retube VTL amp

I have Manley Reference 350's.

Be glad you ain't got KT90's Schieza. The good one's are no longer made, but Kevin Deal tells me the new EH version are a little more lively, hmm what does that mean.

Tube dealers, Kevin Deal, or jim McShane are good choices, you know what your getting and they stand behind them.

I am toob rolling again. The current NOS Phillips @ about 5-10 each depending upon whom you buy them from are pretty good. Better than stock VTL.

The Sylvania's the old one's, I don't like as much as the newer ones. I am finding that more and more. I am not a fan of the Chineese tubes I've heard yet.

Mullard as new, as in new 6550's out. They are new on the market and pricey. If you can hold out a couple of more months those will drop in price like a rock.

I have a new set of 83 vinatge Mullard 12at7's that came in yesterday. $13 each. I will roll those, and give me a day or two to listen and I'll tell you what I think.

loon

I made a rather large omission when I forgot to point out that although the 12AT7 input tubes may not wear out in the electrical sense as quickly as the driver and power tubes do, they are subject to deterioration in the area of microphonics, a problem which if it develops can severely compromise the overall sound of the amps. More than once has been the time my VTL's began to sound vaguely disappointing compared with memory or a solid state reference amp, but still it might take several days to dawn on me that the input tubes had started to exhibit audible resonances - D'oh! Replacement with a quiet pair immediately tightens everything back up and eliminates the creeping sensation that the presentation is beginning to sound confusingly frayed rather than solidly wholistic.

You can check these tubes simply by tapping gently on the glass envelope in various spots with something like a pencil. (Please feel free to cheerfully ignore those who admonish that you 'shouldn't' do this - it won't do any harm as long as you don't go crazy, and it is positively diagnostic, though it's true that a negative test result can't be taken to mean there still couldn't be problems). Any ringing or rattliing heard through the speakers means time to replace, and the louder and more lingering the audible results, the sooner the better. A good tube should display near silence when tapped. I recommend doing this test routinely every time you check the bias settings on the output tubes, since the problem can develop slowly and the deleterious effects are insidious but subtle at first. I would also do this test once a week for about 6 weeks after first installing a fresh pair, because you will want to replace new tubes under warranty if they show any incipient microphony during the break-in period. And although they're much less prone to developing an audible problem in this area, go ahead and do the same test on the driver tubes while you're at it, as they can occasionally become physically noisy too.

Along those same lines, I also recommend that anyone with these or similar amps make a small investment in some kind of resonance-damping rings for the input tubes, at least the inexpensive silicone types if not something more elaborate. They're cheap, they help, and many amp makers now install them as standard at the factory. Anything you can do to cut down on resonance in the input amplifier tubes will likely result in cleaner transient reproduction, more even frequency response with less tendency toward increasing brightness and forwardness under dynamic conditions, and more stable and coherent soundstaging and imaging with an overall greater sense of 'calm' and ease.

groove tubes does a good job at additional quality control on their tubes compared to the factories but you'll pay a premium. Still a better deal than getting hit with the factory markup. I'm not sure they do any additional tube QC or not.

Zaikesman, you seem to do a lot of experimenting with tubes for the VTL...have you (or anyone else for that matter) heard, or heard anything about the groove tube Mullard knock off 12ax-7s. A number of guitar amp guys have really liked them but i've not heard from the audiophile side of things

Piezo: Just as I opined above (and it is only my opinion, folks) concerning retailers who charge a premium for additional burn-in and testing/matching beyond what is done at the tube factory itself (obviously speaking only of new production tubes now), I have not found that paying extra for Groove Tubes-labeled tubes is any guarantee that small-signal tubes will show problems at any lower a rate than just buying them from the low-cost tube sellers who offer matching (sometimes at a nominal fee, sometimes not). The same goes for RAM in my experience; just like buying your tubes from an amplifier manufacturer, I haven't found that the extra cost signified in the relabeling is reflected in any greater reliability.

Andy at Vintage Tube Services indicated to me that this is because (paraphrasing now) the burn-in and testing regimens of most of these outfits is procedurally insufficient to predict meaningful outcomes, and that the cost involved to do it right would be prohibitive applied to new production tubes, which he feels are in themselves typically too inherently problematic or low-performing to justify it anyway.

To what degree that viewpoint is correct or not I don't know, but my best strategy so far has just been to buy new tubes at the lowest cost, watch for any problems to develop, and deal with replacing them under warranty if any do. Whenever I've paid more for supposedly superior burn-in and testing/matching (and relabeling if applicable), I've experienced problems after installation at rates seemingly no lower than when I buy from a discount source or when I walk into a guitar store.

To your question about a "Groove Tubes Mullard knock-off 12AX7", Groove Tubes is not a tube manufacturer but a tester/relabeler/reseller; Mullard is just a legacy trademark name these days, not an actual tube manufacturing company; and VTLs don't use 12AX7's, so whatever the tube you refer to actually is, I'm sorry but I haven't heard it. About your last sentence, I believe that most of the tube amp manufacturers who sell their own relabeled tubes do say they perform some burn-in and testing on them, but again I haven't personally found this claim to correlate with any decrease in defect or failure rates that might justify the often-substantial extra cost.

hmmm, sounds like i may have bought the spheel and just got lucky with the groove tube thing. cheap is always good and your experience level with retubing is a lot higher than mine. thanks for the input.

as to the 12ax7 mullard knock offs are the only ones i've seen marketing them that's why i applied the name. I'm pretty sure they are russian made. The ax7 is a very common preamp tube with a bit more gain than an AU7 and those two are interchangeable. I assumed that there is interchangeability with the at7s as well wich may be a bad assumption. thanks