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Post by novisnick on Mar 27, 2018 16:32:48 GMT -5
Looking at a transformer to better regulate power to my tube amps, anybody using one? Whats your thoughts? Thoughts or comments? Looking at this one.  |
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Post by pedrocols on Mar 27, 2018 16:34:21 GMT -5
Get one. The dial on the top is not accurate but the gauge is.
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Post by Gary Cook on Mar 27, 2018 16:49:09 GMT -5
Hi Nick, do you have some actual data that indicates that you actually do need one? Something like relevant variability in the input voltage to the amplifier power supply AND corresponding relevant variability in the output voltage of the amplifier power supply? You need both because a variation in the input voltage in most cases does not manifest itself in variability in the output. ie; the amplifier power supply does its job and handles the variations just fine.
Cheers
Gary
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Post by audiobill on Mar 27, 2018 16:50:25 GMT -5
Gary, you are assuming a tightly regulated power supply. Not all amps are.
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Post by audiobill on Mar 27, 2018 16:50:55 GMT -5
Nick, a 10 amp unit will be fine.
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Post by monkumonku on Mar 27, 2018 17:11:02 GMT -5
Looking at a transformer to better regulate power to my tube amps, anybody using one? Whats your thoughts? Thoughts or comments? Looking at this one. Just in case you weren't aware, a Variac does not regulate voltage to make it constant but it increases or decreases the voltage proportionately. So for example if your voltage swings from 116-122, a Variac will change the swing either to a lower or higher range but it won't make it a constant 120. It seems to me that this would only be useful if your voltage runs either too high or too low. |
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Post by novisnick on Mar 27, 2018 17:51:20 GMT -5
Nick, a 10 amp unit will be fine. Didnt see a 10 amp unit |
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Post by audiobill on Mar 27, 2018 17:59:18 GMT -5
Ok, but a 20 amp.
Mine is an American made 15 amp unit.
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Post by novisnick on Mar 27, 2018 18:00:09 GMT -5
My voltage at my tube amp Belkin runs steady at 121/122, no wide swimgs.
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Post by Gary Cook on Mar 27, 2018 20:26:46 GMT -5
Gary, you are assuming a tightly regulated power supply. Not all amps are. Not really Bill, I posted "in most cases". That said if an amplifier has inferior design in its power supply then there's a good chance it has inferior sound to go with it. My voltage at my tube amp Belkin runs steady at 121/122, no wide swimgs. Then I'd say there's no benefit to be gained. Cheers Gary |
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Post by pedrocols on Mar 27, 2018 21:57:12 GMT -5
I would also suggest to keep your Tube Amp!  |
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Post by novisnick on Mar 27, 2018 22:14:30 GMT -5
I would also suggest to keep your Tube Amp! ST-120 or the M 125’s ? |
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Post by pedrocols on Mar 27, 2018 22:37:24 GMT -5
I would also suggest to keep your Tube Amp! ST-120 or the M 125’s ? Both! |
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Post by novisnick on Mar 27, 2018 22:43:37 GMT -5
How do I start a “Go Fund Me” account? LOL |
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Post by pedrocols on Mar 27, 2018 23:22:01 GMT -5
How do I start a “Go Fund Me” account? LOL Massdrop!  |
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KeithL
Administrator 
Posts: 10,273
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Post by KeithL on Mar 28, 2018 9:36:55 GMT -5
1)
As a few people have already noted, a Variac is a MANUAL device.
You use it to manually turn the voltage up and down.
It does NOT provide any sort of regulation.
Therefore, it will only help if your voltage is high or low in the long term.
2)
Contrary to what you might think, VERY few power amps have regulated power supplies (either tube or solid state amps).
(Our XPA Gen3 and XPA-DR amps are among the very few that do have a regulated supply.)
However, in general, with most solid state amps, the line voltage doesn't have much effect on performance.
(The maximum output power available will vary a little bit, but the gain and things like THD won't change.)
On the other hand, SOME tube amps will perform somewhat differently if the line voltage is a little high or low... and it may affect your bias settings.
3)
VARIAC is a brand name; the proper term is "variable autotransformer".
They tend to be somewhat expensive, quite heavy, and last a very long time.
(They've been made for years, and you'll see lots of used ones on places like eBay.)
4)
It is important to note that an autotransformer is a REAL transformer - which puts out a line frequency sine wave.
This means that, as long as it's working properly, an autotransformer should not introduce any sort of noise or other problems if you use it to run audio equipment.
(You don't need one "specially rated for audio use" or anything like that....)
You can also use it as a light dimmer for any bulb type that allows dimming.
However, many light dimmers are NOT autotransformers, especially many modern ones, and you CANNOT use them to safely run audio equipment.
(If you try to use some other sort of dimmer to run your audio gear, you may cause serious damage; and, even if it actually works, the output may be noisy.)
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Post by audiobill on Mar 28, 2018 11:30:22 GMT -5
Good explanation, Keith.
A Variac is useful when the voltage in your home changes during a day, not just in the long run.
I check my line voltage each listening session, morning, night or otherwise. Some surprising variability!
I found a US made 15 amp variac that listed for $775 for $95 on craigslist...... |
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Post by 405x5 on Mar 28, 2018 13:20:05 GMT -5
Looking at a transformer to better regulate power to my tube amps, anybody using one? Whats your thoughts? Thoughts or comments? Looking at this one. Yep  |
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