I feel it is time to chime in. I just played around with the tubes in my VTL 7.5. I am actually at a point of loss for now. I changed the 12AU7s for the 12AX7s. Stock Sovteks for both pairs. The 12AX7s give much more gain & better bass & more extended highs than the 12AU7s that I received originally. I purchased the preamp from a gentleman who replaced his ARC Ref 3 with the VTL & had both for sale. He felt the VTL was better than the ARC. He has sold the ARC as well just before he sold the VTL. He had both for sale as he switched to the ASR Basis Emmiter II integrated.
I also heard there was a major update to the ARC Ref 3 since it came out. So I don't know which version he originally had.
It even gets more confusing. I have now too much gain & am missing the warmth of the 12AU7s. I was recommended by VTL to switch back to 12AU7s. Depending on the source will decide which tubes you need. Mine is currently the EMM gear, which is very high output.
Luckily the VTL uses only 2 tubes. The addition of balanced is a very significant benefit & should not be ignored.
On to speaking with the tube rollers out there. They all say it is crazy to spend so much on great equipment & not get NOS tubes. It is like putting small tires on a Porsche. So I am about to purchase some NOS tubes for about $250 or so. Not alot compared to the VTL 7.5. Time will tell. Not even sure if I should buy a few types of tubes for the sake of experimentation.
The sum of my story is the VTL is a little soft w. 12AU7s. Extended at both ends w. the 12AX7s. Both Sovteks (stock inexpensive tubes). Just too much gain w. the 12AX7s. The VTL you heard may have been with a 12AU7s accounting for the softness. For sure it is very very dynamic w. the 12AX7. In the end what is your source will really determine a lot more about the preamps system compatability & what tubes you use.
REmember with only 2 tubes, it makes no sense not to roll tubes. I can understand that have a preamp with a lot of tubes it would be a pain. I am not willing to roll tubes on my amps at this time (maybe the input tubes).
Hope I helped.
I also heard there was a major update to the ARC Ref 3 since it came out. So I don't know which version he originally had.
It even gets more confusing. I have now too much gain & am missing the warmth of the 12AU7s. I was recommended by VTL to switch back to 12AU7s. Depending on the source will decide which tubes you need. Mine is currently the EMM gear, which is very high output.
Luckily the VTL uses only 2 tubes. The addition of balanced is a very significant benefit & should not be ignored.
On to speaking with the tube rollers out there. They all say it is crazy to spend so much on great equipment & not get NOS tubes. It is like putting small tires on a Porsche. So I am about to purchase some NOS tubes for about $250 or so. Not alot compared to the VTL 7.5. Time will tell. Not even sure if I should buy a few types of tubes for the sake of experimentation.
The sum of my story is the VTL is a little soft w. 12AU7s. Extended at both ends w. the 12AX7s. Both Sovteks (stock inexpensive tubes). Just too much gain w. the 12AX7s. The VTL you heard may have been with a 12AU7s accounting for the softness. For sure it is very very dynamic w. the 12AX7. In the end what is your source will really determine a lot more about the preamps system compatability & what tubes you use.
REmember with only 2 tubes, it makes no sense not to roll tubes. I can understand that have a preamp with a lot of tubes it would be a pain. I am not willing to roll tubes on my amps at this time (maybe the input tubes).
Hope I helped.