Improving the Sound of MkIII Tone Bender

[ItsGiusto]

A few years ago I build a MkIII tonebender according to this schematic:



I've never fully liked the sound of it - it's a little compressed and not bassy enough. It doesn't sound as wild as the MkII I built at the same time.

I was wondering if I should modify it. Looking, for example, at what I think is a Fulltone Soul Bender schematic:

I can see that there are numerous differences. Mostly there are resistor, cap, and pot value changes. But there's also architecture differences - the Soul bender has some type of lowpass filter after the volume knob, and very interestingly, C7 is connected via a trimpot to the output of the "dirt" pot.
I'm wondering if I should implement some of these changes, or all of them, but I'm also a little afraid of making the changes and realizing I liked it better before. What would be the effect of these changes, especially the added trimpot connection?

[PRR]

I put the plans together so I don't get whip-lash looking back and forth.

I don't see much difference. R1 is unimportant. 100/220pFd if probably very small. The more-treble side of the tone pot looks different enough to try (tho I wonder if it is a typo). The 500K trim is a real difference worth trying.

[ItsGiusto]

In thinking this over a little more, could the connection with the trimpot be acting as a positive feedback? Like the "positive feedback applications" section here:
https://en.m.wikipedia.org/wiki/Operational_amplifier

It's a transistor, not an opamp, but maybe it had a similar effect, of increasing output gain?

[mac]

Boutique Bender:
That's a C to B variable resistor, NF used in Silicon versions to feed the base.
There is no 10k to Gnd like in the other schematic, R11.

Focus on C6 and C7.

mac

[PRR]

It is negative feedback, reduces gain, BUT it also adds bias to that transistor. Without it, that transistor has no bias, cuts-off small signals.

[Kennt82]

The Earthquaker Devices Tone Reaper is based on the TB MKIII, but VERY bassy. It's a Muff tone stack with unusual values.