Originally Posted by winston9332
Any electrical engineers or technicians have a theory as to what might be causing these issues? is the popping noise indicative of something in the output stage?
Well, I thought I might muddy the water just a bit....I am not an audio amplifier designer but I do work in the field of consumer electronics (PC's) and, without trying to bore anyone, I thought I might look at this from another angle.specifically the EMC angle. This will be a lengthy discussion but it may also be a relevant one. I know some of you know what EMC isothers may not so, in brief, electromagnetic compatibility is the ability of an electronic device to comply with emissions and immunity standards involving electronic phenomena in the US, only radiated emissions (rf energy radiating from the enclosure) and conducted emissions (rf energy conducted out of the device through the power cord) compliance is required. Rf immunity is not required in the US (as it is in the rest of the world) and when talk of the SR6004 in the US having a different power supply than that of the rest of the world, I started thinking about the possibility of Winston's experiences..it would not be out of the question for Winston (or even one of his neighbors) to have some device hooked up to the local electrical system that was conducting nasty rf energy into the electrical system..there isn't a red flag for this occurrence other than a susceptible device being affected. Since it appears there are SR6004 failures outside the US, I don't think it can be so easily pigeon holed to a cheaper power supply for the US versions (cheaper in that components used for a globally marketed power supply would not need to be used, due to the lack of rf immunity requirements in the US).
Let us also be aware that power supplies today are smarter than those of the past.in that they have often have microprocessors that monitor current/voltage/temperature and respond in certain ways when certain conditions are met..they may also respond in unexpected ways when unexpected transient rf conditions are encountered. I can give you one brief example of a large server I was involved in testing recently.the test stimulus was identical to that of what any consumer electronics device would encounter if it were to be marketed and sold globally - and for this test called Electrical Fast Transients (EFT for short) the stimulus was a 1kV 5kHz voltage burst imposed upon the line voltage. I know this sounds extreme but it is fairly standard - most power supplies are designed to be immune from such transients..in this case the server shut down (in a bad way) every time the stimulus was applied, as the smarts of the control circuitry responded in an unanticipated way and thus sent the power supply in to illegal state land. A brief design review and a few additional components later and everything was fine. Be it known, all of this testing only uses certain standard voltage/frequency transient combinations and are supposed to be somewhat representative of what might be experienced in the field..but you can't possibly cover every possibility.
That being said, lets assume that the SR6004 power supply, while passing all regulatory requirements, still has a design weakness (I won't call it a flaw at this point)..and as such, in certain electrical environments (be they radiated or conducted, although I believe conducted would be more likely in this situation), when all the conditions are met, the control circuitry shuts the unit down in an unanticipated way..a way for which there is no user option for reset. Lets also assume the window for this weakness is very small..so perhaps only a small percentage of units sold will experience this anomaly - if this unit is repaired to the same condition as new and then placed back in the same circumstance, those who exploited the weakness very well (Winston) will undoubtedly experience it again. Those who were on the edge of exploiting the weakness may have the POD occurrence only onceor never.or 5 years after purchase.
I guess my point is Marantz makes great amps but they are subject to market pressures like everyone else..design in one country, assembly in another and emc testing by a third party in yet another countryand quality emc testing is not always given a high priority - another example - I needed to acquire an AVR for testing with a new PC that contained a 7.1 audio output and the output needed to be exercised - so off to Soundtrack or Ultimate Electronics (whatever it was at the time) and I bought a $450 namebrand AVR (five letters, starts with a D) that had the requisite inputs..when this unit was tested for radiated emissions (along with our PC) in our chamber it failed the Class B limit by 17dB (that's pretty bad, BTW)!!! To adequately test our PC (also Class B), we needed all other devices to be Class B compliant - so back to the store for an exchange. I didn't bother with another D**** product, as time and time again I have seen certain mfr's place emc as a high priority across all lines and others don't - and I didn't want to waste my time - so I got a Pioneer for an additional $200 - this system passed the same test with 10dB of margin. The point of this example is that non compliant radiated or conducted disturbances either from a device in question or lack of immunity to these disturbances by that same device are pretty much invisible to the consumer - and just as an add-on my experience has shown many (if not most) computer products at your typical Best Buy are non-compliant to some degree - 99% of the time you just won't know it. I would expect the audio equipment world to be close behind and directly proportional to cost.
All that being said, I have no answersI just wanted to think outside the box. I expect when Marantz is done with the finger pointing (this is usually the first step when design and manufacturing and testing all occur in different places coupled with potentially poor outsourced customer service that doesn't get fed back to people that can actually do something about these problems), that they will be busily trying to duplicate these occurrences in emc/powerline/thermal testing - as to whether they actually do anything about it will probably come down to the # of field failures vs. the number of units sold - (and if they can duplicate the failure) and I suspect we don't have access to either of these numbers. If any of you are still awake after reading this, I hope I don't sound too jaded or pessimistic - I believe Marantz is still a good company and I wouldn't care enough to write all this if I wasn't interested in buying one.
Please comment if any of this is unclear - Steve