for future reference Follow the warnings indicated on the unit as well as in the operating instructions Selection of PSU Suitable PSUs for the Phaedrus Audio Ltd PHAB and PHAME preamplifiers and the PHI DI Box are available as line items from Phaedrus Audio They are PHAE PSU 1 10 110V mains plugtop PSU plu
5. S aidb PHAB and PHAME is dBu considerable and no noticeable distortion is evident when operating the equipmentat standard recording industry 10 ee levels of 4dBu OVU or even pro audio higher There is thus considerable scope for R piki experimentation with over driving this vintage circuitry to imag r T O explore its character in gradual overload For example SER peaks may be allowed to reach 18dB above alignment level without clipping The Phaedrus Audio PHAB and the PHAME 10 preamplifiers may thus be used directly to feed modern A to D conversion equipment aligned to EBU or SMPTE 18 standards following the recommendations illustrated EBU CSMPTE right Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved PHI Application and connections Simple DI units utilise a transformer to balance the unbalanced signal and feed it to the microphone input of your mixer or microphone preamplifier This technique provides a x cabinet model reasonably hig h from instrument flat unbalance to balance imp edance as or from amplifier transformer presented to the instrument typically a 2i few tens of thousands of ohms Adequate for a keyboard for example at a push TO ous sufficient for a bass guitar But the tone orto loudspeaker of an electric guitar is completely destroyed unless it drives an impedance hundreds of times greater than can ever be provided by a transformer The only answer is to present the
6. amplifier is 24dB gt 30dB with the high gain switch depressed Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved HT 300V EF86 base from 200 ohm source phaedrus PHILHARMONIC ii ac Sa ree modular line amplifer The amplifier block is a two stage design incorporating an EF86 low noise pentode in the first stage and a paralleled ECC88 high mutual conduc tance double triode as the output stage All the landmark amplifier designs from Mullard s application laboratories specified the EF86 In fact Mullard described the EF86 as a ow noise pentode intended for use as a RC coupled AF voltage amplifiers particularly in the early stages of high gain audio amplifiers microphone preamplifiers and magnetic tape recorders The output stage comprises a dual triode valve in which the two devices are wired in parallel This paralleling of the two triodes has the beneficial effects of doubling the mutual conductance and halving the anode resistance The latter characteristic is particularly valuable in ensuring a low impedance drive to the output transformer The output stage directly feeds the output step down transformer The output is balanced and earth free A modest degree of negative feedback is taken from the anode of the output valve s to the cathode circuit of the input stage to stabilise gain extend frequency response and lower distortion A change to this feedback network is employed
7. guitar to be highly susceptible to the AC electromagnetic fields thrown off by all mains powered equipment Of ten all that is required to solve the problem and reduce the hum and or buzz to a manageable level is to orient the instrument differently so that the pickups no longer intercept so much changing flux But sometimes hums and buzzes prove to be particularly stubborn and intractable regardless of the guitarist s pirouetting When this happens it is usually because of a ground loop or earth loop A ground loop forms when an unbalanced audio signal flows in a circuit in which the signal return usually the cable braid provides a current path which is in parallel with the installation earth This is a problem because all earths are not equal That s to say the installation earth will be carrying certain leakage currents These currents set up a potential across the installation wiring which drives a circulating current in the braid of the audio cable The result is a hum voltage superimposed upon the audio signal The adoption of balanced signals and especially audio transformers should ensure that ground loops or earth loops should NE VER occur Certainly the Phaedrus Audio PHAME by being both double insulated and incorporating an earth free transformer balanced output stage can never create a ground loop in a correctly wired studio However connection to an earthed or grounded guitar amplifier can cause a circulating current s
8. so that simply touching the strings may worsen or improve the buzz In this situation it is recommended that pin 1 of the output connector of the PHI be connected to mains earth ground or a technical earth and the LIFT switch be leftin the down position Chapter 6 Circuit descriptions PHAB amp PHAME The Phaedrus Audio PHAB and the PHAME preamplifiers share roughly the same preamplifier circuit which is illustrated in general form below The differences mainly lie in the input circuitry and attenuator controls Both devices operate with a constant gain amplifier and attenuate the signal reaching the amplifier for level control In the case of the PHAB the valve preamplifier has a fixed gain of 40dB with a switch available to raise this to approximately 46dB The amplifier is preceded by a switched attenuator control offering attenuation of O to 30dB in steps of 6dB A further pad operated by a front panel switch is available to increase the attenuation to 40dB thereby matching the gain of the amplifier and reducing the overall unit gain to unity In the case of the Phaedrus Audio PHAME the preamplifier does not incorporate an input balance to unbalance transformer Instead the instrument feeds to grid of the EF86 pentode via a continuous attenuator pot to ensure a very high input impedance This is vital to ensure the best tone from all electric instruments and especially electric and bass guitars The fixed gain of the
