I've discovered that running the separate outs to two Fender amp creates noise in the system. I have one of those ebtech thingies and it gets right of the noise, but I'm concerned about losing audio quality and punch. Does anyone know of a good alternative? I'm assuming it's an isolation transformer at heart.
 
If further news, I've consolidated to one Sunn 200S with each 15 getting a separate amp. Sounds good so far, but my gig on Saturday will tell me all.

Hello Edwin,  
   I assume that you have already done the whole song and dance with polarity reversal and ground lift, neutral  ground and hot power source checks and so on . Perhaps additional shielding and isolation from the high voltage to the power output tubes . Maybe a power conditioning unit with excellent EMI/RF filtering and ___YES
perhaps an isolation transformer __perhaps ___ Just guessing .

The isolation transformer seems to be the ticket. Anyone know what the impedance of the signal coming out of the DS5(R) power supply is?
 
Actually, maybe I should try my DS5R and see if there's a difference. The blue box is pretty aged, although I would imagine that if it's gone bad, I'd hear hum as a symptom and not broadband noise.
 
I don't think power conditioning is the issue, although it never hurts.

Edwin ,  
 
This isolation transformer has been on my eBay watch list for a while .
I purchased a Cooper CS-10 control surface from this ebay seller about a month ago   and was impressed on it's good condition  and how  well they packed it for shipping.  
 
 Edwin __Grab it if you want it .
http://www.ebay.com/itm/171147691771?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

Edwin, are you sure both amps are plugged to the same socket? I mean, they must share the same grounding to avoid ground loop issues... be sure using the same ground line to each gear on your system (not only amps, but pedals, preamps and outboard gear, too)

I don't speak or write too good in english, sorry... I didn't meant 2 amps on the same socket, but on sockets sharing the same grounding

Thanks for writing. Yes, everything was plugged into one power strip and it was in my home, so there was no interaction with a PA system. Unfortunately, my gig was a casualty of the cold this weekend, so I'll have to wait until Friday to put it to the test on stage. The Ebtech does get rid of the noise, so I'm going to go with that for now.  
 
I did install a new power cable on my blue box power supply and it's possible that I reversed the polarity of the cable, but it seems to me that it shouldn't matter, given that the rectifier changes everything to DC. Also, it would create noise with just one amp connected, not only with both connected.

good to know Ebtech solved that issue

I've had occasional noise issues in some venues with the new blue box power supply (grounded plug) which didn't recur with the older unit (two blade plug). Adding an adapter or cheater plug to the three-prong cable eliminated the noise, so your thought about your new power cable may appropriate. Good luck.
Jon

Isn't there a reason for the third grounding prong?  Like safety maybe?
 
Bill, tgo

Yes, there is. My box, being an older one, doesn't have the ground prong, but I have added them to both of the old Fenders. Fixing a noise by bypassing the ground prong is a quick fix around a symptom that something else is wrong. In a perfect world, there should be no issues.  
 
The issue is that there are more than one path to ground and sometimes the two paths can be at different potentials.
 
What the Ebtech does is break the ground on the signal wire, which allows you to keep the grounds of the devices connected. It's a better, safer, solution, but it doesn't address the underlying problem.