Today I could hear a noise when I put my ears next to the speakers. It is a faint rapid ta-ta-ta-ta sound from both speakers. This noise was not there before from a few months ago. I changed the tubes in both both BHK pre and M1200, and the same noise is still present in both speakers.
I turned off the DAC and the noise is still there. Since the noise is from both speakers I tend to think the source was from the pre.
Does anyone hear this noise with BHK pre? Is it normal?
Mmm pretty odd thing, Donald. When I swapped the tubes a few weeks ago I was in trouble and had to throw away 2 of them (brand new). It was a different noise and not the same from both speakers. Gold Lions from VivaTube.
Did you notice it before rolling the tubes?
Please try removing (gently and accurately) the little boards behind the tubes in your BHK Pre named TP25 and TP26. Clean the pins and pay attention to seat them back in the right position (pins inside exactly their previous holes - be accurate it’s highly dangerous a wrong position!). Be aware: some pre models sports soldered boards, not removable, don’t know if yours is of this type.
I found they can produce noise if not well fitted and cleaned.
One more time: it could happen from 1 speaker but quite odd from both of them at the same degree. Before that, please take your time and give a general check to all connections, power cords, interconnects and so on. Did you try also with different inputs from BHK, swapping cables between inputs I mean?
Did you try with vs without feeding the pre/monos to the P15?
Thanks, the noise was before and after I replaced the tubes. So, it was not from the tubes. The tubes have 2500 hours so it’s time for replacement anyway.
I will find out tomorrow if I can clean TP25 and 26 if they are removable.
At 1 ft. or so from speakers, all amplifiers / systems that I ever owned gave some sort of a faint noise! As long as I don’t hear it at the listening chair, sweet!
I still love my BHK pre.
Do you hear the noise if you have only the amps on? If not, this will help to eliminate the amp as the culprit. It is odd that you hear the noise from both speakers which makes me think that the tubes in the pre are not the problem.
Thank you guys! The noise shows up only when the preamp is turned on. I can only hear it when I get very close to the speakers. It doesn’t not affect SQ. I’ll try Luca’s cleaning method this afternoon first.
Be careful those boards are not removeable on all BHK preamps. Some are soldered in.
Thanks for the advices!
What else do you have plugged into the same mains circuit? I experienced a very strange low level noise problem I wouldn’t describe as ta-ta-ta, but it emanated from both channels. I discovered after much frustration it was caused by noise being spewed in the mains circuit I was powering my components on by computer netwoking gear. Yes, it was so trashy it even got through my Furman line conditioner/stabilizer. Before blaming the pre or the tubes, systematically unplug everything else being powered on that mains circuit (except of course the pre and amp, you need to be able to check if you’ve found the culprit). That’s exactly what I did and, viola, I eventually tracked down the source. I don’t pretend my experience is the cause of your problem, but when you’ve exonerated everything else including the tubes what do you have to lose by trying this experiment?
If your DAC has a volume control, like the DSD, bypass the Pre entirely and see if noise goes away.
I just got back from golf, and I am ready to investigate the noise source from my gears. I have streamer, network switch, IFI Pro PS, and satellite all plugged into P15, in addition to PST, MK2, and pre. So, It could be from the streaming chain. Hopefully I will find out.
I disassembled the entire rack and restacked all gears. With only DAC and pre connecting to the M1200, the speakers are dead quiet. Next, I will add one source at a time to see if I can pinpoint the source of noise.
what tubes did you install in the pre?
I replaced the GL 12au7s with GL 12au7s in BHK pre, and NOS Telefunken 12au7s in M1200.
The noise is gone! I frankly did not know how.
I re-arranged the gear locations on rack. There is less twisting and crossing of cables and PCs than before. Then I added one source at a time starting with PST, then streamer and PS, then network switch, and finally the satellite. I do not hear any noise anymore. One of the mysteries of the audiophile world is solved without finding the culprit. I guess I must have too many wires crossed.
Now the system will need a few hours to recover, and I thank everyone’s input. I am a happy guy now. 
Just reading the above. Good to hear the problem’s solved!
Adding my previous experience with something similar: months ago I had my pre stacked in my PST and the right speaker emitted a somewhat longer ta-ta-ta like sound. Long story short: I rearranged the two with greater distance between them: problem solved.
Having seen Donald’s rack recently, too little spacing could hardly be the problem(?).
The problem, I think, was the result of several connection issues. I have two long stiff power cords that I forced and twisted into the receptacles of M1200, plus I have the interconnects crossing a few power cords from one side to the other. Another issue was my Iconoclasts 4x4 OCC was designed for vertical connection. When I place the DAC and Pre horizontally, the ICs were twisted and stretched a bit (these are very stiff). I think all the above may have contributed to the noise issue.
I moved the P15 to the right side, and moved the PST, MK2, Pre all to the left side. Streamer chain is above the P15. Suddenly the cable arrangement made more sense, and noise is gone!
Glad you found the problem Donald. People may not realize this, but besides tubes, wires are the main culprit on noise in a system. They are great intenna wires and picks up just about every signal in the air and in the power, especially on sensitive front end electronics, it could be quite audible. I had a problem with buzzing from a turntable wire that got fixed by putting a braided sheild and grounding it. Total silence afterwards. That’s why I also never run cables parallel together.
Clean you interconnects. I had an issue the other day with low level hum in my left channel. I simple reseated the xlr connector on the BHK 250 and the noise went away. I than removed the interconnects and cleaned both ends. Everything is quiet as it normally is.
That makes sense, I usually clean them every few months. Lately I have not. I will clean them tomorrow.