9. 1 9Phaedrus Audio Ltd 2011 All rights reserved PHAME Application and connections THRU output to amp output EQ attenuator PHILHARMONIC Tee AMPLIFIER instrument input low gain high gain o Architecture of the PHAME preamp The unit is connected as shown in the accompanying diagrams Direct injection DI provides a clean way of applying instruments to your mixer or computer interface This is especially interesting today now that there are so many plug in effects and amplifier emulations which run as sof tware on the computer host All that is required when working this way is to get a natural signal into the computer s analogue to digital conversion circuits The sof tware will then take it from there loop to amplifier optional computer or recorder to mixer loop thru or computer i f power supply to amplifier optional How to connect the PHAME preamp But if only things were that simple The problem is that a normal passive DI box or a solid state input stage can rarely offer the benefits of a valve preamplifier See Voicing and the valve tube amplifier box Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved Voicing and the valve tube amplifier Guitar pickups are made by winding about 8000 turns of wire on a former or bobbin which surrounds several permanent magnets The resistance of the wire is relatively low but the inductance is highand the device t
10. IRCUIT OF Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved AN AMPLIFIER NOT SO DOING WILL DAMAGE YOUR Phaedrus Audio PHI FURTHERMORE YOU MUST OBSERVE THE WARNING GIVEN BELOW AS FAILURE TO DO THIS COULD DAMAMGE YOUR AMPLIFIER When the Phaedrus Audio PHI is usedin LOUDSPEAKER mode it is important to observe the correct polarity of the signal fed from the amplifier to the PHI To avoid short circuiting the output of the amplifier the earthy side of the loudspeaker signal MUST be connected to the sleeve of the input jack In addition as a precaution ALWAYS operate with the Ground lif t switch in the LIFT position when operating the PHI in this way from amplifier Ioudspeaker output earthy connection usually black core positive connection usually red core Further more the Phaedrus Audio PHI is NOT a dummy load and a loudspeaker MUST be attached to the THRU output so as to provide the correct load for the power amplifier Valve amplifiers especially may be damaged without the correct speaker load connected Flat Cabinet switch The problem with the signal from the amplifier is that it of ten contains many high frequencies which are not reproduced by instrumental loudspeaker cabinet The result is a fizzy over bright signal very different from that heard from the loudspeaker The reason for this is that the loudspeaker and cabinet act together to form an asy mmetrical band pass filter steeply attenua
11. MONIC amplifier circuit is described in detail below in section Circuit descrip tions Mullard Underside View of Prototype Input mixing Pre amplifier Mullard published many reference designs which were used by EMI in developing the REDD amplifiers Phaedrus Audio went back to these same references to develop the PHAB PHAME and PHI products The prototype London Console Mark ll Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved PHAB The Phaedrus Audio PHAB microphone preamplifier is essentially the front end of a single channel of the LONDON console in which PHILHARMONIC modular amplifier is combined with a rotary attenuator switchable pad high pass filter and gain switching circuitry similar to that employed in the famous sixties consoles 18 12 atten P LJ LJ 30 OdB B EF86 20d Ecc88 E 10dB MMM 40dB Eccas In low D D E ond y E gain instrument phaedrus K Ci am lift high PHAME tube instrument preamp LJ phaedrus C pad C gain a HPF 48V OdB 460B PHAB tube microphone preamp PHAB microphone preamp and PHAME instrument preamp PHAME The Ph drus Audio PHAME is a development of the PHAB in which the very high input impedance of the input pentode valve is exploited to provide a very high quality instrumental preamplifier PHI 12VAC only The Ph drus Audio PHI DI Box is a product designed for a phaedrus wide range of applications from live use to the
12. User Manual for phaedrus phaedrus audio com 18 12 atten 7 Y LJ LJ 30 OdB EF86 Q ECc88 E NUM Noe Lr WE E e gt phaedrus E K wom HPF 48V wm OdB 46dB PHAB tube microphone preamp PHAB tube microphone preamp e atten phaedrus am lift PHAME tube instrument preamp 12V AC only phaedrus PHI DI Box ALL TUBE CIRCUIT OUTPUT PHI tube DI box This manual is also available as a pdf download Go to www phaedrus audio com RISK OF ELECTRIC SHOCK DO NOT OPEN Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved Preface About Phaedrus Audio phaedrus phaedrus audio com Phaedrus Audio was formed to design manufacture and sell high quality products for the professional and semi prof essional audio market Phaedrus Audio s founders remain inspired by the music and the recording practices of the fifties and sixties and are motivated to re establish the values of the great audio technology legends of the past with their ideals of transparency hand built quality and serviceability Using modern manufacturing techniques and the benefits of modern component technology Phaedrus Audio s aim is to reproduce the quality and character of classic equipment but in a modern highly reliable and cost effective way Chapter 1 Background The Phaedrus Audio PHAB PHAME and PHI products came about because two recording musicians wanted to ow
