BHK Preamp tube rolling

I was itching to take the plunge and buy the BHK Sig Preamp to go between my PS DS DAC and Pass Labs XA100.5 amps, but after wading through this forum thread and reading about all the mysterious “pulsing, hissing and thumping” I’m having second thoughts. How pervasive are these tube issues? Is it something that most purchasers of the BHK Pre have to deal with, even with the stock tubes? There seems to be a consensus that the stock tubes are inadequate and need to be upgraded to NOS. Is there anybody who loves the stock tubes just as they are?

Me. The problem with these forums is you only get to read about the periphery, not the mainstream. Fact is, out of the hundreds of BHK Signatures we’ve got out in the field, only a small and vocal handful are tube rolling or having an issue with noises. 99.9% of the people using the product, including myself on the world’s most resolving system, are not only happy, we’re thrilled beyond belief.

Take what you read in these forums with an appropriate grain of salt. Really.

1 Like

I’m using a Pre (whole PS Audio system bar the tt and tube phono amplifier). I have changed the tubes in the pre and the S300s and I haven’t noticed the hiss, etc. I hope I don’t but if I did I would expect PS Audio to assist as they seem to be doing for the few it affects. I’m also not sure how much difference the tubes make - I haven’t sat down and tried to make an unbiased comparison.

Paul McGowan said Take what you read in these forums with an appropriate grain of salt.
An excellent point. The forum is populated with the hardcore. We almost look for problems.

It is also worth keeping in mind that those who believe there is an issue will seek out help in the forum. Those who are blissfully happy are busy listening to music.

I have had one since January no issues at all, top notch performance and sound. The stock tubes srr excelent and offer the best sound to start with. Changing to NOS tubes just changes the flavor if you know whst I mean. You really need to hear one in your system Better than the Audio Research I had before plus alot of flexibilty, balance adjustment, balanced ins and outs etc.

Paul, thank you for your response to my inquiry about the extent of the tube issues and the overall customer satisfaction with the stock tubes. Your personal testimony and statistical information is compelling, along with your advice to take the forum comments with a grain of salt. Having said that, I do appreciate the sharing by users of both good and bad experiences, and I totally understand the “hardcores” quest for perfection, being no stranger to tube rolling myself on other tube gear and hearing the subtle differences that make certain tubes shine above the others. I am glad to hear that the noise issues a few have experienced with certain tubes and with the Pre itself are not typical, and that PS Audio has been very responsive to those having those issues.

To change the subject, but still on the topic of tube rolling, it would seem to me that for those using the Pre with the DirectStream DAC that the recent revisions in the DAC software might lead some to experiment with different tubes. Going from Torreys to Huron gives a more detailed, clearer presentation with a larger soundstage and more air that some might want to enhance, maintain or alternatively subdue with a tube change. Many may have based their previous tube decision on Torreys. Is it possible the new Huron version might even make the Psvanes preferred over other vintage tubes like the Tungsram that may have sounded better with Torreys. I wonder if any of the hardcore tube rollers have had a chance or inclination to change their tube preferences following the Torreys to Huron software change. The Torreys to Huron sound change was not subtle and could very well open the door to other tube preferences for those who love to roll.

Rest assured the stock tubes sound great, it’s just PS Audio has allowed for tube rolling that has enabled audiophiles to play, and given the opportunity they will. You also have the best customer support in the industry. If anything goes awry their personal touch is indeed a breath of fresh air, and that’s just icing on the cake when you consider how well this performs.

I was a bit hesitant purchasing equipment with tubes, I’ve been a low maintenance solid state listener most of my life, But I remembered as a kid how smooth my father’s mono Eico kit sounded (probably jump started my quest for hifi sound), that when PS Audio released their BHK line I figured if it was good enough for Paul to have a tube in his top of the line preamp it was good enough for me. One of the best decisions I’ve made in audio, probably only eclipsed by getting the Directstream DAC.

I changed from the stock tubes to the Tungsrams after 2000 hours. No problems with the stock tubes and they sounded great. I had to replace one of the Tungsrams after a few hours. No problems since and that was 1500 tube hours ago.

i haven’t felt the need to roll for Huron. I’ve just been enjoying the improved sound.

darrenv1070 said PSA has my preamp now, so I hope the unit acts up for them during the test and hopefully they replace the main board, I will anxiously wait for it's return. I am back using a Marantz AV8802. A nice unit, but no match for the PSA unit!

