Is my Pass amp overheating?

You just hit the nail on the head Bryon.

I'm not familiar with your particular amp. What I don't understand is why manufacturers don't incorporate user adjustable bias controls in ss amps the way they do with tubes. It's especially relevant in your case where the tolerance in the auto-bias prevents the amp from ever achieving pin-point accuracy. You've just verified where the ultimate potential of your amp lives, as with any ss amp. At least with a fixed bias you can fiddle with it till you find it, not so with yours. If you could, this thing would knock your socks off!

As an after thought, I wonder what Nelson would have to say about this whole thing. You should ask him your self. He has his own dedicated site on DIY.com. It would be a very enlightening experience to say the least. I'd love to be a fly on the wall observing how he tweaks his personal gear.

We're talking apples and oranges to an extent here. I made a comment on Tech Talk under "tubes versus solid state audio amps-the last word". Out side of cranking up the bias optimally, you have the issue of both channels being equally biased. Herein lives everything you're going to love or hate about a particular amp. Without it you have no channel balance, stereo image, frequency extension, or the ability to determine low level resolution, speed, or any other sonic parameter. This is all mind you, relative to how accurate the amp is set up. But my contention is that there is virtually no tolerance available, or range within which balance can be achieved in an ss amp. It's all or nothing when it comes to realizing full potential. It has to be dead on, period. Built in tolerance, aka, auto bias, defeats this possibility and ends up being a compromise. Same thing with servo loop offset.
The reason I believe user adjustments are not incorporated is to safeguard the outputs from very quickly over heating in the hands of incapable owners, requiring additional protection circuitry which in turn costs money to implement. It seems simple breakers installed near the outputs connected to ac would do the trick along with a single meter to visually keep current centered within a pre-determined ball park.

I can't explain technically why this is. Others in the know could weigh in here and describe how electrical behavior equates to sonic outcome in this matter. But I learned early on in this hobby that channel balance is absolutely essential to realizing all of the performance attributes a given amp boasts on it's spec sheet as they relate to your ears. And I'm not referring to the balance knob on your pre. Perceived resolution diminishes simultaneously with the degradation of stereo image. The quality of the stereo image is dependent on how accurately one channel is biased with the other. Remember the definition of "stereo". The accurate placement of sound sources in space. When you don't have this, resolution can't help but suffer since amplitude is not identical on both sides. Probably because quiescent current is lower in one channel and therefore those power transistors are operating with less output. If you are not experiencing "pin point" imaging, regardless of room acoustics, then the bias is off. Any basic amp is capable of this when functioning properly. Not only properly, but potentially better than spec. By the time an amp has been transported to the show room floor, enough tossing around has taken place to knock it off kilter if it ever was right on. You can fool yourself into thinking you're listening to stereo when all you really have are right and left sources. Frequency extension is affected by accurate channel balance in the same way. Especially the bottom end. It is a very good indicator of whether you're in the ball park.

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