Low frequency roll-off

[icecycle66]

What causes low frequency roll-off?
-and-
How do I stop it?

As a bass player building all these pedals I would like to know what causes pedals, distortion and fuzz in particualr, to kill the low frequencies going through them. When I go through my pedals I want to keep the large low notes.

Now, I've seen descriptions of some pedals.  They talk about only applying the effect to higher frequencies while leaving the lower freqs alone, to keep the strength of the low notes.  That's not what I'm looking for.  I want the entire range of notes to be distorted, or whtever, but i want the strengtho of the unclean low note to be just as powerful as the clean low note.

It seem to me:

No effect = BOOM
Effect = *b*o*o*m*


I want:
No effect= BOOM
effect = *B*O*O*M*

[midwayfair]

What causes low frequency roll-off?
-and-
How do I stop it?

As a bass player building all these pedals I would like to know what causes pedals, distortion and fuzz in particualr, to kill the low frequencies going through them. When I go through my pedals I want to keep the large low notes.

Now, I've seen descriptions of some pedals.  They talk about only applying the effect to higher frequencies while leaving the lower freqs alone, to keep the strength of the low notes.  That's not what I'm looking for.  I want the entire range of notes to be distorted, or whtever, but i want the strengtho of the unclean low note to be just as powerful as the clean low note.

It seem to me:

No effect = BOOM
Effect = *b*o*o*m*


I want:
No effect= BOOM
effect = *B*O*O*M*

In pedals, the most immediate culprit of bass loss is the input cap (and the output cap to some extent). At the very beginning of the circuit, you have a capacitor that blocks some low frequencies. It's a high-pass filter. You do this because bass frequencies tend to create lots of distortion. And simply because of the way our ears work, they will be loud without us hearing them as easily. On top of that, because of the way electronics work, higher frequencies will also be amplified comparatively more and more as you go up in octaves, which is why there's usually a tone control that cuts highs to avoid a piercing sound. So you need a lot more bass input to make the bass as loud as it was before the pedal, but to get there, you're going tend to overload the circuit and make the treble too prominent. You need to turn down the effect, which means you're back to square 1 with the bass being too quiet. This is a big problem in compressors.

But then there's another problem. The distortion from bass frequencies is more likely to be unpleasant. It's physics: the wave forms are farther apart, and there's simply more room for "error" in the harmonics. You can hear this easily on a piano. Play a chord on the bass end of a piano and it will sound horrible even right after the piano is tuned. There's also a tonality issue where too many bass frequencies can make the sound muddy. So even if you solved the distortion issue, you could end up with a pedal that just has smeared bass. So you don't want to just put the biggest input cap you can find in the circuit.

Although you could just start replacing input and output caps in the pedals you build, I'd suggest getting out the breadboard and putting together a simple boost or buffer circuit so you can experiment. Start with stock values, and then play with the input cap until you find a value you like. It'll give you a chance to understand how the bass frequencies interact with the input section of any pedal. Expand it to a simple OD or distortion device and mess with the output section.

This generally means that you have to tune an effect specifically for bass with higher headroom, big input/output caps, and then manage the high end so that it doesn't get overamplified. In other words, you make the circuit work more like a low-pass filter.