Please give me the crash course on a Variac

[toneman335]

I have heard about but don't understand how and what a Variac does to a amp and its tone. Can someone explain this to me for example:

. What does it do the amp and its tone?

. I read the Van Halen used this device. What effect did it have for him?

. Do you have to use a special Variac or are they all the same?

. What is an expected cost of one?

Please include any other information that you think is important.

[SatelliteAmps]

Don't believe everything you read about what Van Halen did and did not use.

A variac is a device used to control the AC voltage going into a particular device (usually from about 0-120% of what is put into it, meaning you can hit about 140vac with basic wall voltage). There are different models that can handle more or less current. Expected cost is at least about $150 for a good one.

The idea is that you can drop the wall voltage to starve the amps power supply, trying to get better tone. Some people swear by them. Personally, I don't like them. It's too easy for people to "accidentally" turn them up, and then fry their amplifiers. The sound benefit is arguable. If you want to go this route, a browner or bucking transformer is cheaper, easier, and safer to use. (They are hard wired to drop a certain amount all the time, rather than a variable drop).

[WesKuhnley]

Many people use a Variac, browner, or bucking transformer to protect their high-dollar vintage amps from today's higher mains voltages.
I'd agree, a Variac is unnecessary for the common guitar player, a bucking transformer is cheaper and less likely to cause an issue.

[Prairie Dawg]

Many people use a Variac, browner, or bucking transformer to protect their high-dollar vintage amps from today's higher mains voltages.
I'd agree, a Variac is unnecessary for the common guitar player, a bucking transformer is cheaper and less likely to cause an issue.

The problem with variacs is like the problem with an adjustable bias. Anything that can be misadjusted will be misadjusted sooner or later.

[zzmoore]

Reread the post by Satellite Amps. He tends to have a no-nonsense view of all things magical and mythical in the amp world.
Variac (variable AC) is a trade name. There is no tool called a variac, it is a variable transformer. It's like saying Kleenex, or Skill Saw. They are facial tissues, and curricular saws. There is no tool called a skill saw.
The numbers on a "variac" are meaningless, you will need to monitor the device with a DMM. As mentioned already, especially in a live setting, people love to turn knobs....:rolleyes:
I think you would be better off buying a amp that you think sounds good at 120 volts; the prevalent voltage from a wall (assuming USA). Then, if you worry about such things, you can buy a auto-transformer. Theoretically it will maintain your 120, as long as the wall shows it a constant variable of 80-140 volts.
That is my opinion. I tend to be in the minority a lot, but one gets use to it. ;)
Good Luck

[SatelliteAmps]

That is my opinion. I tend to be in the minority a lot, but one gets use to it. ;)
Good Luck



I like to think of it more as being a part of the silent majority.

[59Vampire]

I have an old variac that I use for turnoing on old amps that havenbeen used for awhile. I turned on an old danelectro that "I hadnt plugged in for 15 years and started slowly over the course of 48 hours,overkill, i know, and it sounds great at full voltage original caps and all.

I always say that if I want to screw with my tone, i will turn the amp ON

[Prairie Dawg]

There is no tool called a skill saw.


Not to be picky, but there's this.

http://www.skiltools.com/en/AllTools/Category/default.html?cid=45

Of course I quite understand your point. People often attribute mythical powers to the variac-er, variable transformer-and it they understood what it did, they'd have a better idea of its uses.

And it does have its uses, one of which is bringing up line voltage slowly.

[AR-305]

Mine lives on my repair bench. I use it as aforementioned to slowly bring up old amps and certain new repairs. My mesa boogie mark iv has a dual primary pwr tranny and a "tweed" setting on the pwr switch for just that purpose. The amp see's about 30% lower voltage in tweed. Most of the newer mesa amps have this feature.

[SatelliteAmps]

Not to be picky, but there's this.

http://www.skiltools.com/en/AllTools/Category/default.html?cid=45




I think that was the point. SkilSaw is a trademark name, not an actual tool. The SkilSaw company sells circular saws under their own brand name.

[terminal]

problem with using a variac for anything other than test and repair: if you run the primary voltage at a reduced voltage, then you run the filaments at a lower voltage, and tube life is shortened.

[Prairie Dawg]

I think that was the point. SkilSaw is a trademark name, not an actual tool. The SkilSaw company sells circular saws under their own brand name.

