hi,
I was looking for something else and stumbled across your post.
I am an electronic Engineer. Your modulation is a slow build up of waves going back and forth, building up much like a bridge collapsing or tsunami building up, wave over wave. You probably are starting with less then 1 hz - you cannot hear this, then increasing until audible range.
I have designed high frequency circuits and networking etc. The signal reflections are causing this and they are caused by "mirrors" in the signal path.
You only bet is to change out each item in your system until you find it. The amp, pre-amp, speaker cable, Interconnect, source etc.
You could try to isolate this by turning on just the amp and speakers, leave it on for 1 day. Try it with just the pre-amp, amp, speaker. Then 1 source, pre-amp, amp, speaker, then another source, pre-amp, amp, speaker until you figure out where in the chain the reflection is.
If you have the reflection jumping across or around the components, then you have a very unique situation - you should write this up. IT is hard, not impossible, for reflections to go backwards through components, it is typically within or between 2 components.
Also, not possible to bench measure, the power supply of one of the units has the slow modulation, so you have to open all the units and measure which unit is creating this modulation when you hear the sound. You will need a scope to see this.
All of this is a lot of work. It might be a lot more fun just to change everything out and start fresh. Unless you type A and have to solve this for enjoyment. |
Thanks for the update. I don't think there is anything in what you've reported which changes my basic recommendation -- step one is to have all of the ac wiring, grounding, and voltages thoroughly checked out.
My instinct would be that dc offset is much less likely to be the cause of the problems than a miswire or a missing wire would be.
Regards,
-- Al |
Just a quick bump to this thread -- with some new info to report:
1) My electrician-friend thinks grounding issues will be easier to check than dc-offset, which suggests he doesn't have the equipment to check the latter at his disposal.
2) The breaking-IC connections and re-establishing them turns out to be a red herring: It's the *POWER* connections that have to be disconnected and reestablished, only.
3) The CD-player transformer doesn't just get extremely hot, it also has an audible hum which I'd never noticed before this most recent round of tests. So the amp and the CD-player are both humming from inside their respective chassis.
Follow-up thoughts are welcome and appreciated as always. |
Okay, will try that experiment. Sounds like a good one. |
03-20-09: Dog_or_man
The dedicated line has a safety ground. Dog_or_man, If I could make a couple of suggestions. First it appears part of your equipment is plugged into an old 2 wire branch circuit fed from the old Square D panel. The new 120V 3wire dedicated branch circuit is fed from the other GE electrical panel, which I assume is the main electrical panel. I personally would not feed an audio system connected together by ics from two different panels. Plug all your equipment just into the new dedicated branch circuit...... After you connect everything to the new dedicated circuit I would like you to try an experiment. Power up your system put on some music and set the volume level to a moderate listening level. Then leave room go do something else for at least 30 minutes. After 30 minutes has past return to the room. Adjust the volume level to where you normally listen to your music. Then sit down and listen...... What is your first impression? Does everything sound ok? After 20 or 30 minutes of listening does everything still sound the same way or worse as you have experienced in the past. Post back your results. Jim |
The dedicated line has a safety ground. |
OK, thanks Jim. Perhaps I misinterpreted Dave's post, and maybe he meant that the dedicated line does have a safety ground, and one which has a proper complete path back to earth, while it is just in the rest of the house that there are some 3-wire outlets with the safety ground not connected. We'll await Dave's confirmation that that is what he meant.
Regards,
-- Al |
.....connecting a wire from the chassis of one and only one component (probably the preamp) to a known earth ground (such as a cold water pipe, a copper stake driven into the ground, etc). That could very well resolve the problem, it seems to me. Careful there Al.... That may not be good advice. We have no way of knowing when the house was built. We only know at this point it was around 1949 from the info given for the Square D panel. And we do not even know that for sure because the house could of been updated in 1949. The power company's 120/240V overhead lateral service drop is triplex attached to an eye bolt connected to the service entrance conductors via way of the weather head. Though the service is old looking it still looks at least late 50s or newer to me. Kind of hard to tell from just looking at the pictures.... I can't quite figure out why the main breaker is a 3 pole 60 instead of a 2 pole 60 though. That is if that is the main. I am sure at some point the main service entrance neutral conductor was connected to earth. That has been the norm for many many years. Also for many years if the incoming domestic water line is metallic then that shall be the earth connection for the service neutral conductor. At this point we can only assume the neutral is still connected to earth. Just guessing from looking at the pictures the last picture is the main panel. Again only guessing. If this is indeed the main panel then the neutral bonding to the enclosure as well the connection to earth ground was done here..... If the electrician ran a new dedicated line from this panel, which is how I read Dog_or_mans post he should have an equipment ground at the receptacle. I can't imagine an electrician installing a branch circuit today with out an equipment grounding conductor. Who knows..... What I do know the safety equipment grounding conductor needs go back to the panel the branch circuit is fed from and connected to ground there. If a ground is not present at that panel then the grounding conductor should be extended and connected in the panel where service entrance neutral is bonded, connected, to earth. 03-20-09: Dog_or_man
The main electrical system of the house has no safety ground whatsoever ("the third pin on these outlets is just for show, Dave") Old house wiring Branch circuits with out equipment grounding conductors is nothing new. And yes many a home owner have replaced old worn out 2 wire receptacles with new 3 wire type. Legal to do so? No..... At any rate because there is not an equipment grounding conductor present at an outlet that does not mean the main electrical AC service is not bonded, connected, to earth. If the service entrance neutral conductor is no longer connected to earth for what ever reason I can't imagine any electrician would leave it that way. |
Whoa! So the whole system (chassis ground and signal ground of all components, as well as all interconnect shields) are completely floating relative to ac hot and ac neutral.
