Call Us: 1-800-PSAUDIO

BHK Preamp - noise

Audio Components Preamplifiers
#1

Hi,

I received my BHK preamp today. I did not change any tubes.
I currently have 2 problems:

  1. As already written in another post by other people, the BHK (not the speakers) produces a high frequency whining tone. Since I can change the volume of this tone by turning off other components, I assume this is because of DC or other power pollution. Unfortunately, the P15 is not isolating the outlet (zones) so I think I will try an Isotek Aquarius so that I can isolate the problematic components (TV, AVR) and avoid having any DC noise causing Transformers to hum.

  2. When all inputs are disconnected from the BHK and the BHK is muted, the background noise that the speakers produce while the M700 power amps are on is as expected and barley audible.
    Once I unmute the BHK, the background noise gets louder but is still acceptable (Volume on 1)
    When I now turn the volume up on the BHP preamp, this background noise gets very loud. Especially at settings where the tubes regulate the volume. For example, at 24 the noise is very high, at 25 it is nearly gone. At louder levels such as 85 the effect worse. This is especially annoying when I use the HT input at level 80. The background noise is no high that I cannot listen to anything then.

Is this normal?
Any recommendation how I can fix this?

Thanks
Chris

#2

I don’t have any comments on #1, but doesn’t sound normal to me. I’ve never heard any high frequency whining from the BHK pre.
#2 is absolutely not normal. I have the BHK pre in my setup and I can turn it up as loud as I want or at any volume level and the system is nearly dead quiet. I have to put my ear right up to the speaker to hear any kind of noise. With you saying the noise is very loud, there is definitely something amiss. I would bring it back to your dealer to have it tested out.

1 Like
#3

I tested a bit more.
When I plug the subwoofer part of my Triton Ref speakers to a different socket while the P15 input is before going through a DC filter, problem 1 is fixed.

The white noise problem is still there. For example, I tested to plug the XLR cables of my Stellar phono stage directly into the M700 power amps. Then, I have a similar elevated white noise level. (The phono amp does not have any volume control) similar to the BHK. But here, the input of would be 100% and no one would connect it this way in the real world. I only listed at BHK volume level 5-10 for vinyls.

When I plug the DSJ XLRs into the M700 Power amp, it is very quite, even at DAC volume level 99, no additional or elevated white noise.

When I activate the BHK preamp, I still have an elevated white noise.
Since I did not use tubes before, is this something which one would expect with tubes in general? While reading reviews for the BHK preamp, I did not came across anyone mentioning this.
Are maybe my speakers too sensitive when being fed with highly amplified input?

Thanks
Chris

#4

I have the same noise but I hear it only when I put my ear about one foot from the speaker. My normal listening position is about 10 feet from the speakers. I too use Stellar Phono, BHK pre, DSD Sr. and M700s all with balanced interconnects. The sound quality is spectacular.

#5

Also try dimming the Pre for #1.

For #2, the Pre itself is reasonably quiet on its own even on 98dB speakers. It’s likely a gain mismatch from the incoming device. The Pre will magnify inbound noise quite a bit. To know if it’s the Pre or connected device, select an input that doesn’t have anything attached to hear the actual Pre noise floor. In my case, the I find the Stellar Phono Pre to be much noisier than the Directstream DAC by about 30 volume clicks. If you’re using an HT pre, you could try plugging an inline attenuator in to see if it will attenuate the noise floor. Rothwells are the best I found. If your HT pre has a gain setting, try setting that to low.

#6

I tried Rothwells but in my system the sound got slightly muffled.
Then I tried a Placette RVC, and I got full transparency.
Highly recommended.
I put the Placette between my Plinius Tautoro and Plinius SA 103 monoblocs.
Speakers are B&W 800 D2s.

1 Like
#7

That Placette might cost the same as OPs HT pre!

#8

The RVC is about 1200 USD.
Not cheap of course, but amazingly transparent.

