It's gotta be something is heating up in the DSP-33. A cold joint or power transistor in my experience are the two most common things that fail. Since it's biamped I doubt it's a power transistor (You'd only lose highs or lows). Since you lose everything it's probably on the digital board. If I recall the DAC is on the analog board (they REALLY do wait right to the end before switching to analog).

If you feel brave. If you can get it in a failing state, try using cooling spray gently. First try a very wide pattern covering everything. If it snaps back into shape you know it's temp related. If cooling fails to bring it back try a reboot (if that works it's probably an IC). Get it failing then try to narrow it down. Since it's so intermittent it may take a while. A heat gun can possibly get it back failing state quickly. Common sense applies on how much heat and how much cool and how fast to apply, it should not need too much in either direction since it's marginal now at room temp.

- Fiddler (IMHO)

If you think listening to music is fun, try learning an instrument.
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