Re: Variacs : Was Re: Amp Rectifiers

[Russ Bradley <wbradley@xxxxxxxxxx>]

So, what I hear you saying is:
A variac won't hurt your circuit as long as you are not letting the 
voltage exceed 120V AC.
The way to use a variac with an amp is to lower the voltage for earlier 
breakup.

Can anybody else out there confirm this?  I have read tons of warnings 
about using variacs with amps, so this is news to me.  But this does 
make sense.  Voltage lower than 120V AC shouldn't burn anything up.  And 
Gerald Weber does recommend low plate voltage on the preamp tubes..

Thanks,
Russ

party_man1@xxxxxxxxxx wrote:

>Richard Smith sez :
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>>In some amps designs, a tube rectifier is prone to voltage "sag" when >the amp is pushed to the max. This sag (lowering of plate voltage) >causes tubes to distort/crunch earlier, changing the tone. Eddie Van >Halen is famous for loving the sound of early distorting tubes, and >would run his amps on a variac to artificially lower plate voltage. >(Don't do it! Eddie can afford to have his amps rebuilt on a regular >basis)
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>>A solid-state rectifier won't sag. Its not a matter of good/bad -- >more >a matter of taste. FWIW, most amps now have solid state >rectification.
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>Hurricane sez ;
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>Richard :
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>The topic of variacs has been a thread that spurs allot of controversy sometimes from those who do not know how to use them . Judging from your e-mail , it appears to me  ( ¿ at least I think ? ) that you know about them and their proper and safe use . But for those that do not , I thought I would add to this thread of amp rectifier's topic that you mentioned about variacs .
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>Yep a varic will help you to get that " crunch " . I put one on my Marshall 50 Watt tube with twin Celestions ( oooo what a sound ! ) and it made it play that crunch distortion at any volume instead of only at high sound pressure levels , and I might comment it never hurt it or cause tubes to wear out quickly or hurt the transformer , I had  this amp 5 years and only replace the tubes once and used it all the time , it was a work horse for me , the fellow who bought it was a Stevie Ray Vaughn type guitar man and fell in love with it at once when he heard me " tweak " it to a small room performance one night . I bought the Marshall at a yard sale , it was beat up with all sorts of little nasty things I had to fix , but most were cosmetic , it was about 7 to 9 years old when I got it .
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>This is a super advantage to maintaining your " signature sound " in any size room . This is important if you have a rig ( tube amp )that's high powered like a Fender Bassman or any tube amp with 50 watts or more . What sounded great in a large hall with lots of people and noise will blow the patrons out of the small coffee shop when you let that puppy get to the sound you desire . The vairac serves to compensate for the size differential of one room from another . 
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>This regulation of input voltage to your amp  is a cool thing as it lowers the voltage and giving you a " safe " way of getting that sound of " crunchville at lower power levels . There have been comments made of this being an " unsafe " thing to do and it can be if you don't realize how to use one properly . The biggest mistake I have seen that has caused problems is when some one turns up the "  rheostat " that controls the input voltage to your  amp and fries something like the tubes and or a x-former ouch !
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>These kind of failures can be remedied and avoided easily by using a volt meter to see where 120VAC is on the rheostat dial exactically , its important to get a true understanding of the line voltage maximum's because some believe that to get the full 120 VAC , you need the rheostat turned to the max position , this  seems the logical thing to do but it ain't .
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>At the optimum setting ( rheostat turned up till it can not be advanced any more ) you might be pushing into your amp 130VAC , 140 VAC or much more as it varies from one city to another or one neighborhood to an other or one variac to an other  as far as individual characteristics that determine what their out put voltage is from the variac. Once you know for sure where the max is on the variac , you are in the " safe zone " @ 120VAC or lower , because no matter how low you reduce the voltage it will not hurt the amp or its innards :-) . If you don't have a multi-meter , just go to a electronic service and repair techs shop and ask them to show and mark where exactically the max 120VAC is , and from there enjoy the ride like Eddie Van Halen and many others who use(d) them , like Hendrix or Stevie Ray Vaughn , etcetera.... .
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>I'm sure that this post will get plenty of " no no no's " it will fry you amp stuff and its O.K.  , but to be honest this type of electric hot rodding is not for the novice , it is however for  the semi-pro , and professional who has already gotten way past the beginners stage and has a great command of what he is doing on stage as well as great command in his tone and chops .
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>For the novice harper :
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>By purchasing a " Fender Champ " type tube amp ( there are suitable others out there in the tube family , it doesn't have to be a Fender ), you will get that effect of the crunch that will more than likely be perfect in a small room , so for you guys , its no biggie not to have a variac .
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>For the semi & pro's :
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>If you have a tube amp with some muscle , the variac is not a bad choice instead of getting an additional ( $ )  lower wattage amp for small rooms . After I sold my Marshall because it was a back breaker ( and more so with the added weight of the variac ) ,  I got ( besides another lighter 60 watt tube Carvin with only one 12" speaker ) , several smaller tube amps because the added weight of a varic to a already heavy cabinet and amp is not what I want any more . I use a Skylark Gibson ( circa 1950's ) & an old timy baby Gretsch ( circa early 1940's ) .  But I still like what a vaiac does , even to these small amps :) , it is a really fine way to "tune in " that sound everyone seeks in a Chicago break up crunch sound for the harp  .
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>Its a matter of choice I suppose . Like the old saying " There's more than one way to skin a cat " applies here & " Look before you leap into a variac " is also a cool  thing to know . But to protect my @$$ , YMMV :) 
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>Sincerely :
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>HR
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>aka:
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>Party_Man1@xxxxxxxxxx  
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