Pot and Kettle Sputtering

[ddavis20341]

I finished a Pot and Kettle knob build a little bit ago, and have been having some problems with it. It's very sputtery, sort of like a gated fuzz - seems like the biasing must be off somewhere. All of the knobs/switches otherwise function as they should.

I'm sure the problem is probably the through-hole 5457's, although I do believe I got them from PedalHacker or Smallbear or some other reasonably reputable source.

In case it isn't, would someone mind interpreting what these voltages mean so I can check them against what I'm reading off my 5457's? I've tried researching it and haven't been able to wrap my head around it (compared to other biasing guides which just list the positions and values). I'm also color blind, which makes checking resistor bands (to see if I messed up and put in the wrong value somewhere) a complete pain in the butt.

Here's a pic of the build and build doc in question:

 

[Alan W]

This is not a good answer, but the Q1 and Q2 specs are what I would get when I test a transistor in my cute little British (sorry, I am blanking on company name…) tester, they’re not directly readable as to what a typical biasing of a device would me. I think, those specs are given as an idea of what an ideal Q would be in that circuit position.

I’m also thinking though, that someone who groks what goes on in circuits, can do a few equations and make those specs suggest a bias point, but that’s not me.

And another uncertainty that I have is that these are being used in a way in the circuit that makes biasing them less critical. In general, @Robert uses trim pots pretty much whenever he has a bias dependent situation.

 

[Alan W]

That said, I’m pretty sure I have a nice working one downstairs. If you want, I can take some measurements for you. It’s one of my favorite, say handful, of clean drives. What voltage do you run it at?

 

[ddavis20341]

I appreciate the answer! I'm in the same boat regarding circuitry - tried to do some equations to figure it out, and got answers that I knew weren't right.

I suspect you're totally right about trim pots - I know they can sometimes add noise unnecessarily when used with JFETs too.

Some measurements would be great! I actually have an original around somewhere - not the Pro Mod, just the standard V2. It's also a favorite, but the non-pro version tended to get lost in a mix, hence the desire to build one of these. I ran it at 9V when I was testing it out.