13. amplifier is extended in both the bass and extra high f requency ranges Due to this unwanted very low frequencies due to traffic or air conditioning rumble may be picked up by the microphones and amplified The high pass filter HPF filters out these frequencies and prevents them from either intermodulating with the wanted signals with in the microphone preamp itself or being fed to downstream equipment This filter section is engaged by depressing the HPF switch 48V Phantom supply An internal phantom supply is provided to power the microphone connected to the input This supply is engaged by depressing the 48V switch on the front panel of the unit Although this supply is designed to ramp up slowly it is NEVER a good idea to switch phantom power onto a microphone on a channel with an open fader because it can create pops and bangs which can damage electronic equipment speakers and fray nerves Always mute any following circuit before switching on the phantom 48V supply To avoid loud transients always make sure phantom power is off when connecting or disconnecting microphones This supply is designed to support the hungriest of microphones NOTE Some microphones may be damaged by having phantom power applied to them ribbon microphones are especially delicate in this regard ALWAYS check what type of microphone is connected and that it is suitable for phantom powering BEFORE operating the front panel switch Ver 1
14. d in China and in the N ic iM he Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved Slovak Republic under JJ Electronics brand name formerly Tesla 12AU7 or ECC82 The 12AU7 is a popular miniature 9 pin medium gain dual triode valve tube and is used in many instrument and hi fi amplifiers Both triodes are used in cascade in the Phaedrus Audio PHI product The 12AU7 is also known in Europe under its Mullard Philips tube anode designation ECC82 This tube is widely available both new and NOS and a number of special quality equivalents are available Current production of 12AU7 takes place in Russia Slovakia and China Phaedrus Audio selects and recommends the long anode plate version of the ECC82 ECC802 S or 12 AU7 valve for application in the PHI DI Box Valve tube lifetime You should replace the valves in the tubes in the Phaedrus Audio products only when you start to notice changes in the sound quality If the gain of the preamplifier decreases noticeably then this is certainly evidence of the onset of valve vacuum tube failure Before this the tone may become dull and transients may be become blunted That said the lifetime of a valve tube is largely determined by the lifetime of its cathode emission and the small signal valves tubes used in the PHAB PHAME and PHI use oxide cathodes which can provide adequate cathode emission for 100 000 hours or more That s over eleven year s co
15. edrus Audio Ltd warrants that the equipment it manufactures shall be free from defects in material and workmanship for a period of one 1 year f rom the original date of purchase unless a longer minimum warranty period is mandated by applicable local laws If equipment fails due to such defects within this period Phaedrus Audio will at its option repair or provide a replacement for the defective part or product Valves vacuum tubes are excluded from the one year warranty but are warranted for 90 days from day of purchase This warranty does not extend to any Phaedrus Audio Ltd product that has been damaged or rendered defective as a result of accident misuse or abuse or by the use of parts not manufactured or supplied by Phaedrus Audio Ltd or by unauthorized modification or attempted repair to the product or by acts of God Nature accident fire flood etc or any other condition that is beyond the control of Phaedrus Audio Ltd There are no user serviceable parts inside This limited warranty isinvalid if the factory applied serial number has been altered or removed from the product This limited warranty is extended exclusively to the original buyer customer of Phaedrus Audio Ltd or authorized retail dealer and is not transferable to anyone who may subsequently purchase the product No other person retail dealer etc shall be entitled to give any warranty promise on behalf of Phaedrus Audio Ltd Phaedrus Audio Ltd makes no other warrant
16. ese must be chosen carefully and be pre screened Replacing the supplied valves tubes with different collectible or high end valves tubes types may not affect any improvement and might cause deterioration of performance phaedrus phab amp leccese EF86 The EF 86 is a low noise pentode originally manufactured by many different factories and branded by Philips Mullard Telefunken Valvo and GEC TESLA and Siemens RFT Many NOS valves are still available Equivalents include the CV2901 the UK service designation for the EF86 and the CV4085 a special quality version for military use The EF86 tube is still being produced in Russia and in the Slovak Republic under JJ Electronics brand name formerly Tesla Chinese close equivalents are also still being manufactured A ECC88 The ECC88 is a frame grid sharp cut off twin dual triode with an internal A separating screen The valve was originally designed for service in the f ront ends of VHF radio receivers The ECC88 E88CC tube type is equivalent to the North American 6DJ8 tubes and the rare military branded CV2492 The transposition of the figures from ECC88 to E88CC was Mullard s way of denoting a special quality build and is equivalent to the US 6922 Russian 6N1P tubes and the Chinese 6N1 gi tube are NOT equivalent NEVER install a 6N1 P in the Phaedrus Audio PHAB or ij iri PHAME product The ECC88 valve is sill being manufacture
