VTL TL2.5---factory installed tubes?

Hello---I recently purchased a used VTL TL2.5 pre here on Audiogon and was wondering if anyone knows what tubes VTL originally installed in this model at the factory.

The seller included several pairs of various brand 12au7 tubes (Tung Sol, Tesla, Phillips), but I don't really know which ones "belong" in there. The Tung Sol tubes were in there when I got it, but those turned out to be way too microphonic, as well as giving off a high-pitched hum. I've got the Teslas in there now, they sound better than the Phillips to my ears. But I have the feeling this preamp isn't reaching it's full potential with these tubes, and I figure a good place to start would be to get the original VTL approved, factory-installed ones.

I e-mailed VTL about wanting to buy new stock tubes from them, but never got a response. Called and left a message, and they never returned my call. What gives?

I'm new to tubes, so any advice would be appreciated. Thanks, Will Herrera
Factory tubes are not always the best sounding. The best thing IMO is to experiment some with 12AU7s or 12AU7As that you can afford and compare. (With tubes, price does not always equate to sound.) You might also want to jump on tubes asylum (audioasylum.com) and do a search for your preamp. It's a popular piece, and you should be able to get some good info on what tubes work well in it.

Ive been down this road with the 2.5. The choice of 12AU7's will definitely be a "preference" sound. I settled on the Telefunken Smooth Plate after trying many such as the Mullard,RCA Clear Top and Black Plate 5814A to name a few. To me the Tele's were best.Smoothest highs and mids, which were a priority to me.

The 2.5 in its earlier iteration used the 6350 driver tubes instead of the new units 12AT7..Not sure which you have..Mine used the 6350 and I liked the vaunted and good sounding 60's Sylvania 6350 NOS types with yellow print label. I got them from Brendan at Tubeworld for ~ $65/pair or so as I recall, a few years back.. If yours uses the 12AT7..again, you may have to try differing brands. My current tube pre amp uses Telefunken 12AT's and I really like them.
Hi again---my TL2.5 is indeed an older version with the 6350 tubes. I was told by the seller that in his experience tube rolling the 6350's didn't seem to make much difference, it was the 12AU7's that really benefitted from tube rolling. And by the way, VTL finally replied to my e-mail, and will happily sell me new stock tubes, but now I'm having second thoughts, I'm starting to think my money will be better spent on some good NOS tubes. Thanks for all the advice, it's much appreciated!
In the new TL 2.5 VTL is using JJ both for 12AU7 and 12AT7.
The NOS way it's very interesting but not cheap! Somebody said wonder about the Amperex BugleBoy on Audiogon. It's funny anyway to try different tubes.