That which we call a rose by any other name and all that. I'd venture to speculate that it is just one of a number of things that had a commercial name at one time that has entered the lexicon and for all intents and purposes has become synonymous with the thing itself .

Saran wrap, anyone? Bakelite? Catalin? Hydramatic? Delco plant? Kool aid? Realtor?

:banana I like this little guy.

[Prairie Dawg]

problem with using a variac for anything other than test and repair: if you run the primary voltage at a reduced voltage, then you run the filaments at a lower voltage, and tube life is shortened.

Not to mention that your tubes won't be doing what they're supposed to be doing if the filament voltage is artificially lowered.

[tapeup]

I like the valuable info I learn from all of you on TGP.

As a result of bands and gigs coming and going in my life, some of my amps don't get used for very long periods of time, sometimes not being powered up for years. I've been wanting to start playing a couple of these amps again but don't want to harm any of the amp's components, as I have heard amps that have been shelved and unpowered for years should be gradually brought up to proper voltage, as one or two of you mentioned above. Is this correct? Should I obtain a variac to do this to my doormant amps, or is it fine to power them up and start using them after at least three or four years of inactivity? Thanks for the help guys!

[SatelliteAmps]

Good question. Some people will swear by this idea. A variac is the safer way to bring amps up to speed that haven't been played for over a year. It may not save anything that is already failing, but it does reduce the initial stress on the parts.

With other peoples amps, I am more cautious and try to go the variac route. With my own personal stuff, I just go straight into the wall. I haven't had any bad experiences either way, but that might just be dumb luck.

[Prairie Dawg]

Good question. Some people will swear by this idea. A variac is the safer way to bring amps up to speed that haven't been played for over a year. It may not save anything that is already failing, but it does reduce the initial stress on the parts.

With other peoples amps, I am more cautious and try to go the variac route. With my own personal stuff, I just go straight into the wall. I haven't had any bad experiences either way, but that might just be dumb luck.

True. I use one myself at times but I'm something of the 'no guts, no glory' school of thought.

Question though. If you've got a tube rectifier, my experience has been that the rectifier tube doesn't actually do anything until you get the line voltage up to about 65-70v and then you get B+ at once. Probably means that in order to get that good slow buildup/reforming you could drop in a solid state rectifier just for that purpose.

[dtube]

True. I use one myself at times but I'm something of the 'no guts, no glory' school of thought.

Question though. If you've got a tube rectifier, my experience has been that the rectifier tube doesn't actually do anything until you get the line voltage up to about 65-70v and then you get B+ at once. Probably means that in order to get that good slow buildup/reforming you could drop in a solid state rectifier just for that purpose.

I always power-up amps with new caps or old amps that haven't been on for awhile with the Variac. I pull all the tubes and use a SS plug-in recto; then watch the Ep on a meter so that I don't over-rate the caps. Once everything checks out, then it gets tubes and a load and powered-up directly off the wall. Works for me; YMMV.
-Darren

[MajorDude]

Ooops...I turned on a dormant Carvin Valvemaster today prior to reading this thread. I think I might have messed up the amp, but I'm hoping I didn't. When I turned it on, I hear crackles, pop and volume cutting in and out. It seemed to go distorted to clean, and vice versa (drive channel). I looked at the power tubes (6LCs), and nothing seems to be out of ordinary. Had it on for about 2-3 minutes.

:hideAny ideas? Take it to a tech or try it again?

[JlMMY]

The last time my amp had crackles and pop it was tubes. I was so interested in the Variac topic that I bought one. Needed it to re-cap my amp anyway. Figured the cost of it was justified ($75 / ebay) since I got the cap job for free. I couldn't help myself so I started Googling for answers and found some college kid that wrote an essay on the lower voltages. He discovered something about even order harmonics? It was all Greek to me. Anyway, I lowered my 1972' Marshall Super Lead to 90, 100, 117v and 120v. I could hear a difference for sure. I would say the lower voltage gave you way more saturation and it was so much easier to play harmonics. I have a master volume on my SL. I would rather have a master volume than use a Attenuator and cannot always run it on 10. With both channels jumped and dimed the sound is killer. I would say if you have an extra $100 than go shopping on ebay and get one. It's all good fun.