Circuit Topology - Blended Fuzz

[BuddytheReow]

BuddytheReow submitted a new resource:

Circuit Topology - Blended Fuzz - A 2-Stage Blended Fuzz Circuit

Another idea if you're looking to design your own circuit is a 2-stage blended fuzz. I will show the overall topology and an application.

View attachment 28037

Here, Stage 1 and Stage 2 look nearly identical. They are. The ONLY difference here is that there is a jumper between stage 1 and 2 going to a potentiometer. This potentiometer acts as a blend control between the two stages.

In my experience using this method it has its advantages and disadvantages. On the plus side...

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[andromedial_stoat]

2 part question:

If the blend pot in this topology is zeroing out on either side of the sweep, then wouldn't an additional resistor on both sides of the pot prevent 0 resistance from being achieved at "0" or "10"?

If these resistors were of different values, would the volume drop still occur, but just at a different point in the sweep?

 

[andare]

In the Fuzzrite, Q1c and Q2c are connected by a 47n cap. Don't know what that does but the Depth control, to my ears, gradually blends in Q2 without blending out Q1, which is why the gain keeps going up. Halfway through there's a volume drop. Apparently this is because the two stages are out of phase.

I would like to know what the resistors across the collectors and bases do to the transistors.

The Bazz Fuss has a diode in that position.

Is it a way to increase the voltage that hits the base? If so, would smaller resistors increase the gain?

 

[xefned]

Could an M/N taper pot help cure the volume drop in the center position?

There's an interesting crowdsourcing of knowledge on the blend pot over at TalkBass, which uses a dual-gang M/N taper pot and a couple of cut traces. It led to the Ultimate No-load Ungrounded Blend Pot. Might be useful in this application. I dunno.

 

[andare]

Could an M/N taper pot help cure the volume drop in the center position?

There's an interesting crowdsourcing of knowledge on the blend pot over at TalkBass, which uses a dual-gang M/N taper pot and a couple of cut traces. It led to the Ultimate No-load Ungrounded Blend Pot. Might be useful in this application. I dunno.

A rev log pot cures that. Apparently the original germanium version used a C350K pot. I can't tell the difference with 500k so I use the latter.

 

[jwin615]

It's early so I'm not really clicking yet but, isn't the blend pot in this case blending between an inverted and non-infected signal?

 

[BuddytheReow]

Yes. When the blend knob is not 100% in either direction there is a volume drop because of that. It does make some interesting tones