Another silly dual-stage overdrive

[Sooner Boomer]

but in this case I'll take a short break from the antiauthoritarianism just this once

don't have to,
https://rationalwiki.org/wiki/Anarcho-monarchism

cheers, Iain

Nae king! Nae quin! Nae laird! Nae master! We willna' be fooled again!

[Vivek]

Is there a concensus on our forum on most preferred range for

Number of gain stages after which there is no additional benefit

Slope and freq of high pass filter before first stage

Need of a high pass filter between gain stages

Slope and Frequency of low pass filters after each stage

Advantage of having variable filter Freq versus fixed filters

Radians where to clip at each stage

Ratio of gain at each stage

[Vivek]

I'm confused regarding the concept of "gain" of 2 stage pedals

Suppose we have clean stages, and first stage has gain of 10 and second stage has gain of 20, it's clear to see that total gain is 200

But suppose we have 2 stages which include clipping (at different pointsof signal due to different signal levels and different diodes), does it convey all information if we calculate the gain of each stage and multiply them ?


Thought experiment

Suppose we have first stage of gain 100 and LED in feedback loop

We follow that with a second stage with gain 2

For second stage, we first try no diodes, then LED, then Si, then Ge diodes in the loop.

In all cases, total gain would be 200.

But all sounds would be different.

What did we really convey by multiplying gain of each stage and stating the result ?

Is there a better way to more exactly state what is going on ?

[Fancy Lime]

Is there a concensus on our forum on most preferred range for

Number of gain stages after which there is no additional benefit

Slope and freq of high pass filter before first stage

Need of a high pass filter between gain stages

Slope and Frequency of low pass filters after each stage

Advantage of having variable filter Freq versus fixed filters

Radians where to clip at each stage

Ratio of gain at each stage

Well, if there was a consensus on all of these, all overdrives woul sound the same, if they stuck to the consensus, and wouldn't that be boring. Changing all those things is what makes tinkering with overdrives so much fun. At least that's part of it.

It's a bit like asking "what is the best cake?". People's tastes are varied. But yes, you can change a lot of details of a recipe and still get a very similar cake.

Cheers,
Andy

[11-90-an]

Suppose we have first stage of gain 100 and LED in feedback loop

We follow that with a second stage with gain 2

For second stage, we first try no diodes, then LED, then Si, then Ge diodes in the loop.

In all cases, total gain would be 200.

But all sounds would be different.

What did we really convey by multiplying gain of each stage and stating the result ?

Is there a better way to more exactly state what is going on ?

i *think* that the sounds would start to come from the clipping/distortion generated by either opamp or diodes, whichever clips first. Also, perhaps it has something to do with diode forward drop, opamp type, etc.

Here's at least what I'm trying to say...

And SIX pages of posts?!   

Don't worry, we're halfway there...

[Vivek]

Is there a concensus on our forum on most preferred range for

Number of gain stages after which there is no additional benefit

Slope and freq of high pass filter before first stage

Need of a high pass filter between gain stages

Slope and Frequency of low pass filters after each stage

Advantage of having variable filter Freq versus fixed filters

Radians where to clip at each stage

Ratio of gain at each stage

Well, if there was a consensus on all of these, all overdrives woul sound the same, if they stuck to the consensus, and wouldn't that be boring. Changing all those things is what makes tinkering with overdrives so much fun. At least that's part of it.

It's a bit like asking "what is the best cake?". People's tastes are varied. But yes, you can change a lot of details of a recipe and still get a very similar cake.

Cheers,
Andy

There can still be some consensus of this type

5 gain stages do not have a perceived tone or feel difference than 2 stage


First high pass should between 50 to 1 kHz, and preferably in the 600 to 800 Hz range. It's not nice to have a high pass of 2 Khz



Etc...


Yes indeed, many pedals do sound like each other.

[Vivek]

Suppose we have first stage of gain 100 and LED in feedback loop

We follow that with a second stage with gain 2

For second stage, we first try no diodes, then LED, then Si, then Ge diodes in the loop.

In all cases, total gain would be 200.

But all sounds would be different.

What did we really convey by multiplying gain of each stage and stating the result ?

Is there a better way to more exactly state what is going on ?

i *think* that the sounds would start to come from the clipping/distortion generated by either opamp or diodes, whichever clips first. Also, perhaps it has something to do with diode forward drop, opamp type, etc.

