Noise Problems in BHK Pre with 6V or 7V Tubes

That’s exactly my experience with the BHK preamp and 6 volt tubes and I tried at least a dozen matched pairs from multiple brands new and NOS. After about a month of 6 volt tube swapping I gave up and have stuck to 12 volt ever since.

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Thanks, Vee. I’m surprised that difference in the sweeps is audible.

I ordered -10dB attenuators, here late this week.

I put my Gold Lion 6922’s back in today. You think the 12au7s are more sparkly? That surprises me. I had some French Military 12au7ws in that sounded dull by comparison. What amp and speakers are you feeding?

Still might buy a Prima Luna E400 pre.

Jack, have you found some 12v that sound as good as the 6-7v tubes?

I did change my attenuators order to -10dB. Thanks.


I was bad about swapping through the 12 volt tubes just to hear the slight changes but the pair I stuck with the longest was a set of early 50’s Raytheon Triple Mica Black Plate 5814’s. Also had good luck with the 50’s RCA Black Plates. As a general rule when you can find a good set from a trustworthy dealer any of the 12AU7’s that were branded for Baldwin Organ Company will be quiet tubes as they were tested and graded before Baldwin would accept them. Raytheon and Sylvania were there biggest suppliers though you can find other brands once in a while. There are a couple of Ebay dealers that do a good job grading and matching tubes. Spin4Cards and Tube Maze so you might want to check their Ebay stores and see what they have. With my 93db speakers I couldn’t get past the extra noise from the 6 volt tubes long enough to tell you whether they sound better or not. Even though I still have the BHK preamp I have switched to a 6SN7 preamp as my primary.

In my experience, it’s been less about what model of tube and more about what sound signature a particular brand and vintage of tube imparts. I’ve found NOS tubes to be warmer sounding with ever so slightly rolled off highs compared to new stock tubes of either 6v or 12v variants.

I have a pair of Stenheim Alumine THREE connected to BHK300 amplifiers.

Therein lies my problem: All the vintage 6 or 7v tubes I tried became unlistenable in short order, due to pulsing, rushing, and volume control noise. All from reputable dealers, all balanced, low noise, tested, matched. The new mfg. Gold Lions have rushing noise, but none of the other problems. I’m pretty hard pressed to gamble another several hundred US on another set of vintage 6 or 7v tubes that are unlikely to work properly. I think I have just answered my own question: on to Prima Luna. One thing I haven’t tried, though, is reducing the current for the 6922’s or 7DJ8’s.

I have settled with Gold Lions 12AU7/ECC82. Enhancement efforts are directed elsewhere.

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What does this mean?

Great choice!

My experience with 12au7 tubes correlates with yours. The 5814 tubes I’ve tried are all mellow and “musical.” I like the RCA black plates quite a bit and have settled on those for longer than anything else. I have also found that using various aftermarket feet also go a long way towards “tuning” the BHK pre and amp to my tastes. At present, I’m using Nasotec ceramic bearing spike/shoes on the BHK pre and Golden Sound Jumbo cones and pads under the BHK 250. Eventually, I’ll get around to trying some Stillpoints SS under them. The Stillpoints definitely kicked my Tidal speakers up another notch with regards to resolution. Out of curiosity, what 6sn7 pre are you using now? I have a DeHavilland Ultraverve III which uses a 6SN7 but haven’t used it in some time.

I am working on enhancing my source(s) and cables. If I ever thought the BHK pre does not meet my expectations, I would do exactly what you did, look for something new. I won’t try to extract more than what it was originally designed for.

Supratek Chardonnay but also have the newest Don Sachs Model 2 I’m testing out. Much lower noise floor with both in my setups.

I’ve hear good things about the Primaluna. It’s worth an A/B to get that sound you’re looking for. The lower voltage would take the noise down slightly, but not enough to be silent–the Rothwells would do better at that.

Vee, everything I have read about the Evo 400 pre was positive. I heard it in a dealer system, and for what that is worth, it sounded very much the direction I want to go. I will miss the convenience of one remote for the BHK and Directstream Sr.

There is one alternative I am curious about: DS DAC>tube buffer>Rowland amps. Any thoughts on that?

After extensive testing, I’ve also found that 12au7s are the quietest, while the 6dj8 family is the most musical, 3D, etc. Some of that appears to have to do with the inherent gain of each of those respective tube families. Best from the 6dj8s are the Siemens Ccas, but you’ll still have some noise. Best 12au7s were the Amperex 7316s and the Telefunken ECC802s. Both are rather hard to find (and they still don’t best the Ccas).

It’s such a shame that you folks are having such noise issues with 6 and 7 volt tubes.
In my BHK, I’ve never experienced this. There is some hiss if I put my ear up to the tweeter, but I don’t put my ear up to the tweeter.
And the sound of the Telefunken 6DJ8 is sublime.


NOS Telefunkens in my BHK are sublime as well. 6922s here. I confess I don’t understand the relevance of measurements at 1-inch distance from the tweeters. At my listening chair the noise floor of a fine pair of 6-7 volt tubes in my BHK is inaudible.


Owlsalum and RonP:
If I had to put my ear up to the tweeter to hear this noise I would be happy as pig in… er, mud. This is not some esoteric exercise in Hi Fi purity.

You certainly want some context to make sense of the figures.

The constraints are arbitrary; I share them in the event someone wants to compare notes. Holding distance constant, the 4-6dB SPL difference between the tube sets with nothing going on at point blank range is telling of how much noisier the 6922s are in my BHK Pre. In another system, these differences can be lesser or greater, depending on the sensitivity of the speakers.

To share an observation we can relate to, you’ll want to measure SPL at the same distance with a calibrated meter dbA-weighted and share the SPL you get. Add your speaker’s sensitivity and seated distance and we have some numbers we can correlate.

My ears are roughly 7 feet from speaker cone and the Stenheim are 93dB efficient. I can hear a faint, gentle hiss when the noise floor emitted at 1 inch is 47dB. It’s forgettable, but noticeable if I think about it. Hitting the mute button vanquishes the noise. At 42dB, this is no longer the case and I cannot hear noise at all from MLP and mute/unmute is unremarkable.

Adding an inline attenuator solves the hiss issue at 47dB, because I’m dropping the noise floor by the attenuation provided, say 10dB because I know I can’t hear the hiss at 42dB.

There are other factors that can affect noise at the MLP like temperature, humidity, environmental noise floor, etc.

Just an update: I added the -10dB Rothwell balanced attenuators at the amplifiers’ input. Life is good, even with the previously troublesome tubes. And to my surprise even the volume control and off (standby) do not pop or click like they used to.

Much obliged, @Vee.