I did exchange e-mails with Mr Madnick. He suggested some actions (manipulating the volume control etc) while the problem was occurring. All to no avail. He was unable to think of any possible cause or solution.
Audio Advisor was also unable "think" of anything but were extremely helpful--they replaced both units and the same problem occurred.
I continued to scan the web and could find nothing resembling my issues nor anything indicating any problems with Audio Alchemy units.
I did isolate the problem to the AA unit-- the DDP-1.
--I eliminated everything piece by piece from the system. Luckily I had my old Conrad Johnson pre-amp. I removed the PS Dectet and used wall warts direct into the wall. ( I purchased replacement wall warts direct from Audio Alchemy).
I even used the DDP-1 with powered speakers (the Audio Engine 2+). The problem existed with this simple "set up." Source>DDP-1>Audio Engines.
I found the problem existed with either source component--Rega RP-6/Classe' CDP10.
Again, the "problem" was extremely vexing because it occurred intermittently and after more than an hour of use.
At this point (and concerned about speaker damage--the fog horn like sound was that loud!)--I sent the second DDP-1 and PS5 back to Audio Advisor. I had to rethink my whole system upgrade.
I replaced my C-J PV10A with a new Conrad Johnson Classic II. I purchased an Bryston BDA-3 DAC and plan on adding a Bryston or Aurender player/server.
I am using the Classe' transport into the Bryston.
I kept the Audio Alchemy PPA-1 phono stage--it is excellent! For use with the Rega. So far so good.
I have to say the most frustrating thing about all this is the Audio Alchemy DDP-1 is it is a superb sounding piece of equipment. Both the line stage and the DAC are superb IMOP. The fact that this problem was present in two different units helps eliminate the "ghost in the machine" theory.
Short of an autopsy (bench testing etc), no one seemed to have any ideas. Something in the unit was "failing" rather dramatically and always after hour(s) of perfect operation. Given the number of units produced what are the odds here?
This "adventure" has led to my wondering if the current move toward "everything in one box" thinking is perhaps 0ver-complicating things. I am back to a rather "packed" rack--CD Player, DAC, Turntable, Phone pre/stage (Audio Alchemy), Pre-amp/line stage, amplifier.
For example--the CJ line stage and the Bryston DAC are in "boxes" larger than the multi function units out there. Is there a trade off in play here?