17. external power supply or in any other way energised when the case is opened and or the circuit board is accessible PHI Exposed valve vacuum tube safety The Phaedrus Audio PHI DI Box has an exposed 12 AU7 ECC82 valve tube In order to ensure safety in all circumstances even if the glass envelope of the valve tube were smashed the exposed voltages ensure touch current is limited to a safe value Nevertheless keep this product away from babies children and pets DISCONNECT THE EXTERNAL PSU AND ALL OTHER CONNECTED EQUIPMENT WHEN REPLACING THE VALVE TUBE Ground earth issues Phaedrus Audio Ltd s PHAB PHAME and PHI products are all powered by external 12V AC power supplies which should be double insulated class II types see above It should therefore be appreciated that BE RELIED UPON PROVIDE A PROTECTIVE OR SAFETY EARTH GROUND This advice obtains IRRESPECTIVE OF THE SETTINGS OF ANY EARTH OR GROUND LIFT SWITCHES 1 A CONNECTION TO EITHER THE PHAB the PHAME of the PHI product CAN NEVER General Safety Instructions e Do not operate Phaedrus Audio equipment near any source of water or in excessively moist environments e Keep your Phaedrus Audio equipment away from babies children and pets e Do not let objects do not fall or liquids be spilled into the enclosure Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved e Situate the Phaedrus Audio equipment away from heat sources or other equipment that p
18. f the output connector of the PHAME be connected to mains earth ground or a technical earth and the LIFT switch be left in the out position Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved dBFS 0g 24dBu Operating levels dBu 4 Because of the vintage of the PHAB and PHAME 18 0 preamplifier designs and their origin in German manufac tured 10 8 14 ni broadcast EA television and imp gt 4 M F radio equipment ee 18 the envisaged UM NR operating level for d pec this equipment is slightly lower than modern recording i digital digital digital industry CUM E as standards When feeding downstream equipment the output level should be set to a nominal OdBu 0 775V RMS This means that if monitoring the output on a standard VU instrument the input attenuator should be set so that the output level reads around 4VU with occasional peaks to OVU on programme On a digital meter this is equivalent to signal peaks reading 6dB above recording industry standard 4dBu alignment level This is equivalent to 10dBu or 8d BFS on equipment aligned to EBU EBU R64 1992 standard and 14dBFS on equipment aligned to SMPTE RP155 as illustrated Ona broadcast standard PPM peaks should be set to read 6 on the BBC scale or 8 on the European EBU scale Output level is sufficient easily to modulate semi pro equipment mixers DAT solid state recorders and many sound cards to OdBF S dBF That said the headroom on the 0
19. g is North American type PHAE PSU 220Euro 220V mains plugtop PSU plug is European type PHAE PSU 220UK 220V mains plugtop PSU plug is 3 pin 13 AMP British type Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved A 12V AC supply is required for the Phaedrus Audio PHAB PHAME and PHI units A direct current DC supply is NOT suitable and will damage the unit If a supply is sourced elsewhere than from Phaedrus Audio it must have the following specifications 12V AC 12 Watt supply or greater gt or 1000mA supply current Must be suitable for connection to the appropriate mains vol tage Must be Class II double insulated Must have 30 regulation or better Must contain one shot thermal fuses resettable fuses or Polyswitches for over current protection UK and Euro units should comply with EN 60950 1 and CE requirements and only PSUs with UL and CSA approvals should be provided on North American units Units supplied to other countries should be verified to comply with the relevant standards which obtain in those territories User Access amp Servicing Phaedrus Audio equipment employs thermionic valve vacuum tube technology and employs hazardous voltages for the high tension supplies THE USER SHOULD NOT ATTEMPT TO SERVICE THE UNIT ALL SERVICING SHOULD BE REFERRED TO QUALIFIED SERVICE PERSONNEL OR FACTORY ONLY RISK eae ett The PHAB and PHAME preamplifiers and the PHI DI Box should NEVER be connected to the
20. he transformer it is buffered by a dual cathode follower circuit The first stage runs at very low current and is biased by a separately derived bias supply This ensures a high and consistent input impedance The second stage is DC coupled to the first and runs in a higher quiescent current consistent with having sufficient drive to overcome the excitation current in the transformer at low frequencies to amplifier or to loudspeaker round lift Loudspeaker input In this configuration it is necessary to attenuate the loudspeaker drive signal before presenting to the DI circuitry and this is exactly what is done when the LOUDSPEAKER INSTRUMENT switch is moved to the LOUDSPEAKER position The attenuation is 32dB In the Phaedrus Audio PHI DI unit this feature is enhanced by the inclusion within the unit of a loudspeaker emulation filter The general response of this filter was illustrated above The LF roll off is accomplished witha single pole RC response The upper skirt of the passband is implemented by means of a single terminated LC filter Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved Specifications Electrical connections phaedrus connecti i Input ction conventions T oun A hot Unbalanced 3 pin XLR Connector Balanced 3 pin XLR Connector UU A Pin 1 Ground Pin 1 Ground i Pin 2 Signal Pin 2 Signal bot redi left dend Pin 3 Connect to Pin 1 Pin 3 Signal cold ve right retu
