[sci.electronics] Mark Levinson JC-2 line amp schematic

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