Either way, I am confident it will return in perfect condition! I am strongly considering selling my PSA BHK 250 amp for a BHK 300 mono pair.

I received my BHK preamp back late today. So I hope to connect it back on the rack at some point this week. I am excited to hear how it sound. PSA did find a couple issues but repaired and updated it for me. Very cool. I will report back once it has a some hour back on it.

OK, I bit the bullet. I bought the BHK preamp direct from PS Audio online, received it promptly and today had my very first listen, fully prepared to hear no improvement in my already fine sounding system. Based on past experiences with preamps I expected to hear a slight degradation of sound quality. No surprise to most of you, such was not the case. Right out of the box the sound of my system with the BHK preamp is appreciably superior to the sound of DirectStream DAC to amps with no preamp.

Until now I have never been happy with any preamp in my system (I’ve tried several, including tube and solid state ones in the $3K to $5K range). My DACs, including the DirectStream, have always been more than capable of driving my Pass Labs XA100.5s with wounderful results. I have been a no-preamp guy my whole life and boasted that the no-preamp set up was as good as it gets. But this BHK preamp is indeed different, and is everything that BHK, PS Audio, reviewers and forum members said it is. It very noticeably improves the sound by making it more dynamic, harmonically richer, livelier, better textured, more cohesive, and fuller bodied with a more realistic soundstage, without adding any audible hint of noise or distortion in my system.

After I get some hours on the preamp with the stock Psvane tubes I’m going to try the Tungsram tubes, although I can’t imagine the sound could be much better than it already is. But then, I couldn’t imagine how much improvement the BHK preamp could make in my system until I actually tried it. Some have described the Tungsram tubes as “taking the preamp to another level”. Specifically, what kinds of SQ improvement might be experienced? I’m guessing any changes would be subtle.

Nice! So glad you stepped up to the plate to hear what we’ve been raving about. Not subtle, eh? clapping_gif

I would sure let this bad boy break in with existing tubes for at least a month. I know you’re excited about swapping them and you should be, but the tubes in there now are quite good and my advice is to get a handle on its sound as the inner componentry breaks in and settles before changing anything.

Have fun and thanks for letting us know!

So after the aforementioned fall down the rabbit hole on tube rolling, here’s my experience so far. I’ve tried a range of tubes from the 6DJ8 and 12AU7 families. Standard caveats apply: your system, your room, your ears may return different results.

From the 6DJ8s - Siemens Cca (early 1960s, gray shield); Telefunken 7308 (1960s); Siemens 7308 (1970s); Mullard 7308 (1970s); and the Tungsram 7DJ8s (cryo-treated).

From the 12AU7s - Amperex 7316 (1950s); Siemens 12AU7 longplates (1950s); Telefunken 12AU7 smoothplates; and the stock Psvane tubes.

Each matched pair were burned in for 48-96 hours before critical listening.

The clear winner was the Siemens Cca 60s gray shield tubes. Amazing detail, dynamics, and accuracy. This was the tube that revealed everything that the engineer put on the track. Period. They aren’t cheap, but they will take your system to that next level. I bought a back up as testament to that. Worth the investment.

The second place finish was a tie between the Tele 7308s and the Amperex 7316s. Both provided excellent sonics. The Amperex was the best 12AU7-type tube. Holographic images floating in the right places within an impressive sound stage.

Third grouping is comprised of the Siemens 7308, Siemens 12AU7 longplates, and Telefunken 12AU7 smoothplates. Great tubes, great sound. Similar characteristics as their above brethren, but just a notch below.

Mullard 7308 placed fourth. Beautiful midrange, but a bit too much warmth in some spots that took away some detail.

Given the pedigree of the above tubes, shouldn’t be a surprise that the Tungsrams bring up the rear. However, that shouldn’t be a knock against them. They are a modest step up from the stock tubes (which are also nice).

In testing, I found Mr. BHK’s above forum comment to be spot on – noting that the overall noise/hiss levels (from the speakers) are generally lower with the 12AU7 family tubes. This was perceptible. As he also noted, there is going to be some hiss level (however large or small) with all tubes in the BHK, the level depending on the gain of your particular amp and efficiency of your particular speakers.

I went from a completely - stick your ear into any speaker driver and check - silent background solid state amp to the BHK, which introduced some hiss through the speakers. However, the sound quality of the BHK was absolutely worth it. An essential addition to one’s system.

Thanks again BHK and Team PSA.

