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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
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almarg
9,670 posts
 
I don't get the breaking and re-establishing IC thing, this has nothing to do with power issues.

Sns, there are two possible relations that I can envision, albeit somewhat vaguely:

-- If a ground is missing somewhere, a component by itself (not connected to anything else except power) would tend to have its chassis and signal ground "float" to a voltage level that is determined by small leakage currents in its power transformer, or elsewhere in its internal circuitry. Connection to other components via interconnects would change that, because the interconnect shields tie together the chassis (and consequently the signal grounds) of the connected components. If multiple components are not properly grounded, they will "want" to float to different levels, but the interconnects between them will prevent that. Temporarily breaking the interconnections will allow the chassis of each component to return to the level that is determined its own internal leakage paths.

-- If the proper ground paths and ac return paths are not present (especially if ac neutral is open somewhere), return currents could be flowing through roundabout paths that may include or be affected by the presence of the interconnects. That conceivably could be causing something, such as a power transformer, to overheat and cause the audible symptoms after a warmup period. For instance, if ac neutral is open, the leakage path through a power transformer to ac safety ground could be breaking down and serving as part of the return path (for a component with a 3-prong plug), which would definitely overheat the transformer. For a component with a 2-prong plug, the return path in the absence of ac neutral could be via interconnect shields to other components and through them to safety ground.

Or something like that; I obviously can't formulate all of this precisely, but my point is that a relation between disconnecting the interconnects and a power problem is very conceivable.

Good point about the overvoltage possibility. Re your suggestions about multiple dedicated lines, etc., those are all excellent suggestions for optimizing sound quality, but I think that what we are dealing with here is a basic functionality and reliability problem, which needs to be resolved first.

Regards,
-- Al
dog_or_man OP
68 posts
 
I've just finished uploading eight images to a thumbnail gallery on a hosting site called imageshack, and will post the link to the thumbnail gallery here. The thumbnails are arranged in two rows of four.

Top row (L to R) :

1) My rig, in its latent state in a rack with no rear panel and front doors open

2) Points of conduit entry to the attic above the breaker (note the small white-painted copper tube, emanating from the wall, just below the elbow of the water pipe visible at right (more about this, below)

3) Electrician-friend's temporary solution to dedicated AC-line. He had two outlet boxes of two outlets each on his truck, so he overlapped the plates a little (background). Undedicated AC line is in foreground. At the moment the CDP, Amp, and Preamp are connected to the dedicated line, and the power supply (which manages the TV and BDP) is connected to the undedicated line

4) Sample of the "controlled chaos" at the back of the stack, including painstaking attempts to ensure that power cords, IC's, and speaker cables only cross at right angles. (Power wraps have no noticeable effect on problem, f-y-i).

Bottom row, (L to R) :

5) Inside breaker-box, made by "Square-D," c.1949. The un-dedicated line serving the home entertainment rig is bottom-left, single breaker

6) Close-up of break in that thin copper tube that emanates from the wall in picture 2, near that elbowed water pipe. I cut this thing with my hedge trimmer shortly after moving in to the house, and it is affixed to an external water spigot in such a way as to suggest that it's a grounding mechanism for something

7) Close-up of the thin copper tube's connection to the spigot, directly below the break -- is this a picture of some sort of grounding mechanism? Should I perhaps have avoided grabbing both severed ends of the thin copper tube, to take this picture? (Nothing happened, by the way)

8) Close-up of the outside breaker panel -- dedicated line is top-right, and it's a split breaker because electrician-friend didn't have a joint breaker on his truck (plans to replace).
jea48
4,266 posts
 
7) Close-up of the thin copper tube's connection to the spigot, directly below the break -- is this a picture of some sort of grounding mechanism? Should I perhaps have avoided grabbing both severed ends of the thin copper tube, to take this picture? (Nothing happened, by the way)
Looks more like a 1/4" water line with a "Tap a Line" water valve connected to the main water line. Commonly used to feed an ice/water dispenser for a refrigerator.

As for the electrical system, it is time for a rewire or at least an update.
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almarg
9,670 posts
 
Thanks for posting the pics, but they do not trigger any particular thoughts for me.

Did the electrician friend make a comprehensive set of measurements of all 3 of the connections (hot, neutral, safety ground) at each of the relevant outlets, verifying that there is in fact a connection back to the breaker box in each case, and through it to the incoming ac; that nothing is miswired or open; that voltages are correct; and that significant dc offsets are not present? Those are the foremost things that need to be done, imo.

Regards,
-- Al
dog_or_man OP
68 posts
 
The electrician didn't do anything comprehensive before. All he did was install the dedicated line. The main electrical system of the house has no safety ground whatsoever ("the third pin on these outlets is just for show, Dave") and nobody has ever checked for openings or DC offset, either one. I was just sitting here thinking that maybe the best thing for me to do is trade-down in the actual sound system, and use the freed-up money to attend to the electrical issue more comprehensively. Indeed it's probably kind of a wonder that something ghastly (not involving sound quality or fried-up left-channel tweeters) hasn't happened already.
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