Variac

Discussion in 'Amp Tech Center' started by muudcat, Oct 23, 2019.

  1. muudcat

    muudcat Tele-Holic Silver Supporter

    Posts:
    821
    Joined:
    Jan 3, 2010
    Location:
    Fountain City, Wi
    Has anyone used a variable auto transformer or variac? I read an interesting article by John Bolinger in Premier Guitar about using one, especially for vintage amps and I have one, a late 50's Supro. I've plugged it into modern current without a problem but was wonder what the consensus is about doing this without lowering the voltage a bit to 115v
     
  2. gusfinley

    gusfinley Tele-Holic

    Posts:
    883
    Joined:
    Jun 11, 2014
    Location:
    SLC, UT
    The danger with running vintage tube amps with modern voltages is all about the power transformer. If it was meant to run from 115VAC and you plug it into a 123VAC mains then two things happen:

    1) Heaters run at a higher voltage - If you would get 6.3VAC with 110VAC, 123VAC would give you 7VAC and you are getting out of spec on the heater were they will wear faster.

    2) High Voltage DC increases - This could be much more dramatic. If you at 110VAC your 300-0-300 Secondary through solid state rectifier would give you around 420VDC. If you feed this 123VAC then your secondary becomes 335-0-335 and your High Voltage DC will increase to 470VDC - a 50VDC increase!

    If you own a vintage amp that is of value, then it is a good idea to run it at its intended voltages. There are two economical ways to do this:

    1 - Variac - If I were to run a variac I would set it based on the filament voltages - right at 6.3VAC

    2- Stepped Voltage reducer - The are usually a 6.3 or 12.6 V transformer wire as an autotransformer that will drop your voltage a given amount. You can't fine tune these, but you can select the best setting. You can make your own ( there are several threads about this ) or you can buy expensive variations.

    The non-ecomical way is a voltage regulator that will give you whatever power you want, but I would only buy one of those if I had a lot of vintage gear and a lot of money to throw around.
     
    uriah1 likes this.
  3. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

    Age:
    60
    Posts:
    17,252
    Joined:
    Mar 2, 2010
    Location:
    Maine
    Seems like a good idea, I have lots of vintage amps and also a variac, but I've never chosen to get that complicated.
    Note that a variac has a knob on top and if you bump it or somebody fiddles with it you end up with some new voltage.
    I was shopping for a vintage voltmeter to mount on the variac rather than using one of my multimeters, but never chose one.
    From what I read the numbers on a variac dial represent the output voltage, but if the wall voltage varies wouldn't the variac output also vary?

    Good luck determining some action or non action!
     
    Owenmoney likes this.
  4. schmee

    schmee Poster Extraordinaire

    Posts:
    7,456
    Joined:
    Jun 2, 2003
    Location:
    northwest
    I have a variac but never really use it. Too much complication to gig with. I'm building a "browner" (stepped voltage reducer) to reduce voltage as soon as I get another project off the bench.
    I had some trouble finding the recommended transformer at a reasonable price, so I bought 4! I'll probably be selling the spares soon, or I might just make kits to sell after I build the first unit.
     
  5. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

    Age:
    60
    Posts:
    17,252
    Joined:
    Mar 2, 2010
    Location:
    Maine
    Do you mean a browner to run amps at below spec voltage for a "brown sound"?
    Or to run your vintage amps at correct voltage to keep them in good health?

    I've remained mildly curious about the legend of EVH running his '67 Plexi 100 on a variac for the early albums and live work.
    Seems like some accept that he did while others don't believe it and chalk it up to Eddies tales of mythical pasts.
    I had the same Marshall, which was different from the '66 and the '68, and to my ear his sound is a sound that particular amp has no problem making at normal wall voltage.
    Of course when I used that amp in the '90s and when EVH used it in the '70s/ '80s the voltages may have been different from the '60s spec it was made for.
    It's pretty safe to say that in the '90s the wall voltage in Brooklyn was higher than in the '60s, so what I found was a "Brown Sound" at boosted wall voltage compared to design spec.
    That liquidy sustain, easy harmonics, clean dirt that could snarl with pick input; all happened at higher than spec voltage.
    So I have trouble believing EVH needed to lower the input voltage on that amp to get that performance.
    Could be wrong of course!

    OTOH I'd presume that running a vintage amp at too high a wall voltage would make the sound brighter and maybe stiffer.
    So a step down to correct voltage would brown the sound a bit I reckon!

    Thinking about the sound of my later 50 and 100w Marshalls I'd note that of several from '69 and '70, they all had a harsh bright tone and stayed clean nearly to full volume.
    That could be partly due to higher than spec voltage.