21. herefore has a rising output impedance The guitar connects to the amplifier by means of a coaxial cable with the inner signal wire surrounded by the earthy screen The construction of this type of cableis nota million miles away from the construction of a capacitor and unsurprisingly the coaxial cable displays a significant capacitance at audio frequencies When the inductive pickup is connected via a capacitive cable a resonant circuit is formed and we can model this and confirm that this creates a musically significant resonant circuit well within the audio band Left trace below This resonant mechanism is one of the principal voicings for the electric guitarist Three factors af fect the resonant circuit the inductance of the pickup the capacitance of the cable and the input impedance of the amplifier essentially the greater the capacitance and the greater the inductance the lower the formant frequency This is why expensive Custom Wound pickups and Humbuckers which have more turns and therefore greater inductance sound considerably more chunky or fatter than standard pick ups It s the major reason why cables really do sound different fatter cables because of their lower capacitance singing better than cheap thin cables The effect of the amplifier input resistanceis to damp the resonant circuit Valve preamplifiers do not do this because of the common value of 1MQ for the bias resistor of the first valve Solid state circu
22. hould pin 1 of the output XLR be earthed grounded elsewhere in the installation This is the role of the GROUND LIFT switch It interrupts the connection of pin 1 of the output XLR to the chassis of the PHAME and to the sleeve and screen of the guitar wiring Adjust the position of this switch to eliminate any ground loop hums Please note as explained in the Chapter 4 that because the Phaedrus Audio products are double insulated they C AN NEVER BE RELIED UPON PROVIDE A PROTECTIVE OR SAFETY EARTH GROUND This advice obtains IRRESPECTIVE OF THE SETTINGS OF ANY EARTH OR GROUND LIFT SWITCHES Buzz The PHAME preamplifier like a lot of modern audio gear is designed to operate from a double insulated power supply If the rest of the equipment in your recording set up is double insulated too for instance you might be using the PHAME with a laptop computer it is possible for your entire audio installation to operate without a mains earth This represents no problems from a safety point of view However it can cause the unbalanced high impedance input of the PHAME to be very susceptible to electrostatically induced mains4nterference The tell tale signs here are a high level audio buzz rather than a hum on the output signal and the phenomenon that the instrument particularly electric and bass guitar is very live so that simply touching the strings may worsen or improve the buzz In this situation it is recommended that pin 1 o
23. ies expressed or implied of merchantability fitness for a particular purpose or otherwise Phaedrus Audio Ltd liability is limited to repair or replacement by Phaedrus Audio Ltd at its sole discretion and in no event will Phaedrus Audio Ltd be liable for any direct indirect special incremental or consequential damages resulting from any defect in the product including lost profits damage to property and to the extent permitted by law damage for personal injury even if Phaedrus Audio Ltd has been advised of the possibilities of such damages Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved Shipping Charges For any hardware defects experienced by the customer while the product is under warranty Phaedrus Audio Ltd will incur the shipping cost to the customer and the customer is responsible for the shipping costs to Phaedrus Audio Ltd s designated af ter sales service office For defective products that are out of warranty the customer is responsible for all Shipping costs to and from Phaedrus Audio Ltd s designated after sales service office Extended warranty and out of warranty services Various services are available from Phaedrus Audio Ltd These include repair services for equipment once the warranty period has expired and the ability to extend the warranty period These are PHAB REP Repair of a defective PHAB preamp charged ata flat rate PHAME REP Repair of a defective PHAME preamp charged ata flat rate
24. instrument with the very high input impedance such as it sees when plugged into a valve amp see Voicing and the valve amplifier section above This is the role of the Phaedrus Audio PHI DI Box The dual valve tube stage acts as an impedance converter presenting the instrument input with an impedance of approximately 1M2 The output of the unit then feeds the microphone input of your mixer computer interface or your PHAB preamplifier einstrument loudspeaker balanced XLR connector to mixer Flat Cabinet Ground Lift IN THRU Mic Out Instrument Loudspeaker BN dps computer or recorder mixer loop to amplifier instrument input The Phaedrus Audio PHI DI Box is connected as shown in the diagrams above Ensure that the LOUDSPEAKER INSTRUMENT switch is in the INSTRUMENT position However note that feeding the output of the PHI into the studio console will negate some of the benefits of the PHI s unique character Use a premium quality microphone preamplifier such as Phaedrus Audio s PHAB for the very best results as shown below Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved line out loop to amplifier instrument input Controls Instrument Loudspeaker switch LOUDSPEAKER MODE As a general rule guitar and bass guitar and certain electric pianos and organs rely on the distortions in their amplifiers and loudspeaker cabinets for the character of their sound Ideally of course
