Odd temporary problem with BHK 250


#1

While listening to music I started hearing a weird whining sound coming out of the Left Channel. When I muted the DSD, the problem persisted, but vanished when I place the BHK into standby mode, but return when taking it out. The problem corrected itself after powering down the BHK then turning it back on. Although everything seems to be back to normal, this odd occurrence is a bit concerning. Anyone else ever have a similar experience with the BHK amps?


#2

I’d be concerned also. If it was me I wouldn’t have that amp connected to my speakers until the cause was identified and fixed.


#3

Did you try switching tubes left/right?


#4

Probably a good idea to disconnect the speakers from the amp until the problem is identified, but it’s the weekend, gonna be tough going without music.


#5

Blow up a speaker and it’s gonna be even longer without music.


#6

I didn’t swap the tubes around. But to do so the amp would’ve had to have been switched off, and switching it off and then back on again seemef to have fixed the problem.


#7

You might just do to see if next time it is in the other channel…otherwise you know it’s not the tubes…


#8

This is a good reminder to get some spare tubes for myself. I hope you get your issue rectified!


#9

If it’s failing tubes the problem will be recurring. It may just take a while. I would remove a failing tube sooner than later.


#10

Are tubes replaced in pairs, if one side goes do you also replace the other?


#11

I would hope it’s not the tubes, the amp is only 4 months old.


#12

You would hope it’s not anything in a 4 month old amp! I’d be strongly inclined to have it RMA’d and send it back for a thorough check.


#13

The tubes should be tested for correct triode response, microphoney, and noise. As long as the tubes are matched based on response, you can keep a correctly functioning tube as long as the new partner tube has matching performance .


#14

If I were you I’d hope it’s the tubes as this is the easiest and most hassle-free bug to get rid of you can have :wink:


#15

Usually, you start debugging with the tubes. If you swap the tubes and the noise switches channels, it’s the tubes. Tubes are pretty reliable, but they can fail.


#16

Are you asking the OP if he replaces both tubes if one is having problems, or what is the correct thing to do?

Usually you replace tubes as pairs, so that they are matched. With some amps, and particularly power tubes, you can get away with a single tube if you can, or the amp automatically adjusts bias. It still makes sense to replace matched pairs, or matched quads. The thing is, you have to trust the tube dealer is really matching pairs, or quads, and that their matching criteria is to tight tolerances. Upscale is your best choice for high quality NOS tubes, although I have been buying my current production EH 6H30s from Cryoset, and have been very happy with them. They run about $90 a pair. If I wanted to buy a pair of NOS Reflector 6H30DR, first you have to find a pair, and then expect to pay a minimum of $250 a pair. BAT has them, but the last time I read on a forum that someone had bought a pair, they paid $300 a tube.


#17

Yeah, for my own learning, not that I own anything with a tube in it. I used to own an Ayon DAC with a 6H30 tube output and I never had any issue with it. I think that tube was rated to 10,000 hours. I was tube-phobic until I bought that Ayon DAC, and I was surprised how good a tube based design could sound.


#18

I like solid state power amps, but prefer tubed preamps. The 6H30 is considered a super tube, used by BAT, Audio Research, and a few others. The thing is AR also uses 2 tubes in the power stage of their reference model 6 and 6 6H30s in the audio stage. The Ref 10 uses 12 tubes… My Conrad Johnson CT5 only uses two tubes. It does invert polarity, which I take care of by reversing the speaker wires.
I have heard good things about Ayon products.
The AR CD9 is their top of the line CD player/DAC, it uses 6 tubes, so it gets really hot. It is a great sounding DAC though.
The thing is the 6H30 is currently manufactured only by two companies, and their is only one brand of NOS. Most other popular preamp uses 6922 or one of the 12AU7 or 12AX7 variants which gives the user numerous NOS options. My last preamp used 6CG7/6FQ7, and there were probably 10 or 12 NOS choices. Look at the tube options for the BHK components. Some people really enjoy rolling tubes, I got tired of it. I finally settled on the Mazda, with Toshiba, and RCA Black Plates close second choices.
I had one tube power amp in a second system, power tubes have a shorter life, and can be really expensive.
Now you know almost as much as I do about tubes, which is not all that much. I even went through a tube tester phase, where I owned three testers. I kept the one that actually does more than tell me good or bad.


#19

Agreed. Tubes can be finicky if they are in a state of disrepair. Your are dealing with a device that is comprised of metal which requires heat to operate. Metal reacts to heat leading to expansion, and contraction when cooled. Powering off could for whatever reason change the physical condition within the tube and cause a problem to either initiate or terminate. Collectively, my system of tube-based audio components make up 57 tube sockets! As much as I have tried to predict and categorize the behavior of tubes, I have gotten cozy with the fact that it just isn’t possible. I deal with whatever challenges tubes present because their sound is simply intoxicating.


#20

Gary, I had the same thing occur with my first pair of BHK300 amplifiers when the amps were only a few months old. A high pitched noise, intermittent to begin with, but became more prevalent over time then I experienced channel imbalance .
P S Audio sent me new tubes which kinda fixed my problem. Kinda in the sense it did cure the fault condition - but in their infinite wisdom P S Audio only sent me one pair, not a quad set, I had to buy a quad set from a UK supplier… One of the many PSA faux pas I’ve encountered!! I also have a BHK250 so I will be able to use the brace of tubes on said 250 amplifier.