To all PS Audio BHK preamp owners *** must read ***

Hey everyone

If you have a PS audio BHK preamp you’re going to want to read this. Before I continue I want you all to know I emailed PS Audio to make sure this was completely safe to try and that it wouldn’t hurt anything or void the warranty. They assured me that it would not void the warranty and it’s completely safe to try. 

It has to do with the bias adjustment for the tubes. The bias adjustment For the 12au7 tubes it comes with is factory set for 4mV. They tell you that you can also use certain 6 volt tubes and the correct bias setting for those tubes is the 5mV setting which is adjusted by moving two jumpers. There is a picture in the owners manual with instructions on how to do this. It’s very east to do, all you really need is a good pair of needle nose pliers. 

I wanted to know if there was any benefit of trying the 5mV setting on the 12au7’s? The gentleman on the phone at PS Audio said he had never been asked that question before and that he would check and get back to me. A couple of days had passed and I opened up my email and there was an email from PS Audio. He said he checked with a few people at PS Audio and they all told him that it was ok to try it and he asked me to get back to him with what I had heard. 

So, I took off the cover over the tubes which is held on with two thumb screws (very clever). I switched jumpers J7 and J8 as per the instructions in the owners manual, put the cover back on and put on the exact same cd I was playing before I changed the jumpers. All I have to say is wow! Right away it was better. There was a slight amount of glare that was now gone. Everything was more coherent. Bass was noticeably better, tighter and more solid. Piano had more weight to it. Massed strings were smoother and more realistic and just more beautiful. All from a 1 mV increase in the bias adjustment. If I didn’t hear it myself on my own system, I never would have believed it. Let’s just say it’s not going back to 4mV ever. I just wanted to share that with BHK pre owners. Take care and stay safe.

Everybody report back. I’m curious. To change tubes, I have to remove tt and top shelf of my rack. I would like to hear from more people before going they the hassle. 

Is your turntable on top of the preamp? Is it not possible for you to just take the preamp off the shelf to access the panel that needs to be removed to get to the tubes and jumpers? If you do have the turntable on top of the preamp this is the first thing I would change. I (hope) must have misunderstood what you said.

I just bought a Shunyata Denali s v2 power conditioner and my same friend is bringing it over on Thursday evening. Two other friends who’ve recently bought one both tell me that it’s amazing and they’ve both told me it’s a significant improvement over the old model which they both had. I’ll report back after it’s installed to let everyone know if it’s as good as they both say it is. Thanks.

Since getting my BHK preamp I have played around with many setting options including the jumpers. I even purchased a 6922 converter to use 6sn7 tubes in the preamp, for that, it is important to keep the jumper at factory setting 4mv. I agree with the rest of the folks on here that when using 6922s/6dj8/7dj8/7308 family of tubes with the 5mv setting it completely transforms the sound, in a good way. I currently have a set of 6922 Telefunken in place-Ironically enough, I have not changed the jumpers back to the 5mV since popping out the Shangaung 6sn7. Perhaps I will later this evening. The one thing I do notice is, if your tubes are not tightly matched and with jumper on the 5mv, they will be more prone to volume pops- I am on the hunt for a set of CCa Siemens for the pre, at that point will roll the Telefunkens over to my BHK power Amp for some expirementation.