What's the gain of this op-amp circuit?

A

Allen Bong

Guest
Hi,

I have been playing with op-amp for the past few weeks and I came
across this circuit

http://www.flickr.com/photos/11236051@N08/4577591378/sizes/o/

If I am correct, the gain of op-amp U1:B is 2, as (R1+R18)/R18 = 20/10
= 2.

But what's the gain of op-amp U1:A ? I cant find the resistor which
is going to ground.

TIA,

Allen
 
Allen Bong wrote:
Hi,

I have been playing with op-amp for the past few weeks and I came
across this circuit

http://www.flickr.com/photos/11236051@N08/4577591378/sizes/o/

If I am correct, the gain of op-amp U1:B is 2, as (R1+R18)/R18 = 20/10
= 2.

But what's the gain of op-amp U1:A ? I cant find the resistor which
is going to ground.
Click to expand...
Complicated, and variable. Does that help?

The answer isn't leaping out at me, but I'm guessing that the three pots
are either tone controls or that this is some sort of a distortion
effect and they control that. Do you know what the circuit is supposed
to be?

Simulating it with Spice might be helpful -- put a signal in, twiddle
the pots, see what happens.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
 
On Mon, 3 May 2010 23:15:29 -0700 (PDT), Allen Bong
<allenbsf6502@gmail.com> wrote:

Hi,

I have been playing with op-amp for the past few weeks and I came
across this circuit

http://www.flickr.com/photos/11236051@N08/4577591378/sizes/o/

If I am correct, the gain of op-amp U1:B is 2, as (R1+R18)/R18 = 20/10
= 2.

But what's the gain of op-amp U1:A ? I cant find the resistor which
is going to ground.

TIA,

Allen
Click to expand...
Wow, that is one ugly circuit!

John
 
On May 5, 2:21 am, Tim Wescott <t...@seemywebsite.now> wrote:
Allen Bong wrote:
Hi,

I have been playing with op-amp for the past few weeks and I came
across this circuit

http://www.flickr.com/photos/11236051@N08/4577591378/sizes/o/

If I am correct, the gain of op-amp U1:B is 2, as (R1+R18)/R18 = 20/10
= 2.

But what's the gain of op-amp U1:A ?  I cant find the resistor which
is going to ground.

Complicated, and variable.  Does that help?

The answer isn't leaping out at me, but I'm guessing that the three pots
are either tone controls or that this is some sort of a distortion
effect and they control that.  Do you know what the circuit is supposed
to be?

Simulating it with Spice might be helpful -- put a signal in, twiddle
the pots, see what happens.

--
Tim Wescott
Control system and signal processing consultingwww.wescottdesign.com
Click to expand...
The circuit is a acoustic guitar active pickup circuit. It was in a
small metal case mounted to the side of the hollow guitar powered by a
small 9V battery. the 4 volume controls are tone controls each taking
care of a range of frequencies.

The circuit was actually traced by me and drawn for easy
troubleshooting. The problem was one of the strings was having very
low output so I suspect one of the tone controls was not working
correctly. This particular circuit was made in Indonesia. I've seen
that some Yamaha guitar are also having the same pickup built in.
I'll try to get one and trace out the circuit.

Anyway thanks for your reply.

Allen
 
On May 5, 3:44 am, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 3 May 2010 23:15:29 -0700 (PDT), Allen Bong





allenbsf6...@gmail.com> wrote:
Hi,

I have been playing with op-amp for the past few weeks and I came
across this circuit

http://www.flickr.com/photos/11236051@N08/4577591378/sizes/o/

If I am correct, the gain of op-amp U1:B is 2, as (R1+R18)/R18 = 20/10
= 2.

But what's the gain of op-amp U1:A ?  I cant find the resistor which
is going to ground.

TIA,

Allen

Wow, that is one ugly circuit!

John- Hide quoted text -

- Show quoted text -
Click to expand...
John,

I agreed with you the design is messy. Do you have a better one that
does the same job? It must be compact and simple.

Allen
 
On Tue, 4 May 2010 18:07:37 -0700 (PDT), Allen Bong
<allenbsf6502@gmail.com> wrote:

On May 5, 3:44 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 3 May 2010 23:15:29 -0700 (PDT), Allen Bong





allenbsf6...@gmail.com> wrote:
Hi,

I have been playing with op-amp for the past few weeks and I came
across this circuit

http://www.flickr.com/photos/11236051@N08/4577591378/sizes/o/

If I am correct, the gain of op-amp U1:B is 2, as (R1+R18)/R18 = 20/10
= 2.

But what's the gain of op-amp U1:A ?  I cant find the resistor which
is going to ground.

TIA,

Allen

Wow, that is one ugly circuit!

John- Hide quoted text -

- Show quoted text -

John,

I agreed with you the design is messy. Do you have a better one that
does the same job? It must be compact and simple.

Allen
Click to expand...
What is it supposed to do?

John
 
Allen Bong wrote:
On May 5, 10:45 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Tue, 4 May 2010 18:07:37 -0700 (PDT), Allen Bong





allenbsf6...@gmail.com> wrote:
On May 5, 3:44 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 3 May 2010 23:15:29 -0700 (PDT), Allen Bong
allenbsf6...@gmail.com> wrote:
Hi,
I have been playing with op-amp for the past few weeks and I came
across this circuit
http://www.flickr.com/photos/11236051@N08/4577591378/sizes/o/
If I am correct, the gain of op-amp U1:B is 2, as (R1+R18)/R18 = 20/10
= 2.
But what's the gain of op-amp U1:A ? I cant find the resistor which
is going to ground.
TIA,
Allen
Wow, that is one ugly circuit!
John- Hide quoted text -
- Show quoted text -
John,
I agreed with you the design is messy. Do you have a better one that
does the same job? It must be compact and simple.
Allen
What is it supposed to do?

John- Hide quoted text -

- Show quoted text -

The circuit is a acoustic guitar active pickup circuit. It was in a
small metal case mounted to the side of the hollow guitar powered by
a
small 9V battery. the 4 volume controls are tone controls each
taking
care of a range of frequencies.

Allen
Click to expand...
With four tone control knobs it's something between a graphics equalizer
and a tone control. Those are the two terms to search on for circuits.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
 
On May 5, 10:45 am, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Tue, 4 May 2010 18:07:37 -0700 (PDT), Allen Bong





allenbsf6...@gmail.com> wrote:
On May 5, 3:44 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 3 May 2010 23:15:29 -0700 (PDT), Allen Bong

allenbsf6...@gmail.com> wrote:
Hi,

I have been playing with op-amp for the past few weeks and I came
across this circuit

http://www.flickr.com/photos/11236051@N08/4577591378/sizes/o/

If I am correct, the gain of op-amp U1:B is 2, as (R1+R18)/R18 = 20/10
= 2.

But what's the gain of op-amp U1:A ?  I cant find the resistor which
is going to ground.

TIA,

Allen

Wow, that is one ugly circuit!

John- Hide quoted text -

- Show quoted text -

John,

I agreed with you the design is messy.  Do you have a better one that
does the same job?  It must be compact and simple.

Allen

What is it supposed to do?

John- Hide quoted text -

- Show quoted text -
Click to expand...
The circuit is a acoustic guitar active pickup circuit. It was in a
small metal case mounted to the side of the hollow guitar powered by
a
small 9V battery. the 4 volume controls are tone controls each
taking
care of a range of frequencies.

Allen
 
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