Anyone having issues with a noisy channel on the BHK preamp

These are a 6922 tube which are what the BHK 250 and 300 amps use. Not the Pre. I would not put these in the preamp. The techs determined it was a tube issue. The boards were just fine.

James, this doesn’t make any sense. 6922 are the 6v tubes spec’d for the preamp. It can also use 12v in the 12au7 family.

The voltage is only one aspect of the tubes. If we test a BHK pre with 6922 tubes in it, it fails the AP test.

So to clarify, you mean don’t use those specific tubes, not 6922 in general?

I guess if it fails the AP test, it’ll never get into Princeton?

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Eh, it’ll work but I hesitate to recommend using them. We regularly get calls and emails from folks mentioning their BHK pre is popping, hissing, etc. They mention that they have tried multiple tubes so they know it’s not a tube issue. The guys in the lab then test it and sure enough, it fails AP. Check the tubes and 9/10 there will be non 12AU7 inside.

That being said, absolutely roll the tubes and have fun with it. Just know that the Pre’s tolerance is only so wide and one could run into noise issues.

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Jamesh,
I don’t understand! According to the preamp manual and Bascom H. King himself, the bias current jumper was essentially in the circuit design to allow optimum use of the 6922 family of tubes. I have been using the 6922 tubes in my preamp since I acquired it without issue until just recently. Multitudes of other BHK preamp owners also favor and are using 6922 tubes according to numerous postings on the PSA forums. So, is it now the position of PS Audio that the 6922 6v. family of tubes should not be used with the BHK preamp?

Ken Harris

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thanks James. I either use the stock tubes or 7DJ8. what is the AP test?

it is a bit confusing as the manual states: It is possible to use a lower voltage tube, such as a 6 or 7 series dual triode. why are 6922 tubes not right for the preamp.

copied from UpScale Audio: Tungsram PCC88/7DJ8

As you may know the Tungsram PCC88 is almost a requirement to make the PS Audio BHK preamp and power amps sound really good. Especially the variety we had gotten from the German government.

Sadly we use them in another product, the amazing Manley Chinook Special Edition phono stage, and have to support those customers.

For this reason we have taken the Tungsram PCC88 off our website and they are no longer for sale.

However if you bought your PS Audio BHK or Manley from us DIRECTLY we will sell you replacement tubes. E-mail us through the website and include the serial number and invoice number from your receipt.

If you bought second-hand THAT DOES NOT QUALIFY! PLEASE DON’T ASK!! There are NO exceptions to this rule. So sorry for that.

This is the tube mentioned by Bascom King as being the best choice for the PS Audio BHK Series preamp and Amplifiers. It is an incredible tube for you folks that own one.

Perhaps “used” is not the word you’re looking for. Not what we approve to achieve a specific performance level might be a better way to put it.

In the manual “The twin hand-selected vacuum tubes that ship with the BHK are the preferred models we recommend and use in PS Audio’s Music Room One reference system.”

And of course you’ve read the few sentences before where it mentions 6 and 7v tubes are supported. As I mentioned earlier, please feel free to roll the tubes as you please, just know that you are more likely to run into noise issues with non 12AU7 than you are with 12AU7s.

I really do apologize here. Wasn’t aware the topic was quite this controversial. I didn’t know I would be digging myself a grave for stating my and the tech’s experience. Non 12AU7 tubes fail Audio Precision (AP) very often.

Our tech guys are awesome and will regularly send out free replacement 12AU7s to make sure the noise isn’t tube related. Almost always solves the problem. In the future, I ask that folks let our tech guys know what tubes they are using in the pre before sending it in.

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I just got off the phone with Larry in service and he was great. i know this issue will be resolved. Thanks PS for having such a great CS dept.

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Did the noise occur before you started tube rolling?

Thanks for your response Paul!

Please understand that I am not looking for a ‘specific performance level’. I am looking for the best sound, which is what I was getting with my vintage Telefunken ECC88’s (and other 6922 6v tubes) before one of the small pc boards located behind the tube developed a noise issue. (It is my understanding that Bascom himself uses these same vintage 6922 tubes in his own preamp.)

So how do I go about getting a replacement board for the defective pc tube board so that I can get back to enjoying the marvelous sound that I was getting from this wonderful preamp with my vintage Telefunkens?

I understand why you don’t approve of customers poking around inside of PSA components, however, I have been trouble shooting audio equipment and replacing defective boards since obtaining my N.A.R.A.S. Recording Engineering Certification back in 1975.

Best Regards,

good question. it did start with NOS tubes but then it happened even with the stock Savane tubes.
i do not use 6922 as i know they are problematic, but use PCC88/7DJ8 TUBES

Same thing happened to me except my situation was not incially repaired by PSA when I sent my BHK Preamp to PSA so they ultimately replaced it.

A word to the wise on tube rolling either DO NOT do it or make absolutely sure your replacement tubes are matched. If they are not and you get the BHK Preamp out of sync even the stock tubes can’t help you.

I feel for PSA as my guess is most of the BHK Prwamp problems are related to people rolling mismatched NOS tubes but then again they encourage it so this can be the result.

good points. i always use matched pairs but i guess it is up to the seller (Upscale, Brent Jesse, etc.) to make sure they are matched. if i knew for sure that tube rolling was causing the issue i would stop right away and stick with the stock tubes which are pretty good.

All of my tubes were purchased through Kevin at Upscale Audio as Platinum Grade matched pairs and matching was verified when received on my calibrated Hickok 6000A Vacuum Tube Tester.
The tubes are not the problem. The noise issue that just recently occurred is apparently in one of the small plugin pc boards which rest behind the tube. (Swapping/switching tubes makes no change in which channel has the noise, but switching the pc boards from one side to the other does.)

hi Ken, i think that will end up being the issue they find on mine. the damn thing is behaving itself now so they cannot replicate the issue. don’t you hate when that happens? :slightly_smiling_face:

Yes… intermittent problems are the worst. Like taking your car in to fix a problem that suddenly disappears when you arrive at the service facility!