mark@mips.COM (Mark G. Johnson) (04/09/88)
The other half of the Mark Levinson JC-2 audio preamplifier is included
herein. Theorists may wish to comment upon its open-loop output
impedance and/or its suitability for driving 400 pF lunatic-fringe
interconnect cables.
! ##########################################################################
!
! Mark Levinson audio preamplifier model JC-2
! Line amp section
!
! First the active amplifier circuit is given, then the feedback net
! +input = node 10, -input = node 20, output = node 50,
! system ground = node 0
!
! Power Supplies & local bypass capacitors
Vplus 80 0 15.0 ! Volts
Vneg 90 0 -15.0 ! Volts
C80 80 0 4.7U ! (micro)Farads
C90 90 0 4.7U ! (micro)Farads
!
! Input stage: complementary JFET diff pairs carrying same bias current
R10 10 0 1.0M ! (mega)Ohms
C10 10 0 20P ! (pico)Farads
J41 D=41 G=10 S=31 Nch TYPE=E212 ! Siliconix N-channel JFET
J42 D=42 G=20 S=31 Nch TYPE=E212
R41 41 80 100.0 ! Ohms
R42 42 80 20.0
J43 D=43 G=10 S=33 Pch TYPE=E175 ! Siliconix P-channel JFET
J44 D=44 G=20 S=33 Pch TYPE=E175
R43 43 90 100.0
R44 44 90 20.0
R31 31 32 60.4
! 500 ohm trimpot with wiper shorted to node 33
R33 32 33 500.0 ! variable
!
! Second stage: interwoven, cascoded with first stage, push-pull
Q42P C=50 B=41 E=42 PNP TYPE=2N4403 ! Motorola bipolar PNP
Q44N C=50 B=43 E=44 NPN TYPE=2N4401 ! Motorola bipolar NPN
! stabilization network
C41 41 50 10P
C43 43 50 10P
C20s 20 50 20P
R20s 20 50 4.7M
!
!
! Now the overall topology in which the active amplifier is embedded
! Signal input = node 1 (from selector switch)
! Output = node 70 (AC coupling mode) or node 50 (DC coupling)
!
R61 1 61 30K ! (Kilo)Ohms
!
! Volume control is a 10K pot. Wiper == node 62
R62a 61 62 5.0K
R62b 62 0 5.0K
R63 62 10 100.0
!
! set gain at DC to unity.
C63 20 63 2.0U ! (micro)Farads
! feedback path
R63 63 64 4.53K
! Balance control.... rotary switch with several selectable resistors
R64 64 50 75K ! adjustable
! coupling cap (switchable in/out)
C70 50 70 2.0U ! hi quality
!
!
! that's all
--
-Mark Johnson *** DISCLAIMER: Any opinions above are personal. ***
UUCP: {decvax,ucbvax,ihnp4}!decwrl!mips!mark TEL: 408-991-0208
US mail: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086