So I just hooked up by new BHK 300 mono amps with the BHK preamp. I’ve been playing music for about 5 hours and just noticed that one of the amps runs considerably hotter than the other.
Both amps sit on top of a stereo rack and have the exact same amount of space and airflow around them.
Is this common?
Thanks
Have you tried them under load? My BHK 300’s fed by BHK Pre under light load are both similar as tested by as infrared temp tester. Each has one spot at 104 and 107 degrees Fahrenheit. The other corners range from 68 to 90 degrees so uncannily similar.
When you say light load I assume you mean playing music at moderate levels. If so than yes for about 6 hours now.
The amp on the right both heat sinks are basically the same temperature. (Warm to the touch) The amp on the left has the right side heat sink of the amp about the same temperature as the right amp. Maybe just a bit warmer to the touch.
The left side heat sink of the left amp is very hot to the touch. So hot I can’t leave my hand on it very long.
If the bias is set higher on one over the other it will run hotter as it stay in class A longer.
I believe the tubes are self-biased so shouldn’t they be the same?
Are the lengths of your speaker cables identical from each mono-block?
Tube bias is different from the amp bias. Amp bias determines when the amp shifts from class A to class AB.
I’ll bet ya the hot one is an oscillator… Try an oscilloscope and look at 200 something kHz…
Check out the third paragraph…
To use a crude gauge - is the one that’s running hot so hot that you cannot touch the heatsink for more than a short second?
Also, does one side feel hotter than the other?
Yes, cable lengths are the same for both amps.
Thanks but I don’t have a oscilloscope.
The amp on the right both heat sinks are basically the same temperature. (Warm to the touch) The amp on the left has the right side heat sink of the amp about the same temperature as the right amp. Maybe just a bit warmer to the Touch.
I left out that the amp that on the left, the left side is hot to the touch. I can only leave my hand on it fora second or two.
Is there anyway I can check the amp bias? Also is there a separate bias for the left and right side of each amp?
I would not mess with it just give PS Audio tech support a call. Something like this should not happen in a $7500 amplifier.
If it’s too hot to touch for more than a second or two, you’ll want to give our service team a call - they can walk you through further troubleshooting and the like to identify what’s causing the discrepancy and get you back up and running.
1-800-PSAUDIO, or service@psaudio.com are the fastest ways to reach them. We’ll make sure you get back up and running
Thank you… I will.
Amp is on its way back to PS Audio. No music for a week or so. 
That sucks man… Well, at least they’re takin’ care of you… If they tell you what the problem was, please share, cause I’ld like to know what it was…
It’s a bit frustrating but stuff happens. I’ve been in telecommunications for 38 years so I see stuff come in brand new not working at all, so I understand.
PS Audio is top notch when it comes to customer service. I always feel at ease dealing with them.
If I had to guess I would think it’s the bias that needs to be backed of a bit. I’ll keep everyone posted.