VAC Signature MK2a pre "phono tube questions"

Hi there I have a VAC pre with MC/MM, upon opening noticed there are two roles of 3 12AX7 tubes in each totaling 6.


1. Anyone have any experience tube rolling these and if so with what?

2. Are they three matched pairs or all matched?

3. They are a Chinese tube that came standard with the pre., anything special about them?
I have found on other gear which came with Chinese 12AX7 tubes they were nothing special and by substituting I found the sound was transformed, sounding allot better using other tubes.

4. Can you mix and match, say the first role Bugle Boys, second Tel for examaple or best to stay with one brand through out.

I have allot of really nice matched pairs but only that.

Any assistance would be appreciated.
Dev, I am surprised that you would ask such a question. From all your reports here, you have a wealth of knowledge and experience.

There never is any "right" way of doing things and this includes the tube set that we ultimately run with in any given link in our system. When it comes to tubes to try in a product, a good starting point is the manufacturer's suggested tubes. But very quickly I find tubes from my stash that far exceeds the performance.

When I owned Aesthetix Io and Callisto components, I mixed and matched tube types in each. The Callisto used 4 6922 tubes. I found the ideal match as one pair of Tele 6DJ8 and a pair of Amperex 7308. With the Io, which used 14 12ax7 tubes, I found 10-12 Tele's worked well with the rest as Brimar 12ax7. I have played the same game with ARC products, LS5 and MCP33, that used multiple pairs of Tele, Valvo and Amperex 6922 with great success.

Just try out all your tubes and see if you find a set of 6 that take the VAC to a new performance level.
Sorry about going sideline a little, but why would such an excellent company as VAC use "nothing special" tubes instead of the best new not NOS there is? This doesn't inspire my confidence in any way. I would want them to find overall best tubes for me instead of me chasing this all over the world. And again I am not talking about NOS. Or maybe I am wrong and they did put the best current production tubes, that just happen to be nothing but average. Do others like LAMM, VTL, Atmasphere, ARC do the same?

Most manufacturers do not use because of cost and availability. Most manufactures buy new tubes by the case and sort them out from there usually from China or Russia.
I am sure most would love to supply nice NOS, but have you tried buying a nice matched pair of Telefunken 12AX7 lately, you will likely pay around $200 and up depending on vintage and type.

Also when you use the Chinese or Russian tubes you have a standard to work with, meaning customers will be able to find the same tubes now and not have to hunt for expensive NOS. So the sound is consistant with what the manufacuter has sold you.

All that being said nice NOS tubes are very good compared to most of what is available new today.
Hi Jafox,

You ask why I would ask such questions, why wouldn't I, you obviously did not know the answers to my question entirely either. I'm always learning, I also like to know what other owners specifically are using or what they have found in relation to comparisions. I'm a fairly new comer also to owning the VAC pre-amp specifically so I had no clue to what these tubes were responsible for. I have read info. in relation to the line stage tube changes and also some with the 300.1 amps but nothing directed to the actual phono section.

As for what tubes come with a specific pce is out of mine and your control and a debate in general which should be taken up and directed to the manufacture but I do agree with in general what Pcosta wrote.

My questions

I see no replies from actual owners as of yet but thanks for the general info.

I do have some info. that was provided by Brent;

- The back row of tubes are the inputs.
- Middle row second gain stage.
- Front row are the low impedance output buffers.

"They all play a part in the sound, but the front set are theoretically under the most stress, so I would avoid putting anything delicate and/or rare in that position."

"The Chineses 12AX7 is currently the best one on the market by far. They are of current manufacture, and remarkable in that regard, though they are from the top 10% of the batch in terms of performance, even before they are graded.
The Chinese tubes are not the prettiest tubes, but they are remarkably consistant."

"With 6 tubes to play with, simply swapping them around usually nets a good result in terms of channel balance, and with passive RIAA, they aren't as critcal to one another."
Hi Dev,

The phono circuit in your preamp is the same as in the Phi Beta, which I'll receive on Friday. I, too, asked Brent about rolling the 12AX7s a few weeks ago and received similar info. One thing I'll add is that he said the back row, the inputs, play the greatest roll in sonics--back to front, in order of decreasing influence. The front pair, under the most stress, have the least influence on sonics and will have the shortest lifespan. He said to place the tubes you care about the least in that position. I'll probably start the rolling process by leaving the Chinese tubes there and placing my fav 1964 USA Amperex 7308 into the back because they have such great focus, resolution, and balance. Then I'll see what middle pair is best for tone. But, of course, I'll ultimately experiment with all positions
Hey Jafox,

I believe Dev asked his question because of this thread that was started just a few days ago.

VAC Thread from 9-5-11

Most of the respondents all seem to have stated that using NOS tubes were no better than the stock tubes that come with the VAC equipment.

