Less gain... less clipping...

[blindsjc]

Whats is the right way to reduce gain on Tonemender
searching avoiding any clipping and with no quality problems?
Since I'm a newbie, details helps a lot. Thanks.

Reference: http://www.runoffgroove.com/tonemender.html

[amz-fx]

make the Level control pot 100k instead of 500k

BUT, it should not clip when you have the Level control turned down, even on the stock unit.

regards, Jack

[cb]

Right... what Jack said.
U1b is a non-inverting op amp and is where the gain is happening.
Gain = 1 + (Resistance_of_the_pot/4k7)
So if the pot is at max, i.e. 500k, the gain is:
Gain = 1 + (500,000/4700) = 107
A 100mv guitar signal would be amplified to about 10.7 volts BUT you only have a 9V battery (I assume) so the signal would get clipped.

You should have 9V of headroom, in reality may be more like 8V.
So working backwards, if we have 8V for our clean signal,
Maximum clean gain = 8V/100mv = 8/0.100 = 80.
Resistance_of_the_pot = 80 * 4k7 = 376k (Ignoring the "1 +", which really isn't significant here)
376k is about 75% of 500k, so if you used a linear pot, you should be able to turn it up 3/4 of the way without clipping. Or if you used an audio taper pot, I'm not exactly sure where that would be, but the point is it should get plenty loud w/o clipping.

[blindsjc]

Oh man, thanks a lot for both.
Now I understand the gain stage of a lot of circuits I have made.
Thanks.

[petemoore]

  Yupp,, depending on...
  Some circuits can get hit with an input voltage that takes them right to ... and would go over the rail .. but, supply limits this.
  Oh yeah, takes them right to undesirable clipping, imo, opamp 'barking' or 'coughing' when rails get 'touched' by signal is to be avoided for the most part. Sometimes that same 'cough' sounds cool if a Fuzz is compressing/distorting that signal..can add serious scrAtch to the attack.
  If your volume control goes high enough and you want to reduce gain/clipping...what cb said^.

[d95err]

If you want to use it as a preamp (i.e you need the gain), you can simply feed it with more than 9V to get more headroom. This circuit automatically bias to half the supply voltage, so you could feed it with 18V or 24V or more. Just make sure the capacitors and opamps can handle the voltage.