minimalistic but good bass overdrive requirements

[iainpunk]

hey, i am planning on building a bass overdrive/fuzz with as few parts as possible.
i have the idea of splitting the signal in to a high gain fuzz and a clean boost and mix them using a variable bride T filter.

i was wondering if some of you guys have good suggestions on what good functions and circuit snippets are? what are features i should implement and what are features you have good experience with? i want to keep the schematic to a minimum, so it fits on a 26x20 pad per hole protoboard

[Fancy Lime]

I have asked myself that question many times and come up with a very different answer every time.

First, I need to say that I dislike the whole signal splitting -> distorting only the highs -> signal recombination. This can lead to phase problems which can make the sound hollow. Not what I want in an aggressive distortion tone. It also just never sounds "right" to me. There is this (possibly imagined) disconnection between the fundamentals and the distortion that rides on top of it. It's a bit like there are two instruments playing in unison. Some people like that, I don't. I want a compact, chiseled-ot-of-granite block of sound from a bass distortion. To get that, the strategy that has emerged as my favorite over the years (and which takes a lot less parts than the splitting approach), is this:

1. Boost high mids or treble (centered at 500 to 3000Hz, adjust to taste) in or before the clipping stage.
2. Clip only the high mids and treble, so that everything becomes more even again. Most easily done with diode clippers in series with a suitably sized cap (topology as in the Big Muff Pi but normally with smaller caps). For a fuzzish sound it may be best to put the clipping arrangement in the negative feedback loop of an inverting opamp.
3. EQ that allows boosting and cutting bass relative to treble. The Big Muff EQ topology works. The single knob bass boost / treble boost EQ that DOD used in many 80s pedals (e.g. FX52 Classic Fuzz) is also great but with more parts.

I would probably start out with an Opamp Muff Fuzz topology, implement the features mentioned above, raise the clipping threshold for more output and tag a BMP tone stack at the end. If  minimalism is more important than flexibility, forget the tone stack and just dial the frequency shaping in the amplifying stages the way you like. I might have time later today to draw what I have in mind. I have something very similar somewhere in my KiCad folder anyway.

Cheers,
Andy

[bushidov]

I have a Darkglass B7K that I really like and tore down and traced all the components and and layout for. It isn't "minimalist" by any stretch, but it did lay down some fundamentals.

If you look at it schematically, you can kind of see the "evolution" thoughts in the heads of their designers.

I am not saying this is exactly what happened, but I wouldn't be surprised if it did.
1. Take a Way Huge Red Llama, which has a really low part count to start. It only uses one IC, the CD4049UBE, which is actually just Craig Anderton's "Tube Like Fuzz" with a couple of passive component value changes. That's the core of your "dirt/fuzz" sound

2. Use a TL072 dual op-amp to create an input buffer in a non-inverting fashion (which can be broken off into the CD4049 dirt/fuzz channel) and an output buffer that also acts as a mixer. If the output is also "non-inverting", make sure that the "blend" pot that is going into the op-amp's non-inverting pin has it's level control before it, and the level control doesn't ground out the signal to ground like a typical volume pot does. It needs to "ground out" to your bias (typically 4.5V). At this point, you are half way there to making a Darkglass B3K

3. If you want to elaborate on the design some more, in between the above two mentioned op-amps, add another TL072 dual op-amp (or swap out the original one with a TL074 so that instead of having 2 chips, you have 1) and add to the design, add some tone shaping and additional gain to get that fuzz, fuzzier, and for tone-shaping, find frequencies you want to boost and cut, for your bass. A lot of these will be hard-wired (not controlled by any pots). At this point, you pretty much have a Darkglass B3K

4. After you got that working, add a bunch of post EQ stuffs. Now you have a Darkglass B7K.

A word of warning, as I am still getting answers for this in previous posts, the more op-amps you slap into this circuit, the more you need to take care of inverting and non-inverting ones, biasing requirements, and what frequencies you do want to boost and cut. For example, boosting 5K on a bass is a bad idea, not because its an uncommon frequency to boost for a bass guitar because there are some good shimmer frequencies in there, but if boosted too much, you will get feedback really easy. Also, there are some "mud" frequencies to avoid/cut. Also, slap bass and regular finger style seem to have different EQ needs. All of these are "to the musicians taste", but Darkglass, being guys who focus on bass effects, seem to think the ideal bands to play around are 100 Hz, 1kHz, 2.8kHz, and 5kHz.

