Isolation Transformer - Use with Cheater Plug

02-21-09: Ngjockey
According to code, the ground is not isolated by the iso and is continuous. The positive and negative are isolated.

And just to add....
For isolation transformers less than 2 KVA, if memory serves me right on the size, the safety equipment grounding conductor from the wall outlet can be used to connect one of secondary winding legs to ground. This grounded conductor, known as the neutral conductor. This connection also becomes the connection for the receptacle/s equipment grounds. A separately derived power system, (an iso transformer), shall have its secondary wired as an AC grounded power system.

In other words the secondary of the transformer can not float. It must have a direct reference to ground.

Forgot about that. That explains a lot about why iso's have gone out of fashion. My wiring has been more creative and with larger transformers. Yes, I should have said neutral instead of negative.

Thanks for the responses. I originally had the pair plugged into the same outlet with the cheater plugs. (I did not have this problem until I replaced my previous power amp.) Without the cheater plugs, the hum is very loud.
Sorry to still be confused - I didn't word my original question very well. Since the Tripp-lite did not solve my ground hum problem, is it at least giving me some protection from shock since I have to use the cheater plugs one way or the other? Or should I just go back to plugging the pair straight into the wall outlet and try something else? (I might try isolating the RCA cords next.) Thx again.

But NGjockey--you are probably using a balanced center pole grounding scheme I'm guessing--in which case there is no neutral--it really is negative.

HHawk: I guess you missed Jea48's humour. Yes, you can still get a minor shock. The iso will reduce common mode noise in the AC line and reduce voltage spikes. Sizing is important. For both a preamp and amp, 1 KVA is minimal.

You might want to do some search and research into "ground loop"

Rives: You guessed right. Shhh.