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

May 04, 2010 7 Replies

Hi,



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



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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


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

Wow, that is one ugly circuit!

John

0

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

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

/10

h

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

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

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