[Flac2Dac]

I just purchased a used VTL 2.5 pre-amp; the latest incarnation, of that model. It has 2 AT7s in the buffer, and 2 AU7s in the gain. It came from the seller, with JJ ECC81s in the buffer, and ECC82s in the gain. He also included, brand-new Mullard CV4024s he never got around to using.

I liked the sound of this unit…with the inexpensive JJs…right out of the box. But after a while, I gave the Mullards a try. I put the CV4024s in the AT7 slots, and did some listening. I liked some things; a bit thicker, and richer in the middle…but ultimately, felt it sacrificed a bit of top-end “sparkle” that I missed. I was originally going to just ask for some recommendations. Since I liked things about both…I wanted sort of the perfect “middle-ground”, lol…if such a thing exists, right?

However, now there’s a twist. I thought I had “accidentally” put the CV4024s in the wrong stage; I put them in the buffer, not the gain. I thought to myself “no wonder, they didn’t sound quite right”. So just a minute ago…I put the Mullards in the gain instead. Then…quickly, after a little research…I realized I had it right the first time; the CV4024s are AT7s, and belonged in the buffer. I corrected the mistake quickly, but I guess my first question now is…did I do any “damage”, by having those tubes mixed up?

Now…let’s talk tubes. Obviously, I’m new to rolling (though I’ve had tube pre-amps in the past…mostly C-J, which were hybrids; so I found they weren’t as sensitive to rolling, as this VTL is); so I don’t want to go too far, too fast. In other words, let’s concentrate on one stage at a time. Where do you get the most bang-for-the-buck, tone-wise; buffer or gain?

If we’re talking AU7s (gain)…I had a friend suggest ’65 Radiotechniques (looks like he must shop Upscale...lol); he said it gave him a nice sparkle. I said “sparkle” isn’t what I was after; the JJs actually had nice top-end. I wanted a combo of the JJs sparkle, and the Mullards richness (of course, at that point…I was only messing with the buffer stage; so maybe the gain is much different anyway). He then suggested maybe the Siemens AU7s. Sounds intriguing; and I’ve always wanted to try Gold Lions too…see what all the fuss was about.

So…what do you think of these 2 choices? Thanks

CD

[bunky]

I would try the Psvane 12AT7-T and the Psvane 12AU7-T.

[Flac2Dac]

I would try the Psvane 12AT7-T and the Psvane 12AU7-T.

Ah, yes; I've heard very good things about Psvane. But where to buy them (other than direct...which I assume, means a slow-boat from China?)

[SteveFord]

Have you considered Sylvanias?
They always made nice sounding tubes.

[Captainhemo]

Ah, yes; I've heard very good things about Psvane. But where to buy them (other than direct...which I assume, means a slow-boat from China?)

http://shop.grantfidelity.com/splash-page.html


Also,
not sure  if you'd be interested, but  there  is a pair of Raytheon, 12au7, NOS in original boxes. Halo shape getter with long gray plates. military grade. $50 pair on the trading post
http://www.audiocircle.com/index.php?topic=117561.0

Might be worth trying, if you don't like, you can always  relist 

-jay

[Flac2Dac]

^^^ Good stuff guys. While all the brand recommendations are welcome...it almost feels as if everyone is just chiming in with their favorite.

That's fine...I asked for opinions; but I do want to focus on one pair at a time...so I'm still looking for that answer on gain vs. buffer stage. Thanks again; looking forward to more responses.

[Captainhemo]

The  link  to  GF was for the Psvane  tubes

-jay

[bunky]

I own several pair of Holy Grail 12AU7 varients that cost upwards of three to four hundred dollars per pair and the Psvane's easily compete sound wise with the best NOS tubes for around one hundred dollars a pair with free shipping.i was not chiming in with my favorite tubes per say but I was giving you a heads up

[Flac2Dac]

I own several pair of Holy Grail 12AU7 varients that cost upwards of three to four hundred dollars per pair and the Psvane's easily compete sound wise with the best NOS tubes for around one hundred dollars a pair with free shipping.i was not chiming in with my favorite tubes per say but I was giving you a heads up

Yeah, right on. As I said...I've heard nothing but good things. Just trying to educate myself, than come up with a long laundry-list of tubes to try.

