New BHK pre... is this normal?


#1

I know of the clicks when raising volume, it’s not that.

Literally just plugged the amp in, and there is quite bad background noise.

I’d put in BHK recommended Tungstram 7DJ8 6v tubes, set voltage jumper (and current as suggested) and sat down to listen
Between volume level 21and 24 there is a very noticeable ‘whistling” tone, which vanishes when the volume relay clicks in at 25.

Toggling between 24 and 25 it’s extremely noticeable.
Tube burn in? Amp burn in?

Will it vanish with more time on it, and is it an indicator of an inherent issue?

Should it sound dead quiet switched on the first time?
Any other preamp I’ve had in my system and been silent.
Scratching my head on this one, frustrating as I’ve waited many weeks for my Amp.

Thanks.


#2

I don’t get any whistling. Actually when playing and not messing with the volume of the BHKPre it is very quiet. As for the clicks, they’re there. It’s only annoying while adjusting the volume. And yes it does make a much more noticeable POP between 24 and 25. I believe there is another louder than normal pop somewhere along the volume line, don’t remember. Yes the pops are somewhat disappointed but in general I set my volume and stick with it. If I was a Volume surfer I’d probably have a different opinion.


#3

Did you try the original tubes prior to installing the Tungstram? Sounds like tube noise. My BHK Preamp is not silent.


#4

Are you listening to speakers or headphones? If I use my Shure IEMs with the BHK, I can hear a fair amount of background noise that isn’t as apparent when listening to my Focal or Audeze over-the-ear headphones. Likewise, my Quad speakers do reproduce a bit of audible hiss that tends to be less noticeable on other speakers. It definitely varies across the volume range as you describe. As knecht wrote, this is normal for the BHK and related to the tubes. You might refer to the ‘tube rolling’ thread if you consider swapping out the tubes.


#5

The only time I’ve had issues with noise and odd behaviour with my BHK Pre have been tube related. Many tubes are 50-60 years old. Many have been used and are resold as NOS. Try some other tubes. There are many recommendations here in the forums. I’m not a fan of the Tungsram tubes I didn’t have an issue with noise but the sound can be easily bettered.


#6

Well here’s an interesting one…
From replies here the problem was suggested to be tube related, so began troubleshooting with that.

I had closed the jumper for current giving 5ma to the valves, so the first troubleshooting step was to knock it back to 4ma, see if that affected the problem.

It did, the whistling sound is gone now.
What?!
The amp seems to be sounding more like what I expected, which is great.

Good result and not unhappy with a solution.
Will let the amp and valves run in then flip the jumper back to 5ma.

Meanwhile I’m just gonna enjoy the rollercoaster of burn in.


#7

What tubes are you enjoying currently? I very much like the Amperex 7308 and for different reasons the Brimar cv4003. Brimars better with upper mid range like female vocals but bass is a bit flabby compared to 7308.

Unfortunately, one of my Brimar pulses (tube rush) and I suspect it will only get worse, though very quiet currently.

As there are few guarantees, I like to keep my tube speculation to <$100 each.


#8

My current favourites are Philips Miniwatt’s in the 7308 flavour. Also very good are Mullard RTC 7308 both of these are good with Mullards being warmer. The Telefunken 6DJ8 are very good too. The Siemens E88CC are very competent.


#9

I tried over a dozen different 6 volt varieties in the BHK preamp and found all of them to be noisier than 12AU7’s. There are a lot more 12AU7 varieties around and they are cheaper.


#10

Fortunately, I’ve used and still have Telefunkens, Siemens, Mullards, Phillips Miniwatts, Other Phillips variants, Amperex’s (Bugles and Orange Globes). All are 6 or 7 volt varieties and none gave me any noise or odd behaviour. The worst tube were rare Lorenz Holy Grails. They had noise, pops and involuntary volume fluctuations. Worst tubes ever and they came from a respected volume dealer on Ebay in Germany.


#11

You have to be careful where you get your tubes. I’ve used lots of 6, 7 volt tubes, all bought from Upscale and I never had an issue with my BHK pre which is a rock solid product.


#12

I’ve received some not so great ones from Upscale, those that shipped with my preamp, the Tungsgram, noisy. All of them.

And one Brimar, sounds like constant popcorn, pop, pop, pop. It’s low but still not what I consider a premium pick of the litter.

I think most tubes are a crap shoot. I might try some of the currently made 12AU7 out there for fun, like the JJ ECC82/12AU7.


#13

I steer clear of Brimar tubes lately. Langrex sold me a quad of 5U4G rectifiers and 2 failed within 4 months of very sporadic use. Old tubes, new problems with these.


#14

I couldn’t warm up to the sound of the “Upscale/BHK super” Tungsrams’.
I finally settled in with the Amperex 7308’s and they were quiet and luscious sounding.
I did find (and a few friends with BHK’s also) that Matsushita 7DJ8’s are dead quiet, reliable and great sounding tubes. And they’re relatively inexpensive.


#15

Thanks re: Matsu, I’ll try some. I’ve had the Amperex 7308 in for months now. Wonderfull sound but wondering what else is out there to discover and enjoy, especially with decent Iconoclast cables now.


#16

Here’s a link to a lot of info about the 6DJ8 and variants of these tubes:

http://www.audiotubes.com/6dj8.htm

There will be a test after reading every word in the link. Certified Tube Maven CTM designation.


#17

The Matsushita’s are very good sounding tubes. Almost Mullard like which is not a big surprise. They were my favorite of the six/seven volt tubes in the BHK.


#18

And they’re around 40 bucks each which makes them a bit easier to try.


#19

I’ve been here before but thanks for the reminder.


#20

Fantastic replies, thanks very much.
I’ve experience of tube rolling 300Bs so thankfully these ones aren’t so painfull!
Great list of tube suggestions and experience.

I DID notice an improvement going from the stock tubes to the Tungsrams, but given the ‘glitch’ I’ve had with the whistling sound (happily now gone) I’m choosing just to let everything run in properly before I overthink things.

After the tubes and amp have hours on them, maybe going back to 5ma will work without the whistling noise?
Will I prefer it to 4…who knows.

Just gonna at least try and chill, enjoy the music and appreciate the great amp I have. :slight_smile: