First day, I've used the VT-1000 to test my whole stock of tubes, rejecting 3 failing tubes and, labeling the matching value for each tube.
Today, I've wondered: "but... what's in my amps, right now?". So, I got the screwdriver and the DIVO unit and started to check all tubes, with some surprises.
Fender Princeton Reverb Reissue
I had a Mullard 12AX7 reissue and, measured 10/11, what is a good new.
I had a NOS RFT ECC81 that measured 9/9 (balanced). Not bad. I leaved it, also.
I had a Tung Sol 12AX7 that measured 9/9 (balanced). Not bad but, since is a fat tube, I've swaped it with a NOS RFT ECC83 that measured 9/9 also.
I had a NOS JAN/Philips 5751, which the DIVO cannot test.
I've decided to throw there a Sovtek 12AX7-LPS that measured 10/10 (balanced).
I had a Tung Sol 6V6GT pair matched by TAD that measured 6 and 9 !!!!. What a matching!.
Since the original Groove Tubes measured 9 and 10 and, they were in a good condition, I mounted them back, again.
Marshall 1923C 85th Anniversary Combo
I had a TAD 12AX7-Cz (selected JJ ECC83S), measured as 10/12. Gainy enough.
I had a TAD 12AX7-Cz, measured as 8/9. In the average for those tubes and, same value as stock tubes.
I had a TAD 12AX7-Cz, measured as 11/12. Over specs, really gainy.
I've swapped the tubes, V3 in V1 (the most gainy first), V1 in V2 and V2 in V3
I had a Sovtek 12AX7-LPS that was detected as worn, and measuring 5/7. Really bad for a PI position.
I've thrown that tube to the trashcan and mounted one more LPS measuring 10/11.
I had a matched pair of TAD EL34-SVT (Winged C Svetlana EL34) and, measured 9/9.
They are under the stock tubes, that measured 10/11 but, I leaved those there by now.
Vox Night Train
I had a TAD 7025-S that measured 7/7. I've swapped it with a Mullard 12AX7 RI measuring 10/11.
I had a Sovtek 12AX7-LPS measuring 10/11. So, I've leaved it there.
I had a matched pair of Mullard EL84 reissues (with TAD Magic Pair 6), that measured 10 both.
I leaved those there.
Some more conclussions
Well, I think I am now clear why I like Mullard reissues. Clearly, they are the more consistently produced tubes. All 12AX7 have same value 10/11. All EL84 measure 10. So, they are a granted bet, specially for V1 positions.
Some people will say that those are hand-picked LPS but, IMHO, they aren't. The harmonic content and grain of distortion is very different in both tubes. They share a nice openess and detailed sound.
Now, the Tung Sol 12AX7 seems to be also consistent but, not at the same level of Mullards. Anyway, they are measuring between 9 and 10 and, most of times 10. So that's why so many people like them. They are a granted bet, also.
But, Tung Sol 6V6GT doesn't seem to be produced so consistently. I've got tubes measuring 6, 8 and 9 but, it seems that 9 is the most usual.
Another consistent tube seems to be the EH 12AX7, this one is usually gainy, measuring between 10 to 12 but, usually 11. I've got just one tube measuring 8 but, maybe it's worn by the use.
Another consistent tube seems to be the Sovtek 12AX7-LPS, but not so consistent as the Mullard reissue. It usually measures 10 by triode. Some triodes are over, some are down.
Svetlana 12AX7 seem very consistent also, with values of 8/9 (same as average JJ ECC83S tube). They are a bit weaker, compared with Mullard, Tung Sol or EH but, still good enough for any position but, I would use them in positions different from V1.
Overall, Chinese tubes are less consistent but, mostly on the gainy side. The drawback is their sound but, they can work very well in cathode-follower positions or, even in PI positions (if you get some balanced one).
The low values of the NOS RFT tubes can mean that they aren't really NOS but, they were already used and "rescued" from any vintage device, as a Radio, Organ or, whatever else. A bit disappointed but, this is the business of some people.
Well, I can see lot of people wondering if the price of this device worths it. And I am with you. It's an expensive investment and, I had to use the credit of my card but, honestly, I am really happy to have it. Now, I know exactly what I have and what I am throwing to each amp position and, this, after several weeks swapping tubes trying to achieve a good tone, totally blind, makes me to highly valuate the information that this device is giving me, which helps to achieve my tone.
Sure, this device will tell you nothing about tone. Each tube has its own tonal characteristics and, you need to check any kind of tube in every position of every amp (at least once) but, once you know how each tube "sounds", you can choose the right one for the right application. This device is of great help for this task so, no regret, well spent money. Some boutique pedals cost barely the same!.