Third world potentiometers #124 build

[67plexi]

After all my voltages dialed in
I rewired the preamp to high plate. The Alpha Potentiometers are the weak link in the circuit
I used alpha in a build a few years ago with poor sound results replaced with 2 watt mil spec PEC.
I ordered a set of 2 watt PEC last night this should get rid of the slight fuzziness.
In this photo you can see the difference in quality A/B pot and a alpha Just look at the wiper.

Steve.

[bluesfendermanblues]

Alpha pot sound must be dye to the cold dry Alaska air

[David Root]

I can't make out much from the pic. Please elaborate, I've never taken 'em apart myself.

[67plexi]

The alpha pot is sloppy and loose in the bore and makes poor contact the wiper is about .005”
On the A/B pot no slop and the wiper is .250” thick smooth and solid.
My oscilloscope tracked noise to the alpha potentiometers and import resistors I replaced the resistors with IRC’s. Yes I followed the heard on the cheap potentiometers no offence but shame on me.

Steve.

[talbany]

Steve
Thanks for all the info.. The more I move away from the Alpha's the better my amps sound IMO..

Tony

[Structo]

Great, another thing to worry about....

[David Root]

Thanx Steve & Tony. I am currently cramming a 50W #13 ODS w/D'lator into a BF Princeton reverb chassis using a previously molested '67 SF Bassman AB165 donor amp.

I don't have enough original pots in the AB165 and had been going to use new Bourns 1/2W import pots for the rest as I don't think I can get PECs or old Allen Bradley 2Ws to fit in the Princeton front apron (it's sloped and not very deep).

I think I'll revisit that decision, unless someone knows of a source for old CTS/Centralab 1/2W pots. I have some 500Ks and 2Ks of those from the '60s and '70s but need other values.