Tubestore Preferred 12AX7

[fu22ba55]

Anybody have any experience with this puppy?

The tubestore.com "Preferred Series 7025"

http://thetubestore.com/preferred7025.html

Claims to be a private label repro of the 60's Mullards.

I'm looking for something rugged & quiet to do non-tone-related administrative tasks like phase inverter, etc...

I like that it has a 6 month warranty, and at $20 it's half as much $$ as the Gold Lion.

Anyone have experience with these? Anyone know who manufactures them?

[beans-on-toast]

I haven't tried this tube but it looks interesting. The current production Mullards are made by New Sensor at the Reflektor plant in Russia. The price is a lot better than the $550 for a pair of NOS Mullard tubes that they are selling at TubeDepot.

I do use NOS 7025's in some of my amps. They are a low noise version of the 12AX7 and are typically used in the first stage where low noise is important.

At this stage, the signal is relatively low. Any noise from the tube is amplified and passed on to the next stage. Keeping noise as low as possible at the first stage keeps the signal as pure as possible. Each subsequent stage adds noise to the signal as it is amplified.

By the time the signal reaches the phase inverter, it is amplified sufficiently that there isn't going to be an advantage to using a low noise tube. There is already enough noise present that the small amount added by the tube is usually not going to be heard. If you stand beside a loud amp and hum a tune, nobody's going to hear you.

You would be better trying the 7025 in the first or tone stage and using whatever you had there in the PI stage.

Setting aside noise issues, it is important to remember that each tube has its own tone and gain. This tube could make a pleasing difference in any position in your amp. It depends on your amp and your tastes. It is always worth trying it to see what happens.

[fu22ba55]

Originally Posted by beans-on-toast

You would be better trying the 7025 in the first or tone stage and using whatever you had there in the PI stage.

I'm looking to do a fair amount of tube rolling in the first stage, but I want to get some good, reliable worker-bee-type tubes for the other stages... Maybe this Mullard clone is overkill.

I know JJs are relatively reliable... should I just stick with those for the non-tone-critical applications?

I'm gonna be messing with a Morgan MP200

[Floyd Eye]

Shuguang. For that money I'll go NOS.

[beans-on-toast]

That Morgan looks like a really nice amp.

The thing about any amp is that you never know what tube is going to sound best in it until you try it. Some tubes will inherently sound better than others in any amp. A tube that sounds good in one amp design may not sound as good in another amp. In part, it has to do with the design of the amp and how the pre-amp tubes are biased.

I would contact the builder and ask if the amp is optimized for a particular make of tube. Ask if they tested the amp with any NOS tubes and see what they recommend.

Since you only have three 12AX7's in this amp, I would roll them all. It is a small investment to get the best sound out of the amp. Try NOS, the 7025, and JJ's. See how it sounds.

[fu22ba55]

Thx beans-on.

I've already talked a bit w/ Joe Morgan about tubes, and he says he ships with JJs just because they're the most durable in shipping, with the least duds... (there are always duds...) He says there's nothing really exceptional about them tone-wise. They're just a good meat-n-potatoes tube.

I'm still sorting stuff out with it tone-wise. I like a super-gainy sound, well into power tube distortion... so Joe is kind of letting me feel my own way since most bass players don't do what I'm doing to the amp. (I do find it more gainy than the Reeves 225, which is what I wanted.)

It came with KT88s, and I'm a dyed-in-the-wool Ampeg guy, so I could simply not wrap my head around the sound. The clean tones were astounding... simply amazing... but I'm not a "clean tones" kind of guy, so when I pushed the power tubes into distortion, they were very harsh... very non-harmonic. (I tried the same thing with the Reeves, and I didn't like the sound.)

Once I switched to 6550s (winged Cs) I was in hog heaven. The amp instantly felt like an old friend. (Joe says I'm the first person he knows of to have run 6550s in this puppy. I think he's shipped 15 or 20 of this unit.)

---

There's just a few things I'm trying to sort out tone-wise, so I wanted to eliminate all the variables... (make sure none of the tubes got janked in shipping.)

I ordered one of the above tubes (tubestore.com 7025) for the PI stage since they offer a "matched and balanced" option for $5 more bucks, and I want to make sure the PI is not effed up before I start rollin'... (I also ordered some Tung Sols to play with, and I have a '69 Fender Twin I never use with some scary-old looking tubes in it. One 12AX7 is a GE, the rest I'd have to pull to read...)

I think the 12AX7 slots are are Preamp, PI, and Cathode Follower.

