ALEPH P SERVICE MANUAL
Contents
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5. R205 R204 C C200 Q TEST POINT OPT201 C207 O Y O D209 O 0206 0207 D208 C206 R207 Q204 R206 x tmr HEG x J METAL CAN TABS UP ES E E HOLE OUT 5 u u I I a a 0205 222 0205 0208 0209 0210 0211 0212 0210 O D211 O D212 O D215 D214 C D213 BOcU 60 4 Oley 143 c cu 2148 lcy 5103 a x uu MILE m m H EVE H ALL LEDS LONG LEAD UP 4 3320 4 4 1N4148 RED WHITE BLACK 4 7UF BLUE 7805 4 7UF SOCKET 24 PINS 29 4752 39PF ZIX450 CRYSTAL 4 7 74HC573 1202 1991 74HC573 4 7UF O LT 1059 8 x IRF610 4 7UF BLUE BLACK WHITE RED B 4752 4 x IRF610
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7. PASS ALEPH P SERVICE MANUAL REV 1 7 PASS LABORATORIES 24449 FORESTHILL RD FORESTHILL CA 95631 TEL 916 367 3690 FAX 916 367 219 PRODUCT DESCRIPTION Version 1 7 The ALEPH P is a high performance Mosfet Class A audio preamplifier intended for maximum performance in reproduction of music It is a simple design having only a single balanced gain stage consisting of a balanced pair of power Mosfets The gain stage of the preamplifier is a single Mosfet operated common source and biased by a Mosfet constant current source To best understand the operation of the preamplifier refer to the schematic of the basic gain stage Q16 and Q19 form the active portion of the gain stage with Q16 receiving the balanced input signal and Q19 receiving the balanced input signal The inputs are capacitively coupled through C9 and C13 R50 and R65 are employed to prevent parasitic oscillation and the D5 6 and D7 8 protect the Mosfets from electrostatic high voltages at the input The Mosfets amplify the input signals and present them at the outputs with the polarity inverted so that the output of Q16 becomes the signal and the output of Q19 becomes the output When using the preamplifier with a single ended input the negative input should be shorted to ground for best performance This is accomplished by using shorting plug between pins 1 and 3 on the XLR input connector The power supply transformer delivers approxima
8. R120 us GENE 521 E o D22 8 8 o D23 xi 2 5 D24 m Riz DT D25 R113 J R114 D27 R115 D18 a he olayl 1 2 8 ae SS R116 SVEIS be i T T T T E o amp 8 d m A gt o 5 m S o Q 2 VIOLET g Z x a z S O ar E D202 D206 B B B B D200 D201 D205 0201 Q200 Q201 Q202 Q203 R203 R202 R201 R200 U201 PT200 C202 c2di 2 D S U200 5 R205 R204 C200 Q204 C206 R207 R206 o U202 U203 ove 038 311HM METAL CAN TABS UP HOLE OUT TEST POINT OPT201 C207 O T O O 0210 D215 D209 D214 O O 0205 0206 0207 0208 0209 0218 0211 0212 D208 D213 aka lol ol lol la m m SI S S SPRE S e ISI el el P el co S ls EI s y m la C O O 0205 0204 C D202 D206 B B B B 0200 D201 D205 D207 0200 0201 0202 0203 R203 R202 R201 R200 OPT200 c202 Di ee D U200 5
9. eceiver module via Q204 inverter buffer The input select and volume controls OPT200 OPT201 are optical interrupters that generate a quadrature pulse train on pins A and B These feed interrupt pins on the micro controller which recognizes rotational direction and speed Test points on the front panel Collector of Q204 for infrared received commands Pins 10 and 11 of U201 for 12 MHz Pin 11 of both latches when volume is being changed Pins A and B of the optical encoders when they are being turned The indicated 5 volt test point or any 5 volt location on the schematic Schematics Fig 1 Mother board main gain stage Fig 2 Power supply Fig 3 Volume control Fig 4 Input select Fig 5 Display board Fig 6 Remote control Fig 7 Reference designator drawing for mother brd Fig 8 Reference designator drawing for display brd SPECIFICATIONS Max Gain Freq Response Distortion Max Out Output Impedance Input Impedance CMRR Output noise Power consumption Dimensions 22 dB bal 16 dB unbal 3 dB 1Hz 100 KHz lt 1 THD 20 volts rms bal out 10 volts rms unbal out 0 800 ohms 20 KOhm bal 10 KOhm unbal 60 dB 5 microvolts 20 20KHz 25 watts 19 W x 11 5 Dx 4 H 9 5 RE arg LOS LAWS ld 875 PIQ Jeujo d udeiv LANI INdLNO LAALAS AYINDA 0 P Be eu mo d SdSC ld JSQUINN AlddNS
10. tely 80 volts for 120 or 240 VAC operation unregulated DC into C28 and C30 which is then actively regulated down to 60 volts at the output of Q23 Q23 is driven by a stack of Zener diodes and the regulated output is additionally filtered by C27 The output muting relay is controlled by the circuits of Q21 and Q22 For the relay to activate both Q21 and Q22 must be conducting Q22 turns on slowly via the charge on C31 while Q21 will only conduct when there is at least 8 volts difference between regulated and unregulated supplies Thus Q22 delays relay turn on and Q21 shuts it off quickly The input selection system schematic shows the simple use of relays to switch four inputs with four poles of connection The input pad settings are as follows only 3 settings 1 3 dB 3 4 56 on 9 7 dB all off 15 dB 1 2 78 The volume control system schematic shows the 8 bit binary relay ladder circuits which perform precision attenuation of the output of the gain stages In order to achieve good common mode rejection performance the output attenuation must be matched far more precisely than can be accomplished with potentiometers and so relays and precision resistors are used The control circuitry is located on the front panel PC board of the preamp The main elements are the micro controller latches infrared receiver and optical encoders U201 is a Phillips 87 752 micro controller running at 12MHz It receives input from the infrared r
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