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back to ask again long sorry

If you recognize the user-ID, then you know the problem I'm about to describe because I've been yapping about it in these forums, on and off, for *years*. I'm only in here to try again because everything I've done so far to try to fix it has resulted in just more credit-card bills.

The sound is perfect for the first twenty or thirty minutes -- always has been, and I always think I've fixed whatever's wrong -- and then, gradually, the sound becomes reedy and increasingly sibilant in the upper midrange and apparently "over-modulated" right around the midrange-tweeter crossover.

If I shut everything off and reconnect everything, the problem often goes away for another twenty or thirty minutes, but not always.

It can't be a problem with components or speakers because everything in the chain has been repeatedly replaced, and many configurations have been sent off for service and returned with clean bills of health.

I don't think it's RF pollution because I've encountered the problem at a friend's house, and fixed it doing the same thing, over there: reconnected everything and had great sound for... twenty minutes.

I don't think it's a cracked RCA input socket because the problem has spanned several configurations of equipment.

I don't think it's a bad interconnect because the problem has spanned several configurations of cabling.

I don't think I'm delusional because non-audiophile listeners have commented on both the unpleasantness of the sound before reconnection, and the improvement afterward.

At all events, something seems to be "building up" in the signal path, somewhere, and the act of severing all the connections seems to cause whatever that build-up is, to be dissipated.

Lately I've been trying to fix this by... well... *reading* -- about everything from PS-Audio Humbusters to Audience Adept Response power conditioners and back to the XDC power filters by Channel Islands Audio. Trouble is, I'm cleaned-out financially and I just really don't feel like spending any more money before knowing with a bit more certainty that more dollars spent will point me more definitively toward getting to the bottom of this. Are there professionals who can help to diagnose the problem, and who are then also knowledgeable enough about the industry to recommend the proper fix?

Current system configuration: (many, many others have been tried!)

McCormack MAP-1 and DNA-HT5, connected directly to dedicated AC circuit via Signal Cable power cords

Arcam FMJ-CD23 connected directly to nearby, undedicated AC circuit, via signal cable digital power cord

Sony BDP-S550 blu-ray player and Panasonic TX50 plasma TV, connected to APC H-15 power supply, which is in turn connected to the undedicated AC circuit via Harmony power cord

Salk Songtower QWT speakers, front L and R, Linn Trikan center channel, Totem Mite-T rear L and R.

signal cable interconnects, element cable cross-connected speaker cables.

Thanks again, everybody.

Dave O'Gorman
Gainesville, Florida
dog_or_man
dog_or_man OP
68 posts
 

Just had a long conversation with a forum member from A-Asylum and he suggests (1) verifying that the house wiring has a good ground, (2) checking to be sure that the un-dedicated line has a safety ground and, if not, tying it to the safety ground on the dedicated line, and (3) checking the AC power for the presence of DC offset. These issues would seem to be of the sort that would explain why problems could be robust to different configurations of equipment, why the problems could get worse after extended use, and why they could seem to be solved after temporary disconnection.

Also, the power transformer on the amp makes an audible hum through the front apron, as well as sending a hum down the speaker wire to the speakers, and the transformer inside the cd-player gets extremely warm after extended listening -- both of which would seem to suggest, in his opinion, the presence of unacceptably high DC-offset.

Thoughts?
acoustat6
357 posts
 
Grannyring said," I would very strongly suggest Silverline Bolero speakers. Not a trace of anything that could cause your ears discomfort. I have very good and sensitive hearing - especially in the upper mids and highs and this speaker is just perfect."

You got that right, check here,
http://www.soundstagemagazine.com/measurements/silverline_bolero/

Bob
almarg's avatar
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almarg
9,670 posts
 
I agree with the AA person. What he is saying is very similar to what I had suggested. When I said that I felt the likelihood of a dc offset situation was minimal I was unaware of the hot transformer and hum symptoms, although I still feel that a wiring problem is more likely to be the cause.

I think it would be best to have a qualified person check out your ac. He should be able to very easily tell if there are any miswired or open connections, along the lines of what I and the AA person suggested, and he should be able to easily measure dc offset with suitable instrumentation.

Regards,
-- Al
lloydc's avatar
lloydc
734 posts
 
You seem to have almost concluded, through component changes, that the problem is not the components. it would be a PITA, but cost very little money, to determine once and for all whether the problem lies in your component chain or power delivery. If you were to set up your entire system the same way, somewhere else - preferably not a neighbor on the same grid - it would show whether the problem lies somewhere in your component chain (or your hearing), or in the electrical delivery system everything is connected to. As an experiment, have you tried hooking things up on different circuits in your house with some long, heavy extension cords? That could show whether the problem is confined to particular circuits. It also appears that the audio part of your system lacks power conditioning of any kind, which can be a red flag.
almarg's avatar
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almarg
9,670 posts
 
Good suggestions, Lloyd, but I think the possibility should be kept in mind that the root cause of the problem may be the power wiring or delivery, but that root cause may in turn have already damaged a component (such as by causing excess leakage in a capacitor or transformer), which in turn may be what is causing the audible symptoms.

So moving the system elsewhere may not be conclusive. The same symptoms could appear elsewhere (as they apparently did at the friend's house), suggesting a bad component, but a replacement component could subsequently suffer similar damage when exposed to the defective ac source.

In my (extensive) experience as an electrical engineer, whenever problems arose that were very difficult to isolate, and experiments gave conflicting or confusing results, often it turned out that two inter-related problems were present at the same time.

Regards,
-- Al
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