variac vs regulator

[Shark Diver]

Read an article about variacs being used to keep line voltafe stable thus ensuring a consistent amp tone venue to venue. Wouldn't a furman regulator do the same thing. The only difference I can tell is that a variac is adjustible. Am I missing something?

[Old Tele man]

...this has been discussed before (http://thegearpage.net/board/showthread.php?t=160927&highlight=variac), but:

VARIAC = "adjustable voltage" but levels changes values under different loads.

REGULATOR = "constant voltage" under changing loads.

[Smokin Tone]

I never hear anyone mention it but I use a APC battery backup made for a computer. Having the battery it offers better surge supression and power conditioning. Also in the event that the power goes out you dont instantly shut down. Anybody else try this?

[Old Tele man]

Smokin Tone -- excellent idea...and not that costly either!

[Smokin Tone]

Thanks Old Tele Man. Yeah, if you have a Radio Shack nearby they sometimes clear them out really cheap.

[landru64]

this is interesting

http://www.apc.com/products/category.cfm?id=15&subid=80

[Shark Diver]

...this has been discussed before (http://thegearpage.net/board/showthread.php?t=160927&highlight=variac), but:

VARIAC = "adjustable voltage" but levels changes values under different loads.

REGULATOR = "constant voltage" under changing loads.

Thanks, for the link. I read it, but now I am more confused. From what that said a variac uses a ratio? So, if voltage changes its output changes? Then what good is it? The article in Musician's Hotline was suggesting that a variac keeps the voltage constant and it was user adjustable, so you could run your amp on a voltage of your choice. This was for keeping your amp tone consistent. How would it do that if it changed with voltage irregularities? I'm missing something.

[Old Tele man]

...you understand correctly, a VARIAC is simply an adjustable "ratio" transformer, and once "set" cannot/does not correct changes in input voltage (just like I wrote above: "...changes values under different loads.")

...a REGULATOR is necessary to compensate for voltage changes/fluctuations.

...so, when would a VARIAC be useful? At the end of a L-O-N-G power chord, where there's been a constant I-squared-R loss, and the VARIAC can be adjusted to "step up" the voltage back to 110/115/120/125Vac, etc.

[Shark Diver]

...you understand correctly, a VARIAC is simply an adjustable "ratio" transformer, and once "set" cannot/does not correct changes in input voltage (just like I wrote above: "...changes values under different loads.")

...a REGULATOR is necessary to adjust for voltage changes/fluctuations.

...so, when would a VARIAC be useful? At the end of a L-O-N-G power chord, where there's been a constant I-squared-R loss, and the VARIAC can be adjusted to "step up" the voltage back to 110/115/120/125Vac, etc.

Thanks!

[Shark Diver]

ok, last question. Would running a variac after a regulator work well if you wanted to keep the voltage to the amp at 110?

[Old Tele man]

...yes, but your electric bill (the "spinning" wheel on the AC-meter) will go sky-high(!) because of the compounded (in)-efficiencies, ie: if VARIAC efficiency is 95% and REGULATOR efficiency is 85%, then together in series, their TOTAL efficiency will be less than 81%!

...that's 25% more than without either device! which means the initial power cord is gonna be "glowing" in the dark (well, not really, but it will get hot, which will cause even MORE voltage drop due to I-squared-R losses).