Mounting a locking bias pot..

[leadfootdriver]

I was thinking about getting some locking PEC pots for bias so I don't have to pull my amp from the chassis everytime I need to bias up..

Should I worry about capacitive/electrical interferance where the the wiring is concerned? I might need to extend the wiring to reach an open spot on the chassis so I can drill a hole to mount the pot.

Any insight would be great!

[soundguruman]

No, for a power supply b minus, it usually won't cause interference.
IF the bias DC has some ripple, and it's very close to a preamp input,
there is some potential to amplify ripple in the audio path.
But some reasonable separation is maintained from the sensitive preamp inputs to avoid that.

Yeah, any time a power wire has a filter capacitor, it's pretty dead interference wise...
the capacitor will kill any spurious signal on that wire. It's just a flat line.

The good thing is to avoid making the power supply wire parallel with the audio path wires.
They can cross, but should not be side by side parallel.

PEC pots? GOOD choice. I wish more amps had them. They are probably about the best ones.
My next build, 2204 in a Hot Rod Deluxe chassis,
I'm going to use all PEC special developed audio tapers. Costs more, but worth it to me.

[leadfootdriver]

Thanks for the info!

I have sourced the locking pots from Digikey.

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[tedmich]

those are nice PEC pots, sometimes I want them a bit smaller and some old Clarostats fit the bill.

Angela's Instruments has these on the Ebay...but there is a price premium!
Clarostat 389 L Series 25K Ohm Linear Taper Locking Mini Pot N O S | eBay

Nebraska Surplus has some of the 1/2" RV6 style pots,

PEC brand 25k linear $3
http://www.surplussales.com/Potentio...SlotAdj-4.html

[leadfootdriver]

Whoa locking pot city! lol Panel Bushing Mount - Slot Adjust, Single Turn - 10k to 99.9k Ohm

[Pedro Vecino]

This is another possibility. Ideal to use different tube sets or different degrees.

[tedmich]

Very nice Pedro, those 10 turn cam locking knobs are very beautiful and can be added to a variety of pots, pretty expensive though! A lot of old high end lab and test equipment had these units.

[tedmich]

as an aside, here is an old piece of locking pot conversion hardware made by Clarostat, I believe.

The top thread is the same as the bottom, only tapered so this nut fit on a standard 1/4" shaft pot and the thin mounting nut would fit up top to lock the shaft, once the set screw was tightened enough to assure the whole unit wouldn't rotate! I got a couple of these when I bought about 20 old sealed RV4 pots from my local surplus guy, Bob at R5D3. They were probably from Tektronix, and much of Bob's stuff is.