Balanced power compatabilty census

I use an API Power Wedge Ultra 116 with my front end stuff (it follows an ExactPower EP-15 used for waveform/voltage correction). The PWU provides separate center-tapped isolation transformers for each of its 6 outlets, with switches that allow you to choose between normal, floating, and balanced power options for each attached component. (This unit cannot provide balanced power to power amplifiers, so I haven't been able to test that application.)

Therefore, the PWU provides a reliable test for how each piece of gear reacts to balanced AC on an individual basis, without throwing in confounding variables. To date I've only used one component that showed no improvement from selecting balanced AC (an older Conrad-Johnson tube preamp), and that one showed no degradation either. All other components tried, primarily SS preamps and digital separates (my phonostage is battery-powered, so it doesn't apply here), showed varying degrees of improvement, from very slight to pretty vast as far as these things go, but again never any degradation. (All these pieces also sounded better fed from the PWU than they did skipping it altogether, no matter which switch position was chosen, so the powerline filtration it includes in addition to the iso trannies would seem to be doing no harm here.)

Based on this evidence, I'd say that balanced AC done properly (independent of any other filters or such that might be included in whatever device is balancing your AC) probably rarely has any downside used for line-level components such as sources and most preamps. If there's a problem with a power or integrated amplifier, I'd investigate whether it could be due to inadequate iso tranny capacity. The issue may have more to do with undesired raising of the powerline impedance seen by power amps than balanced AC per se.

Zaikesman - That's what I thought too and was surprised when it didn't work that way for everything. That's why I started this thread.

Trust me, that 5KVA transformer is not starving anything for power. It is capable of sustained 20 amps in balanced configuration and weighs 120 lbs. The amps I used draw in the neighbourhood of 5 amps at max.

I think it has more to do with how a piece of equipment in grounded internally but I'm not an engineer. Granted, most commercially available products are undersized for amplifiers.

I'd research the forum archives to see what you can find on this subject (and look for contributions written by Sean).

The power transformers on my Welborne DRD 300B monoblocks would audibly "buzz" when I plugged the amps into 2.4kVA Topaz Ultra-Isolator trannis wired in balanced config. It was actually so scary that I would have to unplug them after only 5 seconds.

After weeks of frustration, I shipped them back to Welborne. Embarrassingly, the problem was so simple I could have fixed it myself withing two minutes if I had just calmed down and thought it through - the star-grounding just needed to tightened slightly.

Since then, quiet as can be. No problems with the rest of my components, either.

Just remember to turn off the power at the transformer when not in use because the component's own power switch will only turn of off half of the 120V in 60V-0V-60V configuration.

Darkmo: That last comment I think warrants some elaboration -- my components (except power amps, which don't get the balanced AC) that go on semi-powered standby as well as those that turn all the way off seem to behave the same (meaning the way you'd expect) regardless of whether balanced AC is selected at the Power Wedge's iso-trannies...