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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
sns
3,003 posts
 
One guess. You say sound is perfect for first twenty minutes or thirty minutes. Hard to maintain perfection, only downhill from there. Have you thought you may be setting yourself up for disappointment, any little anomolie is eventually exposed.

If others hear this same problem, perhaps they've been pre-conditioned in the same manner. Have someone you haven't mentioned this problem to come in and hear your system.

Beyond that, I've never heard of this problem in many years in this hobby, most believe their systems sound better with warm up. I don't believe there is any kind of system build up that can lead to such a thing.

You may be on to something with the power conditioning, this should improve sound over long term listening sessions, your CDP is the component that will most benefit from clean power. Try plugging your digital into the amp dedicated circuit, this alone should improve things a bit.
almarg's avatar
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almarg
9,670 posts
 
My suggestion would be to unplug the plasma tv, blue-ray player, and all power conditioners. Then plug all of the stereo gear directly into the SAME ac outlet, on the dedicated ac circuit, using a power strip to provide enough outlets (preferably one that does not include a surge suppressor).

If that does not help, try the same thing but with the undedicated ac circuit.

If either of those steps eliminate the problem, return to the original configuration one step at a time, to determine what is responsible.

Also, if you have a multimeter, measure the voltage between ac neutral and ac safety ground. I'm wondering if one of the ac runs may be miswired.

Also, if any of the components have two-prong plugs, orient the plug to give you the lowest voltage between chassis and ac safety ground, measuring while no interconnects are connected to the component.

Finally, 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.

Hope that helps,
-- Al
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?)
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