My BHK is an early edition signed by BHK himself on the top. Recently, the preamplifier has started to behave erratically. First, the small clicks that are made when changing volume have become extremely high and with very strong pops every several strong clicks. This is happening only in the left channel. In addition, volume starts to drop on the left channel. I have changed tubes several times but this behavior persists. I have switched the xlr cables going to the amplifiers from left to right and right to left and the noises and volume behavior is at then the right amplifier (left channel output), thus the problem is with the preamplifier’s left channel. I have tried selecting different inputs and the behavior is the same. I have tried without any inputs and the behavior persists. The tube settings have never been changed since I bought it and are the original factory settings. This behavior is erratic in the sense that, sometimes, when I listen to music, it disappears and suddenly comes back during the listening session.
I remember reading somewhere that this behavior was reported occurring in some early production samples of the preamp and needed the main board to be replaced. But I can’t find the post.
I shall appreciate any help. If needed, I can send the preamplifier to PS Audio, but it is going to be very expensive.
Have you tried giving PS Audio a call?
Not yet. Will contact Paul if there are no suggestions.
Even though you have swapped tubes in it still sounds to me as a tube issue.
Have you checked the position of the tube bias switches and put the stock 12V tubes back in?
I changed tubes five times. Each time a new set. And I exchanged their positions. The jumper settings are the same through the history of the preamplifier and according to the instruction manual, they are ok.
You’ve done your due diligence so it appears to be a bad board. Depending on how yours is mounted you might or might not have to send it in so call them.
So cool that it’s signed by a total legend. I’ve had mine for a few years as the original owner and have changed input tube voltages back and forth a few times. You doing 12 volt tubes and know how to ensure? My hunch, like Elk said previously, is tubes, but it could be more serious like your OP suggests.
Just sent an email with the complete post to Paul and Scott. Let’s see what they say.
I had similar issue and the culprit was the vertical board behind the left tube, called TP25
Some models have boards removable others not. If in your case it is removable (and paying attention not to bend the board’s pins and inserting accurately all the pins inside their proper holes, very very important be careful) you can try swapping the left board with the right board. The noise goes on the opposite channel? Dang, you have found the culprit.
I also have this issue.
How can you tell if the board is soldered or not?
With delicacy simply try to remove it. If removable it comes out effortless.
Thanks, I just want to avoid damage.
I am going to take the preamplifier to a local PS Audio dealer. Although I did not buy it from him (when I acquired the preamp he was not a dealer) he is a friend and he told me he will check it. I do not dare to remove the said boards because I do not know if in my case they can be removed.
I just checked mine and they seem to be soldered. Hopefully yours are not soldered so it would not have to go back to PSA.
The louder clicks are also only left channel for my pre, but after playing for a while they are normal volume (i.e. same as right channel).
Also please let us know what PSA says about it.
Ok. Will visit the PS Audio dealer this week.