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edwin
Senior Member
Username: edwin

Post Number: 1670
Registered: 5-2002
Posted on Tuesday, December 03, 2013 - 10:41 pm:   Edit Post

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.
sonicus
Senior Member
Username: sonicus

Post Number: 3141
Registered: 5-2009
Posted on Wednesday, December 04, 2013 - 12:52 am:   Edit Post

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 .
edwin
Senior Member
Username: edwin

Post Number: 1671
Registered: 5-2002
Posted on Wednesday, December 04, 2013 - 2:00 pm:   Edit Post

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.
sonicus
Senior Member
Username: sonicus

Post Number: 3148
Registered: 5-2009
Posted on Thursday, December 05, 2013 - 9:52 am:   Edit Post

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
mario_farufyno
Senior Member
Username: mario_farufyno

Post Number: 1028
Registered: 9-2008
Posted on Tuesday, December 10, 2013 - 12:40 pm:   Edit Post

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)
mario_farufyno
Senior Member
Username: mario_farufyno

Post Number: 1029
Registered: 9-2008
Posted on Tuesday, December 10, 2013 - 12:43 pm:   Edit Post

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
edwin
Senior Member
Username: edwin

Post Number: 1674
Registered: 5-2002
Posted on Tuesday, December 10, 2013 - 1:17 pm:   Edit Post

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.
mario_farufyno
Senior Member
Username: mario_farufyno

Post Number: 1030
Registered: 9-2008
Posted on Wednesday, December 11, 2013 - 7:54 am:   Edit Post

good to know Ebtech solved that issue
jon_jackson
Intermediate Member
Username: jon_jackson

Post Number: 188
Registered: 12-2008
Posted on Wednesday, December 11, 2013 - 7:16 pm:   Edit Post

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
lbpesq
Senior Member
Username: lbpesq

Post Number: 5615
Registered: 7-2004
Posted on Thursday, December 12, 2013 - 8:42 am:   Edit Post

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

Bill, tgo
edwin
Senior Member
Username: edwin

Post Number: 1675
Registered: 5-2002
Posted on Thursday, December 12, 2013 - 9:43 am:   Edit Post

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.

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