Tubes in VTL Deluxe Preamp

I have a VTL deluxe preamp, purchasing it from an authorized dealer in the late 1990's, it was purported to be a demo unit.

Whats a bit odd in comparing the various related threads, is that the unit has 6 tubes. It is fitted with 3 - 12AX7 and 3 - 12AT7's. All of the other threads convey a different mix. The split, looking at the unit from the front - on the side of the circuit board facing front, is 3 - 12AX7, then 2 12AT7's, and then on the other side of the board, a 3rd 12AT7 on the far left, again looking at the unit from the front.

Is this the correct mix/order?

The volume level of the system is slowly decreasing, there are 2 VTL-MB250 amps which have recently been retubed, so I suspect its the preamp tubes that may be needed replacement.

The unit currently has TungSol 12AX7's, and Jan Phillips for the 12AT7's. I have seen other types available, to inlcude mullard. While I dont want to go nuts, I would rather retube this so that it actually provides improvements. The amps hook up to Martin Logan Request speakers.

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Ron, your thread caught my interest because I have a VTL Maximal preamp from the same era stuffed away in a closet. I would also be concerned about the correct mix/order of tubes. To start with, Audiogon Bluebook states manufacturing date as late 1980’s, and you purchase as a dealer demo in the late 1990’s.

Looks like units with M/M phono had 5 tubes and with M/C phono had 6 tubes. Check out the links below, and look at the serial number plates on each.

On this unit at ebay, it’s easy to see the 3 tubes closest to the power supply (left side in picture) are 12AT7’s. The other 2 appear to be either a 12AX7 or 12AU7.

On this unit at Canuck Audio Mart, I can’t tell about the tubes from the picture, but the description says it uses 3 - 12AX7’s, 2 - 12AU7’s, and 1 – 12AT7 (6201).

I did also find one that had 6922’s, but it had been modified for them.

If you haven’t already, it’s probably going to be a good idea to post in some other audio forums on the net.
Very interesting, I did check the tag on the back, Model - Deluxe M/C, Serial AD3202M/C. Your right that the MC has 6 tubes, and I confirmed that the first 3 in the ebay unit, and the one I have are the 12AT7's.

The other listing indicates 3 12AX7's.

I have never used the MC output, do you know what it stands for and how its used?


I have never used the MC output, do you know what it stands for and how its used?
Is yours labeled MC output?

M/C generally means moving coil phono which should be an input.