Series resistor opamp input

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Series resistor opamp input

Postby jnee88 » 06 Jan 2017, 03:09

Can you use a pot wired as a series resistor on the input of an OP amp? I have built the Red Fuzz from General Guitar Gadgets and placed one between the 1meg input resistor and the input cap.

Seems to work well. But at the highest resistance the high end drops a bit. I used 250k,I am going to try 100k.

Is there a reason no one uses one?
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Re: Series resistor opamp input

Postby phatt » 06 Jan 2017, 11:21

jnee88 wrote:Can you use a pot wired as a series resistor on the input of an OP amp? I have built the Red Fuzz from General Guitar Gadgets and placed one between the 1meg input resistor and the input cap.

Seems to work well. But at the highest resistance the high end drops a bit. I used 250k,I am going to try 100k.

Is there a reason no one uses one?


If you think about it you already answered the Q. :secret:
Yes it can be used to alter top end but not ideal, there are better ways. You need to bypass the series resistor with a small cap to keep the high freq.
Just look at all the classic valve circuits and you will often see a a small ~500pF cap across a 500k series resistor, it's a basic bright circuit.
Phil.
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