Any opinions on the Siemens or GL; or are they far beneath this crowd, because they're only double-digits per pair. 

Oh, also...any thoughts on possible damage; or did I likely do nothing, by temporarily mixing-up my AT and AU7s?

[Captainhemo]

I'm pretty new to all this  but   aren't the  12AU7 and  12AT7 interchangeable in a circuit ?   Or, does this only  apply  if you are  going from the 12AT7 to the lower gain  AU7 ?

-jay

[Tubeburner]

I owned the VTL 2.5 a few years ago and rolled numerous tubes except the Psvanes. I found the VTL likes Telefunken the best for my tastes.

Enjoy!

[JakeJ]

Flac2Dac,

I'll answer your questions to the best of my knowledge (grain of salt theory applies here).

1)  Highly unlikely you did any damage by misplacing tubes.  Small signal tube and their associated circuits are pretty forgiving and you should have heard some change in the sound to indicate a problem.  Both tube types are similar in heater current draw and plate voltages so it's doubtful any damage was caused.  Add that to the fact that you caught your mistake almost immediately reducing any possible damage to nil.

2)  There may be others that argue this but generally tube rolling in the buffer stage produces little to no change in sound quality.  The gain stage, however, is another story.  I use a VAC CPA-1 MkII preamp which has two AX7s in the buffer and two AU7s in the gain and Kevin Hayes has stated that the buffer stage has no effect on the SQ.  Having rolled tubes in both stages I can attest to that.

Hope that helps,
Jake

[Flac2Dac]

Flac2Dac,

I'll answer your questions to the best of my knowledge (grain of salt theory applies here).

1)  Highly unlikely you did any damage by misplacing tubes.  Small signal tube and their associated circuits are pretty forgiving and you should have heard some change in the sound to indicate a problem.  Both tube types are similar in heater current draw and plate voltages so it's doubtful any damage was caused.  Add that to the fact that you caught your mistake almost immediately reducing any possible damage to nil.

2)  There may be others that argue this but generally tube rolling in the buffer stage produces little to no change in sound quality.  The gain stage, however, is another story.  I use a VAC CPA-1 MkII preamp which has two AX7s in the buffer and two AU7s in the gain and Kevin Hayes has stated that the buffer stage has no effect on the SQ.  Having rolled tubes in both stages I can attest to that.

Hope that helps,
Jake

Thanks Jake; your answer is a great help.

I suspected there was no damage. Again...I don't know much about this stuff yet; but it does seem these are low-current tubes...and with them having the same pin-layout, etc. I'm sure I'm not the first guy to get them mixed-up. Things sound "normal", now that I've corrected the issue; but you know us 'philes. We just want to be sure there's nothing to worry over.

I also suspected the gain stage...would be the one to concentrate on; you know...if you're just concentrating on one. So...I know they're different units, your VAC and my VTL; but any fav AU7s?

[Flac2Dac]

I owned the VTL 2.5 a few years ago and rolled numerous tubes except the Psvanes. I found the VTL likes Telefunken the best for my tastes.

Enjoy!

Added to the list of candidates; thanks!

[JakeJ]

I am running a pair of RCAs I got from Andy at Vintage Tube Services a couple of years ago.  Pulled and tested them about a month age and they still test as strong as new!    I also have some used Telefunkens that do not test near as strong that sounded smooth but not as good as the RCAs.  My recommendation is try tubes made before 1959 if you can afford them, or Psvanes, again if you can afford them.    There are a few new production 12AU7s on the market that aren't bad and you might try the cryogenically treated versions of those.

[bunky]

Circa 1959 Amperex Holland 7316 PQ Longplates were the best sounding tubes that I ran in my VTL TL 2.5 and unfortunately they go for $200 a pop.i also tried Mullard CV4003's from Upscale Audio and circa 1962 Seimens Nickel plates from Brent Jesse.the Second best sounding tube I tried in the TL 2.5 was the circa 1955 CBS/Hytron 5814WA and they did everything well but are very hard to find .i still have the TL 2.5 in storage because it sounds great and it belonged to a friend who belonged to another board who had passed away. if you insist on buying NOS 12AU7's and don't want to spend $400 for a pair of tubes I would suggest circa 1959 thru 1963 Amperex Bugle Boy long plate 12AU7's or the mid 1950's CBS Hytron 5814WA if you can find them.these tubes are not cheap but with NOS you have to pay a premium for the good ones.

