Properly connecting an isotaion transformer

Vman: You can do exactly as you stated and achieve good results. The key here is how good the isolation transformers actually isolate their output from the line and whether or not the transformers & dedicated line are up to passing enough current without signal degradation.

For best results, isolation transformers should have a noise reduction of -120 dB's, very low capacitance and never be asked to deliver more than 60% ( 75% at max ) of their rated output. This would mean that a 2500 watt ( 2.5 KVA ) transformer should be run below 1500 watts of steady state draw with peaks held to below 1875 watts ( slightly over 15 amps ). These figures incorporates a "fudge factor" in terms of headroom if manufacturers are being a little "liberal" with the power ratings of these transformers. Otherwise, running an isolation transformer at or near rated capacity will actually introduce non-linear distortions into the system, defeating the purpose all-together. Sean
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Sean: Thanks for the excellent information. It is really going to help me as well as others who are contemplating using isolation transformers. From the numbers you've provided, I personally need to run two more dedicated 15amp circuits on top of the existing dedicated 20amp. Then place a 2.5kva iso transformer for the amp circuit and a slightly larger than 1kva iso transformer for my source equipment.

Again, thanks for the excellent information!

Vman: Run 20 amp circuits all the way around rather than two 15's and the one 20 amp. The cost difference is next to nothing and the difference in potential performance due to lower source impedances with future upgradability ( current draw ) make it worthwhile.

As far as running two more lines, you may only need one additional line but two more transformers. That is, IF the current draw on all of the devices combined for that secondary line are less than 15 amps or so. If you need more current than this, use the two lines as you first suggested.

As i mentioned, there's nothing wrong with running one line for digital and analogue. That is, so long as they are thoroughly isolated from each other. If you're using the transformers that i think that you are, you're good to go. Sean
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Sean: How far apart do I need to keep the isolation transformers from each other? And how far from the equipment (TV, Pre-amp, Amp, etc.)?

I'm probably going to end up running 2 more dedicated 20amp circuits (as you've suggested). I'd like to run each dedicated into an isolation transformer and then on the back side terminate into a Hubbell.

Fortunately my system doesn't draw too much current so my isolation transformers don't have to be very big (taking into consideration your comments earlier about overhead). I have the Sunfire Cinema Grand II amp which is only 225x5, small compared to many that are used. Vman

I don't know what you have for speakers, listening room or listening levels, but i wouldn't run an amp that size with anything smaller than a 20 amp line and a 2.5 KVA transformer. I would really prefer to see an even larger transformer for this amp, but 2.5 KVA will work for most people with "reasonable" speakers and listening habits.

The reason that i say this is that at low impedances with insensitive speakers, this amp can pull GOBS of current with big peaks or when standing on the throttle. As a side note, this amp benefits quite noticeably from clean power, moreso than some other designs. Adding additional filter capacitance into the power supply also helps with bass impact and to further lower the noise floor. If you're not running this amp in balanced ( XLR ) mode, i would highly suggest checking into it. This amp, along with all other Sunfire products, does not use "standard" XLR pin configurations though, so verify compatability with your Pre/Pro before going that route.

As far as placing the transformers, the greater the distance from each other and the equipment, the better. Given that the field that they generate is directly related to the amount of current being passed, the one to worry about the most would be the transformer feeding the amp. Magnetic fields decay as a square, so moving the transformer twice as far apart results in four times the reduction in magnetic field strength. Having said that, i would keep them FAR away from any type of cabling if possible, as some cables make for excellent "antennas" to feed noise into the system. Sean
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