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How am I frying all my amps? Oscillating? Help

Hi. So I'm on my third amp this year.

I had an Adcom GFA-7000 for many years which I gave to a buddy for his birthday so I could get a Krell. The Adcom used to "hum" or "buzz" for five minutes then stop, then start again a few hours later. It wasn't noticeable with the music playing. Also, when nothing was playing, it would pop and hiss when the volume was turned all the way up as if the volume control was directly connected to the speakers and was shorting them or something. It ran for nine years and is still going strong today. It did none of these things when I first got it.

Then I got a Krell KAV-500. There was always something wrong with this amp because it wouldn't turn on when I first got it. Then it did turn on and I used it and it would hum like the Adcom and its volume control noises were even worse. Then it exploded and got sent to Krell for repair (still not back). Also, the Krell would make a horrible buzzing sound when only RCAs or XLRs were plugged into it, no speaker wire (and I tried a dozen different cables as it took only one to reproduce the problem). And when you muted or turned off the pre-amp, the thing would send a horribly loud buzz through the speakers. It did not do this when I first got it.

So I got a Classe CA-200. This amp was dead quiet and had zero problems. Two nights ago I noticed the volume control was being noisy. Last night I noticed the amp hum. So I looked around, and of course, now the thing exhibits all the same traits of the Krell except quieter: volume control noise, buzz when the pre-amp is off or muted, buzz with only ICs connected. I expect it will get louder until it blows up as per the Krell.

My system has changed dramatically between the three amps. There are two commonalities for all of them: Goertz MI2 Veracity Cu speaker cable and Thiel CS1.5 speakers. The Zobels are on the speakers ends of the Goertz cable.

In addition to the speakers and wire, the Krell and Classe have two more in common items: Cary Cinema 11 preamp and PS Audio Ultimate Outlet.

The Adcom never really died. The Krell and Classe look like its going to take about two months each but I find it difficult to believe a Line Conditioner or Preamp can cause this kind of damage. That leaves me to think they are oscillating due to the Goertz cable but I don't know nearly enough about it for this to be anything but an uneducated guess.

I leave everything on all the time. What am I doing to my amps? :-(

Thanks!
leoturetsky
leoturetsky OP
103 posts
 
The Adcom was plugged directly into the wall. The Krell was plugged into the wall for half its life. Can't see what a functioning line conditioner can do to an amp, either its getting non-shorted power of the right voltage or not, right? And I ran my own dedicated lines, three in fact, though I'm only using two currently.

Oregon, what in the power system could slowly fry an amp except for under/over voltage which would affect everything else in my house too?
tobias
1,534 posts
 
A simple test of the outlet would tell you if there were an AC problem. From your description, it really sounds like the AC supply would be the first place to look.
newbee
4,093 posts
 
Don't know about your speaker cables, but some designs do cause ossilations in an amp. Remove your present cables and try some old fashion 12 guage copper cables and see if that solves your problem. If so, you can then simply refocus your attention on proper cables.
oregon
608 posts
 
Honestly, I know nothing about electricity. To me, it's black magic. All I know is rain.
But, my feeling is if you can simply use different outlets and the amps behave themselves, this is simplest test. Be certain it is a completely separate run of course. This won't cost you any $. Normally, I'd say this is a very, very long shot.
However, since you now say that YOU ran some dedicated lines (especially if it were ME who ran the lines), then why not double check them by using my experiment? Cheap, won't hurt.
A line conditioner could be bad as well. If the same conditioner was in the loop with the Adcom, Classe and Krell, it might have been damaged, now defective.
These are all uneducated, wild, off the handle guesses.
I used conditioners and power surge protectors for a bout a month many years ago. I feel they have no value, just make things more complicated and may even poorly affect the sound. But that's just my opinion.
Luckily, here in stormy Oregon, I have not had a surge.
All these power conditioner things are hokus-pokus.
Also, i turn my equipment off whenever I'm not listening.
These are my srewy, rain sogged opinions.
leoturetsky OP
103 posts
 
Tobias, what is this simple test of an outlet?

I just broke out my Fluke MM. The voltage at the wall is 123.0. The voltage at the power cord to the UO is 123.0. The voltage at the outlet end of the UO is 123.0. The voltage at the power cord to the amp is 123.0. Both UPSes in the computer room report 123.0.

What else is there to look at please? What principle of electricity in physics that isn't voltage can cause this anyway?

Newbee, if I swap in some lamp cord, how will I know the problem is gone? These amps aren't even supposed to be susceptible to oscillation from what I understood and the Zobels are there but I too seem to think this is where I should be looking.
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