BHK 250 Hum

Audio Components Amplifiers
21

Yes, correct. The RCA to XLR converters don’t “convert” anything. They just eliminate one of the conductors and you do not get the benefits of balanced.

22

Hi Paul,
Thanks for the reply on the XLR coverters. My main question though still remains. Why do I hear a hum in both speakers when connecting any source, be it the DirectStream or my Oppo BDP95 or my Mystere CA21 tube preamp via RCA to the BHK 250? When using XLR the hum is gone. I never ran into the hum with any of my other amplifiers when connecting any of the before mentioned components via RCA. I tried many different ways to narrow down on the cause. Everything plugged into the P15, everything plugged into the wall, only plugging in the DirectStream and BHK250, nothing else-both ways, directly into the wall outlet and via the P15, the hum was always audible the same way in the speakers. Only when I plugged nothing into the BHK250, with just the speakers connected would it get rid of the hum. I also tried removing the ground pins, with no noticeable change. Obviously, I am not the first BHK 250 owner that experienced that same hum when using RCA. I just did not see the cause or the remedy mentioned anywhere in this post and of course hope there is a solution to the problem.
Thank you for your help.

Kind regards,
Arne

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23

Because the the BHK 250 is fully balanced and the sources you’re connecting, particularly the Mystere are not. I have been down this same road with the BHK amps and those are the solutions I gave you earlier.

24

Hi Jack,

I understand that the amplifier is fully balanced, but why does it feature an RCA input when it doesn’t result in a hum free connection?
I had a couple of high end amplifiers in the past, of which none were burdened with any hum to my recollection when connected via RCA.
Maybe the were not fully balanced, but I believe they were!? I had a Mark Levinson 333, as well as a NewClear NC1000L and also a pair of Emotiva XPR 1in the past, and they were quiet without hum using RCA as far as I remember.
Well, if the BHK doesn’t like RCA connections, I guess my only two choices are to dump the BHK amplifier or the Mystere preamp.
Thanks for your help.

25

The only way to know if the amp is fully balanced is to look in depth at the spec sheet unless the manufacturer mentions in the ad copy. Many manufacturers offer XLR inputs as a matter of convenience so the customer doesn’t have to change cables. Same is true of many preamp manufacturers too. The Levinson is a dual Mono amp, as is the New Clear and the Emotiva’s are mono’s so different configuration. Have you looked at the Jensen transformers as they may solve your problem and let you keep the gear you have.

Look at the PB-2RX

26

I am experiencing this same issue. When I have the BHK 250 connected to the speakers with no inputs going into the amp, the amp is silent. Also, when I use balanced cables from my DirectStream DAC into the BHK, it’s also silent. I have a PrimaLuna Dialogue Premium preamp that I’d like to use, but no matter what, I can’t connect it without a hum. I’ve tried just about everything I can think of, with the help of some of the people at PS Audio:

  1. Lifting ground on the BHK and PL, in different combinations. This lessened the volume of the hum a little, but was still too loud

  2. Running a ground wire from the chassis of the PL to the chassis of the BHK. This did nothing for the hum.

  3. Plugging the BHK into the “filtered power” outlets of my Stellar P3 power plant instead of into the wall so that both the PL and BHK are plugged into the P3. No change.

  4. Removing the P3 from the chain and plugging both the BHK and the PL directly into the wall using the same outlet. No change. Did this with and without the ground wire going between the PL and the BHK. No difference.

Some other things that I’ve tried:

  1. Borrowed a Rega Aehtos integrated amp from a local dealer. Plugged this straight into the wall and it was dead silent. This was with my DSDac plugged into the P3 and using the single ended connections.

  2. When my PrimaLuna preamp and PrimaLuna Dialogue Premium HP amp are both plugged into the wall on the same outlet, I do not get a hum. When I then plug the PL preamp into the P3 and leave the PL amp plugged into the wall, I do get some hum, but it’s not as loud as the hum from the BHK.

I’ve tried just about everything I can think of here, and I do not want to be forced into buying a different preamp and using only the balanced connections. I agree with what others have said in that the amp should not come with single ended inputs if it very prone to this issue. I would not have purchased it if it only came with XLR inputs, because I need single ended.

Any other last ditch efforts anyone can think of here before I call PS audio and request a return on this? I’m still within my trial period, and this is looking like the most likely outcome at this point.

Thanks

27

Sorry to hear that. What RCA cable are you using to connect the preamp to the BHK?

28

I have the Acoustic Zen Matrix Reference, and the Acoustic Zen Wow single ended interconnects. I’ve been using the Matrix Reference to go between the PrimaLuna preamp and the BHK. When I was running the DirectStream DAC directly to the BHK via balanced, I was using the Purist Audio Aqueous.