This is my first dead-simple turret board amp, so the tubes are kind of naked... they can't hide too much behind the circuit, so I expect this will be a good platform for tube rolling. The 6550s sounded 180 degrees different than the 88s.

Once I get it sorted, etc... I'll post a review, pics, clips, etc, etc... The original plan was to do a shootout with the Reeves 225, but that might be a moot point now that I'm running 6550s. (I could always throw the 88s back in there and re-bias for a shootout.)

[beans-on-toast]

I look forward to the review and pics.

It sound like a very basic design. Simple is often an indication of good tone. The nice thing about a turret board amp is that you can modify it all you want and it is always fully reversible.

Some of the low noise tubes like the 7025 have a bit less gain than the 12AX7. It would be interesting to know if this is the case once you've tried it.

Maybe a pedal like a VT on the input will give you the grainy sound that you are looking for.

You might find this of some interest.

[Staccato]

This is the most important tube, the phase inverter...

Go for their Sovtek LPS, or a Sovtek LP (either one). And, you should consider buying from Doug at Doug's Tubes. He's the Tube Man!

[AdamR]

Just ordered some tubes from Doug, great to work with.

[fu22ba55]

Originally Posted by beans-on-toast

You might find this of some interest.

That is an interesting read. The idea that the PI is what's actually distorting (not the power tubes) is revelatory to me, and a sea change in my thinking. I will have to re-read for sure. But I have to say... switching from KT88s to 6550s (without touching the PI), the output-stage distortion was night and day... different enough to make me keep a $2K amp I was thinking of sending back.

Originally Posted by beans-on-toast

It sound like a very basic design. Simple is often an indication of good tone. The nice thing about a turret board amp is that you can modify it all you want and it is always fully reversible.

Joe is very interested in my opinion of the amp, especially since I'm not trying to get nice clean tones out of it. I have to say... for clean tones... for pick-attack stuff, this amp is a superstar.

He warranties the amps for life, so long as they're not modded... so right now if I were to change anything, I'd have him do it.

The tone stack is... interesting (for lack of a better term.) Joe made some interesting choices:

His description of the amp was "his take on an SVT, but with the Ultra-Hi on all the time, and without that "weird thing" SVTs do in the mids" I'm paraphrasing... but that's pretty close to a quote. This thing has mids, mids, mids, on tap. Waaaay more than an Ampeg. It either makes the 'pegs sound scooped, or like there's a big mid bump on this thing. One or the other. (And the highs will cut your privates off at 20 paces. If you've ever been trapped in the hot spot of a Fender Twin... that's what this thing is capable of. Joe has a lot of Vox AC20-flavored guitar amps in his stable, and some of that comes through in this amp. Very British.)

Couple that with the trannies: he's got custom Mercury Magnetics trannies that claim to produce "inaudible" low frequencies...

So you're kind of looking at an SVT with the Ultra HI AND the Ultra Low ON ALL THE TIME, but without the loss in mids.... so, more of EVERYTHING, whether you want it or not.

It's pretty potent. I'm actually trying to rein it in a bit.

Originally Posted by beans-on-toast

Maybe a pedal like a VT on the input will give you the grainy sound that you are looking for.

You're not the first to suggest I get a VT, and I'm sure my wife and bank account would thank you, but I'm not a "pedals" guy. I'm a plug-in-and-go guy. I've got a B15N, V4 and SVT, and the MP200 is gunning to fill the 200W slot between the V4 and the SVT. It's looking good.

Originally Posted by beans-on-toast

Some of the low noise tubes like the 7025 have a bit less gain than the 12AX7. It would be interesting to know if this is the case once you've tried it.

This thing is so easy to access, I'll be rollin' more tubes than a 12-year old rolls a Schwinn Stingray in San Francisco.

Originally Posted by beans-on-toast

I look forward to the review and pics.

I want to do a "proper" review with clips, etc... soon, but here's a gut shot to whet your appetite:

[coreyfyfe]

Originally Posted by fu22ba55

So you're kind of looking at an SVT with the Ultra HI AND the Ultra Low ON ALL THE TIME, but without the loss in mids.... so, more of EVERYTHING, whether you want it or not.

So it's an SVT set flat?

Seriously though, it's a perdy little thing, looking forward to hearing some clips...

[beans-on-toast]

Originally Posted by fu22ba55

That is an interesting read. The idea that the PI is what's actually distorting (not the power tubes) is revelatory to me, and a sea change in my thinking. I will have to re-read for sure.

You have to take these things with a grain of salt. The PI's contribution to tone is underestimated and that's a good point.