Here's at least what I'm trying to say...

And SIX pages of posts?!   

Don't worry, we're halfway there...

So we did not convey anything much by calculating and stating total gain of a 2 stage pedal.

I feel It is essential to also understand headroom  and signal strength at each stage (what I call clipping radians since that incorporates signal level with level at which signal is clipped )

[Mark Hammer]

Cascading gain stages that clip is a matter of adjusting the gain, bandwidth, and clipping thresholds of subsequent stages.  Vivek is correct in being a little befuddled by the multiplicative aspect of gain over multiple stages.  Diodes in the feedback loop will constrain the maximum output of a stage.  Any intention to re-clip in a subsequent stage requires bringing the level up a bit to suit the diode complement in the next stage, but since one starts out with a reasonably hefty signal from the preceding stage, not much gain is required of the subsequent stage to again reach a clipping threshold.

And since Gus astutely brought up the topic of BMP stages wih his ASDF circuit, you'll note that the Big Muff has two identical clipping stages, with the same gain and clipping threshold in each.  Variations of that circuit in various commercial pedals have toyed with differentiating the characteristics of clipping stage 1 vs 2.

[Gus]

Nice!  I should have known you've covered this ground long ago.  And SIX pages of posts?!   

I think it is cool you posted the circuit. 

Years ago I traced a bluesbreaker(there was no schematic posted on the web at the time I could find) and when I saw how the circuit was set up I thought that was very cool.

More experimenting with the interaction between gain stages is something I think is "better" than the TS like circuit

[Vivek]

My friend Dr Buffa made a web page where we can change transfer function, gain, high pass for each stage in a virtual amp

and can add more virtual stages

and hear the effect of adding one more gain stage in real time

or effect of changing high pass filter in real time

https://mainline.i3s.unice.fr/AmpSim5/

[Vivek]

Cascading gain stages that clip is a matter of adjusting the gain, bandwidth, and clipping thresholds of subsequent stages. 

While one pot to adjust gain of 2 stages looks elegant

It seems to impose a constraint on the relationship of gains of each stage

For example, guitarist cannot say in the one gain pot scenario "Lets keep gain of stage 1 at 150 and then only change the gain of the second stage till we get the tone we like"

or " lets see if high gain followed by low gain is better than low gain followed by high gain"

[FiveseveN]

guitarist cannot say ...

Have you ever met a guitarists that wished for more controls on their gear? How about one that can properly define "gain"?

[marcelomd]

I think the "gain" in the gain knob of a pedal is a leftover from the time where you needed to crank the gain knob on an amplifier to get distortion. Nothing else. Even if internally there's a change in amplitude of the signal, the perceived effect is a change in tone/timbre/voice.

Personally I prefer other names. Distortion, drive, dirt, dtc.

The confusion with the term "gain" goes even deeper. In most tube amps, the actual signal gain is fixed and the "gain" knob is an attenuator. Sometimes this knob is called "volume". Sometimes there are two such attenuators, gain and volume (or master).

[Vivek]

Fulltone Plimsoul had 2 gain stages, with individual control of the gain of each stage

http://revolutiondeux.blogspot.com/2012/03/fulltone-plimsoul.html




There are some interesting videos on the Interweb that show the effect of tweaking each stage independently

[Mark Hammer]

Interesting circuit.  I doubt the full 100k of that dual-ganged pot are needed to tame the clipping of the LEDS, and suspect there islikely a missing parallel resistor, but that's just speculation on my part.  That said, it's kind of a different take on the one-action-changes-two-parameters control that Gus's ASDF and the Bluesbreaker gain employ.

[Vivek]

Stage 1 of plimsoll has its own control, labelled "Sustain"

So each stage's gain is controlled independently.

Gus has one pot change gain of both stages

[rockola]

Now available at a Github near you: https://github.com/rockola/wattbreaker

[Mark Hammer]

 

I guess it was bound to happen eventually.

[Marcos - Munky]

Finally built one. Surprisingly, not in a 1590A, but in a transformer can (or whatever it's the correct name) I had on my parts bin. It's the first bluesbreaker-like circuit I built, and it sounds very good. I really liked the sound of this one plugged into a clean tube amp and using a strat with single coils.

[Mark Hammer]

Nice!  I'm honoured.