RE: Variacs : Was Re: Amp Rectifiers



Actually, I used an Altair Attentuator (sadly no longer made) on my guitar=
=20
amps from around 1975 till last years (when I got smart and started using=20
50 watt amps instead of 150. never blew up a thing.

maurice

At 08:17 AM 4/6/04 -0400, you wrote:


>Why I believe Variacs are a bad idea:
>
> >From http://www.drifteramps.com/safety.html
>
>VARIAC - Sure, Eddie Van Halen made use of a variac to get his tone.  A
>variac is a VARiable AC supply.  Running an amp at a higher voltage than it
>is designed is a sure way to ruin the amp.  Likewise running at a lower
>voltage can cause serious problems due to the heaters in the tubes running
>too cold, which can lead to cathode stripping, which leads to shorter tube
>life, which can sometimes cause other problems.  The best way to use a
>variac is NOT to use one.  A variac is to only be used for repair and
>building purposes as a piece of bench test equipment.  EVEN if you use a
>variac to regulate your line voltage, which is a good thing seeing how line
>voltage can vary from place to place AND most vintage amps were designed to
>run at a slightly lower voltage (110VAC) versus what most line voltage is
>now (120VAC), having one on stage is just asking for your drummer, or=
 anyone
>else nosing on the stage to play it and see what kind of fun they can have.
>
>-----Original Message-----
>From: owner-harp-l@xxxxxxxxxx [mailto:owner-harp-l@xxxxxxxxxx] On Behalf Of
>Russ Bradley
>Sent: Tuesday, April 06, 2004 5:45 AM
>To: party_man1@xxxxxxxxxx
>Cc: harp-l@xxxxxxxxxx
>Subject: Re: Variacs : Was Re: Amp Rectifiers
>
>
>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 :
> >
> >
> >
> >
> >>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)
> >>
> >>
> >
> >
> >
> >>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.
> >>
> >>
> >
> >=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >
> >Hurricane sez ;
> >
> >Richard :
> >
> >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  ( =BF 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 .
> >
> >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 .
> >
> >
> >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 .
> >
> >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 !
> >
> >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 .
> >
> >
> >
> >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.... .
> >
> >
> >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
>.
> >
> >For the novice harper :
> >
> >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 .
> >
> >For the semi & pro's :
> >
> >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  .
> >
> >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 :)
> >
> >Sincerely :
> >
> >HR
> >
> >aka:
> >
> >Party_Man1@xxxxxxxxxx
> >
> >
> >
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