25. ion required to demonstrate that the products meet the requirements of the Low Voltage Equipment directive has been compiled and is available for inspection by the relevant enforcement authorities The CE mark was first applied in 2011 Richard Brice Technical Director January 2011 Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved Appendix TEST PRO FORMA Product PHAB PHAME Tested by 1 1 Vi volt ___ Volts TP1 1 1 Volts TP2 Gain set dB 40dB or LOW GAIN position High ain test Pass Fail Distortion test Pass Fail PAD test Pass Fail Frequency response test HF 3dB extension Frequency response test LF 3dB extension Pass Fail Phantom 48 supply test N A Listening test Pass Fail Product PHI Tested by o Gain test Pass Fail Distortion test Pass Fail Frequency response test HF 3dB extension Frequency response test LF 3dB ex tension Listening test Pass Fail Serial Number Serial Number Pass Fail Pass Fail Pass Fail Pass Fail Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved
26. its on the other hand due to their higher bias currents and lower circuit impedances can have a major damping ef fect on the input signal destroying so much of the character imparted by the resonant circuit see right hand trace above In short the formant frequency is absolutely crushed and the character of the voice destroyed Amongst many other reasons this so many solid state guitar preamplifier designs fail to have the spring and life of a good vae amplifier the precious signal is choked before it reaches literally and metaphorically first base Controls O r ae instrument ph drus C a lift m high PHAM tube instrument preamp rotary attenuator gain switch ground earth lift Input attenuator The input attenuator is a good quality high value potentiometer just like the volume control on an amp Set this control so as to drive the appropriate level to the downstream equipment see Operating Levels section Gain select low high The gain select switch should normally be set to the low position In the high position it is possible to overdrive the tube preamplifier circuitry froma guitar This setting is for low output instruments and or creative effects only Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved Ground earth lift Hums and buzzes are the bane of an audio engineer s life Unfortunately it is the nature of a high impedance unbalanced instruments like an electric
27. ly wired studio However connection to an earthed or grounded guitar amplifier can cause a circulating current should pin 1 of the output XLR be earthed grounded elsewhere in the installation This is the role of the GROUND LIFT switch It interrupts the connection of pin 1 of the output XLR to the chassis of the PHI and to the sleeve and screen of the guitar wiring Adjust the position of this switch to eliminate any ground loop hums Please note as explained in the Chapter 3 that because the Phaedrus Audio products are double insulated they CAN NEVER BE RELIED UPON PROVIDE A PROTECTIVE OR SAFETY EARTH GROUND This advice obtains IRRESPECTIVE OF THE SETTINGS OF ANY EARTH OR GROUND LIFT SWITCHES Buzz The PHI DI Box likea lot of modern audio gear is designed to operate froma double insulated power supply If the rest of the equipment in your recording set up is double insulated too for instance you might be using the PHI with a laptop computer and USB interface it is possible for your entire audio installation to operate without a mains earth This represents no problems from a safety point of view However it can cause the unbalanced high impedance input of the PHI to be very susceptible to electrostatically induced mainsinterference The tell tale signs here area high level audio buzz rather than a hum on the output signal and the phenomenon that the instrument particularly electric and bass gui tar is very live
28. n a classic console from the nineteen sixties Ideally a famous EMI REDD all valve vacuum tube mixer used to record The Beatles But those desks make a collection of hen s teeth look positively prosaic as well as cheap So we set about researching with the idea of producing a replica console In order to do this first it was necessary to have a design for the amplifier modules around which the mixers of this vintage are organised In the famous EMI REDD mixers these amplifiers were either the German manufactured V72 S amplifiers or the very rare EMI built REDD 47 amplifiers Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved j ij i Brounbuch tut f r Rundfnktechnk der Rundfunkanstalten der Bundesrepublik V 72 V72 and REDD 47 modular amplifiers Ironically despite the fact that many more V72 amplifiers exist than do REDD 47s the EF804 valves which the German amplifiers use are no longer in current production and are becoming very expensive whereas the EF86 and ECC88 E88CC valves employed in the REDD amplifiers remain in production and are widely available So a new amplifier designed from the common source of Mullard s ref erence audio designs and thereby sharing a common heritage with the REDD amplifiers was developed We called this amplifier the Phaedrus PHILHARMONIC literally music loving This PHILHARMONIC amplifier forms the heart of the Phaedrus Audio LONDON Mark IT console The PHILHAR