(Interesting responses that went against my instincts as well. I find that using NOS tubes in my Lamm hybrid amps yields small, yet significant, improvements in the sound quality. However, I don't own VAC equipment, (although I wish I did!), so I don't know for sure that using NOS is the way to go.)

My two cents worth.
Hi Wrm57,

Congrats! and thanks for that added info., what you wrote in relation to position really provides clarification of such and greatly appreciated. I assumed such but this now confirms.

Hi Kurt tank,

ya I read that thread also but no one really appeared to be specific in relation to the phono stage only tubes and now that we have this info. we know and such will assist with any others interested.

Next will be the actual comparisons and in the end the findings, unfortuantely mine will have to wait a bit because my amps are still in break-in mode and I don't want to miss out on hearing any sonic differences due to such.

I have some very nice matched paires from different manufactures on hand and will most defiantly be trying and comparing, hopefully Wrm57 will report back his findings.

Hey if it works out the stock tubes work than that will be a bonus but I would be shocked just because of my past experience with other gear doing such, time will tell.

I'll probably start the rolling process by leaving the Chinese tubes there and placing my fav 1964 USA Amperex 7308 into the back
Unless you have specific confirmation from Kevin or Brent, I'd think twice before putting an NOS 6DJ8/6922/7308 into a slot designated for a 12AX7. They are both 9 pin miniature dual triodes but unless the circuits are specifically designed for it, they are not direct substitutes by any means. I realize that Randy White and Dan Wright and some others have circuits into which they can be subbed, but I do not remember reading anything that indicates that that is the case w the Ren pre-amps (great unit, BTW.)
D'oh! I meant medical grade Amperex 12AX7. I mentally misfired because I had VAC install a 6922 switch for the 8416 tubes (at their recommendation) in the linestage and was thinking the tubes I'll use to roll that position. No, I'd never put a 7308 into the 12AX7 socket. :) Thanks for catching it.
My point was missed entirely. People new to tubed gear ask such questions. Those with much experience, especially those with a stash of coveted tubes from yesteryear know that the only way to determine if the tubes they have will work .... is to try those tubes themselves.

As for questions concerning why tube manufacturers don't load up their gear with the best tubes is simple.....there is no best tube. And a manufacturer must be able to provide a suitable stock for production and customer support. There's just not enough of any NOS or UOS tube type for a manufacturer to rely on. So their only choice is to install the crappy Sovtek and EH tubes throughout. For those of us who know the benefits of getting these replaced by other tubes, we are on our own. And often we hear the performance of products that far exceeds what the manufacturer ever experienced.

We all try various tubes in our DACs, phono stages, line stages and amps, and with a lot of effort and a little bit of luck, we find a set with a result that can truly be so impressive. A Tele 12ax7 may sound good at one place but very disappointing at another. And the same for an Amperex 6922 or a Mullard EL34.

As many proponents of SS gear would claim, we tube fans are just chasing one set of colorations with another. That's ignorance. No device is perfect. I have no tolerance for tonal coherency problems, but there is always a tradeoff with noise level, resolution, dynamic contrasts, portrayal of space, etc. The key is to experiment enough and deal with as few tradeoffs as possible to achieve the overall system magic. When a tube is discovered in a link that before was our reference at that link, opportunity arises elsewhere. It's simply not possible to do this with SS.

No manufacturer of a tube product will ever be able to provide a tube or tube set to you that will come close to the set that you ultimately discover that you like for yourself.
Yes, they might. When I am ready to order my LAMMs I will get in touch with Vladimir and discuss with him exactly that along with some other things. Or even if I get a used one. I may still have to try couple of sets but not dozens of them. And I would have no intention to roll tubes back and forth depending on particular recording though it might actually make sense. Unless perhaps if I decide to make compilations using something like Studer 810 deck. Now that would really be audiophile fun.
Sorry Inna, but not a chance. No manufacturer listens to my system in my listening room. Tube selection is not about one component but rather for the entire system. What Vladimir might be able to suggest to "optimize" your LAMM product n the test bench guarantees not at all that this is the ideal r preferred by you in your system.

Rolling tubes for a given music type or even a specific recording would be to much for me as well. I guess this is why many people have multiple phono cartridges with multiple arms or replaceable armwands.
Right. But you know I might just invite Vladimir over for coffee. Anyway, I think many here with LAMM either use what he supplies or some particular military or medical grade Amperex. And with VAC I don't know.
If it were my VAC, I would ask VAC.
I asked VAC. VAC recommended tube rolling. In fact, Brent strongly recommended (three times!) installing the switch to accommodate the 6DJ8 family instead of just the stock 8416 tubes primarily because the latter was only made by Amperex and the former would give me a wide variety of "sonic flavors" (his phrase) to choose from.
I have no idea about the particular Chinese 12AX7s that VAC supplies, but don't dismiss them just because they are Chinese. Some of the best 12AT7s I have ever heard were made in China, supplied to me by the Billington company in England. Admittedly, they were "select" types. But they killed Mullards, GE Gold Star 6201s, Philips, and a few others I compared them to. (The Gold Stars took second.)
Good luck finding real NOS Amperex etc.
Yeah, luck is indeed needed with NOS.
Hi Lewm,

