Bought a Variac - what do I do with it?

The_Nuge

Senior Member
Joined
Dec 12, 2010
Messages
1,958
Reaction score
1,479
Hi!
I bought a Variac, well the German equivalent of one, the other day to use when testing amps and stuff. Big old 0-250V 10A thing, probably 30-40 years old, but works as intended.
Everyone has heard of Mr. Van Halen using one to get his tone - what's the trick to doing stuff like that? Anything one shouldn't do?

Cheers

Es
variac.jpg
 

Dblgun

Junior Member
Joined
Sep 8, 2019
Messages
24
Reaction score
28
Yeah, don't do it. EVH used a variac to drop the voltage to his amp to around 90vac which ultimatley consumed a large number of components. Depending on your wall voltage you may be able to make use of the variac to drop voltage to your amp to the 117vac that most older amps were designed for but if your amp is a modern unit it will be designed to run on the 121-123vac found in most circuits today. Variacs are generally used for diagnostics and repair of electrical components but not commonly used for normal operation.
 

Gtarzan81

Senior Member
Joined
Jul 19, 2010
Messages
8,178
Reaction score
23,882
1. Old US amps were designed around 110 instead of the 120 we have now.
2. You can go down a bit in voltage but do NOT go up.
3. The EVH thing dropping to 90 volts was y because he ran the heads wide open. Supposedly dropping the voltage a bit helped get the same sound and take it a bit easier on components.
4. Some plexi clones have a switch to do this feature internally. See Metropolis.
 

Soul Tramp

Speaker Snob
V.I.P. Member
Joined
Jul 19, 2012
Messages
7,765
Reaction score
19,148
I rarely use my Variac. It's comforting to have on hand, but not terribly useful. I think the last few times I used it was to test/measure output transformers.


Variac.jpg
 

Pappy58

Senior Member
Joined
Dec 2, 2014
Messages
3,795
Reaction score
8,040
I rarely use my Variac. It's comforting to have on hand, but not terribly useful. I think the last few times I used it was to test/measure output transformers.


View attachment 424828
Thats a nice one.... I have a cheap chinese unit but it works good. It's used when I powering up a new build the first time, or firing up a suspect piece which is blowing fuses or is a complete unknown. In building some tweed clones, I have noticed that most PT's have secondary voltages 10-20% higher than spec at 125vac in. Dialing it back to 100vac puts them right in spec, and also changes the tone. So imo there is some value in using one for a vintage or vintage clone amp.
 

The_Nuge

Senior Member
Joined
Dec 12, 2010
Messages
1,958
Reaction score
1,479
I've used mine while fixing my Boogie MK IV - it's useful for adjusting the mains voltage to spec so that the internal voltages can be accurately compared to those noted on the circuit diagram!
 

ErictheRed

Senior Member
Joined
Dec 8, 2009
Messages
5,917
Reaction score
7,425
They aren't toys, I don't see what purpose they would serve it you aren't doing real electrical work. It isn't going to change the tone of your amps unless you run it at such extremes that risk damaging components. It's also potentially dangerous if you don't understand what you're doing. The fact that you created this thread makes me a little concerned for your safety, to be honest.
 

The_Nuge

Senior Member
Joined
Dec 12, 2010
Messages
1,958
Reaction score
1,479
They aren't toys, I don't see what purpose they would serve it you aren't doing real electrical work. It isn't going to change the tone of your amps unless you run it at such extremes that risk damaging components. It's also potentially dangerous if you don't understand what you're doing. The fact that you created this thread makes me a little concerned for your safety, to be honest.
Well I've managed to build a Dumble and a Soldano clone, and also do most of maintenance on my amps, without killing myself or burning the house down...
 

The_Nuge

Senior Member
Joined
Dec 12, 2010
Messages
1,958
Reaction score
1,479
1. Old US amps were designed around 110 instead of the 120 we have now.
2. You can go down a bit in voltage but do NOT go up.
3. The EVH thing dropping to 90 volts was y because he ran the heads wide open. Supposedly dropping the voltage a bit helped get the same sound and take it a bit easier on components.
4. Some plexi clones have a switch to do this feature internally. See Metropolis.
The Mesa MK IV I bought uses a different tap on the PT to lower the overall voltage of the amp as far as I can tell (all the voltages I've measured drop when the amp is in "tweed" mode) - I actually prefer the sound of it in that mode!
 

ErictheRed

Senior Member
Joined
Dec 8, 2009
Messages
5,917
Reaction score
7,425
Well I've managed to build a Dumble and a Soldano clone, and also do most of maintenance on my amps, without killing myself or burning the house down...
Okay cool, have fun with it. Let us know how it goes if you start messing around.
 

RAG7890

Senior Member
Joined
Jul 11, 2010
Messages
17,525
Reaction score
31,668
I must admit I thought of buying a Variac to set & control the Voltage at 240V but our supply is pretty good here.

The other recent application was to use it to run a US Amp at 120V but it doesn't help overcome the Frequency issue & getting a Variac to run 240V / 50Hz down to 120V / 60Hz is painfully expensive from what I can find.

Changing the PT is was easier but for this particular Amp I'm not sure it is possible & the builder is painfully opinionated & not interested.

:cheers2:
 

jojo

Senior Member
Joined
Sep 26, 2009
Messages
1,584
Reaction score
1,037
1. Old US amps were designed around 110 instead of the 120 we have now.
2. You can go down a bit in voltage but do NOT go up.
3. The EVH thing dropping to 90 volts was y because he ran the heads wide open. Supposedly dropping the voltage a bit helped get the same sound and take it a bit easier on components.
4. Some plexi clones have a switch to do this feature internally. See Metropolis.
Yes and old Orange and Matamps run best at around 108 volts .My amp tech told me this. Many people have issues with theirs because they weren’t made for modern wall voltages . Since I bought a variable power transformer and started stepping the older orange Amps down to 108 volts I’ve had zero issues with them.
 

NHTom

Senior Member
Joined
Jun 7, 2014
Messages
739
Reaction score
967
Johnny Wickersham of Social Distortion runs them on his Satellite amps......Probably some interviews, etc where it's discussed with him,

NHTom
 

irocdave12

Senior Member
Joined
Jun 21, 2011
Messages
3,010
Reaction score
4,108
This is what I do with mine when I’m not using it to dial in juicy fat brown sounds from my amp collection. Needless to say the neighborhood punks quickly disclosed the location of my missing garden gnomes. There lots of other household uses too.
 


Latest Threads



Top