2. amps-preamps
  3. 1233540319

Audiophile quality variacs to decrease voltage?

I have an older 30 w.p.c. tube amp that should be run with 110-115 Volts coming into the unit. The average voltage coming from my AC lines is 124 volts, which puts the operating voltages inside the amp well above what it should be, and will cut short the life expectancy of various components and tubes in the amp. I purchased a newer model 10 amp variac to reduce the incoming voltage to the amp, but quickly found that the sound quality was noticeably reduced with the variac in line, at any voltage set between 100 and 124 volts when in use. Are there any "audiophile quality" variacs available, or some that "sound" better than others? I researched power conditioners that might have the feature of reducing output voltage, but the only solution I found were the new PS Audio Premier power plants that can do this. Unfortunately, they retail for $2,000, and my budget does not allow for such a purchase. Even at used prices, their reliability seems to be an issue from posts I have read on them. Any suggestions from others who have suceeded at reducing voltages without ill effects? Thanks for your help!
bigshutterbug
microstrip
180 posts
 
You do not need an autotransformer. Just buy a 115 - 9V transformer (I think 3A, 30W will be enough for your power amplifier) and wire the secondary in series with the mains feeding your amplifier. If you connect it the proper way you get 124-9 = 115V. If you get 133V just reverse either the primary or secondary winding terminals - not both at the same time!

After checking you should put everything in a nice box.
almarg's avatar
Ag insider logo xs@2x
almarg
9,670 posts
 
Excellent suggestion by Microstrip.

Just to make sure it's clear to everyone, the primary would be connected across the ac line, in addition to the secondary being connected in series between the hot side of the ac line and the hot side of the outlet on the box into which the amplifier's power cord would plug. The neutral side of the ac line would be wired straight through the box to the outlet for the amplifier (in addition to going to one side of the primary). Safety ground would also be connected straight through, as well as being connected to the metal box.

It would also be prudent to put a fuse in the box, at the input, perhaps 4 or 5 amps slow blow.

Regards,
-- Al
eldartford
4,262 posts
 
Albertporter...Of course I understood his question. He measured 124 volts but it makes sense to be a bit skeptical of such a measurement. If it were my measurement I would double check my reading, (even I have been known to make a wrong reading)and if it still looked like 124 volts I would somehow check the meter (or try a different meter).
By the way, the two sides of my power measure 115.6 and 114.5, which I believe is typical.

My suggestion to measure the other leg of his power was related to troubleshooting the reason for a 124 volt reading. I never suggested running another line.

If he absolutely must drop his voltage your transformer suggestion is clearly the best way to do it. Patching in a nine volt 3 amp booster transformer scares me.

My main point was that I think his amp will do fine on 8 percent high voltage, and he really doesn't need to do anything.

To repeat my question...what voltage regulation is the power company supposed to supply? Maybe you can get the power company to fix your "problem".
eldartford
4,262 posts
 
Another thought...I seem to remember that the distribution transformers that step down the voltage for your house have taps that are supposed to be connected so as to give you the correct voltage. Go after your power company.
bigshutterbug OP
381 posts
 
Thank you everyone for all of your helpful suggestions. I will double check my meter as Eldartford said for starters.
If my voltage is still high, then I will consider the Hammond Step-down transformer at $360. The Tice Titan/Powerblock would be nice, but well beyond my budget for this system. The idea of purchasing a much more affordable transformer like the ones mentioned by Microstrip and Ngjockey sound even more appealing, but by the time I added the necessary parts to it to make it safe, useable and semi-attractive, it may be close to the price of the finished Hammond Albert talked about. Albert, does yours sound close to what you get straight from the socket? Thanks again everyone, for your ideas!
More to discover