Tone Stack Question and How to get a "hotter" output

[buildafriend]

hey guys

I noticed that the tone stacks inside of the big muff and the tone bender 3knob react similarly on the output. they seem like more of a band pass filter to me. while with other tone knobs I hear the bottom end remaining the same while the high end is attenuated or possibly being boosted. The tone pot of the rat is very nice to my ears.

How could I integrate a tone stack that works similar to the rat pedal into a tone bender pedal? is it possible?

Also, I am using low gain MP39's and some AC125's. Do you know of any ways to get a slightly hotter output? When I step on my fuzz at max volume from the pedal output, it's pretty much the same level (from a listeners perspective) as the clean signal. I want it to be able to BOOST!

Thanks regardless.

[garcho]

The type of tone stack you say you don't want is called a 'Bandaxall'. It's a high pass and a low pass filter with a potentiometer mixing the two; just like you mentioned, a band pass. However, there is no boost, there is only attenuation.
The type of filter you say you want is simply a low pass (bleeds the treble to ground). It's similar to the tone knob on your guitar. It's 1/2 a Bandaxall. Again, there is no boost, only attenuation.
Regarding the gain issue, try reading through the debugging thread and then get back to us.

[Thecomedian]

passive filter vs active filter. a passive one always will attenuate. gain stages before or after will counteract this to an extent. Otherwise, an active filter is the only way to prevent this. Most common is an op-amp with feedbacking to maintain gain at the specific size, no increase or decrease, while being able to "tune tone".

you can use a single transistor as well, though you're talking about using more power and changing the design a bit.

[Mark Hammer]

Okay, let's take a gander at a BMP schematic and tone control.

The 100k tone pot essentially pans between a lowpass filter, formed by the 39k/.01uf combo, and a highpass filter, formed by the .004uf/100k combo.  To do what you want, you can simply eliminate the .004/100k pair.  Do you need the Tone pot, as shown?  No.  So let's scrap it.

What we end up with is a 39k resistance between the output of the 2nd clipping stage, and the 0.1uf input cap on the last transistor stage.  In tandem with the .01uf cap to ground, that forms a single-pole lowpass filter, with rolloff starting around 408hz.  To achieve a "round" or "full 'n buzzy" tone, you would need to make that rolloff variable, and allow it to go up a bit.  It doesn't need to go way high up, because a single-pole filter is rather shallow and still lets through some top end.  happily, the location of the rolloff can be set by altering the value of that 39k resistance.

Our calculations need to be tempered by the standard pot values available to us.  For instance, it wouldn't do much good to do our calculations and decide we need a 73k or 41k pot, because those don't exist.  Ideally, we need to be able to set reasonable min and max filter settings, such that the full rotation of our new tone pot has some use.

If we went with a 10k fixed resistor, in series with a 50k pot - reverse log, C taper may be best - and kept the .01uf cap to ground, the rolloff would shift from 265hz at max resistance (10k+50k) to 1590hz at min resistance (10k+0k), which ought to give a pleasing range from more muffled than stock, to nice and throaty.  If you want something that has even more buzz, then you could either drop the value of the cap to .0082uf, change the fixed resistor to 8k2, or both.

The component values on your units may differ from those shown below, but the principles are the same.