1K Fuzz's pot to 500R: correct way doubt!

[Plexi]

We can see the hated/ineficient 1K pot in many classic Fuzz's.
Mainly, in the well-known Fuzz Face.

Time ago, I build a FF with the middle option: now I'm in doubt with it...
As I know, the three ways have a different action.

Assuming the resistor is ~500R: I whant to get the last 50% of the normal 1K pot.
Anyone can explain which would be the correct one?

[Phoenix]

The first arrangement will give you the range of 1-5 on the standard 1k control.
The second will give you 5-10.
The last will change the bias point and increase the gain slightly, but give you a similar fuzz range overall (ie: 1-10).

Oh, and as drawn that is for an NPN fuzz (electrolytic backwards for PNP fuzz).

[Plexi]

Thanks Phoenix!
I was/am in the right path :-)

Sure..I forgot to clarify: the violence of the high gain silicon NPN make that potentiometer worst.

[anotherjim]

Plexi, have you tried Si power transistors. Big cases and live parts to insulate usually, but lower Hfe. What about the "medium power" ones in TO-39 cans like 2n3053 or BFY50? Hfe of some can be as low as 30-50. T0-39 case is not that much larger than small signal transistors.

[Plexi]

Let me check! Time ago I found a couple of transistors like you describe.
I remember the datasheet says that support high amount of voltage (>250v) and ~40hfe

[Plexi]

Found it!
It's the KSP92: hfe ~40, but PNP

I'll try the one you say.

[GGBB]

The first arrangement will give you the range of 1-5 on the standard 1k control.
The second will give you 5-10.

Only as 0-10 apply to a linear pot, so we'd have to know what a "normal" fuzz pot is to the OP. The "proper" pot to use in a fuzz face is a reverse-log pot, so if we apply the circuits using one of those (10% taper to be precise), the first arrangement gives you 0-1, and the second arrangement 1-10, since - in theory - a 10% reverse log pot has the mid point of its resistance at 10% rotation or "1".

I wasn't aware that the 1k reverse-log fuzz pot was hated or inefficient - but the linear variety certainly is inefficient. If even the C1k isn't doing it for you, then although the theory of all this is simple, in practice this is more tricky than it looks because of the reverse-log taper factor and the fact that standard pedal pots lower than 500R are scarce - especially the reverse-log variety. The first arrangement is fine if you only want low fuzz. For only high fuzz sounds, the second arrangement would "feel" worse with a B500R pot than would the standard setup with a C1k pot, so you'd need to be sure to find a C500R pot and even then it doesn't improve much.

There is another alternative however which also isn't as ideal as say a C100R pot in series with a 910R resistor, but will probably work better than the second arrangement with a B500R:

In parallel with the 1k resistor, have the C1k pot in series with the cap with pot lugs 1 and 2 jumpered. Even better if you can find a C500R pot. This gives you 1k resistance to DC, and 500R (1k || 1k) or 333R (500R || 1k) to AC/fuzz. By adding a resistor in parallel with the fuzz pot you can bring the fuzz resistance down lower, but beware that this also flattens out the pot taper so the "feel" is adversely affected - the lower you go the flatter the taper.