Tube Upgrades for CJ MV-52?

1st, The MV-52 was essentially a modded("improved") version of the MV-50.
2nd, The MV-52 used 6FQ7's, not 6SN7's
Based on My Experience With the MV-55 for some time, here are my choices in order of preference.
El-34's
1. Mullard Xf2 double getter
2. Svetlana (current production)
3. GE USA (Big Bulb)
4.Electro Harmonix
5.Tesla EL-34S

12ax7/5751
1. Telefunken
2. Amperex Bugle Boy
3. Tungsol
4. Sylvania (blk Plate) 3 mica 5751

Again, these are personal opinion's based on My Tastes,system,and amp.
Cheers,
Shred

I am an MV-55 owner. I have gathered that it is true, as the above post suggests, that the operating parameters of the older Sovtek EL-34 were assumed as the standard in engineering the applied bias value of this circuit. c-j advises that other tubes may not last as long as you are accustomed to in these amps, and I found this to be true with the Telsa's. Having said that, however, the Telsa's did sound much better, and I ran through several pairs before trying the Svetlana's. These sound even more complete and correct, and I have experienced very good reliability with them. I strongly recommend giving the Svetlana EL-34's a try for any c-j 50-series owner. The 12AX7's are usually Chinese or Sovtek as supplied stock. E-H tubes are Sovteks, but I haven't tried the newer LPS version. The regular E-H and Sovtek 12AX7's are not the best choices to me. The Tesla sounds better than these, but I've experienced a couple of premature deaths with them, a strange thing with an input tube. Svetlana still does not make this tube, as far as I know. My number one choice for new input tubes is the Yugoslovian EI, but these have been known to have a higher frequency of noisy examples manufactured, so pre-tested may be better (the amp circuit doesn't actually sound very sensitive to this factor, however). The EI's have superior tonality and extension, and have lasted a long time. As for the 6SN7 drivers, I got only slight improvements with a couple of NOS varieties over the stock Sovteks, and don't consider it worth the cost and bother in this amp (Sovtek is the sole current manufacturer of this tube). Happy listening!

How many of each does it take, 12ax7, 6sn7 and EL34s? I have some nice tubes that I simply don't use.
If buying new, I am very partial to Svetlana. They are very similar to mullard 12ax7s. Haven't looked at 6sn7s much. Also, Svetlana makes a very sweet EL34 for about $20 that is actually rated at max of 25 watts-get a little more bang for your buck.
Finally, from what I was told, CJ tends to make thier equipment a little differently. They supposedly engineer each piece to use a tube with specific qualities. Contact CJ and ask what they suggest.

For the 6SN7 position, the best choices are RCA black plate, very old (1940"s) Sylvania or if you can afford them, 5692 RCA ruby base.

For the 12 AX7's the Sovtek is great bang for low bucks spent, better sound may be had from Amperex Bugle Boys, Telefunken and Mullard.

You will have to experiment with the EL34's. The obvious choices for new (value priced) is the Tesla E34L and the Electro Harmonex. I prefer the Tesla much over the EH in this test.

Again, if money is not an issue, the old Mullard and Amperex EL34's were the best sounding and best ever built tubes of this type.