My 4B-ST runs Hot

You mentioned that the amp seemed hotter on the right side of the top. The 4B-ST is a symmetrical construction, with the heat sink modules each containing a separate channel of amplification, with the twin toroid amps occupying the center of the chassis. The only other factor I can think of that might cause excessive heat on one side (given the symmetrical internal layout) is a badly adjusted DC offset. I think your problem merits a call to Bryston, since excessive heat will decrease the life of the solid state parts and output transistors.

My 4B-ST runs warm on the top and warmer on the sides as there is little space between the heat sinks and the sides of the cabinet. Never too hot to touch but the sides do get verrrry warm...

Argent, have you tried swapping the amps input cables left for right to see whether their are any sources issues? Ie now the left side is hotter than the right. Similiar experiment would be to swap left for right speaker leads (with source correctly connected) to isolate whether there are any "load" issues. This info will probably be useful if you talk with Bryston.

My speakers have a 90 dB efficiency, 8 ohms nominal impedance, recommend 110 watts for amp power. The 4B-ST should kick them around the block no problem. The funny thing about all of this--Bryston is the distributer for PMC monitors in the US and Canada. PMC uses Bryston amplifiers when they test their speakers. I thought I was buying the best possible match for my amp. Oh well, I'll just put a bag of ice on the amp and it'll be fine. Just kidding :) I forsee a call to Bryston in my immediate future. Hopefully the amp will not be out of my life for long. By the way, if you all have never heard of PMC speakers, you should check them out. You might find it interesting to know that PMC (Professional Monitor Company) boasts that about 90% of all CDs made are mastered on systems using PMC monitors. Thanks for all the help.

Alright, just a follow up. I put the amp through the paces tonight for about an hour. It stays cool for about two songs (rock, R&B) at a pretty good volume. Then it begins to warm up pretty steadily, favoring the right side of the amp. After about an hour of playing, moderate to loud volume (classical, single vocalist and small assortment of instruments) I checked out the amp. The left side of the amp is merely warm, both the heat sinks and top of the amp are the same temperature. The right side of the amp is too hot to leave a hand on for long. The heat sinks on the right side are scalding also. The heat is present from the front of the amp to the back of the amp on the right side. I did not record the temperature as I do not have a thermometer to check it with, but I figure it was pretty damn hot if I couldn't leave my hand on it. Now, the interesting thing is that when I stop the music, the right side of the amp slowly returns to the same warm state the left side of the amp is at. I plan on calling Bryston soon.