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|previous: MHelin ||View Thread|
|3/12/1998 7:09 AM|
|R.G.||Re: Fuzz Face for the people!|
>...Not all PU's like FF's low input impedance. If
>anybody ever builds a FF or designs a PCB for it, >it would be better to put a 100k preset there for >Q1 collector resistor
There is a PCB layout for the basic FF available at GEO as a toner package.
The more common solution to the low FF input impedance is to put a series resistor in front of it all, like the 50K pot in the "Fuller mods" schematic in my "Technology of the Fuzz Face" paper.
I have recently completed a new PCB layout I call the Omni-Face, which is a single board that can be used to build any one of the variants on the basic
FF circuit. This includes an on-board trimpot position for the input pot, which can also be used to wire in a panel mount pot for this like the '69 pedal.
Changing the collector resistor not only changes the bias point, but also changes the open loop gain on the first transistor. Maybe good, maybe bad, depending on the sound you like.
The ECG and NTE substitutes are VERY rough substitutes, and the 102A and 158 are used for every PNP germanium device. Some of them can sound good, but you have to select and/or measure them all. There is a wide variation of gain and characteristics on these devices; I think that they are actually several different original types, not a single type.
EDN recently published an idea for using one power transistor and a couple of simple IC's to make a preset temperature controller that can be glued to a single device. That might fit the temperature control need.