Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => AmpTools/Tech Tips => Topic started by: GuitarPilot65 on February 15, 2012, 02:21:07 pm

Title: Variac for both AC & DC use?
Post by: GuitarPilot65 on February 15, 2012, 02:21:07 pm

Is there such an animal out there?

Title: Re: Variac for both AC & DC use?
Post by: Willabe on February 15, 2012, 02:28:19 pm

Why do you need that?

If you have a DC sup. just use the variac to feed the primary of the PT or use a variable DC sup.


                Brad   

Title: Re: Variac for both AC & DC use?
Post by: FYL on February 15, 2012, 02:54:40 pm

Quote

Is there such an animal out there?

A Variac is an auto-transformer and only works with AC (well, it also attenuates DC because of it's winding resistance but not significantly).

(http://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/Pot1.jpg/800px-Pot1.jpg)
(From Wikipedia)

The DC version is a rheostat, a really big wire-wound potentiometer.

Title: Re: Variac for both AC & DC use?
Post by: John on February 15, 2012, 05:06:29 pm

When I was looking for a variable AC supply, I ran across lots of the DC as well, and they were pretty cheap. But don't recall seeing one that did both.

Title: Re: Variac for both AC & DC use?
Post by: jjasilli on February 15, 2012, 06:48:14 pm

Yes, you can have a variable DC power supply, but it's not a variac.  A variac is called a variac because it is used to VARy AC.