Tuberolling SRM-007t

Recently I have bought a Stax 007t system. Reading in many mails on this forum how great the system can sound when using different tubes, I ordered 4 NOS Mazda/Brimar 6FQ7 tubes. I put these in the 007t amp and adjusted the voltages as described on several postings in this forum.
However, for some reason, for 2 tubes out of the 4 I'm not able to get 0 V adjustment when balancing the 2 triodes in the tube.
I measure 0.13 V difference (max). My questions are:

- what is the consequence of this deviation on sound performance?

- Could it possibly damage the amplifier/headphone?

- Does this have implications on the lifetime of the tubes?

By the way, the sound is great.. Much more open then with the standard Ei tubes.

Try dropping your meter range down one setting to the mv setting and try your adjustments again.
Let the tubes burn in more and redo all your settings.
No you will not damage the amp, tube wear will not be to much a factor at that setting.

You can't damage the amp no matter where the adjustments
are. 130mv of difference between the two sides of the
same tube is negligable. If it was 3 or more volts, then i
would replace the tube. Best to match the sections of
the tube on a tube tester, and use only tubes matched
to a few percent.

I was able to get tvr3 and tvr4 very close to 0 volts (balancing the triodes). However, tvr1 was problematical (balancing the tubes to each other) and tv2 was only a little better (balancing the tubes to ground). My suspicion is that close enough will work. A tenth of a volt difference is not a big deal here, relative to the amount of current involved ,and shouldn't affect anything (that's closer than I could get with tvr1). I got to within 1/2 volt and was happy. Bear in mind that those voltages are going to start swinging wildly, much more than what you've set them at, as soon as music starts to play.

eidt: Those who know more than I have spoken

Thanks all for your advise, I'm glad it can not cause any longterm damage or so. I wil readjust the pots after some burn-in. How long does it take to burn in NOS tubes in the SRM-007t?

By the way, I'm also going to try some RCA cleartops that have seen a cryogenic treatment. I am very curious what the effect of this treatment is. Has anyone used these before?

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I'm trying some 6SN7's that have been cryo treated, but have only had them a very short time. You might want to try and scare up a set that hasn't been treated to do a comparison.

EDIT: the cryo tubes I'm using are in another amp. I'm in the process of trying to see just what cryo treatment does.

I own the 006t amp and have to use a similar procedure to bias the tubes. When I installed some GE tubes a couple of months back I had the same problem i.e. I couldn't get one of the tubes adjusted to 0v.

I recently installed some Mullard tubes and using what I learned from the previous biasing fiasco (I took me over 6 hours to get done ) I was able to get the tubes within 0.003 mV in much less time. One of the "tricks" I used was to get each adjustment within 0.5V and then walk away for a few minutes to let the wild swings settle down. I also let the amp warm up before beginning the adjustments.

The tubes themselves may have something do with how easy, or difficult, the biasing is. The Mullards just seemed to have less of the wild swings that the GEs exhibited.

Hirsch,

I didn't know the 6SN7 was a replacement for the 6FQ7 tube. Do you think it would work in the 006t amp as well?

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It's not a direct substitute. I used cryo 6SN7's in another amp. However, the two tubes are related. As I understand it, the 6CG7 is a nine-pin version of the 6SN7.

It's I N C R E D I B L E... I was writing the same thread about the very, very interesting toberolling on the SRM 007t.

I'm testing from some weeks a lot of tubes 6FQ7 comparing the different sound I can hear to the SRM 717 SS and especially with my setup: R10/Angstrom.

As many of you know, my idea is to "tuning" the Stax system to the R10 combo, just to give a bit more of "musicality" to the electrostatic cans that is so much detailed and precise, things that would be against a certain pleasure in listening as the dynamics cans have more. And in this point the R10 has the first place between all the headphones (IMO and IME).

I can to tell sure the the RCA Cleartop shields are the most brilliant and detailed tubes, the second place we have the Ei, than the GE, and than others brands not so much good (as Golden Dragon, National Gold). But with the RCA the sound is too much "electrostatic", even if incredibly detailed and precise, I'm not looking for this with the Omega...

The first place absolutely for "musicality", we also can to tell warm and soul, are the Brimar/Mazda U.K... you can really listen the "triode sound", magic!

I just want to tell you my last experience with these fantastic tubes. This evening I replaced for another time the Brimar, a very selected quartet, I regulated near to the perfection the bias on the amp. (as Hirsch said there are some regulation (tvr-1 & tvr-2) not so easy to do... but I had a very good result.

Well, with the Brimar U.K. I have the incredible surprise: the Omega II is very, very similar to the R10, or better the Omega System is very, very musical with a beautiful intimacy, in the same grade of the R10/Angstrom. I was thinking... now I have another R10, but in a open version, I can to name them R10 II because the different is an upgrade of the R10 to a openest-clearest and very detailed cans.

I never experimented a so big different in changing the tubes like in the stax amp (system). And for this reason I prefer the 007t to the 717 because you can have the possibility to change the sound as you prefer.

The Brimar 6FQ7 are the only with a littlest glass, may be this is the secret... but I 'm not an expert of tubes... just I believe to my ears.

So I recomand the Brimar for the best performance of the Omega II. (I'm speaking considering my source, my cables, my ears and my comparison with the R10/Angstrom setup).

I'm still waiting for the last 6FQ7 quartet, the Philips (may be they are the Sylvania), but I think that would be very hard to have better performance than the Brimar/Mazda U.K:

Best!
Nicola

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Hmmm...I think I need to get some of those.

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Wow, I just don't think I want my 007t to sound any more warm and musical.

I've got a six-pack of nos RCA clear-tops that I will eventually roll into my driver, however, at this time, I dig the sound of the system as is too much to mess around with it.

But thanks for the info, Nik!

I tried a set of the Brazilian RCA cleartops, but they simply didn't provide enough definition. The GE 6CG7's that the amp came with sounded more distinct. I'm now running Sylvania 6CG7's with the shield, and those are showing more promise than the RCA's. I'm starting to accumulate 6SG7's and have others I can try (with more inbound). The actual sound of any of the tube sets has taken between 50-100 playing hours before it appeared. Before that amount of time, they're all dull and confused to a greater or lesser extent.

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I'd have to agree with that. I wasn't too impressed with the Mullards when I first installed them. After 24 hours of playing time they're getting better. Don't know yet if they will get to the level the GE's.

From the posts here it seems that the 6CG7 tubes (the ones with the shield) are better than the 6FQ7 tubes.

Hi guys,

the same positive impressions of the Brimar/Mazda U.K. 6fq7 is confirmed and I want to add some other things:

1) These tubes gives a heart to the Omega System

2) With these tubes I do not need to go so up with the volume control, I'm listening with less volume respect to the RCA cleartop shields, I think because the space between each instrument are really "black" and not so "air" or "clear" as with the RCA, and this give to the listener the sensation of a full-body sound, that is what you looking for with the volume control.

Best!
Nicola

Today the Brazilian RCA Cryo treated 6FQ7 tubes roled in.
Indeed, for a good apples to apples comparison I should also test the non-treated.

But for the moment (after 100 hours burn-in time) I will compare them to the Mazda/Brimar and Ei tubes to have some reference.

To be continued...