Voltage regulation

I have noticed that my dedicated mains power slowly fluctuates between 124 and 127 volts. Nothing seems to correlate like furnace - refrigerator turning on and off - time - day of the week etc. I'm looking for something that would keep the output a steady 120V without constricting the current. I'm not looking to break the bank but would like any and all suggestions.

The reason I'm looking for this is because I have a tube integrated where the bias goes up and down with the voltage fluctuations.

I have an APC H15 that includes voltage regulation. I've seen it light up for both boost and trim on the voltage but it rarely outputs exactly 120 hz. Right now it's reading 121 Vac in and out, but it's generally a little higher.

I don't know if it's more of a sound quality issue or if it's just "hard" on components to have it fluctuate all the time.

There may be some components that will hold it at exactly 120 hz, but consider this a heads up that not all of them will.
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Time out for a funny answer. Use the isolation transformer that you bought from me, I believe that it performs voltage regulation as a byproduct of the energy being stored and released.

There are products made for audio that are called voltage regenerators. Generally these units are considered the best surge protectors and I imagine are set to a desired voltage.
I do not think that feeding a high quality internal power supply a steady voltage would reduce dynamics. The power supply circuit should have the ability to respond appropriately to the demands the music puts on it idependant of instaneous current draw. If the power supply is that good though... I get your point, that an external steady voltage should not be required. I can't see how it would hurt however.
Chuck It raises the output voltage by 3V. That pushes the output to 130V. Other than that the Topaz Isolates only. No regulation.
Hey Everyone Thanks for the responses. Any recommendations for a sub 1k budget limit (new or used).
There's some 5000VA/50Hz Sola MCR (works even better at 60Hz) on Ebay for $600. Heavy and expensive shipping. Insist on bolted/strapped to palette. These are noisy, so they have to be mounted remotely, if possible. The MCR is only 3% regulation but have much better CMNR than the CVS models. The SolaHD site has a technical/FAQ section that's educational.

Wouldn't recommend a tap-switching regulator for audio.
Do you hear the difference when the voltage fluctuates? Or you are concerned because you think it might do something bad to your amp etc.? In any case, I doubt that there is such a device for under $1k used that would consistently do it without polluting the current and/or restricting the dynamics. In the past the best audiophile devices of this kind were Accuphase and Burmeister, and they are probably still very expensive used. But even they may not be able to do what you want them to do on a permanent basis. The last time I saw Accuphase here, I think it was $2000 or so.
Some manufacturers have great voltage regulation built into their products. My Burson PI-160 integrated has their own in house voltage regulators and gone are the days when I had to listen at night to get the best out of my system. It sounds the same all day long now. I live in an apartment and the competition for power had its negative effects until I came across this Burson. They claim less than 1% voltage fluctuation and I believe it. I've never heard anything so sound good.
And clean.
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10 volt swing per day WOW. As far as linear power supplies they are generally designed to work with +/- 10% of the standard 120v. So for me I would think 132v would be my upper limit. At any rate I have been trying to keep my bias down. I've lost 4 tubes in 4 months. All in different locations in my integrated. 2 tubes blew when no music was playing.
My personal measurements taken at my house rarely see over voltage . What I have seen however, especially in the summertime are very low voltages, as low as 90 volts. I don't think it's simply the utility company rolling a brown out, because my folks up the street never have the issue. In fact, anytime the compressor for my central AC kicks in, I've seen the street light dim, regardless of summertime demand conditions. I think the transformer on my street isn't rated high enough, or the lines feeding it don't have enough current behind them. During these extreme brownout periods, I turn off as many motors as I can, but I wonder if I'm doing any harm to my audio system.
I use tubed amp and a voltage regulator Exact Power EP15A...it holds the current at a constant 120 volts....good for tube life and also sound. there are others out there that do the same thing.

It could be the Single Impedance Output Transformer in your amp. Have you called the manufacturer or distributor and asked the question as to why this (blowing tubes) could happen?
Thanks Irish - Yes both the distributor and manufacturer both are aware of that problem. They have been very good about tube replacement too. I think I'm on the last step of things to look for and try before sending it in for repair.