29. ntinuous use So do not replace valves tubes just because they have seen a few years service Phaedrus Audio Ltd can provide sui table valves tubes as spares which af ter a burn in period are screened for best performance in your Phaedrus Audio product These are available as line items PHAE 12AU7 Selected 12AU7 ECC82 type valve PHAE ECC88 Selected ECC88 type valve PHAE EF86 Selected EF86 type valve Please contact your dealer or Phaedrus Audio Ltd for current prices Chapter 5 Instructions for use Phaedrus Audio s PHAB PHAME and PHI products employ valves vacuum tubes as the ONLY ACTIVE DEVICES in the audio path Valves vacuum tubes and their associated circuitry need time to reach an electronic equilibrium before they will operate at optimal specifications Please therefore allow these products to warm up for at least 5 to 10 minutes before using them in your signal chain To prolong the life of your valves tubes it is recommended that you turn off these units when not in use Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved i i x computer or recorder 4 3 microphone to mixer microphone or computer i f power supply Typical connection set up for the PHAB PHAB Application and connections Mixer and computer interface manufacturers operate in a very competitive environment Even a small mixer must by definition contain 8 16 or perhaps 32 microphone amplifiers Similarly a compu
30. ply 12V AC Power consumption 8 Watts PHI Specification Circuit configuration 2 valve vacuum tube design Output Balanced transformer coupled Maxi mum output level XX just prior to waveform clipping 1kHz Input Unbalanced high impedance Maxi mum input level INS TRUMENT 2V RMS Maxi mum input level LOUDSPEAKER 100V RMS Gain 18dB Power supply 12V AC Power consumption 2 Watts Phaedrus Audio Ltd reserves the right to alter these specifications without notice Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved Declaration of Conformity The Manufacturer of the Products covered by this Declaration is Pheedrus Audio Ltd head office address The directives covered by this declaration are 89 336 EEC Electromagnetic Compatibility directive 73 23 EEC Low Voltage Equipment directive The products covered by this declaration are Phaedrus Audio PHAB microphone preamplifier Phaedrus Audio PHAME instrument preamplifier Phaedrus Audio PHI DI Box The basis on which conformity is being declared The manufacturer hereby declares that the products identified above comply with the protection requirements of the EMC directive and with the principal elements of the safety objectives of the Low Voltage Equipment directive and that the following standards have been applied IEC INTERNATIONAL STANDARD 60065 Audio video and similar electronic apparatus Safety requirements The technical documentat
31. recording um PHI DI Box studio Partnered with the PHAB it provides a solution for poet GRENET almost any instrumental or vocal preamp application OUTPUT Construction or star earths grounds and curly tracks Given their vintage the V72 amplifiers and the REDD 47 amplifiers were built on a metal chassis with the components hardwired onto tag strips Although Phaedrus Audio equipment uses printed circuit boards to ensure consistent performance and reliability the equipment follows classic practices suchas star earths and natural contour tracking just like hook up wire PHI DI Box Every Phaedrus Audio PHAB PHAME and PHI product is hand assembled and individually tested A test pro forma is provided with every unit Phaedrus Audio offer comprehensive service for products both inside and outside of their warranty period star earth point natural contour tracking with curved corners and shortest paths Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved Chapter 2 Warranty and Service Please register your purchase with Phaedrus Audio at www phaedrus audio registration htm This will simplify service amp repair should you need this service Your name will be placed on our mailing list unless otherwise requested for future updates and new product announcements Service If you experience a problem with a Phaedrus Audio Ltd product contact support phaedrus audio com TELEPHONE 44 207 193 4609
32. rn Outp ut common ground scree Unbalanced 3 pin XLR Connector Balanced 3 pin XLR Connector Pin 1 Ground Pin 1 Ground Pin 2 Signal Pin 2 Signal Pin 3 Connect to Pin 1 Pin 3 Signal PHAB Specification Circuit configuration 3 valve vacuum tube design Output Balanced transformer coupled Maxi mum output level 18dBu 1kHz Input Balanced transformer coupled Maxi mum input level 8dBu without PAD 18dBu with PAD at 1kHz Goin 40dB 1dB normal setting approximately 46dB high setting Attenuation 30dB to OdB in steps of 6dB minusa further 10dB by engaging PAD Frequency response 40Hz to 15kHz 1dB 15Hz to 30kHz 3dB Distortion 0 275 1kHz 4VU OdBu gain 40aB 176 40Hz 4VU OdBu gain 40dB Noise lt 120dB referred to input Power supply 12V AC Power consumption 8 Watts Phantom Supply 48V DC up to 5mA PHAME Specification Circuit configuration 3 valve vacuum tube design Output Balanced transformer coupled Maxi mum output level 18dBu 1kHz Input Unbalanced high impedance Maximum input level Effectively infinite Signals 2V RMS not recommended Gain 24dB low gain setting gt 30dB high gain setting Attenuation Continuous Max 6OdB Frequency response 40Hz to 15kHz 1dB 15Hz to 30kHz 3dB Distortion 0 275 tkHz 4VU OdBu gain 40dB 175 40Hz 4VU OdBu gain 40dB Noise lt 120dB referred to input Power sup
