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Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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Original Message

Here is one, but it might be too small.

Posted by Al Sekela on March 12, 2010 at 12:15:03:
B&K Precision makes one with 350 VA rating for servicing hot-chassis equipment (primarily antique radios). It has a range of output voltages. The price at Digikey is $240, and it is a non-stock item.

However, the volt-ampere rating might be too small for your amp. Check the amp nameplate and multiply the rated voltage and current to estimate the VA requirement. For good sound, an isolation transformer should have at least double the VA rating.

You need to investigate further to see what your problem is. If the amp's power transformer hum is caused by excessive line voltage and not DC on the AC, then a variable autotransformer will let you set the line voltage where you want it. A more expensive alternative would be a fancy audiophile conditioner that regenerates the AC and lets you control the output voltage and frequency. Raising the frequency lessens the stress on the power transformer in the amp.

If the amp's transformer hum is caused by harmonic distortion of the AC, then my recent post below has some options for you.