On Sat, 29 Oct 2011 00:49:32 -0700, DaveC wrote:

10 kohms for all fixed resistor should work...

Hi Tomi. Thank you for your advice. I have enjoyed your creative designs for
many years.

Do you have any comments on my revisions of the circuit (ie, are caps
recommended? should I be concerned about cross talk if I take resistors from
all 4 channels to drive the sub woofer? etc...)

Cheers,
Dave

---
Why not go active and get rid of the caps altogether?


..LA-+---[10k]-+-[10k]-+------------- -(LA+LB)
.. | | |
.. | | +V |
.. | | | |
..LB-|-+-[10k]-+--|-\ |
.. | | | -+ 10K
.. | | +--|+/ +-[POT]-+
.. | | | | | |
.. | | GND -V | +5 |
.. | | | | |
.. | +------[10K]---+---+-|-\ |
.. | | | --+-- -(LA+LB+RA+RB)
.. +--------[10K]---+ +-|+/
.. | |
.. +--------[10K]---+ GND
.. | |
.. | +------[10K]---+
.. | |
.. | |
.. | |
..RA-+-+-[10k]-+-[10k]-+
.. | | |
.. | | +V |
.. | | | |
..RB-+---[10k]-+--|-\ |
.. | -+------------- -(RA+RB)
.. +--|+/
.. | |
.. GND -V

Seems to work pretty well...

Version 4
SHEET 1 880 968
WIRE 112 -544 48 -544
WIRE 224 -544 192 -544
WIRE -96 -448 -528 -448
WIRE 32 -448 -16 -448
WIRE 48 -448 48 -544
WIRE 48 -448 32 -448
WIRE 112 -448 48 -448
WIRE 224 -432 224 -544
WIRE 224 -432 176 -432
WIRE 256 -432 224 -432
WIRE 112 -416 80 -416
WIRE -96 -352 -432 -352
WIRE 32 -352 32 -448
WIRE 32 -352 -16 -352
WIRE 80 -352 80 -416
WIRE -528 -240 -528 -448
WIRE -416 -240 -528 -240
WIRE 64 -240 -336 -240
WIRE 112 -240 64 -240
WIRE 240 -240 192 -240
WIRE -432 -192 -432 -352
WIRE -352 -192 -432 -192
WIRE 64 -192 64 -240
WIRE 64 -192 -272 -192
WIRE -272 -144 -336 -144
WIRE 64 -144 64 -192
WIRE 64 -144 -192 -144
WIRE -176 -96 -240 -96
WIRE 64 -96 64 -144
WIRE 64 -96 -96 -96
WIRE 128 -96 64 -96
WIRE 240 -80 240 -240
WIRE 240 -80 192 -80
WIRE 272 -80 240 -80
WIRE 128 -64 96 -64
WIRE 96 0 96 -64
WIRE 112 112 48 112
WIRE 224 112 192 112
WIRE -336 208 -336 -144
WIRE -96 208 -336 208
WIRE 32 208 -16 208
WIRE 48 208 48 112
WIRE 48 208 32 208
WIRE 112 208 48 208
WIRE 224 224 224 112
WIRE 224 224 176 224
WIRE 256 224 224 224
WIRE 112 240 80 240
WIRE -240 304 -240 -96
WIRE -96 304 -240 304
WIRE 32 304 32 208
WIRE 32 304 -16 304
WIRE 80 304 80 240
WIRE -528 688 -528 -240
WIRE -432 688 -432 -192
WIRE -336 688 -336 208
WIRE -240 688 -240 304
WIRE -144 688 -144 656
WIRE -48 688 -48 656
WIRE -528 832 -528 768
WIRE -432 832 -432 768
WIRE -432 832 -528 832
WIRE -336 832 -336 768
WIRE -336 832 -432 832
WIRE -240 832 -240 768
WIRE -240 832 -336 832
WIRE -144 832 -144 768
WIRE -144 832 -240 832
WIRE -48 832 -48 768
WIRE -48 832 -144 832
WIRE -528 928 -528 832
FLAG 144 192 +5
FLAG 144 256 -5
FLAG 80 304 0
FLAG 144 -464 +5
FLAG 144 -400 -5
FLAG 80 -352 0
FLAG -528 928 0
FLAG -144 656 +5
FLAG -48 656 -5
FLAG 160 -112 +5
FLAG 160 -48 -5
FLAG 96 0 0
SYMBOL Opamps\\LT1007 144 160 R0
SYMATTR InstName U1
SYMBOL voltage -240 672 R0
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V3
SYMATTR Value SINE(0 1 1000)
SYMBOL res 0 192 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res 0 288 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 208 96 R90
WINDOW 0 -43 58 VBottom 2
WINDOW 3 -37 60 VTop 2
SYMATTR InstName R3
SYMATTR Value 10k
SYMBOL Opamps\\LT1007 144 -496 R0
SYMATTR InstName U2
SYMBOL res 0 -464 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 10k
SYMBOL res 0 -368 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R5
SYMATTR Value 10k
SYMBOL res 208 -560 R90
WINDOW 0 -43 58 VBottom 2
WINDOW 3 -37 60 VTop 2
SYMATTR InstName R6
SYMATTR Value 10k
SYMBOL voltage -48 784 R180
WINDOW 0 -50 102 Left 2
WINDOW 3 24 16 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL voltage -144 672 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL res -80 -112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R7
SYMATTR Value 10k
SYMBOL res -176 -160 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R8
SYMATTR Value 10k
SYMBOL res -256 -208 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R9
SYMATTR Value 10k
SYMBOL res -320 -256 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R10
SYMATTR Value 10k
SYMBOL Opamps\\LT1007 160 -144 R0
SYMATTR InstName U3
SYMBOL res 208 -256 R90
WINDOW 0 -43 58 VBottom 2
WINDOW 3 -37 60 VTop 2
SYMATTR InstName R12
SYMATTR Value 5k
SYMBOL voltage -336 672 R0
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V4
SYMATTR Value SINE(0 1 1700)
SYMBOL voltage -432 672 R0
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V5
SYMATTR Value SINE(0 1 2300)
SYMBOL voltage -528 672 R0
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V6
SYMATTR Value SINE(0 1 4260)
TEXT -562 952 Left 2 !.tran .005


--
JF