either DAC or transport is giving troubles...

My preamp is passive and there is no problem with it.
I've recently discovered that by switching the digital inputs it sounds OK for a while and than the left channel dims out and becomes mushy and undetailed in comparison to the other one. The same experiments were made wiht different input of my preamp. As I've mentioned before, my analogue setup sounds OK with the same preamp.

This DAC was pleasing me, but I wouldn't break my head on where and how to get it fixed. I just need an idea of the good used alternative in $600 range for listening mainly red-book CDs and HDCDs. Meridian 518??

Could also be a preamp problem - try a different input as well.

Have you tried switching the interconnects between the DAC and the preamp from right to left ? This would tell you if it is one of the cables. If the transport or digital cable were the source of the problem, i don't think that the DAC would lock onto the signal. You might also want to try plugging the output of your DAC into another input on the preamp. You could have developed problems in the one specific input or jack of that mode. Sean
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Since both channels come from a single data stream I don't think that the problem is in the transport. More likely the output stage of the DAC has lost a channel. I may be wrong, but I don't see how a transport or even digital cable problem can selectively affect one channel.