Other things to look at is when boosting right before a fuzz, don't boost low frequencies, even though this is for a bass and you would be tempted too. Distorting bass frequencies create a lot of mud. Low pass filter out stuff and distort/amplify higher frequencies, as to bring the bass back in is the reason you have a blend knob in the first place. Another thing I've discovered is that 800 Hz to 1kHz is actually a range you want to boost on a bass, if looking for clarity in a mix. Shelving sub 100 Hz frequencies and under and also cutting out 4 kHz and above have done well for me in mixes, so a pedal that does that automatically can be a help.

I say all of this to say, I am not expert or anything, but from my experiences, this is what I tend to do, and the above reasons would be why.

[iainpunk]

im not really fan of the darkglass sound/type of bass distortions, they sound really fake to my ears.

First, I need to say that I dislike the whole signal splitting -> distorting only the highs -> signal recombination.

i don't like that either, i am doing it differently:
small boost > split >    fuzz > blend the fuzzy bass with the clean midrange and blend the two trebles using a filter mixer
                            > clean >

this gives high sustain bass and clear midrange and optionally clean/fizzy treble.
the crossover between bass and mid should be at 300Hz and the trebble at 2k, using a bride-t//rc bandpass mixer, ill draw when i have time

[marcelomd]

If you look at it schematically, you can kind of see the "evolution" thoughts in the heads of their designers.

Between steps 2 and 3, there is some shaping happening. A notch filter which cuts +- around 400Hz. The same topology found in the Sansamp Bass Driver (which cuts 800Hz). Then two low pass filters after the distortion stage, to tame fizziness. This kind of filter is pretty common I think.
To me, this is the "core" of the darkglass sound to me.

[Nitefly182]

Focusing on keeping the parts count as low as possible is probably the wrong way to go if you want a bass drive with worthwhile features. Guitar pedals that sound great with 7 parts sound like garbage with bass because they aren't often concerned with low frequency clarity. Or they just chop out everything below ~100hz because it causes problems.

This is all a matter of taste but you'll probably need to cut bass on the front end of the circuit and then add it back later if you want definition in the drive tone. IMO this requires at the very least an active EQ circuit. A passive tone control won't deliver the same punch.

I like parallel processing the clean signal with a low pass filter so you're only blending in the real low end from the clean. No clank and no treble from the dry signal. The sound is much more natural that way. And you can still distort a wide swath of the basses range. The crossover point doesn't have to be where the clipping starts and stops. It just helps to have clean low end mixed with the distorted low end to make things sound huge.

Build a rat with a james tone stack and some recovery gain though if you want to go low parts count.

[Fancy Lime]

im not really fan of the darkglass sound/type of bass distortions, they sound really fake to my ears.

First, I need to say that I dislike the whole signal splitting -> distorting only the highs -> signal recombination.

i don't like that either, i am doing it differently:
small boost > split >    fuzz > blend the fuzzy bass with the clean midrange and blend the two trebles using a filter mixer
                            > clean >

this gives high sustain bass and clear midrange and optionally clean/fizzy treble.
the crossover between bass and mid should be at 300Hz and the trebble at 2k, using a bride-t//rc bandpass mixer, ill draw when i have time

If you want bass and treble distorted / compressed but the mids dynamic, you can simply put a bridged-T or twin-T filter before the clipping section. Or the bridged-Pi filter that Darkglass like to use. You need to get the depth of the notch right in relation to the gain range in order to get the clean mid punch without a whole in the mid frequencies. Easier if you forgo the gain pot and just give it fixed gain. A recovery stage with a bit of mid boost may be a good idea. Can all be done with very few parts. One-knob bass fuzz! Damn, now I want to have one of these, too...

Focusing on keeping the parts count as low as possible is probably the wrong way to go if you want a bass drive with worthwhile features. Guitar pedals that sound great with 7 parts sound like garbage with bass because they aren't often concerned with low frequency clarity. Or they just chop out everything below ~100hz because it causes problems.

I'm going to have to disagree here. Bass drive pedals do not need to be more complicated than guitar pedals to sound amazing, they just need to be designed properly with bass use in mind. Just taking a guitar pedal and increasing a few cap values doesn't cut it mot of the time. The frequency profiles where bass and guitar live in a band context are very different. Low mids sound mighty on bass but muddy on guitar. High mids are essential for guitar but if you want them on bass very much depends on how many guitar players the band has and what they play.

This is all a matter of taste but you'll probably need to cut bass on the front end of the circuit and then add it back later if you want definition in the drive tone. IMO this requires at the very least an active EQ circuit. A passive tone control won't deliver the same punch.

What does passive/active have to do with "punch"? Most passive tone stacks cut mids because they were designed for guitar amps with awfully mid-heavy speakers but you can make a passive tone control as punchy as you want.

