Sencore Pr57 Iso Trans, Power Conditioner for amp? - diyAudio
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Old 25th March 2015, 02:15 PM   #1
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Default Sencore Pr57 Iso Trans, Power Conditioner for amp?

Hi, posting under Tube Amps because that's what this is about, giving my little airtight amp the right voltage ...

In the past I've used Iso Transformers as power conditioners for my tube power amp, just to clean up the line a little, and--- this is the real reason-- to ramp down local line voltage to a nice 117volts. That doesn't ride the power tubes as hard as the 123, 124v that the elec company sends me.

Worked well and is still working; I've moved coasts and didn't bring the Iso Transformers.

I was wondering if I might use a Sencore Pr57 unit to do the same thing. Looking at a good deal on same, and just wondered if any red flags would appear in using this full time as a voltage-trimming / line-cleanup source for power.

Sencore is yes, test equip, and does a lot of other things, but *it is an iso transformer*. (My amp uses about 1/3 the current of the capacity of the sencore, so all safe and overhead good.)

Anything that says this might not be a good idea ?
Thanks for the advice.
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Old 25th March 2015, 05:15 PM   #2
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The PR57 will work, but it's kind of a wast of instrumentation. And you're going through two transformers, one of which is a variac. Why not try finding an adjustable isolation transformer like the RCA isotap. These turn up on eBay all the time and are a lot less then a Sencore.
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Old 26th March 2015, 06:02 AM   #3
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so, you are going to drop all that coin to achieve a 7 volt difference in supply voltage? Because I don't read that unit as having any ability to "clean up" line transients.
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Old 26th March 2015, 02:31 PM   #4
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As mentioned, looking at a really good deal on the Sencore, so not by any means extravagant. A new, straight-iso, toroid from Hammond or similar --would cost several times the price.

In that galvanic isolation happens re the transformer section of the sencore, I'd have thought that comprised leaving behind mains/ground-borne hash or line noise from other gear on the circuit. Not so ?

Regardless, it's the voltage-trimming that I'm after, and on the back end that comprises savings in new power tubes. My amp is auto bias, so I can't lower values myself beyond winding down the wall voltage a little.

As mentioned above, on the other coast I did this with straight isolation transformers and it worked quite well. There I used a second one on my tubed preamp, which I thought couldn't hurt. Truth was that the pre tubes were being run well within their design voltages, and there was even a soft-start circuit in the pre, so not so valuable there as in the power amp. Where output tubes were being run pretty hard in class A so a couple volts really did extend power tube life.
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