Can anyone help me with diagnosing an electrical problem somewhere in my system?

How old is the house wiring?First thing I would look at is the receptacle your plugged into and make sure ancient wiring and $.10 cent plug are’nt melting down from the current draw of a power amp...Next I would,immediatlly upon smelling odor unplug everything and confirm smell is indeed coming from inside amp.Next I would look to see if something is causing a dead short in your amps.The only thing I can think of would be an energized neutral backfeeding into the amp...

Years ago, I had a McIntosh MC275 amp fail (under warranty) with a loud pop through the left speaker. The system went dead immediately but there was the acrid smell of burnt electronics. The company repaired it without issue and it has worked fine since then. However, for the first year or so, it always produced a slight odor. It finally went away. Apparently a tube shorted and destroyed a few components in the process.

I suppose the same is occurring with your repaired amp. If it is playing normally, I would give the odor a chance to diminish on its own. Of course if the odor is getting strong, I would shut it down and contact the repair facility at once to report the problem.

Hopefully not a problem!

Best, Fred

If nothing else was connected to that outlet other than the amps, I would look at the wall receptacle and see what sort of shape its in.

It could be a simple as a loose screw on the back of the receptacle, which could be heating it up.

Given that two different amps resulted in the same result, i would follow the aforementioned advice and check the outlet. Are you using the same aftermarket power cord? 

I used the same power cord run from the power conditioner. Since posting I tried it again and noticed the left channel is out. I am about to check the fuse inside.

Left channel out? Now a different scenario is presented- you may have a short on that channel- perhaps speaker cables touching each other, or a shorted woofer. If that is the case you may have damaged both amplifiers in the same way. This needs to be checked right away before any other amp is installed in the system!

For an electrical item to run and smell.. It could be a capacitor dying (and leaking fluid) or a transformer overheating.
Since the channel has died. I would say you lost a big capacitor.

Thanks, Elizabeth, I crossed all of the tubes and it's still the left channel that's out so I guess I send it back to the manufacturer

I would strongly suggest you listen to Atmospheres advice
 get a voltmeter on that channel Wires speaker etc ASAP and see if something is shorted.
 You need to find the cause not just replace and chase your tail.
 Best,
 JohnnyR

I checked impedance for both speakers and they matched so I don't think they are a problem. I got the Art Audio back from Music Technology, it was a rectifier, and everything sounds good. Thanks, all, for the help.

I sent the DAC back to Mytek. They couldn't find a problem with it but for a fee they replaced it. No more problem.