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Old 26th February 2004, 12:50 AM   #1
Thunau is offline Thunau  United States
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Default Next logical step in that quest for symetry?

While gathering parts for the AX and looking at different transformers I thought why not balance the AC before it hits the power supply? I used to run on balanced power in my recording studio and the gear sounded great on it. So I asked a friend of mine who originally hooked me up with the balanced iso transformer if he had another one (I left the old one installed at the studio when I closed down and moved out). He said yes, so after a quick trade for some speaker cabinets I ended up with this 75lb. 5000VA monster in my office.
Click the image to open in full size.

It measures dead on +61V/-61V to within 0.01V most of the time. Hard to say how close the windings are because the voltage fluctuates a bit, but it reduced what little hum I had in the system by at least a few dB to almost non existent. I have to put my ear right to the woofer to hear it.
I would think it makes sense to power the A-X from it. Doesn't it?
"Most people just say what they know, the wise ones know just what to say."
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Old 26th February 2004, 03:02 AM   #2
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Location: Columbia, SC
There are other potential issues, such as increased isolation from RF, DC, and digital artifacts in your AC line.
All to the good, of course.
I picked up a few isolation toroids from one of the surplus houses a couple of years ago and have been very pleased with the result, especially since they were quite cheap. I added some odds and ends from my junk box and ended up with power supply boxes for nearly nothing.


EDIT: It's been my experience that it makes more difference in the low level stuff like preamps and crossovers, than later in the chain. But that's not to say that you shouldn't pursue it for an amp.
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Old 26th February 2004, 06:41 PM   #3
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I have some nice monster isolation transformers 120 to 120
which have an electrostatic shield between the primary and
secondary, and I find that properly grounded, the shield makes
a real difference. We use them here, driven by Variacs, on our
test benches. The elimination of capacitive coupling between
primary and secondary is just as important as the additional
waveform cleaning offered by the transformer.
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