Thanks for this last round of replies, you guys read my posts more closely. Thx.
@terry9 may be on to something. Narrowing it down, I now think its my DAC more than anything else in the system. Possibly amps too when dead cold.
- Last three days in a row, system sounded just fine after 1hr warmup - all left plugged in.
- At 3+ hours warmup I do notice a bit more 3-dimensional layering and sound coming from the sides and slightly behind me with this particular all-tube system. Big transformers in amps warm by then!
DAC:
My DAC is a NOS R2R Ladder design with a chip (not resistor type) and a TUBE in the circuit. At first I thought I had a failing tube or something, changed it to my spares. Nope, the prior tube was fine. Not the tube in the dac.
- For some reason if I completely unplug my whole system and everything sort of discharges for longer than a week, its clear I need more (2-4hr+) time for warmup the first re-engagement of the whole system from dead-cold.
- I accept the situation closer to what @terry9 shared above. Now re-learning again my particular DAC may benefit by turning it on for a bit sooner before listening, particularly if the DAC has been unplugged and off for a week+. Seems to benefit with earlier power-on time.
Back to playing the system daily now. No issues, 1hr warm up is just fine.
Thanks for some of the more helpful replies here. ✅👍