3 Likes

Yes, the CCA tubes are special, I have three Valvo that are likely made by Siemens and they are excellent tubes; I had been using them in my Decware preamp.

The CCA is a very special classification of tube.

It is my understanding that they were for use in the early European post (phone) systems.

The tubes were selected and perfectly matched from the lowest noise tubes available.

From what I had read, maybe 1 out of a 1000 manufactured would meet the specifications.

I had 2 quads of TFK CCA’s that I acquired for $600/quad, sold them for $1500/quad years later.

All 8 tubes had different batch and date codes, but all 8 matched perfectly.

Their noise measurements were the lowest of any 6DJ8/6922/7308 type that I had ever measured and all measured perfectly identical.

I have added the BHK back into my system. I took Paul’s advise. I removed my entire system, removed everything. As this unit was part of a multi channel set up I had been using the BHK in HT bypass the entire time. This time I reversed the set up, I now use the BHK as my main preamp ( since I also almost never watch movies anymore ) and set up the room for music 1st and foremost. The Marantz can take a back seat!

Sweet sound! I am so happy with the sound. I have one question, are the RCA and XLR outputs separate inside the unit? I know they can be both used as say for main speakers and a sub. BUT I wonder if it’s possible for the firmware to be updated so that the outputs can be set up to have say one the outputs be shut off. Where this would be handle ( needed ) is in HT bypass mode. I’d rather use the XLR output of my Marantz AV8802 to control the subs for movies, but use the BHK to control subs with music listening. Right now I have to run two cables and unplug the RCA outputs on the BHK every time in bypass mode. Kinda a pain.

Paul??

They are not separate and cannot be controlled separately. A great idea but that is not what we did.

Here’s a question for you audio experts and tube gurus out there. I see advertized 6SN7 to 6922 adapters that supposedly allow any 6SN7 tube to be inserted in any 6922 tube position. Can such an adapter work successfully with the BHK pre, or is that asking for trouble?

The reason I ask: I have in my tube collection many pairs of NOS 6SN7 tubes including 1940sTungSol round plates, 1940s Sylvania Black Base, 1952 Sylvania Bad Boys, and several other 6SN7 tubes that sound amazing in my other tube amplifiers that accept 6SN7 signal tubes. It would be interesting if these tubes could also work in the BHK.

The logical answer is: “No, don’t try it. The circuitry is not designed for 6SN7 tubes.” but I thought I’d ask anyway.

The swap will work ins some applications, but depends on the circuit and I do not know anything about the BHK pre’s circuit. :slight_smile:

For example, the 6SN7 pulls twice the heater current. Some designs are happy to provide this much current; others, not.

The 6922 provides a great deal more gain than a 6SN7, so the entire circuit would operate differently with less gain.

I am far from a tube expert however.

Joseph Grogan said

Here’s a question for you audio experts and tube gurus out there. I see advertized 6SN7 to 6922 adapters that supposedly allow any 6SN7 tube to be inserted in any 6922 tube position. Can such an adapter work successfully with the BHK pre, or is that asking for trouble?

The reason I ask: I have in my tube collection many pairs of NOS 6SN7 tubes including 1940sTungSol round plates, 1940s Sylvania Black Base, 1952 Sylvania Bad Boys, and several other 6SN7 tubes that sound amazing in my other tube amplifiers that accept 6SN7 signal tubes. It would be interesting if these tubes could also work in the BHK.

The logical answer is: “No, don’t try it. The circuitry is not designed for 6SN7 tubes.” but I thought I’d ask anyway.


Yes that is a logical answer. However, when I look at the 10K plate load line on the 6SN7 curves, 5 mA of plate current is close to the 0 grid volt curve and thus could draw grid current and is not a satisfactory operating condition. The 4 mA current would just work with about -1 V of grid voltage and might be worth a try. Of course with those octal to 9-pin adapters, the grill over the tube area would have to come off and the tubes would stick up above the top of the preamp - but otherwise it may function OK and could sound good.

1 Like

Thank you, Bascom, for your generous response to my hypothetical question. So, if I were to try a 6SN7 tube with the adapter I would need to set the preamp voltage setting to 6 and leave the bias at 4 ma? The only reason I would even entertain the experiment is that the Tung Sol 6SN7GT round plate is the best sounding 6SN7 tube I’ve ever heard in my headphone amplifier and main amplifier, and I have a few select NOS pairs just sitting in a drawer for several years. The purist in me, however, hates the thought of an adapter in the signal path.