Further thoughts regarding internals of the RIDGE pedal

[Vivek]

I feel that the RIDGE pedal is innovative in that it got many existing ideas together

We always had pre-distortion EQ.
Some pedals have it variable, for example WAMPLER ECSTACY
RIDGE has variable pre-distortion EQ

We always had mid boost since TS days
Tech 21 Character series made it variable
RIDGE has variable mid boost

We always had post-distortion EQ.
so many pedals have BMP, SWTC, Baxandall tone controls
RIDGE has variable post-distortion EQ

We always had digital control of analog circuitry since Rockman, Chase Bliss...
We always had midi
RIDGE has digital control and midi to save and change presets


Elektor variable fuzz and many other rubber diode based clippers showed us how to have variable clipping/ variable transfer function


Here we have variable clipping, adjustable by two pots that provide DC control voltages to the bases of T1 and T2


But RIDGE got all these existing ideas into one box !!!


One of the big things I feel about the RIDGE is the single knob control of the clipping characteristics called "MOOD". This would most probably be done by a microcontroller, since it needs to be controlled by Midi messages.




It is well understood that there will be volume changes if you change clipping from let's say (+1Vvp/ -1Vp) to ( 0.5vp/-0.1vp)

Hence a volume knob is essential. When we clip too drastically, smaller signal will exit the clipping stages and we will need to boost the final volume exiting the pedal.

A Drive knob would act the same as a regular drive knob in a pedal. Set the clipping style with the mood knob, then adjust drive with drive and final volume with volume. There would still be some combos of mood/drive that sound very similar. If you set Mood to clip at 1vp and Drive to send 2Vp signal to the clipper section, that would sound similar to setting Mood to clip at 2vp and Drive to send 4Vp signal to the clipper section.



I began thinking, what if I tried to make an all-analog, simplified variable clipping, variable Pre and Post EQ, variable Mid version after getting inspired by RIDGE. Then the design goals would be:

Have a variable High Pass before the distortion. Maybe take some hints from VFE focus or Baxandall Bass control

Have a variable Low pass after distortion. Again, may be inspired by VFE focus or Baxandall Treble control

Have a mid control before distortion. Either gyrator based, or Baxandall Mid or others. Maybe semi parametric like Boss MT2.


And then use something like the Elektor Variable Fuzz in the middle since I need variable clipping characteristics.

But Elektor used two pots to be able to independently adjust the clipping level of the top half and the bottom half of the input wave. The big thing about the Ridge was to simplify the UI and change clipping control to only one knob.

I dont want 2 clipping controls. it is too difficult to adjust 2 pots. Many settings are redundant. For example (Top clipped at 1Vp, bottom at 0.5Vp) is same as (Top clipped at 0.5Vp and bottom clipped at 1Vp)

I need one clipping control that does what Ridge does

See this : https://youtu.be/4nfjqkkmqiU?t=166


1: Full CCW : No clipping or very slight clipping




2: Around 9 O Clock : The bottom progressively starts to get more and more clipped while the top remains intact. Asymmetrical soft clipping




3: Around Noon : The top now starts to get clipped, we start to have symmetrical soft clipping




4: Further clockwise : We now start to morph to hard clipping on the top and soft clipping at the bottom part of the wave




5: Still further clockwise : Now we have hard clipping on both sides of the wave. Symmetrical hard clipping




6: and towards end of travel clockwise : we now see extreme high gain, severe symmetric hard clipping



If we have a clipper stage that changes clipping characteristics based on control voltages (Elektor Variable Fuzz, for example)

then the challenge is to have a "Mood" knob that creates the correct DC control voltages for the clipping.

This is a facile task if we had a microcontroller.

But I have begun to feel that it is possible to design a Mood knob ( maybe dual pot) that creates two control signals (one of each side of the wave) as fully analog circuit

Maybe something as simple as this:



Which emits DC voltages at its output like this :



which we could use to control the clipping of the top half of the wave

and on the other pot of the dual pot, we use different resistors/diodes to get a different control curve, to control the clipping of the bottom half of the wave.

And together, the dual pot can create 2 DC control voltages which can control the clipper in a very similar fashion as the RIDGE.

[Vivek]

Notice Elektor's trick to use the 2 clipping pots to also create Vref !!!

[FSFX]

I had been looking at ways of doing this and here is a suggestion using something like a TL084 op amp to vary the clipping levels.

[Vivek]

Great job FSFX !!

I feel that the trick is that the DC control voltage for clipping the positive swing of the Audio is different than the DC control voltage for the negative swings.

That is why RIDGE also does Asymmetric clipping.

Could you try to use dual pot for clipping level, and set it up so that it works like MOOD knob on Ridge ?

[FSFX]

Varying the ratio of R5 and R7 with U2 will allow you to offset the clipping.

[Vivek]

The offset is not fixed !!!

It varies with knob position

Please see the Scope screenshots of RIDGE

All that has to be done with one knob !

[MrStab]

So, to rephrase the challenge:
Only Resistance A changes until centre point,
Only Resistance B changes after centre point?

Maybe you could do it with just a single pot and electronic switching to determine which clipper is assigned the pot, and which is assigned a fixed resistance. Centre tap to trigger a flip-flop or some nonsense.

Or even just a push-pull pot? Compromise, but not on panel space.

[Vivek]

We need one (dual ganged) pot that generates the following two control voltages (Red curves)

(One control voltage for top clipper, other control voltage for bottom clipper)



Purple numbers are zones of the mood control. I renumbered the oscilloscope screenshots in my original post to match these.

[Axldeziak]

We need one (dual ganged) pot that generates the following two control voltages (Red curves)

(One control voltage for top clipper, other control voltage for bottom clipper)

It's doable if your willing to go full mad scientist.
(Just having a bit of fun with the concept.)
But it would work.

[Musikermomo]

Hello and thanks for the great thread!
Thought about using a rotary switch like these?

https://www.google.com/search?q=24+step+rotary+switch&prmd=isvn&sxsrf=AJOqlzUPpHoUVZ6Qzs6Jy_opUCu7kNAG_w:1673681840860&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiGoN3cxsb8AhXUiv0HHVwcD-MQ_AUoAXoECAIQAQ&biw=393&bih=712&dpr=2.75

[FSFX]

We need one (dual ganged) pot that generates the following two control voltages (Red curves)

(One control voltage for top clipper, other control voltage for bottom clipper)



Purple numbers are zones of the mood control. I renumbered the oscilloscope screenshots in my original post to match these.

Can be done. Blore Edwards is a company in Wales (GB) that will make custom potentiometers for you.

[niektb]

can't you get (close to) what you want by faking a log (or anti-log) pot on one half of the dual pot?