Boss GE-7 "level" boost/cut - 20k pot instead of 10k?

[aion]

GE-7 schematic for reference: http://www.hobby-hour.com/electronics/s/schematics/boss-ge7-equalizer-schematic.png

What (if anything) would need to be adjusted in order for this part of the circuit to be adapted to a 20kW pot (TS tone control)? Would it work as-is or would a person need to adjust the proportions of the resistors to get the same behavior?

I like the boost/cut functionality of this level control over a typical output volume control for "balance correction" situations where getting all the way to zero is pointless - e.g. an EQ circuit like the GE-7. It's just more user-friendly having the center be flat. I understand pretty well how it works—it's basically a Tube Screamer tone control, but with a corner frequency of 7 Hz so essentially full-range, and the resistors are set so it's almost exactly 15dB (5.54) as advertised. But I'm having a hard time wrapping my mind around the importance of the actual pot value, and how this application is different from the TS tone control.

[snap]

just recalculate R24 & R25.

[aion]

(Do you mean R26 and R27?) Since this is a non-inverting configuration, would the input resistor have any impact on the actual gain structure other than dropping the load on the input?

If I was tacking this onto another circuit could I do it with just that single op-amp (5/6/7 of IC4) and some coupling caps?

Thanks.

[snap]

R24/25 was referring to swapping VR1-VR7 (a misunderstanding).
For changing VR8: R26 & R27, and possibly R2. You want to put this section into the Pearl-Eq?

[aion]

Yep, that's what I'm looking at doing. I always liked being able to tweak the GE-7's level so you could use it as a frequency-driven boost pedal as well - like placing it right before a drive pedal to essentially get a second channel out of it and bring out different clipping characteristics.

Could it feasibly replace the entire first stage of the EQ - that bizarre parallel-transistors bit? I would normally think to tack volume stuff on the end of a circuit, but the GE-7 puts it before the frequency sliders and I think that makes perfectly good sense in a unity-gain circuit like this one.

[PRR]

> 20k pot instead of 10k?

Just do it.

The ill-effect is a wider zone of "not much happening" at center. At the ends the effect is the same. You also get an insignificantly lower hiss level. All in all, not worth re-calculating everything.

[blackieNYC]

BTW, I swapped my ge7's op amps (4558s?) for TL072s and lost a fair amount of hiss.

[aion]

Thanks so much for all of your help. I feel like I "leveled up" in my understanding of op-amps after diving into this (along with the Pearl PE-10 in another thread, which this question is related to) and figuring out the "whys" to accompany the "whats" that you guys all generously provided. I was having a hard time finding a good technical explanation of what was going on until I came across this:

http://www.ecircuitcenter.com/Circuits/op_bandcut_boost/op_cutboost.htm

It helped me see the GE-7 level control as basically a full-frequency (high pass above 7 Hz) boost/cut tone control. I understood the two extreme ends, but I was having a hard time understanding what was happening in the center position of the pot where the gain is 1. But reading through that article and playing with the SPICE models, I realized that in the middle position, the attenuation at the input is the exact inverse of the gain at the op-amp, and it clicked from there.

Anyway, I doubled all the resistors to accommodate the 20k pot, and left the 10uF cap in place since it's full-frequency anyway and we're talking a difference of 7 Hz vs. 3 Hz. Haven't tested it out yet but I think this is going to be perfect.