BHK preamp - headphone hum..?

Hey kind folks,
Anyone else experience significant headphone hum when using with BHK pre?
I am using a mid fi pair of cans. They work pretty darn good on other sources…but have nasty distortion when i insert into my lovely BHK pre.
Any suggestions?


I would try a different cable first. It sounds like a ground issue.

Other than the expected volume clicks, not really something I’ve heard of before. Have you tried different headphones and different inputs at all?

Thanks fellas. I’ll muck around some more on the wknd and report back. Cheers! T

This morning I turned on my system and heard a very pronounced hash (noise) coming from right speaker. After troubleshooting, found it was BHK PRE. I swapped a set of PCC88 tubes (2500hrs) for another pair of PCC88 tubes and problem solved. If it is hum, I would hit the cable first, understand the HP output is single ended, not pseudo balanced like the XLR outputs. Also, if the main speakers are OK, then it is not the tubes. I would suspect the HP or cable. I would try another HP w/ same cables to rule out HP, then HP w/ another set of cables to rule out cables. Then call PSA…:nerd_face:

Interesting. When i playback on speakers all is well.

@tj-sully - Hum to me is low freq. My issue was noise floor just jumped way up on right speaker… however, mine was clear as day on the speaker and HP.
Local to one channel?

Thanks for all of the feedback Cardi. Some great input! Tubes could certainly be to blame, and the reason TJ only hears it through the headphones is because they’re right by his ears and are a little more sensitive than the speakers. TJ, when you get a chance, keep us posted if other headphones also produce the noise.

I just misread his post, my apologies… changing pre tubes is 5min so I would do that and then go after the HP, then cable, then call James…:nerd_face: hum versus noise… my issue was noise floor jump up big time on right speaker… this is my first tube pre/amp so I got to witness a bad tube for the first time. This pushed me into starting my trek as a tube whore…

Haha, isn’t this fun?:smile:

All good…

Thanks boys for all the wicked feedback.
Hey Cad, i tried changing the tubes…i have a old set of organ tubes 12AU7s. But it didn’t make a lick of difference. I will try some other headphones if i can find a set. Its weird b/c the hp’s worked fine a few months ago (not a huge headphone guy). Thanks again fellas and i’ll keep you posted. Cheers! TJ

Is it hum or distortion? In your heading it states “hum” but in your narrative you describe it as distortion which are VERY different sound anomalies and which are a result of VERY different causes. Can you provide more detail as to what exactly the sound problem is?

Hum in tube gear is often a grounding or ground loop issue. Distortion is often tube related. You switched tubes which did not affect the sound anomaly so I assume we are dealing with a ground related hum issue. Or…

One of the most difficult issues to deal with when it comes to headphones and headphone amps is impedance mismatches. Please post the exact make/model of your headphones so we can ascertain the impedance and compare that to the specs of the BKH Pre.

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Hi Terry!
I had the same issue with my BHK pre, and it went away when dimming the display. It is probably the display driver generating a noise that’s leaking into the audio circuit… (in my case the right channel)


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Mats and all-

I had the same issue with Audeze LCD-X. The suggestion to dim the display solved it completely, and also made a noticeable improvement when listening to loudspeakers.


I also get super slight hum from my speakers, but that’s in part because I’m using AHB-2, which have a literal “silent” noise floor, so as soon as you plug anything analog at all you raise the noise floor, but the only time the humming is really noticeable is if I try and listen with IEMs. I’m pretty sure the noise would be even less noticeable for any more traditional amps. As like my rear speakers which also have RAAL ribbons have the same “ear on the tweeter audible noise floor” without the extra component in the middle, when the AHB-2 was absolutely silent when powered directly off my receiver.

With my speakers I need to literally hold my ear to the RAAL tweeters to hear the noise floor and my normal cans while I can hear it while there is no music playing, its hardly audible and not noticeable.

I also do hear increased noise on the right channel when the display is on like others mentioned, but I don’t like leaving the displays on anyway, so no harm there. It would be nice if the noise floor was a tad lower, but I can’t imagine it really being viable to make it so for anything using tubes without spending tons of money.

I’m pretty sure it’s just limitations of the tech. Outside of the latest Class-D/H/AAA amps everything else has an audible noise floor anyway.

Oh also my main speakers are 90db sensitive vs the 86db of my surrounds.

Anyway, the only one that bothers me is IEMs, but I kinda figured it wouldn’t be able to drive them cleanly to begin with given at least these ones have 115db / mW sensitivity.

Also while the noise was more noticeable at first (when the tubes were fresh) it’s gotten a lot better as the tubes got some hours.