🚀 go-pugleaf

   From: ah335@cleveland.Freenet.Edu (Richard Banks)
   Date: 17 Dec 1992 00:14:05 GMT
   Organization: Case Western Reserve University, Cleveland, OH (USA)

   I'm constructing a purpose built distortion producing circuit to
   be used to add gain to audio signal of an electric guitar.

   The circuit uses 4 stage op amp noninverting configuration to
   produce a gain of 1855 running off a 9V power supply.

   My problem is the unit is acting like a noise gate, when the signal
   attenuates the circuit "cuts off."  Therefore it is very quiet,
   but does not produce long sustain, which is what I want.

Without a complete description of the circuit nobody will be able to give
you much in the way of useful advice.  That said, I'll go out on a limb and
predict that from your description of the effects, it sure sounds like at
least one of the op-amps is running with DC gain, and some offset voltage
is throwing it into clipping with no signal present (causing the quiet),
and when your guitar signal is large enough to overcome this, you hear the
distorted sound.

   The value of the feedback resistors are 100k and the value of the
   power resistors is 220 ohm.  

What is a "power resistor" in this context?

   Also on a side note, what is the best op amp config to use
   for distortion, inverting or noninverting?

The non-answer is to not use op-amps at all.  ("Op-amps are for weenies.")

If you insist on using op-amps, and are using diodes in the feedback loop
to generate distortion, an inverting configuration is best because it
doesn't have the minimum gain deal that a non-inverting stage does.

If you insist on using op-amps, and use the op-amps themselves for
distortion (yechhhh!), or using diodes outside the feedback loop for
distortion, then a non-inverting stage is better due to input impedance,
noise, and gain issues.

   I would think noninverting, because inverting amps cause
   a lot more bias current at high gain.

Why do you think inverting amps configurations cause a lot more bias at
high gain?

  -- Don