Bazz Fuss and ABY problem

[markfeltwell]

Hi,
Love building my own pedals and so have naturally started with a couple of easy ones (bazz fuss and ABY). But I have a problem when I use them together.
I play bass and use 2 amps, one clean and one dirty. So I built an ABY to split my signal, I place all of my effects though one amp keeping the other completely dry.
The problem occurs when I use the Bazz Fuss, I notice a dip in volume in the clean amp and when I turn down the volume of my dirty amp I can actually here distortion throughout eh clean amp. I've adjusted the volume control on the fuzz pedal and that has no effect on my clean amp. However, if I turn on one of my other pedals before the Bazz Fuzz in the chain (no effect on ones after in the chain) it solves the problem, the volume is back to normal. These other pedals are store bought, I tried 2 bazz fuss pedals and it didn't correct the problem.

So, does anyone know what might cause this to happen. I don't want to have more than one pedal one if I can help it. I've built a few Bazz Fuss pedals and they are all the same. I've added photos of the schematics I've used.

The Bazz Fuss schematic:
ABY switch schematic:
Bass rig:

[stallik]

I'm sure someone will pipe in with a better explanation but it seems to me that you might be hearing an impedance issue. If You switch on another pedal and that one contains a buffer you might not hear a problem so perhaps the solution might be to incorporate a buffer in the aby?

Alternatively, an active aby might be in order. I've built Geofx's hum free aby but that might need an upgrade to the isolation transformers to cope with the bass frequencies

[markfeltwell]

Thanks, I thought that a buffer might be the solution but putting it in the fuzz pedal instead as this doesn't happen on any other pedal I use. That being said I only use true bypass pedals in my rig.
Is there a way I can sort the impedance on the fuzz pedal?

[MrStab]

by ABY, do you mean your signal is always split, not just switched between? because you should really use an active splitter for that, regardless of the fuzz situation. i agree that a buffer could solve the volume issue. as for the interference issue (clean amp being dirty)... it could also be caused by impedance, if it's the strongest signal processor in that area and is introducing interference to the weaker, loaded-down other-side of the split. if both sides of the split are "healthy" (low impedance) then they're less likely to bother each other.

[robdean]

'True bypass' can be a great solution to certain specific problems, but so can buffering. Passive AB switching is notorious for causing problems in unbuffered signal paths, especially if there is a high gain pedal involved. Ironically, many fuzz circuits need to be placed early in the signal chain as they require unbuffered input. If it were me, I'd test the fuzz to see if it clearly craps out with a buffered input. If it does not, I'd try buffering the ABY and listen to the result. If it sounds good, it is good. If you are listening with profound suspicion and are not entirely sure if it is quite as good, it is probably fine!

Your images are not showing in my Tapatalk app so I don't know if the unused output signal path of the ABY is being switched to earth. That's a passive measure that might help.

Buffers solve a lot of problems: I'd say they solve a lot more than they cause, but it comes down to careful choices in specific situations rather than buffered or unbuffered being 'better'.