TUTORIAL Fuzz Face and a Request From All of You
- Thread starter BuddytheReow
- Start date
Feral Feline
Well-known member
I came across a Face-Bender flavoured kit from Seeker Electric Effects.
Thought it would be fun to stick the Bender values on a switch, so I drew up a schematic; but then I had a question for you all, so I redid a simplified version of the schematic and made it as compact as I could while still being legible:
The question I have is about the BIAS pot. I originally had lug 1 tied to two (as above in Szukalski's post of the TRIMMED FACE), but examining the pics from the Seeker build-page, I noticed there seemed to be no trace to/from lug 1. So I revised the schematic, but only after searching online to see if that was a thing. I found but one schematic that featured this oddity of trace-routing, drawn by DoitFuzz over on DIYSB, in post-#14 by Antonis. Antonis suggests that Lug-3 is the one that's left hanging out in the open in this schematic, though there's nothing marked on it to indicate that.
Definitely Lug-3 is connected to Q2's collector in this instance:
I know I should breadboard it, but just wanted to see what people think; also maybe to vet my schem(s).
Should I deviate from the way it LOOKS to be, ie Lug-1 unconnected, or stick with tying Lug-1 to Lug-2 ?
I don't have the PCB to trace it properly, but I see no reason why Lug-1 shouldn't be connected to Lug-2.
Props to Seeker for this fun-looking little F-B variant.
Thought it would be fun to stick the Bender values on a switch, so I drew up a schematic; but then I had a question for you all, so I redid a simplified version of the schematic and made it as compact as I could while still being legible:
The question I have is about the BIAS pot. I originally had lug 1 tied to two (as above in Szukalski's post of the TRIMMED FACE), but examining the pics from the Seeker build-page, I noticed there seemed to be no trace to/from lug 1. So I revised the schematic, but only after searching online to see if that was a thing. I found but one schematic that featured this oddity of trace-routing, drawn by DoitFuzz over on DIYSB, in post-#14 by Antonis. Antonis suggests that Lug-3 is the one that's left hanging out in the open in this schematic, though there's nothing marked on it to indicate that.
Definitely Lug-3 is connected to Q2's collector in this instance:
I know I should breadboard it, but just wanted to see what people think; also maybe to vet my schem(s).
Should I deviate from the way it LOOKS to be, ie Lug-1 unconnected, or stick with tying Lug-1 to Lug-2 ?
I don't have the PCB to trace it properly, but I see no reason why Lug-1 shouldn't be connected to Lug-2.
Props to Seeker for this fun-looking little F-B variant.
darwin999
Well-known member
It makes no difference, both approaches are equivalent.
Consider the case where lugs 1 and 2 are soldered together. If the pot is turned a nonzero amount CW from zero, then all current will flow through lug 2 (and no current into the pot's resistive element thru lug 1). That's the only way the 2 lugs can stay at same voltage (remember, the lugs are soldered together), since there is finite resistance in the segment of the pot's resistive element between where lug 1 and lug 2 connect to it. Only when turned fully CCW, i.e., if lug 2 and lug 1 are connected at the same point on the pot's resistive element (i.e., for the case of an idealized pot*) will lug 1 carry any current - in this case, the two lugs would share the current.
* By idealized pot I mean that the resistance between lug 1 and lug 2 is zero when the pot is turned fully CCW. Many pots are non-ideal in this regard, in that there is some small resistance between 1 and 2 when fully CCW - in such case, for this situation, no current will flow thru lug 1.
Consider the case where lugs 1 and 2 are soldered together. If the pot is turned a nonzero amount CW from zero, then all current will flow through lug 2 (and no current into the pot's resistive element thru lug 1). That's the only way the 2 lugs can stay at same voltage (remember, the lugs are soldered together), since there is finite resistance in the segment of the pot's resistive element between where lug 1 and lug 2 connect to it. Only when turned fully CCW, i.e., if lug 2 and lug 1 are connected at the same point on the pot's resistive element (i.e., for the case of an idealized pot*) will lug 1 carry any current - in this case, the two lugs would share the current.
* By idealized pot I mean that the resistance between lug 1 and lug 2 is zero when the pot is turned fully CCW. Many pots are non-ideal in this regard, in that there is some small resistance between 1 and 2 when fully CCW - in such case, for this situation, no current will flow thru lug 1.
darwin999
Well-known member
Added comment: The one difference is with regard to noise pickup. Leaving lug 1 unconnected, floating in the breeze, is functionally a small antenna which can conceivably pickup RF noise. Soldering the 2 lugs together removes that possibility, and thus is better practice.
Feral Feline
Well-known member
Thank you Darwin999!
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