Question Conundrum: what possible reason for a Pre-Amp channel attenuation?


Active Member
As the title of this query implies, I have a conundrum about one channel of a Zone 2 Pre-amp output of a Yahama Z9 DSP. I use a Quad 606 stereo amp for "Zone 2" distribution from the Yamaha. I use the Pre-Amp Outs from the Z9 and these feed into the Quad inputs L & R. Last year I discovered that the RH channel speakers were not functioning properly. The LH speakers were fine, producing expected amplified sound sources, but on the RH side there was just the mere faint hint of sound. In other words, the channel was not totally dead. Eventually I got around to troubleshooting and switched the inputs. It seemed to prove that the RH channel of the (Quad) amp might need attention. I sent it off to Quad for attention, but this took some weeks. It arrived back yesterday (31.01.19). When I connected it up, there was a "thump",followed by some rather worrying "buzzing and agricultural noises". I switched off and reset the connections and left it until today. Today, there was still a bit of a "thump" on switching on the Quad, and this was before the Yamaha was fired up, but everything seemed otherwise OK.
When I put a source through it I had exactly the same situation as I had had before.. the RH channel was producing only what could be a very attenuated tiny sound, whilst the LH channel worked fine.
Unfortunately, because of the very very tight installation (up against a wall, on shelving) I cannot easily access the back on my Yamaha to remove and reset the Pre Out Zone 2 cables, which I suspect might need doing as part of the process of further trouble-shooting. However, that may or may not give me a proper diagnosis.
What I have done, which arguably I should have done before sending my Quad amp off to the manufacturers,(for which I have paid over a hundred quid, for the replacement of ostensibly just a power-board capacitor,) is to use a split feed from the LH Z9 Pre-out cable (which I know works fine) to supply both Left and Right Quad amplifier inputs. This has established the integrity of the 606, since both sides of the speaker array now work fine, except that I don't have "proper stereo". As a workaround pro-tem it gets all speakers (of several sets around the house in "Zone 2",) working at least.
What has puzzled me, having given some detailed background to this situation, is WHY should the pre-out signal on the RH channel be apparently so attenuated? In "schoolboy logic" I should have thought that the signal being output from the Yamaha would either work properly, or not at all. It is almost as if the signal level needs "increasing" to match that of the correctly working LH side.
I have spoken to a contact at Yamaha and he advised me that initially the first port of call was to take out and reset the RCA connections of Zone 2 Pre-amp Outs. I did explain the difficulty of accessing this area , but in any case he did admit that it might not prove the case one way or the other. If that happened to be the case, then the only remaining option, a major operation here, was to return the Z9 to "the Vets" for attention. I still am at a loss as to why there appears to be a "sort of Pre-amp out signal loss" .There is something there, but it ain't enough!
If anyone has a clue about this I would be grateful to know. I should add that the installation has been in place, untouched or without any interference, for a good many years, but I have heard of instances whereby connections can become a bit "Oxidised" despite being not readily exposed to the atmosphere.

Thank you for reading this far! As I said, I would be grateful for any suggestions or explanations.



Active Member
Yes thank you for that .It has been suggested by my contact at Yamaha. However whilst not ruling it out,the cables I use are high quality made to order (from Singapore) which doesn't mean they cannot go walkabout, but arguably are less likely to do so!

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