Unique problem - one channel silent under different variables

Hi Denis,

As you’ve surmised, it sounds like the preamp has a problem that needs to be sorted out via professional troubleshooting. The symptoms you’ve described don’t point to any specific cause, as far as I can tell.

But as Jond indicated it sounds like you are not following the proper turn-on and turn-off sequences (with the power amps being turned on last and off first). Also, it sounds like you are disconnecting and reconnecting the RCA cables that connect the preamp to the amps while everything is powered up, which is definitely bad practice and could conceivably damage your speakers.

That said, I wonder if disconnecting the RCA cables and then re-connecting them WITHOUT switching the channels would have the same effect as what you have observed when you disconnected and re-connected them with the channels reversed. It could be that the channel reversal was not what restored normal operation, but rather a transient of some sort caused by the disconnection and reconnection itself, that might have temporarily zapped the defective preamp circuit back into normal operation.

Or if the problem is temporarily fixed only if the channels are reversed when the cables are disconnected and reconnected, that may just be due to the happenstance of the resulting transient being different when the reconnection for the problematic channel is made to a different amp than previously.

Good luck. Regards,
-- Al

Denis, I found a thread from about two years ago at another forum in which the OP had a problem with an intermittent popping noise in one channel of a Cary SLI-80 integrated amp. That amp was introduced in approximately the same timeframe as your SLP-98 preamp.

In that case the problem turned out to be caused by a bad Jensen copper and oil capacitor. It was mentioned by several people that those capacitors had high failure rates in times past, apparently including at least some of the years in which those components were manufactured. It was also said that Jensen confirmed that they had had a bad run of those capacitors.

I was thinking that a bad capacitor might be consistent with the symptoms you’ve described even before finding that thread. It might pay to have a technician (not necessarily a Cary person) replace all of the Jensen caps in your unit.

Good luck. Regards,
-- Al

Thanks for the clarifications, Denis.  Apologies if I inferred too much from your initial post (which I did). 

I have found that if I leave the preamp on constant standby, the issue is resolved.

That's obviously a key finding, but again it doesn't point to a specific cause as far as I can tell.  But have you done enough experimentation to be certain that what fixes the problem during the minutes following a cold start is switching the cables, as opposed to just disconnecting and reconnecting them, or not even doing that but simply cycling the power at the corresponding time intervals?

Best regards,
-- Al
  

While it is true that the coupling caps could be having a problem, its not been explained how this is alleviated by swapping channels!

Yes.  Which is one reason I had asked:

... have you done enough experimentation to be certain that what fixes the problem during the minutes following a cold start is switching the cables, as opposed to just disconnecting and reconnecting them, or not even doing that but simply cycling the power at the corresponding time intervals?

Best regards,
-- Al
 

I’m not sure I understand this. In this latest experiment was it the speaker cables that were switched (per Yogiboy’s suggestion), or the interconnect cables (as seems to be implied when you said "the right channel is supplying the left amp")? Or was it both that were switched?

Also, previously you had found that switching the interconnect cables after a few minutes had fixed the problem. And that leaving the preamp in standby when it was not being used also eliminated the problem. And that popping had been heard in both channels. Not sure how to reconcile all of this.

Perhaps two problems are present. Or perhaps the preamp is the only problem, but its condition has worsened to the point that both channels are now affected in a similar manner, and the preamp is intermittently injecting either DC or some transient from its right channel output that is causing the left channel amp to which it was apparently connected during this latest experiment to shut down.

It all seems very inconsistent. But in any event I would not conclude at this point that the amp is necessarily the only problem, or even that it necessarily has a problem.

Best regards,
-- Al