VAC Signature MK2a pre "phono tube questions"

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?

Inna

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