    Small vintage Fender (or Supro) amps are less likely to be too bright too clean, but they may be getting hurt by the voltage even as they sound great. Vintage Princeton PTs are already stressed and burn out.
    Vintage Supro amps are great but made with some pretty fragile parts, so would be worth c=some conservation efforts.
     
  6. uriah1

    uriah1 Telefied Ad Free Member

    Posts:
    20,469
    Joined:
    Feb 12, 2011
    Location:
    Around
    old ones like Eddies and new ones.
    and I think they are more now.
    Never had much luck those or attenuators
     

    Attached Files:

    • var1.JPG
      var1.JPG
      File size:
      40.3 KB
      Views:
      27
    • v2.JPG
      v2.JPG
      File size:
      47.3 KB
      Views:
      27
  7. schmee

    schmee Poster Extraordinaire

    Posts:
    7,456
    Joined:
    Jun 2, 2003
    Location:
    northwest
    -7% and -12% browner. Reduces line voltage by that amount. Been going to do it a long time. I may or may not use it. My old amps sound fantastic at way high plate voltage. (6V6's at 460 volts) But I do worry!
     
    telemnemonics likes this.
  8. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

    Age:
    60
    Posts:
    17,252
    Joined:
    Mar 2, 2010
    Location:
    Maine
    Yeah the term "brown" or "brown out" was in use regarding a drop in house wall voltage before it was used for guitar sound.
    Fender ran some very high voltages in the 6v6 amps and those are now even higher.
    I keep a supply of old stock 6v6 since they are fairly easy to find cheap on ebay, and are likely to hold up better at high voltage.

    I'm surprised we don't see more reference to using something like your browner running vintage Fender 6v6 amps?
    Everybody seems to have an attenuator so they can keep their non master amps near meltdown, but hardly anybody seems to run something to correct the voltage for vintage amps.
     
  9. schmee

    schmee Poster Extraordinaire

    Posts:
    7,456
    Joined:
    Jun 2, 2003
    Location:
    northwest
    The voltage reduction thing has been "threaded" a lot. Maybe google "Buckminster".
    I just use JJ's now. A fresh set of NOS RCA Blackplates took out the OT in my 65 BFDR one hour into a gig years ago. Been using JJ's ever since.
     
    telemnemonics likes this.
  10. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

    Age:
    60
    Posts:
    17,252
    Joined:
    Mar 2, 2010
    Location:
    Maine
    I've seen discussions of voltage reduction but it seems to be a small number of people making a large number of comments.

    Compared to attenuators that seem so common there are lots of users who buy amps that only distort at high volume, for the sole purpose of getting distortion at low volume with an attenuator. Makes little sense to me but to each their own!

    I like my non master amps at all volumes, but for low volume dirt I find a good tube amp with extra preamp gain and MV is generally better for that purpose. Or Muffs and Tone Benders into a clean amp!
    Again of course my taste is just IMHO.
     
  11. Cysquatch

    Cysquatch Tele-Meister

    Posts:
    392
    Joined:
    May 2, 2019
    Location:
    Grovetown, GA
    From everything I've read, Eddie didn't use it to get a special sound, it was a way to keep from blowing his head off with those amps. It's actually stated in the article the OP referenced:

    “I’d bought another Marshall amp, and I had no idea that it was actually a European model. I plugged it in, and I'm waiting for it to warm up and thinking, I got ripped off here, there’s no sound coming out! Pissed off, I came back an hour later to give it another shot. I’d left the amp on the whole time. I didn’t know it was set on 220, so when I turn my guitar on it sounds like a full-blown Marshall, all the way up, except really, really quiet. That was when I realized there was something going on with the voltage ... so I went down to a place in Pasadena and asked if there was some kind of industrial-size variable transformer that would let me adjust voltage, and they introduced me to the Variac. It's just a huge light dimmer. I plugged it into the amp and controlled the voltage from that. That became my volume knob. I would set the voltage depending on the size of the room we were playing, getting all that feedback at any volume.”

    https://www.premierguitar.com/artic...lowing-van-halen-on-a-quest-for-power-control
     
  12. 24 track

    24 track Doctor of Teleocity

    Posts:
    14,073
    Joined:
    Nov 6, 2014
    Location:
    kamloops bc
    schmee likes this.
  13. rolandson

    rolandson Tele-Meister

    Posts:
    306
    Joined:
    Jul 14, 2017
    Location:
    Cascadia
    I used one of these...
    [​IMG]
    ...when playing in unknown circumstances, in conjunction with a power conditioner and an accurate multimeter. It all fit nicely into a camera case. I'd take from the house and drop the cleaned up power to 117V and feed that to the older amps.

