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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
elevick
2,638 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
dog_or_man OP
68 posts
 
Hey, thanks to those who've already logged-in with a thought; please don't take my silence as disinterest or lack of appreciation -- I'm teaching a three-hour class and they have their break right now. Will respond in more detail approx. 9:30 eastern.
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uru975
684 posts
 
20 or so years back was an electronic tech for a few years, Almarg's thoughts on a capacitor problem agree with mine. Moving pieces in and out till you find the one that seems to cause things after 20 or 30 minutes should reveal at least the unit.
mrderrick
292 posts
 
I'll take a stab at this. You mention that you have moved different components and speakers in and out and still experience the same effect. Could it be that you have a tolerance to "fatigue" that wares off after about 20 - 30 min and then sets in? Sometimes I experience this when initially setting up a new set of speakers. At first they sound all right, but after listening for a while I can feel the fatigue setting in and know that I haven't got them positioned correctly yet.
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