They aren't saying that distortion and tone doesn't come from the power tubes. They do. But rather, the PI's tone and distortion is passed on to the power tubes and together they contribute to the overall tone of the power stage.

Where distortion, which includes harmonics, comes from depends on the amp. On some amps, there are individual stages that barely break a sweat. On other amps, stages are pushed into distortion and pass it down the line. Each stage has its own character and tone. Power supply sag also contributes to distortion, so does the output transformer and the speakers.


Nice amp pics! Clean and uncomplicated.

[fu22ba55]

Originally Posted by coreyfyfe

So it's an SVT set flat?

Definitely not.

My SVT with the mids cranked all the way up does not have as much presence in the mids as this thing. (Across the board: low mids, mids, and high mids)

This thing is a mid monster. (In a good way. It's good to have them on tap, and you can always cut them. But even when you cut them, it's never "scooped" sounding.)

[Jim C]

IMO, the best bang for the buck is to buy used Mullards (which can be branded as Eico and others) on eBay for approx $30 each, or my personal favorite, used Telefunkens (branded as Dynaco and others) for $40 each. I think the materials and attention to detail by the labor force is not as good now as it was then.
Honestly, I think these tubes from the 60's (assuming they test well) will still outlast new units.

[fu22ba55]

Originally Posted by Jim C

Honestly, I think these tubes from the 60's (assuming they test well) will still outlast new units.

Ultimately, that's the way I'd like to go (NOS or used), but at this point I'm trying to establish a baseline. Not troubleshooting, per se, but kind of.

I don't have tube-testing gear, so I like the idea of buying from tubestore.com or Doug's (looks great btw, Thx @Stacatto) since they can check if the tube is balanced. My primary concern right now is the PI. Once that's square (I'm just OCD... I like having a thoroughly-tested tube in there), then I'll roll the others like crazy, and maybe try some spendy ones.

I don't know enough about tube sellers on eBay to know who's selling good stuff, how they test it, and what's just old junk they're hanging out there for suckers like me.

[Handyman]

For what its worth, don't waste your money getting matched sections for your preamp tubes. There's no benefit to matching these for the circuits they're used in.

[fu22ba55]

Originally Posted by Handyman

For what its worth, don't waste your money getting matched sections for your preamp tubes. There's no benefit to matching these for the circuits they're used in.

Thx. I'm only balancing the single PI tube. I'm not matching them (to each other like power tubes).

Everything I've read says having a well-balanced tube in the PI stage is a good thing, but for the rest, not so much a biggie.

Is that a correct assumption?

[Jim C]

I'm not sure what well ballanced means; either it tests to within specs or it doesn't.
IMO, the biggest difference in preamp tubes occurs in the V1 slot and (if used) the driver tube. The others make a much smaller difference.
Don't believe the smoke and mirrors posted on some spots on the interweb.
These were made long ago before SS devices were conceived that just happen to offer some sonic characteristics for audio. Some were of higher quality than others. I have yet to find one made in the last 10 years by the Russians or the Chinese that was better than either German, British, or US stock from the 60's-70's.

Also, look at the number of transactions and feedback rating on eBay as well as the numbers they have posted on tube testing. Most of the bigger sellers are much more honest than any new tube seller; some offer money back guarantees.

[fu22ba55]

Originally Posted by Jim C

I'm not sure what well ballanced means; either it tests to within specs or it doesn't.

Full disclosure: I know nothing about building or repairing tube amps. I only know how to buy them and break them.

But here's my understanding of a "balanced" tube:

A single 12AX7 contains two identical triodes. The tube can test "within spec" but one of the triodes could be working a little harder (or less hard) due to manufacturing tolerances. (Yet the tube still tests within spec overall.)

This is no big whoop in most applications, but it is more important in the phase inverter stage:

In a Class AB (push-pull) amp the PI splits the signal sent from V1 into two signals, one of which is phase reversed. If these two signals are not complimentary (if one is stronger than the other) then you could have issues. (hum, or too clean, or too dirty (the wrong kind of distortion.))

Thetubestore.com charges an extra $5 to check for evenly balanced triodes, and DougsTubes.com charges $2 for the same test.

I'd rather spend an extra $2 to test the tube, if I'm gonna be putting it in a $2000 amp.

I don't think the PI affects the tone (like V1) so much as it affects performance. That's my (relatively newfound) understanding, anyway.

Originally Posted by Jim C

Don't believe the smoke and mirrors posted on some spots on the interweb.

True dat.

[JimmyM]

an svt with the ultra-hi on? ooch! can you dial it back to a more reasonable level, too?