1 Like
#9

Like Vee recommended, if you haven’t already, try isolating the pre. Only have the Pre connected to M700s, and then M700s to speakers. Everything else disconnected. See if you still get the same level of noise. Also, how loud is this noise? Is it very apparent from the listening position?

Also, something I find very surprising is that you can listen to vinyl at volume 5-10 on the pre. Even with 98dB speakers. Unless you prefer to listen at REALLY low levels, this would be extremely quiet in any system I’ve listened to with the BHK pre.

#10

When I disconnect all inputs from the preamp, only leave the output to the M700s, I still have the problem once I switch from mute to volume level 1. So I think the cause is the preamp itself.

The “normal” white noise my speakers are producing when the M700s are on, is not audible from my listening position, which is ~3-4m away, only when I put my ear against the speaker. However, the elevated noise level when unmuting the BHK is audible from my listening position. If I would listen to Hard rock at very loud levels, I would not hear it but since I also listen to classical music or when watching movies, there are quiet times and then it bothers a lot. This would be similar as if someone would buy an OLED TV and then the black would not be black but more like a grey. Maybe I am overly sensitive or I hear too good,

Yes, indeed, that also came as a surprise to me. I have a denon DL 103R MC cartridge which only has 0,25mV so I should set the stellar phono to high gain. Now, I can even listen at medium gain and still have the BHK well below 20. I do not listen extremely loud but since I have a rather small room.

In general, I am not dissing the BHK, the vinyls never sounded better before in conjunction with the stellar phono.
For my taste, the white noise is too loud but maybe this is a general tube thing.

Thanks

#11

thanks Philippe, but not sure how this would help me…:slight_smile:
If the BHK is producing the white noise, when I put a passive component which is a separate volume control in between the power amps and the preamp, how should this reduce the noise?
In general, I could get rid of the BHK preamp and only use the RVC but then I would need to switch sources manually but unplugging the XLR cables…

#12

The Placette or Rothwell attenuators can help.
Look at the Rothwell website for a good explanation.

#13

Is HT mode off?

#14

Yes, it’s off.
Maybe exchanging the tubes with quiter ones could help to reduce the (white) noise floor?

#15

I use a tube phono stage with a 0.2mV Koetsu and it is dead quiet. I use a mains conditioner with full cross contamination isolation. I’m amazed the P15 does not have CCI implemented.

The Isotek products do, but there are also single supply isolation and conditioning units made by Isol-8 (another Nic Poulson business) that are reasonably priced and will tell you if the BHK pre is the issue.

#16

ok thanks. I have ordered already an Isotek Aquarius.
Currently, I only use a DC filter before my P15.(which already helps a lot, otherwise the P15 transformer and also the BHP preamp are producing noises but that noise comes directly from the device itself and not via the speakers)
I will check and let you know in case it is any better then.
Otherwise, I am currently checking if there are any quite tubes available just for testing. (low noise, low microphonic)

#17

I had an Isotek Aquarius about 11 or 12 years ago. Very popular. I only change to a regenerator as I was using a Class A SET amplifier. My regenerator buzzed as well. As I use very low power mostly digital kit I’m back using a conditioner with component isolation, low inductance etc. Even the $600 ifi PowerStation mains block has component isolation and is very popular.

#18

I like your TV analogy. Thanks for giving the test a shot. The noise seems to be coming from the pre. It might be worth having your dealer test it. Though tubes can be nosier, the BHK pre is next to silent in every system I’ve heard it in. Specially with you going balanced throughout.

#19

Just to add for completeness: Received my Isotek Aquarius today and it is still the same.
At volume level 85, 10 cm before the speaker, recorded with my Samsung galaxy, it sounds like this:
Noise

#20

Sorry that I haven’t read the entire thread, but that sounds exactly like what I have heard from a bad tube. If you haven’t tried changing them, it’s cheap and easy.