Anyone having issues with a noisy channel on the BHK preamp

I now have owned two of the BHK preamps. The first developed a noisy left channel after about three years. long story but i ended up with a new one and it developed the same issue, but worse, in about three months. it is not tube related as i have swapped tubes and even used different ones (and changing the jumpers as needed). the noise is even audible through headphones so that rules out the amps.

Has anyone had issues with this and if so, do you know what caused it (as I have no clue) and what was done about it. It is truly perplexing as i know i cannot be only one that has had this issue.

thanks.

Mine did, the input board was failing (or a component failed on the input board) and was replaced under warranty.

Hey Kent! In most cases when it develops a noise like this, it’s tube related. The fact that you’ve swapped tubes and you can hear it in the headphone amp leads me to believe that it may be similar to Brett’s situation and it might be the input stage. Give Mark or TJ a buzz and they’ll be more than happy to help you out.

hi James, good to hear from you. Actually the unit is back at PS but it is such a puzzle that I have had two of them with the same issue.

Scott S. and Larry are working on it.

Gotcha, didn’t realize our guys were already looking at it. As mentioned, most cases it is a tube if there’s a noisy channel. Sometimes something funky will happen in shipping and a new unit will have a bad channel, but it’s very rare for a unit with some miles on it to develop this problem. I do wish it didn’t happen to you twice though.

yes thanks. I must have ticked off the preamp Gods somewhere J

Kent Tager

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Yep, same issue with noise in right channel. Swapping/switching tubes did not solve the problem, however, switching the small pc boards (located directly behind each tube) from one side to the other resulted in the noise moving from the right channel to the left channel. Switched the boards again and the noise followed the suspected bad board. Was advised that it was against policy for PSA to simply send me a replacement pc board. Had to box up the unit and ship to them for service (at a cost of about $180 for shipping & insurance). They’ve had the unit for a week now… no word from them yet about the diagnosis/repair.

I just looked up the RMA for your pre and it appears we’ve repaired it and already shipped it back to you. The email addresses are inconsistent in our systems, so this may explain why you haven’t heard from the tech guys. They said we received the pre with the wrong tubes installed. Installed the proper 12AU7 and it’s working properly now.

Jamesh… I removed my NOS Telefunken E88CC tubes and stuck some cheap JJ E88CC’s in the preamp before shipping the unit to you. (I don’t think the JJ’s would be considered ‘the wrong tube’, just not a preferred tube.) Regardless, the issue (noise) persisted with a half dozen various tube pairs that I own. Hopefully, the technicians replaced the defective board before shipping the unit back to me.

Hi James, thanks but you are looking at the older unit that was returned about three months ago.

The new unit was returned with the stock tubes and is still there.

Kent Tager

thanks Ken, i appreciate your response. for me the issue is they are not able to replicate the problem and so it is sitting behaving itself. i hope they will check those boards out like you suggested, as it is definitely not a tube issue.

thanks Brett. i hope they will check out that possibility on my unit.

Kent… my problem board is in the right channel.The noise, even though low level, can be heard at the same level, independent of the volume control setting, and independent of whether or not a source is actually playing through it. They should be able to hear the low level hash noise up close through the midrange & tweeter drivers of the right speaker (compared with the left speaker which is dead silent). Although the noise is very low level, in my dedicated listening room, I can easily hear it from my listening chair (which is how I became aware of the problem in the first place).

that is so interesting. for me it is anything but low level. it is about 10-12 db higher in noise/hiss over the right which has a normal amount of hiss. it is so loud that my wife could hear it between music tracks from the kitchen.
i wonder how many others have had this issue.
and you are correct in that it is independent of source or volume setting.

Kent… I suspect that I have caught mine in an early stage of failure. (Problems with boards rarely gets better over time!)

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Hey Kent, have you been using stock tubes or tube rolling?

hi, i have used both stock and NOS. i do change the jumpers when needed but this seems to occur no matter what the tube being used.

Sorry for the confusion, but my reply was for Ken sending his pre in last week.

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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.