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watsi2 1st November 2007 12:37 AM

low ac voltage question
I searched forums and didn't find any answers.
Would a low AC voltage say 100 to 105 volts be a problem for an original good sounding Grommes 24pg amplifier.

And no the house current is OK at close to 120.

Just wondered if using a variac to run an original good sounding amp a little shy of 117 would be easier on transformers etc.

What does everyone think?

Thanks, Watsi2

18thell 1st November 2007 02:26 AM

You can use a autotransformer, or use a variac. On the market, there are stablizer. Which method ? Your choice.

watsi2 1st November 2007 08:08 AM

variac soft start and low voltage operation
I am currently using a variac to provide a very soft start. And I noticed that the tone seems nicer at about 100, to 105 volts max.

Also when I shut it down, I slowly drop voltage and my little Grommes will produce nice tone down to 50 volts or less.

My question to the group.s. Is there any reason that I should not use these methods of operation? I can't think of any with my very limited knowledge.

The more I read and study tube audio books it seems that only a small amount of learning occurs. I will buy and repair some gear, and build amplifiers soon.

I have been reading posts on this Forum for sometime and find it very informative!


Colt45 1st November 2007 12:47 PM

Dropping B+ isn't a problem, but dropping filament voltage can cause some.

but.. 105v.. <10%... good enough. You could wire a 12v transformer as a buck deal to drop the mains from 120 to 108, if you want, and free up the variac. If the sound is related to B+ change, = shift in op point, and not fil change, you could always modify the PS some.

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