Bizarre issue (Audio Alchemy) first post here is unfortunately a "cry" for help. 
I recently purchased an Audio Alchemy DDP-1 DAC/pre amp. I paired it with the PS-5 power supply upgrade.
I am using a Classe' CDP10 player with option to run the transport to the Alchemy DAC or the Classe' DAC to the Alchemy analogue stage.
The rest of my system is a Rega RP6 with an Audio Alchemy phono stage and a Krell KST 100 into Revel M-20 Performa speakers. Interconnects are all Blue Heaven II's save for a PBJ phono to DDP-1 and a Moon Black Dragon digital connect from Classe' out to the Alchemy digital in.
Everything is plugged into a PS Audio Dectet.
I am gradually upgrading everything.

Here's the problem.
The rig runs exceptionally well-- no complaints re: the sound--until after a few hours there is a 'sudden" loud fog horn sound from the speakers. I mean LOUD! Literally blasting. I can find no reference on line to a similar sound. This sound is not impacted by the Alchemy volume control and can be eliminated only by shutting the system down. It does not return upon re-start until an hour or so later.
I suspected the Krell. I replaced the Krell with a pair of powered Audio Engine 2's and after a while same problem returns.
I removed the phone pre-amp using digital source only--and problem remained
I then suspected the power supply for the Audio Alchemy and returned it to the retailer --it was replaced and sure enough after several hours of perfect running the fog horn returned!
I am now planning to contact the retailer and have the DDP-1 replaced. I also will e-mail Peter Madnick at Audio Alchemy.

Thanks to anyone hanging in to this point. I am wondering what the knowledgeable folks out here think.
Any thoughts and advice would be greatly appreciated. 

I have to say--the Audio Alchemy units are terrific. Great sound (especially at the price point). I am somewhat certain the issue is somewhere with one of the three AA units--process of elimination has me down to the DDP-1.
I agree that you should remove the  PS Audio Dectet from your system.  It is possible the fuse in the unit could be a causing your noise problem.  
Great suggestion! Will try that --plugging the external power supply (PS-5) into wall (hospital grade wall plug). 

Never thought to consider the Dectet as possible source of the problem.

 The problem is a strange one--appears intermittently and after hours of play with no problem at all. Impacts both analog (records) and digital (CD's).

Will keep you posted.

see above.
I used the Dectet successfully with old system-- Linn Axis--Classe CDP10-into Conrad Johnson PV10 to the Krell no problems.
(only the Krell into the High Current input). No problems.

So far with PS-5 powering the AA units plugged into the wall (Rega, CD player into the Dectet) seems to be fine--at least now. 

It sounds like the Audio Alchemy DDP-1 DAC/pre amp with the PS-5 power supply upgrade needs to be plugged direct into the wall plug and not connected to the PS Audio Dectet.   Please keep us posted on how this works.   

"Inside the PS-5 are two separate, regulated power supplies: one for analog circuits, the other for digital and control circuits, which provide each the unique power qualities required to maximize their performance. These discrete supplies are routed into the DDP-1 (DAC/Preamp/Headphone Amp) through a special multi-pin connector on the rear of the unit for easy connectivity.

Additionally, the AC-to-DC conversion is performed inside the PS-5 to prevent interference with the sensitive analog audio circuits inside the DDP-1.  A balanced supply with separate analog and digital/control feeds, separate positive and negative rails for analog circuits, and large banks of storage capacitors for better filtering and improved dynamics".

Based on the above technology, my assumption is the Audio Alchemy PS-5 Power Supply needs to be plugged DIRECT into the wall plug and not the PS Audio Dectet.   
Yes I think the PS Audio Detect needs to be totally removed, use some cheap power strips if u need to. Try this out and let us know what happens.

Matt M
Here's the latest.
(I did follow advice and plugged the PS-5 power supply directly into the wall)
After several hours of trouble free operation "it" happened again. Loud horn like noise. I "played with" the volume control on the DDP-1 and this time the noise was impacted it cut in and out. I also noticed the volume indicating numbers on the DDP-1 turn red (opposed to normal black) and commence flashing.

I then turned everything off.
After a few minutes I powered everything up and --no problem.

At this point I called Audio Advisor and spoke with a tech.  He agreed the suspect, having replaced the PS-5 power unit--was likely the DDP-1. He noted microprocessors can go awry. Though not a common occurrence. 

They are shipping out a new DDP-1 (I will return the unit I have when it arrives). I have to note Audio Advisor couldn't be easier to deal with. I will break everything in my system down and re connect--carefully! Then it's crossed fingers time.

You folks here have introduced an interesting area for consideration.
The Dectet has worked fine--the Krell is plugged into the "high current" section and everything else into the two other "isolated" sections.

Set up instructions for the Audio Alchemy--DDP-1, PS-5 power unit and the PPA-1 phone pre do not get specific about ultimate power sources. I am pretty sure the problem was not the Dectet. Obviously some protection between the wall plug and expensive equipment is a must.

I am going to contact Peter Madnick at Audio Alchemy with all this and see what he has to say. Obviously if it is the DDP-1 Madnick will get the unit back from Audio Advisor. The issue of the Dectet and power sources is worth some expert advice regardless.

Hopefully the replacement DDP-1 will resolve the issue.  

We are entering a brave new world here. The DDP-1 is a very sophisticated piece of equipment--far more so than the old (and simple) Conrad Johnson it is replacing. That complexity is precisely why I am buying the Audio Alchemy units. I am ultimately going to add digital storage/player to the front end. (in the interim I am likely going to use my AK240 as a music source into the DDP-1).

I have to again note just how good the Audio Alchemy units are sound wise and offer a lot of flexibility. Hopefully I just got a "bad" DDP-1.

Also--this forum has a lot of benefit. I plan on being here regularly! Also will update you on how this "adventure" goes!
Received a new DDP-1 from AA. I have a replacement PS-5 so two "new" replacements now.
Also have original Audio Alchemy PPA-1 phone pre-amp.

Plugged into the Dectet after several hours of great sound from records only the awful horn like sound returned.

I am going phone only (the problem occurred while using digital AND phone sections of the DDP-1) I am removing the more complex stage of the DDP-1 for the basic line stage from the equation.

After shutting everything down I followed advice above and plugged the PS-5 direct into the wall receptacle--so far so good.

If the problem returns I am down to the Krell KST 100 (admittedly an older piece of equipment).

Only info I have gleaned thus far is the problem is not mentioned anywhere --I have Googled it to death. (blaring horn like sound) and apparently appears after the system has been up and running for a while (hours) AND after shutting the system down the problem is not present on immediate system re-start) --somewhat intermittent.

I promised to keep you up to date! ;-)

I am going to phone or e-mail Mr Madnick at Audio Alchemy and Paul Barton at PS to what these experts have to say.

Somehow, I doubt the problems are with the Audio Alchemy units.
We'll see (or hear).....

I knew this was a great forum!
I just spoke with Audio Advisor and sent an e-mail off to Peter Madnick He replied almost immediately and noted someone seeing my post here had forwarded it to him (he didn't have e-mail for me).
Thanks to whoever alerted him to my plight!

Will keep you posted!
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?