L
Les Cargill
Guest
DaveC wrote:
Les Cargill
It should be. If you are concerned, check with a meter first.
--
Les Cargill
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D
Don Pearce
Guest
On Thu, 27 Oct 2011 09:11:17 -0700, DaveC <invalid@invalid.net> wrote:
d
hum.Or, as is not uncommonly done these days in portable digital players,
establish a floating ground for the purpose of providing and signal for the
(floating) load, so that the difference between the output and the floating
ground can become negative.
Which raises the question I was pondering recently: is it OK to connect 2
computers' sound cards' grounds together?
No. You will certainly create a ground loop which will result in mains
d
K
krw@att.bizzzzzzzzzzzz
Guest
On Thu, 27 Oct 2011 17:59:59 GMT, spam@spam.com (Don Pearce) wrote:
"OK" (i.e. not dangerous). As long as the computers are plugged into the same
circuit, it's quite possible that he can get away with it, assuming line
levels. If hum is a problem, coupling capacitors or cheap audio transformers
will usually solve it.
This is certainly likely but not a foregone conclusion. In any case, it'sOn Thu, 27 Oct 2011 09:11:17 -0700, DaveC <invalid@invalid.net> wrote:
Or, as is not uncommonly done these days in portable digital players,
establish a floating ground for the purpose of providing and signal for the
(floating) load, so that the difference between the output and the floating
ground can become negative.
Which raises the question I was pondering recently: is it OK to connect 2
computers' sound cards' grounds together?
No. You will certainly create a ground loop which will result in mains
hum.
"OK" (i.e. not dangerous). As long as the computers are plugged into the same
circuit, it's quite possible that he can get away with it, assuming line
levels. If hum is a problem, coupling capacitors or cheap audio transformers
will usually solve it.
D
DaveC
Guest
This kinda kills the project, doesn't it? (At least, the straightforwardis it OK to connect 2 computers' sound cards' grounds together?
No. You will certainly create a ground loop which will result in mains
hum.
d
solution.)
The alternative is...?
Thanks.
D
Don Pearce
Guest
On Thu, 27 Oct 2011 11:12:00 -0700, DaveC <invalid@invalid.net> wrote:
Capacitors have been suggested, but they don't help. If they are big
enough to pass bass, the ground loop is still there. It doesn't
require a DC connection to function.
d
Transformers. You can buy decent ones in Maplin for use in car audio.is it OK to connect 2 computers' sound cards' grounds together?
No. You will certainly create a ground loop which will result in mains
hum.
d
This kinda kills the project, doesn't it? (At least, the straightforward
solution.)
The alternative is...?
Capacitors have been suggested, but they don't help. If they are big
enough to pass bass, the ground loop is still there. It doesn't
require a DC connection to function.
d
N
NT
Guest
On Oct 27, 5:11 pm, DaveC <inva...@invalid.net> wrote:
NT
I've yet to have a problem doing it.Or, as is not uncommonly done these days in portable digital players,
establish a floating ground for the purpose of providing and signal for the
(floating) load, so that the difference between the output and the floating
ground can become negative.
Which raises the question I was pondering recently: is it OK to connect 2
computers' sound cards' grounds together?
The PS for the powered speakers is via "wall wart" (not grounded).
Thanks.
NT
D
DaveC
Guest
Hi Tomi. Thank you for your advice. I have enjoyed your creative designs for10 kohms for all fixed resistor should work...
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
J
John Fields
Guest
On Sat, 29 Oct 2011 00:49:32 -0700, DaveC <invalid@invalid.net> wrote:
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
---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
D
DaveC
Guest
Thanks John. Good simple design.Why not go active and get rid of the caps altogether?
Can you suggest a good op amp for such an audio application?
Is it possible to use single-supply amps throughout?
Thanks,
Dave
J
John Fields
Guest
On Sun, 30 Oct 2011 02:26:06 -0700, DaveC <invalid@invalid.net> wrote:
I used an LT1007 in the simulation.
Did you run it?
---
Yes, but you'd have to use caps on the inputs and outputs and
reference the opamp + inputs to Vcc/2.
--
JF
---Why not go active and get rid of the caps altogether?
Thanks John. Good simple design.
Can you suggest a good op amp for such an audio application?
I used an LT1007 in the simulation.
Did you run it?
---
---Is it possible to use single-supply amps throughout?
Yes, but you'd have to use caps on the inputs and outputs and
reference the opamp + inputs to Vcc/2.
--
JF
D
DaveC
Guest
No tools.Can you suggest a good op amp for such an audio application?
I used an LT1007 in the simulation.
Did you run it?
I made the L & R op amps fixed gain and added input level control pots:
<http://i43.tinypic.com/2hh3y12.jpg>
Comments?
Thanks.
D
DaveC
Guest
D
DaveC
Guest
Can't find them on Mouser.I used an LT1007 in the simulation.
Suggest another one that's good for audio?
How about LM833? ::
<http://www.national.com/ds/LM/LM833.pdf>
The SR and GBW beat the 1007... ;-)
Thanks.
D
DaveC
Guest
Is the type of resistor important (wire wound, etc.)?
Thanks.
Thanks.
J
John Fields
Guest
On Sun, 30 Oct 2011 21:44:33 -0700, DaveC <invalid@invalid.net> wrote:
http://www.linear.com/designtools/software/
---
Looks OK.
