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.

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.

I know how to set up an audio system thank you, I’ve been doing this for 40 years.  Yes, I know how to access tube panel. No my TT is not sitting directly on top of the preamp. Lots of unhooking to access tubes due to rack. 
Stop assuming everyone is stupid

geee wiz


I never once implied that you don’t know how to set up a system, I was simply asking a question. If you go back and read your original post on this subject (you know, the one I noticed you deleted) that’s what it sounded like based on your vague description. The comment about the tube panel was not directed at you either, how could it be, I don’t know you and have never met you, it was simply letting everyone know how easy it was to do. I don’t assume anything about anyone, especially if I have never met them and don’t know them. Again, I was simply asking a question. I still don’t understand why you can’t just reach behind your preamp and unplug the power cord and disconnect the cables and just pull it forward off the shelf?
The only thing I found stupid was your reply, are you always this angry?

Hi Scot, I just wanted to let you know that I tried setting the bias to 5mv with my Amperex 7316 tubes. I didn’t notice a big change in the sound. However, I am probably one of the worst people for this experiment. I have really bad aural memory and as a result I dislike doing A-B tests.

I may try it again, after all, it’s free. I don’t doubt that you heard a big improvement, there are just so many variables involved with different systems and ears, that I’m more surprised when people agree.

If you get a chance to try the 7316 tube, do it. I really like this tube in my BHK preamp.