My preamp arrived and I checked out the VAC 12AX7s. Construction looks identical to my Psvane 12AX7s without the gold plating on the pins. So that means they're almost certainly made by Shugang, which also makes the Psvanes. They're really quite good!
Hello Dev,

You asked me to report back on tube rolling the phono section of my Phi Beta, which has the same circuit as your Sig 2a. I've had it for a week now and I'm ready to make a few preliminary observations after rolling a variety of high-quality 12AX7s, including 1964 Med Grade Amperex (very pricey), mid-'50s RCA long blackplates (one of my favorites), late-'50s Tele ribbed plates, and mid-'60s Lorenz (German-made Amperex). I have several pairs of each and I've tried them in different permutations in the first two positions. Because this circuit is so transparent, all changes in tubes affect the sound quite dramatically. Much to my surprise, however, so far the stock VAC tubes sound best to me. They are very balanced with excellent soundstage and tonality, weight and authority. They just sound "right," perhaps because VAC spends quite a bit of time tuning the sound by ear. I do find myself wanting a tiny bit more extension in the treble, and slightly faster transients, but this is perhaps because my tubes have quite a bit of time on them. I've ordered some Psvanes (I had a pair but wrecked one), which I expect to match this circuit very well since they appear to be of the same manufacture as the stock tubes (Shugang) but at a higher level of quality. I'll report back when I've tried them.

I'll add that I'm extremely impressed with the phono section itself. It's quite a bit better than I was expecting, and holds its own extremely well against my Steelhead II. I'm actually not sure which one I prefer. The Manley (which I've rolled extensively and optimized to my ear) is perhaps more dynamic, with more drive and extension. And it's more flexible in that it allows gain and capacitance adjustment. But the VAC is perhaps a bit more organic and natural. And it has plenty of gain even for a .2 mV cartridge. I could easily live with either, though I'm glad to keep both. Mine is MC/MC. At my request, Brent modified it to allow manual adjustment of impedance loading, unlike the stock Phi Betas, which have user-chosen fixed loading. He built these ingenious screw terminals that allow me to slide in resistors of my choice (I use nude Vishays) so I can really fine-tune the loading for any cartridge. For 100k loading, e.g., I use 10k resistors. It's both extremely flexible and extremely transparent. What a great company! I'm completely in love with this preamp. And you're right, it's a brilliant match with the Bryston 28B-SST2.
Hi Wrm57,

thanks for that information in relation to the phono section, look forward to your further results when you get your tubes.

Great to read that you are also happy with the pairing, I know of a few others whom also pulled the trigger and now have the same combo and truly enjoying.
Follow up: I found the VAC 12AX7s to be better than the Psvanes in this phono stage--more open and balanced. The Psvanes are tonally richer but and not as extended in the highs. I just ordered another set from VAC as back ups.

thanks for the update, how many hours does your unit have on it now.

Kinda wondering if it is broken-in as of yet.

If so a recap of comparisions to your Manley specifically, once I have my 500 or so hours logged in with my 450's then at that time I will be wanting to do some phono comparisons.

When talking to Brent or Kevin did you happen to get any information in relation to the phono they have been working on.
My preamp is a dealer demo so it had a lot of time on it. The phono stage, however, had a cap replaced and the screw terminals for impedance loading installed, so those changes require some break-in, as do the nude Vishays I use for loading. In my hands, the unit's been on for three weeks with probably 130 hours of playing time (I work at home and listen while I work). So, you're right, the phono section is probably not quite fully burned in, but close.

I probably should have mentioned that the Psvane tubes are not fully burned in yet. Psvane recommends around 100 hours and I have probably half that on them, so their character might change. But the sound has stayed pretty consistent so I doubt they'll change much. Brent was pretty emphatic that the VAC 12AX7s are his favorites in the Sig phono circuit. He has quite a collection of NOS 12AX7s but prefers the stock ones in there. I have to agree.

I'm coming to the conclusion, subject to revision, that the Manley phono stage is a bit better. The VAC is excellent, don't get me wrong. I completely enjoy it and could easily be happy with it alone (if I only needed two MC inputs). But the Steelhead, right now, anyway, is more dynamic and throws a deeper, more articulate sound stage. My cartridges are all pretty low output, ranging from .2 to .28 mV. The VAC MC sections provide 60 db of gain, which is certainly enough for all of them to sound great. But the Steelhead may be selected for more gain yet, hence the increased dynamics. Running through the VAC linestage, the Manley sounds superb, better than I've ever heard it.

Since I'm running three arms (soon to be four) on two tables, it's good to be able to choose different phono sections for different arm/cartridge combos. But if I had to choose, at this point, anyway, I'd take the Manley. I haven't talked to VAC about the new stand-alone phono stage.