there's a service manual available and on p5-1 there's a diagram that has a couple sections
fed from the DSP (digital Signal Processor) that (end) results in left and right channels signals
outputs (how's that for plural phrases) but another path takes the digital signals directly out
to the digital and optical outputs.
these sections seem to do a bunch of things, I am probably oversimplifying and misleading,
like process the SACD's DSD into PCM, and do some x-bit processing before
doing the Digital-to-Analog thing.
my guess is the only place you could "hear" analog signals is at the end of this signal chain
and anything before this end stage back to the output of the DSP section is all digital
and will need a different class of tools to inspect, let alone.determine what's going on.
if you're willing to play with the unit to try to figure out what's wrong you can pull the
cover and identify the chips for this general DAC area. use a wooden stick and poke around
trying the chips and the parts - maybe a loose solder connection - you'll need a magnifier
and good eyes to look for any possible solder problems. also, if you have freeze spray
then after warmup (and the sound problem appears) use a narrow spray on each chip
to see if it's a heat issue (sound clears up after spray).
you can use an air cleaner (dust buster type) test the spray for coldness - typically when
duster is held upside down or at an angle.
when did this problem start, assuming it wasn't a day one problem. second - I'm assuming
you've verified it's not a (RCA) cable connection problem and the cables test Ok elsewhere.
next, you've tested the RCA outputs into a known working input. if you use an external
DAC then swap its cables at the receiver/preamp/amp with the HD841.
lastly, if all this overwhelms ( I tend to overdo the advice thing - it was an absolute mandatory
process in the jobs I held), these HD841s are sleepers and are not overpriced in the
used market - I bought mine on eBay earlier this year for very little $$.
my best guess is somewhere in the last stages, in the analog section, and that's if the
sound is correct but distorted - in other words the digital to analog conversion works
since it's not random noise (bit conversion didn't work). It would be the I/V conversion
or some signal in that last chip not getting set for the chip or as simple as a bad cap.
(and very last thing - could be the muting circuit if there is one - these make me nutz).
if it is a chip, it can be replaced even if its a surface mount, takes a lot of care since
there are hot-air repair stations and if a soldering gun/iron is used - has to be super
fine tips, etc. find the replacement chip is either easy (mouser, digikey) or hard.
Bob
