Hum in BHK 250 & Speakers

I just bought a used BHK 250 and fired it up this afternoon. After some toe tapping and massaging my face from the giant grin I started moving cables around and noticed a hum from the speakers. Seemed odd as I’ve never had any hum with my previous Linn amp. I turned off and unplugged everything on that circuit and still the hum. I unplugged the single ended connections to my preamp and still the hum was there. Then I noticed a very similar hum coming from the amp itself.

Any ideas or thoughts?

Have you tried powering it down, removing the AC Power, and reseating the tubes?

Is the hum in both channels?

BTW - congrats on the 250. I have one and I really like it.

I will try that, thanks for the suggestion. Interestingly the buzz or hum reminds me of the sound I get when I first turn on my Tube headphone amp…

Try the 99cent trick and use the 3 prong to 2 prong as it sound like its causing a ground loop.

no luck with reseating the tubes, still have the same hum/buzz. Wonder if it could be OLD tubes?

Could be some DC or noise on the line causing the transformer to vibrate. My BHK 250 hums on occasion, but almost always my wife has a torchiere floor lamp with a hi-intensity halogen bulb turned on in the room above. It’s also possible the toroidal transformer has loosened slightly, but I haven’t attempted that fix so can’t help there.

Thank you for the suggestion. Odd that I found the ONE I bought 20+ years ago and that killed 98% of the hum/buzz in the speakers. Still have same actual sound coming from the amp, louder from the back by the tubes but inaudible from the listening position. Now I have to figure out why this worked, lol.

Oh yeah the fun begins. In my HT rack a new Marantz was nuts buzzy, but Anthem not. The switching transformer did not behave. I have dedicated 15 amp going to P10 with 2 amps, 1 Processor, 1 UHD, Firestick, Projector and networking stuff…all in P10. Both the OPPO and Epson caused buzzing. Both were the ONLY two 3 prong devices. 2 of those and bam gone…but I stuck with Anthem anyways. I still don’t know why all things in one P10 to one 15 amp dedicated circuit would do that. One thing might be cause is its a double breaker (2 15 switched in one slot) as I ran out of space in my panel. Now that I think about that I would have shut off the other 15 and see if it went away…oh well…

When you mix Single Ended and fully Balanced components in the same system chances are good that one of them will require a cheater plug to eliminate a ground differential hum. As long as they’re all connected to a grounded conditioner/regenerator no issue. And yes if you get real close to the back of a BHK amp you will hear tube hum.

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good info, thank you. I was worried I got a bum unit or one in need of repair.

Nope you are fine and tubes are fine.

Interesting thought. For my HT that had the hum, its all xlr except for my ceiling speaker amp which is only single ended. but when I turned that amp off, the hum was still present.

If it’s plugged in and connected then it’s still in the chain.

even with the switch off? Guess that makes sense if the group is still connected. I dont think I pulled the 4 RCAs, I cannot remember if I pulled the plug or hit the switch.