Tone stacks before versus after distortion/overdrive/fuzz circuits

[bifurcation]

Hey, wondering if any of the experts could articulate common things to expect when shaping tone before the dirt part of a circuit.

I get that a lot of circuits cut bass before the dirt circuit, but are there common effects one gets when you don't do that? (as opposed to rolling off bass after the distortion circuit.)

Is it just because bass tone range has more power and will sonically dominate the output? Or does it add a character, woofyness etc?

 

[zgrav]

I think it comes down to whether you want your distortion to reflect frequencies that you are going to turn down, or whether you just want the distortion to come from the shaped sounds after the tone controls. If we at least pretend we can hear higher level harmonics it makes a difference. If there aren't boxes already that have tone shaping on each side of the distortion, maybe there should be. Some of that happens routinely when the pedal is not at the beginning or the end of the chain.

 

[HamishR]

Distorting lower frequencies can add to wooliness of the sound. I love the sound of the Marshall Supa Fuzz because of this - it's a Tone Bender with a bigger input cap than standard and that is part of the reason it sounds so fat and fuzzy.

But in general too much bass into clipping leads to a looser, less well-defined sound. That's why you sometimes see a pre-clipping bass cut called "tightness" or "body". In an overdrive I am obsessed with trying to keep the lows big but tight. It seems that the key is to reduce the amount of lower frequencies before clipping and increase them afterwards if you want a fuller sound. There is usually a bit more to it than that but this is something I have learned from experimentation and from good advice I have received.

 

[phi1]

To me it’s helpful generally to think of how harmonics (intervals above the fundamental frequency) are created when a signal is clipped. When you clip lows, you end up with a lot of congestion in the low mids. There’s also excess highs after clipping. That’s why the typically topology is cut lows before clipping, cut highs after clipping. Think of a Timmy, generally regarded as very “transparent“ tonally. But Looking at the circuit it cuts bass before and highs after, it’s just tuned so that the resulting eq sound similar to the input. (Of course having Both Bass and Treble Knobs helps you dial it in How you want, and you can basically get rid of the low and high cut with those knobs maxed, to hear how un-transparent it sounds without cutting lows and highs).

Another thing (I’m still wrapping my head around this) seems to be that op amp circuits are more sensitive to bass frequencies before clipping than jfet circuits. With jfet circuits, cutting some bass before clipping is helpful, but done at seem to need to be as drastic as op amp circuits. On op amp circuits, I believe full bass before clipping really overloads the op amp and makes it extra bassy.

 

[Chuck D. Bones]

I agree with all of the points raised by Zgrav, HamishR & Phi1.
Just about every dirt pedal does tone shaping before, during and after the clipping stage(s). On some of the pedals, that tone shaping is user-adjustable. The TS is famous (notorious) for its mid-hump, but most dirt pedals have some kind of mid hump. Bass is cut going into the distortion stage and treble is cut coming out. The Rat and Expandora do that.

For sure the low frequency signals are stronger and left to themselves, will overwhelm everything else.

If you want to have some fun experimenting, get two graphic equalizers and put one before a dirt pedal and one after.

To Phi1's point about JFET vs opamp distortion, JFET dirt pedals tend to distribute the distortion and bass cut over many stages. Every JFET contributes some distortion. Every coupling cap is small to reduce some of the bass. Opamp dirt pedals tend to concentrate the bass cut and distortion in one stage. There are some notable exceptions, such as the Crunch Box, Shredmaster, Thermionic, etc.