Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ncusack on March 07, 2014, 01:21:35 pm

Title: Potentiometer Wattage Rating Help
Post by: ncusack on March 07, 2014, 01:21:35 pm
Hello everyone,

I'm wondering about the use of 16mm Pots in tube amps. Has anyone done this and is it a safe practice? I am wondering specifically about the TT Electronics P160 series of pots. The Log pots appear to be rated for 0.1W and the Linear are 0.2W and the voltage rating is 200VAC which im assuming is RMS so I think that's about 460VDC.

Let me know your thoughts and experiences.

Cheers,

Neill
Title: Re: Potentiometer Wattage Rating Help
Post by: HotBluePlates on March 07, 2014, 04:49:13 pm
What do you want the pots to do?

Said another way, what amp and in what control positions do you want to use these pots?
Title: Re: Potentiometer Wattage Rating Help
Post by: ncusack on March 07, 2014, 06:07:21 pm
Im looking at building something close to Geezers Little wing project with 6bm8 tubes. I'm just curious if they could be used for all positions, Gain control, Tone Stack and pressence in that setup. B+ should be around 320DC
Title: Re: Potentiometer Wattage Rating Help
Post by: HotBluePlates on March 07, 2014, 06:48:32 pm
Im looking at building something close to Geezers Little wing ... I'm just curious if they could be used for all positions, Gain control, Tone Stack and pressence in that setup. ...

I'm trying to get you thinking about this yourself.

Gain, Bass Treble, Volume and Reverb controls all have a coupling cap preceding them, so the d.c. voltage rating is immaterial.

Imagine you have 100vac across a 1MΩ pot. 100v/1MΩ = 0.1mA. 100v * 0.1mA = 0.01w. So it looks like the power rating is also immaterial, with respect to even unlikely a.c. signals.

The spec of "100mV max Sliding Noise" seemed a little much, but I'll admit not being familiar with that spec for other pots.

Seems like you should have no problem using them.
Title: Re: Potentiometer Wattage Rating Help
Post by: tubenit on March 07, 2014, 08:42:16 pm
I've used the mini-pots for yrs on numerous amps. No issues yet.

With respect, Tubenit