Seems to me that that is your problem!!
And beyond that, I wonder if ac neutral is connected to a true earth ground near the breaker box and the ac inlet to the house. If not, as you said you may potentially (no pun intended) have worse problems than with your audio system. Such as no safe path to ground for lightning that may hit the power lines. Your electrician friend definitely has some things to check out.
Assuming this more serious potential problem is ok, as far as the audio problem is concerned I would try (as a temporary experimental fix, pending getting the wiring redone) simply connecting a wire from the chassis of one and only one component (probably the preamp) to a known earth ground (such as a cold water pipe, a copper stake driven into the ground, etc). That could very well resolve the problem, it seems to me.
Regards,
-- Al |
The electrical work shouldn't cost that much money, trading down will defeat your whole purpose. My first inclination remains over- voltage on your AC is causing at least some of your problems.
You are part of the way there already with the one dedicated line (if this is wired up comprehensively). You do need to properly ground this line, measure for dc offset, voltage and check for all the things Al mentioned, the measurements and check out should cost very little. Only after determining whether these are issues should you proceed further.
You could also borrow a power conditioner from the lending library at the Cable Company, shipping is the only up front cost. This should tell you something about the quality of your power.
I don't know about your knowledge base or handy-man skills, but DIY saves tons of money. I did all my own wiring after gaining requisite knowledge. Eventually, you will find every single inch of your power delivery system is critical. Everything from power in to your house to delivery into IECs on equipment is subject to improvement. One of the biggest payoffs in audio. |
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. |
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 |
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. |
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). |
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 |
All the power related stuff sounds reasonable. I don't get the breaking and re-establishing IC thing, this has nothing to do with power issues.
I don't recall if this has already been mentioned, but it sounds like you may have an over-voltage situation as well, this causes hum in my isolation transformer. Other than the hum, I haven't had any other issues.
Proper grounding of dedicated circuits is absolutely critical as well. As I previously mentioned, you should get all equipment off the non-dedicated lines, all kinds of crap rides in on shared grounds and mains. Digital will benefit most from clean AC, all your video equipment should be on seperate lines from audio equipment.
You should have 3 dedicated lines, one for amp, most likely straight into wall, another for CDP and preamp, a third for video components. You'll never get to the bottem of anything until you do this.
Next, get a quality power conditioner for digital and preamp, maybe amp. At this point you'll be able to make a correct diagnosis as to possible issues with the sonic palatte of audio components. |
I agree: the trouble seems partly due to contagious failure whose root-cause has never been identified. I always write too much on these things and my OP was *way* out of hand, but at this moment the most relevant points seem to be:
1) Similar problem years ago with Parasound stuff, couldn't be verified on three separate benches
2) Similar problem regardless of assorted gear-swaps in the meantime
3) Audible transformer hum in usually stone-silent McCormack amp, both through the front apron and down the speaker wires, and
4) Breaking and re-establishing the interconnect connections seems to fix everything for a while.
...It would seem that we're pointing squarely in the direction of either inadequate grounding or excessive dc-offset or both, as root causes of other things that aren't otherwise scientifically explicable.
Anyone think that conclusion, in the wake of the four salient points listed, isn't justified, or importantly overlooks other possibilities that should be addressed first? |
Ok, that's great that you have a friend who is an electrician.
An isolation transformer would eliminate problems with dc offsets, assuming the offset was not so severe that it would cause the transformer itself to overheat or have other problems. But I don't think an isolation transformer would be relevant to the other possible causes that have been mentioned.
