Anyone having issues with a noisy channel on the BHK preamp

Very sorry to hear Ken. Give our tech guys a buzz. If need be, they can expedite things. It left here working perfectly.

that is so frustrating and terrible to hear. what does their service report show what was done to correct it initially.

Maybe this info will be of use for others who tube roll. from Brent Jesse:

Hi Kent,

“Thanks for the update. I was not aware that your PS Audio used 7DJ8 tubes and was designed with the 7 volt heater circuit. This will account for the noise as the 6DJ8 tubes are running at an elevated output due to the higher voltage on the 6.3V filament.”

This might explain some issues with using 6922 tubes. i in no way claim to understand what all this means. I think PS would make everyone’s life easier, including theirs, if they were very specific in the owner’s manual about tubes that can be used and tubes that cannot.

Frustrating indeed Kent! Especially since I had already diagnosed the problem and advised them what part needed to be replaced before ever contacting them. I requested that they send me one of the small pc boards that sits behind each tube, to replace the defective one that was noisy. They refused to do that and advised that the preamp would have to be boxed up and shipped to them so that they could thoroughly check out the unit (at a cost of $175 shipping & insurance).

So, they get the unit, determine that I am using the ‘wrong’ tubes (another story), install new tubes, say eveything sounded fine, and shipped the preamp back to me.

Evidently, my problem is intermittent, just as yours Kent! The difference is, when mine was acting up, I was able to determine what I believe to be the problem since when I switched the small pc boards from side to side, the noise moved to the other channel. Anyway, now they are requesting that I contact the service technicians to ‘expedite’ things. Really???

Damn that sucks big time. i personally think that PS has one of the best CS depts in the industry, but this time they dropped the ball. I was speaking earlier today with Larry in service and he told me that the older units had it where you could pull the boards out of their sockets and then put them back in. He said that newer units do not have that option as they are soldered in. I think they need to update their owners manual and be very specific about which NOS tubes can be used. Brent Jesse had sent me a sent of 6922/6dj8 and they were totally wrong (see above). Until the unit started getting noisy i was getting great sound with the Mazda 1960s France made 7DJ8.

again i can appreciate your frustration. i hope you are able to play music. at least in my case, the DSD DAC makes for a pretty good preamp, though nothing like using the BHK Pre.

good luck to you.

Sorry you guys are having these problems. I’ve felt your pain. A couple of months ago, on the recommendation by Bascom I tried a new matched pair of 6NS7. With 5 hours of use they caused the noise issue in one channel and the input board had to be replaced under warranty. Going back to the stock 12au7 did nothing to change it. The 6SN7 did sound good though, unfortunately.

I think both the manual and the forum should be updated and/or scrubbed of the apparent disconnect between the man that designed the preamp and those building and supporting it. I suspect Bascom has higher grade parts in his preamp that tolerate the additional current draw the 6/7v tubes require.

If the 6/7v tubes in general are NOT a good idea because they pull enough current to stress a part and damage the unit but otherwise ‘might’ work…it should be strongly worded as such. I’ve had the preamp for nearly 3 years and do not intend on using anything but 12v tubes to avoid the issue.

I realize 6SN7 is not listed in the manual but when Bascom says he uses them and they sound great - what more endorsement does one need. Additionally, a number of owners have posted their positive experience with the tubes too. He’s listed a number of other tube models that he says work as well and a few that he says should not be used, a couple years ago in the tube rolling thread.

PSA has great customer service. They took complete care of my repair but it and those with issues currently could have been completely avoided if we’d not be lead astray by both the manual and forum posts by Bascom (not just some random person) that apparently have since been determined by engineering to not be valid.

WOW! Just learning today of this current draw issue with the 6 volt tubes. I’ve been running nothing but variations of expensive NOS 6922/6DJ8 tubes in my BHK preamp since purchase 14mths ago. Now my unit is evidently fried!

I have read the PSAUDIO forums daily for several years now and this is the first mention of this issue that I have seen. This could possibly become a nightmare for PSA as I suspect there could possibly be hundreds of BHK owners using vintage 6 volt tubes in their units.

based on my posts earlier Kevin Deal, who probably knows more about tubes than just about anyone really likes the use of the Tungsram PCC88/7DJ8. he included them with the preamp but he never mentions any other tubes including 6922, etc.

please see my posts about the 7DJ8 tubes per Kevin Deal

Yep, I got the two sets with my purchase from Kevin.

