Hi my name is Christoph and I am living in Germany , so please forgive my bad English.
I own a PS BHK preamp and a BHK 250 amplifier for about 3 month. Now I have a problem. As soon as I power up the amplifier the bass chassis of my loudspeakers bunch out even without any signal. At the left channel nearly to the max, the right channel only a little bit. Changing the channel with the xlr interconnect at the preamp doesn’t make any difference. Therefore the issue must be the BHK 250. Does anybody have an idea about that problem? Thanks a lot for your help!
I would measure the DC voltage on the amplifier’s speaker terminals.
It should be very close to zero volts.
I would expect it to measure less than 0.1 volts.
From the looks of your woofer, I would guess there is at least 1.0 volts DC on the left channels output.
Does it happen just at turn on and then subside?
Or will it stay like that as long as the amplifier is powered?
Does music sound OK?
It stays like this as long as the the amplifiers are powered. The bass energy at the left speaker is weaker than at the right speaker.
I would measure the DC voltages on the speaker terminals with no input and the speaker cables disconnected.
In theory your left channel has more DC voltage measured than the right channel.
If so, I would swap the left and right channel vacuum tubes.
Measure again and see if the voltage on each channel changes.
If it did you have a defective tube.
If no change it is probably time to get in touch with PS Audio service.
I will try this. Thank you a lot for your support 
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I swapped the tubes now. No change at all.
It appears that your speaker cables are connected out of phase. Make sure the are connected correctly at both ends.
Until you have access to a digital voltmeter, I would swap the speaker cables just to prove what is going on.
With the right speaker hooked up to the left channel’s output, it should now have the most “bunch out”.
And the left speaker should now have less than before.
The speakers are connected correctly. I swapped the speaker cables already and yes then the right speaker bunched out more.
Did this system ever work properly?
If so, have there been any changes made? Anything at all, like cables or components?
I doubt if this will do anything but did you ever turn off the amp completely with the rear panel switch?
The system sounds still good, the only thing I noticed was the weaker bass performance at the left chanel and a lower sound pressure level as usual. I don‘t know exactly how long this problem exists, I noticed it by accident. I changed speaker cables from left to right, also tubes, disconnected the power cables abd stated again, disconnected the preamp, chooses another wall socket etc… no change at all.
It looks like DC on the amplifier output if I am understanding correctly. You should contact Jurgen at HiFi To Die For and explain this to him so he can help.
O.K. Thank you Paul
For the record, my BHK measures 0.008 volts DC on the speaker terminals.
Would be interesting to see what yours measures.
Have you checked the loudspeakers with your meter to see if they are still both intact? Remove speaker cables and set the meter to ohms and measure across the speaker binding posts.
Thank you for the advice. I measured approximately 4 Ohm at both channels.
With my old amplifier everything seems to be normal.