Friedman Golden Pearl -- more drive mod?

[mordechai]

I am building up a version of the aforementioned circuit using pedalpcb project...here's the schematic:

https://www.pedalpcb.com/docs/AurumDrive.pdf

The topography is a little different than your standard Tubescreamer.  Can anybody suggest which resistor I should adjust if I wanted it to have more available drive?  Is it R4 (the 2K2 coming off of the feedback loop)?

[idy]

Upping R5 will give higher minimum and maximum gain. Changing gain pot to...2M... would give you twice the maximum gain... that's an awful lot, could be noisy....

The resistor you asked about affects the tone control mostly.

[POTL]

R4 is responsible for the gain, the greater the difference between R4 and the gain potentiometer, the greater the gain, more gain and volume.
The tone potentiometer is responsible for the gain (yes, this is just the second gain adjustment), it is located in series with R4; the higher their total value, the lower the gain.
C5 forms a High Pass Filter along with R4 and a tone potentiometer.
The larger the capacitance of the capacitor, the more frequencies the circuit amplifies, the more the capacitance is greater than the middle and low frequencies.

[mordechai]

Thanks, this is very helpful.  I will lower the R4 a bit (down to about 1.8K) and change C5 to maintain the frequency ratio accordingly.  I think I might also beef up the input cap from 22n to 33n, just to give it a little more heft overall.  To compensate a little, would you suggest upping R6 to 20K so keep the output from getting too clunky with the increased input cap value?

[Kipper4]

I'm a little confused about what you mean when you say. "More available drive"?

By drive do you mean clipping? Gain?

R6 is part of the network that sets the gain for the second op amp. How does it affect it?

What do you mean please?

[Mark Hammer]

I echo Rich's question.  Drive that extracts more distortion from the circuit, or drive that takes the clipped signal and pushes the amp harder with it?

Do note that, with a 9V supply, and use of yellow LEDs for clipping elements, when you aim for more gain from the op-amp, you will likely be hearing op-amp clipping before getting any appreciable increment in LED-derived clipping.  Indeed, if you drop the value of R4 to get even greater maximum gain, I'd suggest doing a little experiment and lifting one end of the yellow diodes.  My guess is that you won't really hear much difference between running the LM833 with that much gain with and without the LEDs.

[mordechai]

Apologies for the lack of clarity.  I am trying to push the clipping diodes a bit harder, in part because I want to try using BA282's instead of 4148's, and I believe they have a higher clipping threshold.  I like they way they sound in some other OD's I cooked up.  I want to be able to get the same level of crunch from these diodes (maybe a hair more than stock, actually) so increasing the way they are pushed seemed to me to be the way to do it.  But I'm open to suggestions.  I also might swap out a different op amp to see if the character of the op-amp clipping you described, Mark, can affect the tone differently.