BHK 300 and speaker hiss

Hello. I’m in Day 3 of having new BHK 300’s (~45hrs run-in so far) that may replace my VTL MB-450 Signature amps. I have a hiss coming from my speakers that I didn’t have with the VTL’s. It’s loud enough that when seated in the listening position, and it is audible when no music is playing. I had read in one of the reviews that these were supposed to be dead quiet.

Have any 300 owners had the same issue? Possible fixes?

Thanks, David

I’ll leave the resolution to those in the know. My 300’s are silent. Albeit in an all PS Audio System with Siltech cabling.

Describe your system from source to speakers and whether you are balanced or single ended. It will help others.

Source is a DSD Sr., balanced interconnect. The only thing that changed in the system is switching out VTL’s for the PSAudio mono blocks. Essentially dead silent with the VTLs, noticeable hiss with the BHK’s.

And, let me say that when I say “audible”, it is when the room is silent (no furnace or other fans, or other noise producers). And audible at a low level to be sure, but loud enough that once you hear it, you can’t help but hear it.

Are both channels equally ‘hissy’? If not, try swapping the tubes from the left amp to the right amp and vice versa. If it moves sides, you’ve a noisy tube. Alternatively, replace the set of tubes you have with a different set and see if that changes things.

Thanks, P_B, as I think the right is a bit noisier than the left. Kind of off topic, but the reason why I bought the BHK’s a few years before I planned to, was that I re-tubed the VTL’s and had three new Gold Lion KT-88s pop, and that was enough for me to give up on tubes. I wonder if New Sensor is having some quality control issues, if it turns out the GL 6922 that came with the amp is noisy?

Did u see this? Hopefully pasting the url will work. :slight_smile:

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@timm - great link and it seems like an easy fix. Would be interested to know his speakers? A lot of info on that link… yeah, the search function on the forum works pretty good…

timm, I didn’t see that result when I did an initial search. Probably the way I worded my initial search. Thanks.

@cardi I have a pair of Thiel 2.4 SE’s.

@flyingparrotsme-com- looking to understand how efficient - ?dBSPL… 87dB, pretty efficient; however, not overly efficient as over 90dB… let us know if the DAC switch helps?

An alternate question is what volume setting do you normally use with the DS? Engaging the attenuator, if you are not already using it, will require you to raise the volume by 40 to get the same output. That makes a big difference in the perception of the hiss since it is dropped by 20 dB. Of course if you listen at 60 now, you will top out with the attenuator engaged (though the DS goes to 106 with the attenuator engaged).

Not sure what it means, but i have always had a bit of a hiss from the speakers (using a BHK 250), but it is not audible from the listening chair. However when i mute the BHK preamp the hiss disappears totally. The hiss is pretty smooth without any other noises such as pops or crackles, so my guess is that is pretty normal.

My BHK 300s, and before 250s, hum at a low level, worse with unbalanced cables. It’s such a low level, I think it adds character to my system.

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The attenuator fixed the issue. I suppose this is workable, as most of the time now the volume for my listening is between 90-106, and if I need some extra oomph I can dial back and turn the attenuator off.

However, I am from the “Don’t run things at 100%” school. Does running essentially full out have any concerns? Do you know if there is a sonic difference with or without the attenuation? I don’t think I detected any, but I was getting tired.

Thanks for everyone’s help.

Absolutely no concerns running full out. With respect to the attenuator, some folks think it sounds better without it. I tested it several times when I wasn’t using a preamp and a few times I thought it sounded better out of the circuit, but more often than not I thought it didn’t make a difference.

It seems counter intuitive that running something at 100 would be harder on gear but, in fact, it’s not true. Actually, running electronics in the system at 100 is a good thing and non taxing at all. That might not be true for a car or a power amp pushed to
its limits, but a preamp or DAC are happiest when your foot slips off the brake.

The amps work harder when the signal from DAC or Pre is attenuated. Got to make up those dBs somewhere.

Brother - Did you ever get a straight and helpful answer to your question? I have exactly the same experience as you with my Signature preamp. I’ve switched out the tube, thinking that might be the culprit, but it was not. Thanks! - Jim