--
JF
They're free:Can you suggest a good op amp for such an audio application?
I used an LT1007 in the simulation.
Did you run it?
No tools.
---
http://www.linear.com/designtools/software/
---
---I made the L & R op amps fixed gain and added input level control pots:
http://i43.tinypic.com/2hh3y12.jpg
Comments?
Looks OK.
--
JF
J
John Fields
Guest
On Sun, 30 Oct 2011 21:47:34 -0700, DaveC <invalid@invalid.net> wrote:
The input pots, OK. The feedback pot, probably not.
Plot the change in output voltage as a function of wiper position to
get a better handle on it.
--
JF
---http://i43.tinypic.com/2hh3y12.jpg
Should all pots be log taper?
The input pots, OK. The feedback pot, probably not.
Plot the change in output voltage as a function of wiper position to
get a better handle on it.
--
JF
J
John Fields
Guest
On Mon, 31 Oct 2011 00:16:15 -0700, DaveC <invalid@invalid.net> wrote:
You can buy them directly from Linear:
http://www.linear.com/purchase/LT1007
---
Go for it; they're a lot cheaper!
--
JF
---I used an LT1007 in the simulation.
Can't find them on Mouser.
You can buy them directly from Linear:
http://www.linear.com/purchase/LT1007
---
---Suggest another one that's good for audio?
How about LM833? ::
http://www.national.com/ds/LM/LM833.pdf
The SR and GBW beat the 1007... ;-)
Go for it; they're a lot cheaper!
--
JF
J
John Fields
Guest
On Mon, 31 Oct 2011 01:11:57 -0700, DaveC <invalid@invalid.net> wrote:
Don't use wirewound.
5% 1/4 watt carbon film is fine.
--
JF
---Is the type of resistor important (wire wound, etc.)?
Don't use wirewound.
5% 1/4 watt carbon film is fine.
--
JF
D
DaveC
Guest
Only a single supply (in the amplified speakers) is available to power thisIs it possible to use single-supply amps throughout?
---
Yes, but you'd have to use caps on the inputs and outputs and
reference the opamp + inputs to Vcc/2.
[J. Fields]
circuit. I can tap this supply for my circuit:
<http://i41.tinypic.com/2vlo2t2.jpg>
I've added input & output caps. Are these values sound? ;-)
How do I go about getting a 1/2 Vcc ground reference? (See my non-EE
attempt.) What values to use for the divider resistors?
What needs to be reference to the new "ground"? Everything between the input
caps and output caps?
Thanks,
Dave
D
Dave Platt
Guest
In article <0001HW.CADEF1F900A742BFB02069DF@news.eternal-september.org>,
DaveC <newsgroups> wrote:
somewhere around 4k7 each, and add a few uF of bypass capacitance
around one or both resistors. 1k would give a stiffer reference if
you don't mind the additional power consumption.
If you can spare an op-amp section, you can get a better (stiffer) ground
reference than you'll get with just resistors, with lower power
dissipation (I think). Use R16 and R17, and a small cap from the
junction point, to create a Vcc/2 reference, but do not "ground" this
directly to your internal reference point (the rectangular-looking
ground symbol). Instead, feed this to the noninverting input of an
op-amp section, feed the op-amp output back to the inverting input
(i.e. create a unity-gain follower), and use the op amp's output as
your ground reference. In this arrangement R16 and R17 can be
high-value (100k?) as their junction point will be looking into a
high-impedance op amp input.
"bottom ends" of the potentiometers, as you have drawn them. *NOT*
the V- input to the op amp(s), of course.
You might want to add "pop preventer" resistors at the inputs and
outputs... say, 100k to DC ground, from the "outside" end of each of
the DC-blocking capacitors.
--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
DaveC <newsgroups> wrote:
If you want to do it with just resistors, you could make R16 and R17Only a single supply (in the amplified speakers) is available to power this
circuit. I can tap this supply for my circuit:
http://i41.tinypic.com/2vlo2t2.jpg
I've added input & output caps. Are these values sound? ;-)
How do I go about getting a 1/2 Vcc ground reference? (See my non-EE
attempt.) What values to use for the divider resistors?
somewhere around 4k7 each, and add a few uF of bypass capacitance
around one or both resistors. 1k would give a stiffer reference if
you don't mind the additional power consumption.
If you can spare an op-amp section, you can get a better (stiffer) ground
reference than you'll get with just resistors, with lower power
dissipation (I think). Use R16 and R17, and a small cap from the
junction point, to create a Vcc/2 reference, but do not "ground" this
directly to your internal reference point (the rectangular-looking
ground symbol). Instead, feed this to the noninverting input of an
op-amp section, feed the op-amp output back to the inverting input
(i.e. create a unity-gain follower), and use the op amp's output as
your ground reference. In this arrangement R16 and R17 can be
high-value (100k?) as their junction point will be looking into a
high-impedance op amp input.
Pretty much... each of the op amps' noninverting inputs, and theWhat needs to be reference to the new "ground"? Everything between the input
caps and output caps?
"bottom ends" of the potentiometers, as you have drawn them. *NOT*
the V- input to the op amp(s), of course.
You might want to add "pop preventer" resistors at the inputs and
outputs... say, 100k to DC ground, from the "outside" end of each of
the DC-blocking capacitors.
--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!