colorsound one knob fuzz gain control

Started by zhx, August 13, 2008, 04:39:56 AM

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zhx

I built the One Knob ages ago, and really like it. I was wondering though, if it was possible to add a gain control.
http://fuzzcentral.ssguitar.com/schematics/oneknobfuzz.gif

My first tought was to add a 1K pot from the BC109 to ground.
But maybe a fuzz face type solution would be better: put the pot at the 1K / 10 uf to ground.
like this:
http://fuzzcentral.ssguitar.com/fuzzface/fuzzfacenpnschematic.gif

Any opinions/ideas/success in this kind of project?
Thx!

foxfire

i would start with the fuzz face method.
rylan

slacker

I'd go for the fuzz face method or try the axis face style smooth control http://fuzzcentral.ssguitar.com/axisface.php this has the same effect as lowering the guitar's volume pot and cleans up the gain nicely.

zhx

Ok, I tried the fuzz face gain ctrl, and it didn't work too good. The fuzz cleans up nicely with guitar volume knob, so I'll goo with the Axis Face method...


mr.adambeck

Okay, so I'm building the one knob using the dragonfly layout:



From what I understood, in order to create a gain control, I simply replace the 1k resistor with a 1k pot.  So I wired the two solder points of the 1k resistor to my breadboard to try out the pot, but it's not really changing the gain.  What this ends up doing is creating a gated effect as I tape off the pot, and not creating less gain.  Any ideas as to what a proper gain control would be?  I'm liking the way it cleans up with my input volume, so I may just end up putting an audio taper at the front of the circuit, but I'd prefer to have a proper gain control if possible.  Thanks.

Nitefly182

Quote from: mr.adambeck on July 19, 2009, 08:30:04 PM
Okay, so I'm building the one knob using the dragonfly layout:



From what I understood, in order to create a gain control, I simply replace the 1k resistor with a 1k pot.  So I wired the two solder points of the 1k resistor to my breadboard to try out the pot, but it's not really changing the gain.  What this ends up doing is creating a gated effect as I tape off the pot, and not creating less gain.  Any ideas as to what a proper gain control would be?  I'm liking the way it cleans up with my input volume, so I may just end up putting an audio taper at the front of the circuit, but I'd prefer to have a proper gain control if possible.  Thanks.

Most fuzz faces dont sound good without the gain pot dimed. That might be what you're hearing.

SonicVI

Quote from: mr.adambeck on July 19, 2009, 08:30:04 PM
Okay, so I'm building the one knob using the dragonfly layout:



From what I understood, in order to create a gain control, I simply replace the 1k resistor with a 1k pot.  So I wired the two solder points of the 1k resistor to my breadboard to try out the pot, but it's not really changing the gain.  What this ends up doing is creating a gated effect as I tape off the pot, and not creating less gain.  Any ideas as to what a proper gain control would be?  I'm liking the way it cleans up with my input volume, so I may just end up putting an audio taper at the front of the circuit, but I'd prefer to have a proper gain control if possible.  Thanks.

You don't just simply replace the 1K resistor.  Look at a fuzz face schematic and see how the pot is wired. The outer lugs would replace the resistor and the wiper would connect to the 10uF cap. I suspect you may not have it wired correctly.

mr.adambeck

Quote from: SonicVI on July 19, 2009, 11:31:17 PM
You don't just simply replace the 1K resistor.  Look at a fuzz face schematic and see how the pot is wired. The outer lugs would replace the resistor and the wiper would connect to the 10uF cap. I suspect you may not have it wired correctly.

So if I make a trace cut between where the 1k resistor was and the cap, then connect the wiper to the board so that it's on the same strip as the + of the 10uf cap, it should work?  Is that what you are saying?

slacker

You can't cut that track because then you'll break the connection between the bottom of the 150k resistor and the jumper to the right of the 10u cap.
I'd do it like this.
Remove the 1k resistor and the 10u cap.
Connect one of the outer lugs of the pot to the bottom row of the board, that's ground. Connect the other outer lug to the second row from the bottom, the one where the positive end of the 10u cap was.
Then cut the track on the 3rd row up just to the right of the emitter of Q1, above where the positive end of the 10u cap was. Connect the 10u cap with positive end on the 3rd row to the right of the cut you just made and the other end to the bottom row. Connect the wiper of the pot to the right hand edge of the 3rd row.
That should do it :)

mr.adambeck

Slacker-- Thanks, it worked!  However, the fuzz loses top end and becomes muffled sounding as the gain is reduced, where as it retains it's tone if I turn down the volume knob, so I've decided to use an Audio Taper as the gain control instead.  One thing I did that I like is that I put the 1k resistor on one side of a pot, and a higher value, much grittier sounding resistor on the other, so I now can make the fuzz go from it's smooth sounding normal state to a sputtery, gritty fuzz with the turn of a knob.  Sweet!