33. roduce heat e Ensure Phaedrus Audio equipment has adequate ventilation Improper ventilation will cause overheating and can damage the equipment e When cleaning Phaedrus Audio equipment remove all connections to the unit including power and gently wipe with a clean lint free cloth if necessary gently moistened with lukewarm or distilled water Use a dry lint free cloth to remove any remaining moisture NEVER use aerosol sprays solvents or abrasives on Phaedrus Audio equipment e Phaedrus Audio equipment should be serviced by qualified service personnel or returned to Phaedrus Audio Ltd when an object or ob jects have fallen into the enclosure or liquid has fallen into or been spilled into the unit or the unit has been exposed to rain or high humidity or the unit does not operate normally or exhibits a marked change in performance or the unit has been dropped or the enclosure has been damaged Chapter 4 About Valves Vacuum Tubes Valve tube types The Phaedrus Audio PHAB and PHAME preamplifiers employ an EF86 pentode input valve tube and an ECC88 or E88CC valve tube as the output device Positions for 5 the valves are very clearly marked on the PCB silkscreen O as indicated in the illustration The valves tubes that i are installed in Phaedrus Audio s products during assembly are selected to give the best possible performance We offer versions of all products with NOS rather than current production valves But th
34. ter interface designer has to shoe horn a microphone amplifier into a box with a host of other features and a noisy semi digital environment Unsurprisingly these amplifiers are designed on a careful budget and contain some compromises Hence the use of a few dedicated stand alone microphone preamplifiers solely designed with sound quality in mind can transform the quality of your recorded signals That is the aim of the Phaedrus Audio PHAB tube microphone preamplifier to offer just such a no compromise microphone amplifier in a product which incorporates the standards and qualities adopted in classic recording gear A block diagram of the PHAB is given below The unit is connected as shown in the accompanying diagrams phantom 9 48V pad 7 MIC IN E microphone amplifier ENE GUT OaE hpf attenuator PHILHARMONIC T AMPLIFIER 40dB y 46dB o Architecture of the PHAB preamp Controls Input rotary attenuator Pad and Gain switch The PHAB microphone preamplifier operates with a constant gain amplifier and attenuates the signal reaching the amplifier for level control This is NOT common with modern equipment in which the gain is adjusted by modifications to the feedback network Yet this approach was completely standard in the 1950s and 1960s Ver 1 1 Phaedrus Audio Ltd 2011 All rights reserved _ 18 12 atten e B S E EF86 _ gu Eccas E 10d8 MM 40d8 gt gt phaedrus
35. ting treble above about 4kHz and gently rolling off the bass the The signal from the amplifier may therefore be greatly improved by the incorporation of an electrical filter which reproduces the electro acoustic band pass of the loudspeaker cabinet To this end the Phaedrus Audio PHI DI unit is enhanced by the inclusion within the unitof a loudspeaker emulation filter which imprints the response of a typical closed back guitar cab onto the signal The general response of this filter is illustrated above Essentially the response falls away gently in the bass peaks in the mid treble and falls away rapidly above about 4kHz as Shown in the figure very Ground earth lif t A ground loop earth loop forms when an unbalanced audio signal flows in a circuit in which the signal return usually the cable braid provides a current path in parallel with the installation earth ground Small potentials in the installation earth ground wiring drive a circulating current in the braid of the audio cable The result is a hum voltage superimposed upon the audio signal Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved The adoption of balanced signals and especially audio transformers should ensure that ground loops or earth loops should NEVER occur Certainly the Phaedrus Audio PHI by being both double insulated and incorporating an earth free transformer balanced output stage can never create a ground loop ina correct
36. to effect the gain switching from 40dB to 46dB in the PHAB and from 24dB to gt 30dB in the PHAME less feedback being applied to achieve higher gain In the case of the Phaedrus Audio PHAB microphone preamplifier the grid of the input pentode is driven from the input transformer In the case of the PHAME this transformer is not fitted Performance At recording industry line up OVV 4d Bu the magnitude of all distortion components ona 1kHz sine wave input are less then 55dB below fundamental This and the A weighted noise response relative to maximum output is illustrated below Ver 1 1 9Phaedrus Audio Ltd 2011 All rights reserved High Pass or Rumble filter HPF The input stage in the PHAB is fed by a 1 7 v tic Len transformer When a capacitor is included in series 7 7 with the transformer primary it is usually short circuited out of circuit the capacitor forms a sa 7 half section filter with the primary inductance of T the transformer primary resulting in a sharp cut off high pass filter The response of the PHAB va with and without the rumble filter is illustrated right IkHz HPF response phoedrus oudio HPF response 19 12 10 PHI circuit description from instrument or from amplifier unbalance to balance transformer output Ac The system diagram for the Phaedrus Audio PHI DI Box is shown In effect before the signal from the instrument is applied to t

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