    Until I got tired of all the work. Then I went cheap solid state power amp / modeling pre amp. I didn't care after that.

    Now I use it at home.
     
  14. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

    Age:
    60
    Posts:
    17,252
    Joined:
    Mar 2, 2010
    Location:
    Maine
    Yeah I've read that too, and I'm still not convinced.
    Using a variac as a volume knob is not really realistic, no matter what voltage the PT is set for or designed for.
    Not only that but the Marshall he used for the majority of his early live and recorded sound was one of the less loud Marshalls that had a wider range of distorted sound than the next version of the 100w Marshall that was possibly double the actual RMS wattage.

    The last bit of data is that Eddie has stated that he tells funny stories to interviewers as often as the funny stories we get from him.

    The core of this might be the idiots who presumably offended him and his music by assuming his sound came from his gear.
    Nugent was similarly offensive and asked to try Eddies rig because he wanted Eddies sound.
    They reportedly each played the other guys rig and the sound followed the player, not the gear.
     
  15. 24 track

    24 track Doctor of Teleocity

    Posts:
    14,073
    Joined:
    Nov 6, 2014
    Location:
    kamloops bc
    I have the same unit !
     
    rolandson likes this.
  16. Wyatt

    Wyatt Tele-Afflicted

    Posts:
    1,113
    Joined:
    Nov 3, 2004
    Because of the lack of isolation, I never really considered a variac a safe solution for long-term gig use, it's a bench tool.
     
    Last edited: Oct 23, 2019
  17. muudcat

    muudcat Tele-Holic Silver Supporter

    Posts:
    821
    Joined:
    Jan 3, 2010
    Location:
    Fountain City, Wi
    thanks for all the comments. Being a person of little electrical knowledge, I have to go with those who know, so what I have is a Staco 1010, with a digital voltage readout plugged in. Really didn't cost that much and will allow me to use the old Supro without fear of frying it. The amp had been serviced once I bought it with a 3 prong attached and some caps replaced but it has the original transformers and of course is tube rectified, 15in. speaker and a glorious tube trem
     
  18. bftfender

    bftfender Friend of Leo's

    Posts:
    4,259
    Joined:
    Dec 21, 2017
    Location:
    York PA
    i flip the switch on this..def allows for a whole new dynamic..you can slam the amp harder with more gain without more volume...like having another amp laGrange (2).jpg
     
  19. Milspec

    Milspec Friend of Leo's

    Posts:
    3,994
    Joined:
    Feb 15, 2016
    Location:
    Nebraska
    face.jpg Just get one....an American built one and not the red shell over-seas ones built today. When you open one of those new ones up you will see why very quickly. I recently purchased a Stacco unit from a lab cheaper than the over-seas junk and it is built like a tank!

    The reason I bought it was that I run some amps from the '40's and restore old tube radios that are even older. Does it make a difference with your vintage amp? Depends on what is coming out of the wall really. They were normally designed around 117 volts max in '40's and '50's and around 120 in the '60's. (give or take). Running your amp at higher than designed voltage can cause cumulative damage. The thing is that you need to know what you are getting from the outlet first. At my house, it runs 116 - 119 and often is right at 117 except peak times of the day. So, there are no risks for my '60's era amps in my view as I am in the range already and only slightly above the design limits for the '40's era amps.

    When used on my '40's amps and those early tube radios, it does make a difference in sound running the voltage at 116 - 117 compared to 119. The radios are much clearer sounding and the amp is more note articulate to my ears. So yes, it is a good tool to have.

    Now, there are many who like to scare you into believing that you are going to do all kind of damage if the control knob was "bumped" sending too much voltage into the amp, likely by people who don't own a quality variac. My Stacco dial has a good deal of resistence to it so bumping the unit will not move the dial one bit. You have to physically turn it and even if it was cranked all the way up to 100 percent....it just means that you are getting 100% of the wall voltage, it doesn't actually increase it. so it is no more damaging than if you plugged in directly.

    IF you can find a good one for a good price, pick one up. They are worth it, just make sure to get a voltage meter (kill-a-volt or something) so that you can see what the outlet is sending and what you are dialing in.
     
  20. Milspec

    Milspec Friend of Leo's

    Posts:
    3,994
    Joined:
    Feb 15, 2016
    Location:
    Nebraska
    Oops, I didn't see this posting until I posted....looks like you did the same thing as me then really. I think you made the right call.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.