I like parallel processing the clean signal with a low pass filter so you're only blending in the real low end from the clean. No clank and no treble from the dry signal. The sound is much more natural that way. And you can still distort a wide swath of the basses range. The crossover point doesn't have to be where the clipping starts and stops. It just helps to have clean low end mixed with the distorted low end to make things sound huge.

Build a rat with a james tone stack and some recovery gain though if you want to go low parts count.

That would be an IdiotBox Blower Box, then. Not a bad place to start.

Cheers,
Andy

[iainpunk]

maybe i need to clarify, my favourite bass pedal at this moment is a heavily modded Jfet/Si hybrid fuzz face, with a scoop control (scoop is adjustable freq/depth), i want that muddy rumble, but not the soaring midrange, i like my midrange to be clean-ish i use a eq in parallel for that. i really don't like the "darkglass sound".

[Fancy Lime]

maybe i need to clarify, my favourite bass pedal at this moment is a heavily modded Jfet/Si hybrid fuzz face, with a scoop control (scoop is adjustable freq/depth), i want that muddy rumble, but not the soaring midrange, i like my midrange to be clean-ish i use a eq in parallel for that. i really don't like the "darkglass sound".

"heavily modded" anything does not really help us much. That could mean anything. Do you have a schematic? Or sound samples? Or both?

Andy

[Nitefly182]

maybe i need to clarify, my favourite bass pedal at this moment is a heavily modded Jfet/Si hybrid fuzz face, with a scoop control (scoop is adjustable freq/depth), i want that muddy rumble, but not the soaring midrange, i like my midrange to be clean-ish i use a eq in parallel for that. i really don't like the "darkglass sound".

Add a variable notch filter to the existing circuit and you'll be done.

All my advice was about trying to avoid muddy tones but if that's what you're looking for the job is a lot easier.

[iainpunk]

maybe i need to clarify, my favourite bass pedal at this moment is a heavily modded Jfet/Si hybrid fuzz face, with a scoop control (scoop is adjustable freq/depth), i want that muddy rumble, but not the soaring midrange, i like my midrange to be clean-ish i use a eq in parallel for that. i really don't like the "darkglass sound".

"heavily modded" anything does not really help us much. That could mean anything. Do you have a schematic? Or sound samples? Or both?

Andy

i couldn't remember the name, but i found it, it was based off of the Univox Square Wave without the clipping diodes but with a bridged-T filter, the bridge resistor was 100k, the caps were 5,6nf and the ground resistor was 10k fixed + 100k pot. its travel is from -3dB at 300Hz to -16dB at 1kHz, i always had the scoop control quite high.


i used it in an active mixer together with a 3 band eq pedal that boosted the midrange (around 600Hz narrow Q) and cut bass and treble (100Hz and 4kHz very wide Q) and just mixed them, it fit very well in the mix, with the guitar using up the 1K and the 300Hz regions, i used the 100, 600 and 3k regions, according to my calculations
i was thinking about recreating that 'W' shaped EQ curve for this pedal as well.

cheers,
Iain

[Rob Strand]

Between steps 2 and 3, there is some shaping happening. A notch filter which cuts +- around 400Hz. The same topology found in the Sansamp Bass Driver (which cuts 800Hz). Then two low pass filters after the distortion stage, to tame fizziness. This kind of filter is pretty common I think.
To me, this is the "core" of the darkglass sound to me.

The circuits have a very similar structure and use very similar circuit blocks.  And if you look at the Bass Driver thread on free stomp boxes from 2007 to 2009 there is a user darkglass who built a clone.

[Rob Strand]

i don't like that either, i am doing it differently:
small boost > split >    fuzz > blend the fuzzy bass with the clean midrange and blend the two trebles using a filter mixer
                            > clean >

this gives high sustain bass and clear midrange and optionally clean/fizzy treble.
the crossover between bass and mid should be at 300Hz and the trebble at 2k, using a bride-t//rc bandpass mixer, ill draw when i have time

If you don't like the Darkglass or the blending types perhaps you should consider the maestro bass brass-master.    Not simple but maybe you can strip it back to the mode you like.

Demo of clone,
https://www.youtube.com/watch?v=TbgeebehU5k

Yes, Close to the Edge, (starts around 1:00)
https://www.youtube.com/watch?v=GNkWac-Nm0A

[iainpunk]

so i have experimented with parallel bazz fuss and idiot wah, which are then mixed with a filter, letting through the highend from one and letting through the lowend from the other, and sweeping between which one gets high and which one gets low. the prototype works well, but the bazz fuss is a bit to high gain and midrangey for my tastes, independent of the mix amount, i think i'm going to add a bridge-T to the bass fuzz side to make it work better with the midrange heavy fixed wah side