We get a lot of bass players asking about bass fuzz and I usually recommend the Red Mud, which is the big green Russian BM although I know bass players who love other BM's, and distortions on bass.
I was working on a few of my Russian Muds and started testing them with an old P bass I had lying around to see the different qualities each had on bass. The issue with most guitar effects when used for bass is you loose the bottom end which is normally filtered out so as not to make the effect too muddy on guitar. This is what the Big Bottom was designed to "fix". The Russian style BM's tend to keep a fairly tight, but big bottom end intact but I thought there was room for improvement if it was to be used primarily as a bass pedal.
After playing around with component values and types, running into the scope and playing through this circuit I wanted to make a few options available and started playing with the clipping stages to see what effect that had on bass.
Clipping diodes make a huge difference in the BM circuit and different materials and brands will clip at a different voltage and have a different frequency response to what they clip. I've rarely messed around with LEDs as clipping diodes (my Tripletone used them) but when I have they seemed good on bass so I thought I'd work on them in this circuit.
Testing different colour diodes gave different results so I listed everything I had and started mixing and matching them for what I thought sounded good.
After a lot of testing and soldering I ended up using a hybrid of different colour LEDs and germanium diodes in both clipping stages. The first stage is asymmetrical with the second stage a mix of different coloured LEDs and germanium.
This allows for a wide frequency range with good clean gain up to a certain point.
As I was using very high gain silicon transistors, with LOTS of bottom and and wider freq range on the clipping the gain was getting very muddy on anything over about half way and was becoming very messy anywhere near full.
I decided to fit a HI/LOW sensitivity input switch which pulls the saturation right back on the LOW setting and allows higher gain, or active pick ups to be driven into the circuit without loosing clarity. It also lets the effect go to an almost clean preamp with the volume on full and the gain bought up to just over unity.
Switch it to the HIGH setting and everything opens up and it becomes a bottom end beast. It sounds great on guitar on the HIGH setting making me think I should offer it as both a guitar and bass effect, so I messed around with transistor biasing a bit to make it work with both well, but primarily on bass, or downtuned guitar.
I added my flat mids toggle switch as lots of bass players love those punchy mids and it really does work well on bass. I'm not a huge fan of BM's with flat mids on guitar but it really does fill out those bass frequencies nicely. My MIDS toggle leaves the tone stack in the circuit but pulls the normal mid scoop up to a flat response so you can still shape the tone.
Once I was happy with the circuit I emailed Tone for some artwork. At first he was a little stumped but then sent through this artwork with BLACK written in Russian with a small "Black" in the last character. As usual, I loved it.
The first batch of these are out tomorrow. They are not limited edition and I will make more, like all my other pedals, as I get time.