Re UncleJeff's comment, yes, undoubtedly something is misbehaving after warming up for 20 minutes or so. But considering the history of similar problems with multiple components over the years, it would seem that something else (such as problems with the ac wiring or grounding) is causing damage to some part or parts, and that damage is in turn resulting in the misbehavior after warmup.
Regards,
-- Al |
These are great action-items to checklist my way down. I'll try to get my electrician friend to come over and look into the earth ground and the DC-offset first, and then maybe take things from there in the direction of an isolation transformer. ...Yes? |
I still say that something is warming up and then misbehaving. |
Hi Dave,
I have seen this problem before in other amps and preamplifiers. What you have is a capacitor or resistor in the power supply of the amplifier or pre amplifier that is changing value. If I were a gambling man I would bet that you have a resistor in one of the power supplies that is in the process of failing or that the resistor is changing its value due to heat. If you are experienced with a fluke and know how to read resistance bands, you could check the resistance values before powering up your equipment and then check the values after an hour to determine what values have changed and are out of specification. |
I tried some Signal cables a while back and thought they made my system sound like the way you are describing. I tried a Harmonic technology AC-11 power cord and the system sounded much smoother. Also, the Salk speakers are very revealing and detailed. Many of the Cd's you listen to may sound bright in this system. I would throw some tubes in the signal path if I was you. A lot of good suggestions; especially by Almarg. Doesn't cost anything to verify his suggestions. If you can't figure it out, ask for some help in your area. |
|
Dog_or_man,
At what level would you say you listen to music on your system? Moderate, above moderate or loud? |
Al's last point is a good one and begs more backstory: I've been eating components *and* speakers during all of this, at a rate that doesn't otherwise make sense. The whole trouble started most of three years ago with some Parasound gear that would develop a "whooshing" sound in one channel, almost like when one of your ears is full of water, that could be dissipated by wiggling the IC between the pre- and power amp.
Is that the exact-same problem I'm having now? No, of course not -- but the person from AA with whom I spoke on the phone suggested that, if the mains had an insufficient earth ground, and/or significant DC offset, these problems would compromise the components' ability to deal with the cr*p that was being handed to them from elsewhere in the signal path, like RF or digital noise, and could even lead to damage.
I've eaten a left-channel tweeter in one expensive pair of speakers, a left-channel midrange in another (using different amplification), and sent three different amp/preamp combos away for service, with varying conclusions coming back from the manufacturers. As often as not, even noticeably audible problems with the electronics have not been repeatable on the bench -- which would further suggest something having to do with power, no? |
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 |
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. |
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 |
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 |
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?
|
I can understand your frustration, try speaker cables or interconnects that are not detailed and/or roll of high frequency response. Buy a mellow 1980s era Onkyo or Sansui integrated amp or receiver through your local Craigslist.org, ($75.00 +/-) and see what happens, you should be able to sell it again if you don't like it. |
"Static buildup in capacitors" sounds to me like a non-technical person trying to be technical. Also, static is most severe when humidity is very low, which is the opposite of what you've got in Florida.
In principle there shouldn't be significant dc offset from your power grid, because if you live in a typical house your ac is coming from a transformer on a nearby pole, and transformers don't pass dc. I suppose improper grounding somewhere in the path nearby could result in an offset, but I would think the other possibilities that have been mentioned are more likely (including the ones I suggested about problems in your house wiring).
Regards,
-- Al |
Yes -- I've even tried using the bluray player as my front-end for listening to redbook CD's, and the same things happen. One commenter in another forum suggested "excessive DC offset on your local grid," and another suggested "static buildup in your capacitors." Do the folks in here think either of those could be the problem and, if so, what would be the remedies? |
fascinating - does the same thing happen when you are using the BluRay and watching your Plasma? |
Get a Class A amp.
According to a guy on another thread, it takes a week to warm up. |
Worth a try, though a hum problem might also be related. The amp makes an audible hum, both in the speakers and physically -- through the front apron -- but not so much so as to be obviously indicative of a performance problem.
Also, I'm not sure but I think the hum in the speakers has an added, click-click-click component when the larger problem is occurring, and not when it isn't -- but I could be imagining that part.
I'd love to hear the Silverlines, but I'm hesitant to continue swapping-out boxes before ruling-out for certain if the problem is electrical in nature. |
Is the Arcam the only source unit you have? Maybe you have a turntable, tuner, or some such you could try, to see if the Arcam may be the culprit?
Good luck,
Dan |
I should tell everybody one more thing.
Sorry this is coming out in dribs and drabs, but I have a hunch that this might be an important detail: I started shoveling money at my stereo in the first place because an old configuration of gear and speakers developed this *bizarre* characteristic that several different techies were unable to recreate on their own benches: After extended listening, the left channel would develop a "whooshy" kind of noise, almost like the sound your ear makes when it has water in it, and would attenuate in volume, eventually to zero.
