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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
 
"could you describe the exact configuration that was being used when you tried the equipment at your friend's house and heard similar symptoms? That may help to rule some things out with greater certainty"

Yes, and thanks for all the helpful suggestions! At the friend's house we had the Arcam FMJ-CD23, McCormack MAP-1, and McCormack DNA-HT5, connected to a single un-dedicated AC line with no video or other sources, and the speakers and speaker cables were my friend's. Disconnecting and reconnecting was carried out because we wanted to try different interconnects -- which seemed to fix everything (just as this sort of thing always does), until I got back home with the new cables and listened in my own place for another twenty minutes.
albertporter's avatar
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albertporter
4,949 posts
 
In my opinion you're hearing the system settle into it's real sonic signature once the initial "compression" and false warmth has been wiped out with warm up.

I fight this in lots of systems I've owned, I'm INCREDIBLY sensitive to high frequency problems, I want the tonal balance to be as close to perfect as possible on nearly 100% of my software.

It is possible but very difficult.
ghosthouse's avatar
ghosthouse
4,279 posts
 
totally sympathetic to what must be a maddening situation...the question I'd ask is what HASN'T been changed? Given all the equipment and cable changes, the cause must be with something that hasn't changed. If I undertand corretly, the problem wasn't apparent at a friend's house after listening more than 20min? but was apparent after you got home? (Could it be some kind of weird static charge build up? or power supply issue?)
elevick
2,636 posts
 
Albert Porter is right.
I think you just have a component that is incompatible.
My suggestion is to borrow some pieces from friends. Try a different amp and see how you like the system then? Do this with the rest of the gear too. Odds are you will need to replace 1 piece in your system.
I've seen this before with very "accurate" speakers. They sound great at first but once you settle in, your ears start to burn.
Find other Audiogoners in your area and ask for help?
almarg's avatar
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almarg
9,670 posts
 
Ok, so it sounds like the plasma, the blue-ray player, and the power conditioner are not responsible.

Behind my other suggestions was the thought that one of your ac runs may be miswired, which at some point in the past may have damaged a part such as a line-filter capacitor in one of the components. Perhaps after 20 minutes of operation it then breaks down further, due to either heat or exposure to voltage, resulting in a leakage path between ac and chassis (which is usually common with signal ground, and in the case of components that have a 3-prong plug, is also common with ac safety ground).

Interconnects for single-ended (rca) interfaces tie the chassis of the connected components together electrically, so disconnecting and reconnecting them would conceivably have a relation to either stored charge or voltage stresses involving capacitance that is in electrical proximity to the ac line.

Also, it's very conceivable to me that a compromised line filter capacitor in one of the components would be the kind of thing that would not show up when you sent the components back to the manufacturers for them to check out.

Obviously I can't quite formulate all of this precisely, but the bottom line is that I am suspicious of the ac wiring and grounding, and that it may have caused effects something like these. I'm envisioning not only miswiring in the sense of interchanged connections, but also, perhaps, the possibility that an ac neutral run is open, creating a round-about return path involving interconnects, safety ground, and/or other components.

Regards,
-- Al
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