There’s little difference between 6 and 7 volt tubes in the BHK. They both run at 6 volts.

My unit is older with the removable servo boards but they’ve never gone bad on me.

after all this is resolved, I too may go back to a 12 volter. however a set of 6922 tubes were immediately not right, but i have used the 7DJ8 for years. maybe they screw the preamp up but it takes longer

Unless I’m mistaken, 6922/7DJB draw twice the current 12AU7, ~300ma vs ~150ma and thus stress the components more. I suspect one of the components in the circuit is a touch underrated so when a slightly out of spec 6v tube is used it fails.

I never had any issues first BHK preamp running stock tubes for 1.5 years and I have never had an issues with my replacement BHK preamp in over 2 years running stock and then replacement stock tubes.

The only issue I had was with platinum match NOS tubes from Upscale.

I wonder how many issues, if any, people have had with their BHK preamps running solely stock tubes.

i would bet not many

I bought my BHK Pre used, and it came with a set of 6922 tubes. It has a intermittent humming noise issue if it’s turned off and then back on within seconds. It normally goes away once I turn it off and wait for a few minutes before turning it back on. Not sure if this is the same issue that you guys are experiencing.

what i have been getting in one channel is a loud crackling hissy sound. i am not at all proficient in all this, but the one set of 6922 tubes i had were immediately noisy and they hand picked by Brent Jesse. maybe they were just bad but i would be thinking about going back to the stock tubes.

I hope PSA is able to fix the problems several BHK preamp users have described in this thread. It has to be really frustrating to experience ongoing problems in an expensive piece of gear.

I’m just a new BHK preamp owner whose 30-day trial period is almost over. I’m leaning toward keeping the preamp because it sounds so good, but the tube and/or circuit board problems reported here have raised a few doubts in my mind. I am pretty sure that I will not be diving into tube rolling any time soon, which will at least protect me from tubes that draw enough current to stress out my preamp’s circuits.

I have heard a lot of talk about how Bascom King preferred the 6922 tubes in the BHK Pre, but I have had trouble locating a direct statement from Bascom stating that preference. In fact, I recall reading or hearing about someone asking Bascom directly about use of the 6922 tubes, and he said that he would not have specified the 12AU7 tubes in the design if a different tube would have been a better choice in the BHK Pre. (Unfortunately, neither a forum search nor a broader Google search turned up that quote from Bascom when I searched recently - so it may just be a creation of my less-than-perfect memory.)

At any rate, the BHK is a great preamp, and I’m hoping that sticking with 12AU7 tubes will save me both money and headaches.

Best of luck to all.

First couple dozen posts from 2016:

History repeating itself.

Looking at several videos of Paul interviewing Bascom, Bascom does discuss designing early prototypes of the BHK Pre using tubes from the 6922 family, and he thought that the Tungstram 7DJ8 sounded the best of the bunch but was no longer being made. In looking for an alternative that was currently being manufactured, he tried out the 12AU7 because it was a good match for the circuit he had designed. He then modified Arnie Nudell’s prototype to run the 12AU7, which sounded “exceedingly good” and became the stock tube for the BHK Pre.

Although PSA appears to continue to want to allow BHK Pre users to roll tubes, it would be helpful to have a list of tubes that are safe to use and to provide warnings of any risks associated with the use of tubes that draw high levels of current.

One thing I have never understood unless Bascom specifically said that the unit he was using was off of the post Beta production line why people would assume that his hand built unit was the same as the one they have. If that is not the case then while his circuit design would be the same it is highly likely that the parts quality and tolerances are much different which would allow him more freedom in tube rolling. While as an experiment I tried almost two dozen different pairs of NOS 6 and 7 volt tubes from all of the major players other than Telefunken I didn’t find them to sound any better than the 12 volt tubes and they were all noisier. So back to the 12 volts I went and never a problem as long as the triode were closely matched. I have plenty of pairs of NOS 12 volt tubes that play brilliantly in other gear that won’t work well in the BHK as it is the quirkiest piece of gear I have ever owned in over 50 years when it comes to tubes. I’ve got pairs of NOS tubes that are and have been fine in tube based DACs and phono stages, which should be more critical, that won’t work in the BHK.