If I went to the back of the stack and wiggled the left-channel IC between the pre- and power amps, I'd hear a series of loud pops in that channel, and then everything would work just fine again, for awhile. As I say, it was for this reason that I started swapping-out gear in the first place, but what the ancient problem and the current one seem to have in common is a tendency for "build-up" to be dissipated by mechanical processes at the back of the stack.
Does this shed any new light? |
I think it is your sensitive hearing and fatigue. I feel very stromgly this is your issue. Only one way to fix this for good in my humble opinion. Here it is. Change your speaker to one that is less forward and better matched for your hearing. A speaker that won't offend with a very wide range of gear and wire.
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.
I, like you, have owned many systems and the Bolero is made for folks like you with sensitive hearing. Crazy thing is this speaker is still detailed and very transparent. Not front row, but rather more set back in the audience. Smooth and easy to listen to highs. You are drawn into the music and not shouted at.
Just my two cents from a distance. I may be wrong, but it sure seems you need a different audio experience.
I am sure there are other speakers for you, but this Bolero is one I know about. I have not heard another quite like it. Calling the Bolero warm does not go far enough. It it a radical departure from most of today's hyper detailed, front row perspective speakers.
Bill |
How do I "use a multimeter to check if one of the AC runs is miswired"? And how do I "orient" a two-prong plug? How do I diagnose, and what do I do about, an "open AC neutral run"? Set the multimeter to read ac volts, on a scale that is greater than 120V, such as the scale that many multimeters have that reads 0 to 300VAC. Then for each outlet measure the voltage between hot and neutral, hot and safety ground, and safety ground and neutral. How to orient a two-prong plug, if any, I explained in my earlier post. I'm referring to the fact that if the two prongs are not polarized (i.e., one is not wider than the other), they can be plugged in with two possible orientations. If an ac neutral run is open, it should become apparent by performing the multimeter measurements described immediately above (i.e., you will not see any voltage between hot and neutral). If you don't have a multimeter, or other ac voltmeter, or you don't feel comfortable doing these things, try my other suggestions first and if they don't lead anywhere perhaps you know someone nearby who has experience making electrical measurements. One more possibility occurs to me: Somehow either a large dc offset or an ultrasonic oscillation may be being sent into the speakers (both would be inaudible), causing speaker driver or crossover elements to heat up excessively, producing the audible symptoms after the 20 minute period. Not sure what might cause that, given that you've apparently tried multiple amplifiers, and I'm not sure how a dc offset would affect the midrange-tweeter part of the spectrum, but I thought I'd mention these possibilities in case they trigger some further thoughts. Regards, -- Al |
Sns: Do you mean to suggest that I should connect the preamp, poweramp, and cdp to the same line conditioner and thence to a single outlet on the dedicated line?
Almarg: How do I "use a multimeter to check if one of the AC runs is miswired"? And how do I "orient" a two-prong plug? How do I diagnose, and what do I do about, an "open AC neutral run"?
Ghosthouse: The problem was "fixed" when we did a quick break-and-reconnect at the friend's house, and did not recur until I was back home, but it seemed unlikely to me that it would have happened at the friend's house in the first place, if the problem was in my home. Thoughts? Could the whole thing be attributable to the fact that my central AC and furnace air-handler are located about 28" away from the left speaker, on the other side of a thin plaster wall?
Uru975: Can I give specific instructions to an aftermarket tech, that will reduce the likelihood of a "false negative"? The Arcam CDP, in particular, gets *really* hot after it's been running for awhile, and other owners have said that theirs don't.
Mrderrick: Listener fatigue is certainly possible -- anything's possible -- but would that fatigue "reset" after such a short interval of time needed to break and reestablish the ic connections? Sometimes the problem has been "fixed" in as little as two minutes.
Cyclonicman: How do I "check the quality of electricity being delivered to the community, voltage fluctuations, etc." and what do I do when the results turn out to be bad? I've been thinking this could be it: We have a municipal power company here in Gainesville, Florida, and they... well... s*ck, frankly. |
Heat. I had a Saturn Car that would just stop running after 20 minutes of city driving, but never on the freeway. As it turned out the fuel pump had a contact that started to arc when the engine got really hot.
20 minutes. Something in system gets to a certain temperature and then goes 'off'.
That's the best I can do for you. i don't want to talk about how many mechanics and dollars were involved with tracing this problem/ |
Since you fixed everything and it even occurs at your friends house, maybe it's the quality of electricity being delivered to your community, voltage fluctuations, etc. |
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. |
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. |
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. |
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 |
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? |
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?) |
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. |