[Flac2Dac]

^^^ Hey guys; thanks for all the glass advice so far. It's a little overwhelming, for a guy new to tubes; buying vintage stuff, seems over my head at this point. But the feedback is still welcome; it gives me something to shoot for! 

For now...I probably will keep it simple, and try something NOS. Seems like Psvane is the way to go, if you're going that route; so they're high on my list.

Not to hi-jack my own thread; but...I also have some interest, in possibly modding the VTL 2.5. I really, really like it, at the price; so of course...rather than leave well enough alone, I'm thinking "can I take what's great about it...and make it even better", lol. IDK...really, I'd probably like to just experiment, with replacing the caps...maybe some new RCAs, etc.; nothing too drastic.

My first thought was to contact Paul Grzybek, of Tube Audio Design (TAD) and Bizzy Bee fame. I had a Belles 21a, with the requisite Auricap upgrade; and the seller told me Paul had done the work for him. A quick search, revealed Paul has passed (though it was more than a year ago, he was apparently only in his mid-40s. RIP).

When I had my C-J pre-amps...Bob Backert's RHB was a name that was on my radar. Anyone else, have any good (or bad) experiences; or vendors they can recommend? What's the best place, for like mod and capacitor talk? Thanks

[bside123]

Other than VTL itself, George Merrill of Analog Emporium is the authorized tech for VTL gear.

http://www.gmanalog.com/

George is renowned for his expertise in turntable design and audio consulting along with his years of research, tech work and strong opinions.  George is super to work with!

That being said... since you are new to tubes, as well as having just acquired the VTL 2.5, why not be happy with simply spending some extended time listening to the preamp, learning about tubes and their respective sound(s) and then settling on the tubes that work well for your preamp and system. One simple step at a time, in a cost effective manner... just sayin'. 

BTW, I own a VTL 5.5 preamp. Yes, it was upgraded to the latest mods and standards by George, after I had it for a long while and knew it well.

[Ericus Rex]

^^^ Hey guys; thanks for all the glass advice so far. It's a little overwhelming, for a guy new to tubes; buying vintage stuff, seems over my head at this point. But the feedback is still welcome; it gives me something to shoot for! 

For now...I probably will keep it simple, and try something NOS. Seems like Psvane is the way to go, if you're going that route; so they're high on my list.

NOS = New Old Stock.  Vintage unused tubes are called this.  Psvanes are new production.  If you want to go new production that's fine.  But you're in the good fortune of using 12AU7s and 12AT7s.  There are oooodles of good 'old stock' 12AU7s for sale out there so the prices are down (compared to 12AX7s, 6DJ8s and many 6SN7s).  And 12AT7s are somewhat rarely used in audio so their prices are even lower.  You can roll in some very well respected pairs of those tubes for not a lot of dough.  Take a look at TCTubes.com.  They are selling Amplitrex-matched Sylvania 12AT7s for $46/pair and Raytheon 12AU7s for $39/pair.  Both pairs are cheaper than the new production Psvanes and Gold Lions.  And you can be assured that they will be well matched using the Amplitrex tester.  And if you want to spend more...well, they can help you out there too.

[Flac2Dac]

Other than VTL itself, George Merrill of Analog Emporium is the authorized tech for VTL gear.

http://www.gmanalog.com/

George is renowned for his expertise in turntable design and audio consulting along with his years of research, tech work and strong opinions.  George is super to work with!

That being said... since you are new to tubes, as well as having just acquired the VTL 2.5, why not be happy with simply spending some extended time listening to the preamp, learning about tubes and their respective sound(s) and then settling on the tubes that work well for your preamp and system. One simple step at a time, in a cost effective manner... just sayin'. 

BTW, I own a VTL 5.5 preamp. Yes, it was upgraded to the latest mods and standards by George, after I had it for a long while and knew it well.

'Cuz I'm an audiophile? Can't leave well-enough alone...lol 

Kidding aside...it's sage advice, of course. Mostly...I've bounced around, with gear; now that I've found something, that really feels like a "keeper"...I just want to see, about wringing every ounce out of it. But you're probably right; especially about the tube-rolling. It seems to be a smorgasbord out there.