Best M8080 NOS tube for CJ preamp line stage?

Starting to get into some tube research, having recently replaced the tubes in my CJ pre-amp. I am still using the stock M8080 for the line stage, but am interested in upgrading with a pair of matched NOS, maybe Mullard or RCA. Suggestions?
Have tried different valves in my cj classic pre se.Have found the mullard m8080/cv4058 nos valves to be the best.Upgraded my classic to se.This was a excellent mod,well worth the money.Have had issues with left channel tube rush getting noisy.Have you had any problem's.
no problems really; just waited too long to replace the m8080's and did it with stock dealer tubes. The difference in sound sparked a new level of understanding re. the potential sonic impact of tube rolling. I know I can do better so will give the mullards a shot. do you have a year recommendation?
Nos mullards are hard to find.Conrad Johnson have replacments.I was lucky enough to find 20 sets 1972 at a very good price.
The Mullard M8080 that c-j sells is New Old Stock. A few years ago, soon after I bought my MET-1, the 6-channel preamp that uses M8080s, I bought a BUNCH of different 6C4s/6135s. Virtually all the 6C4s were highly microfonic and so bad I tossed them in the trash. I understand that the 6135 is a heavy-duty version of the 6C4, and the few I found, maybe a half-dozen, are not microfonic and sound plenty OK; I use them in the surround and SW channels. I use only the M8080s in the front-3 channels and have had NO problems with them. I have a trio that I removed from the front-3 channels after about a thousand hours that are just lying about; if you want them, they're yours for $15 Priority Mailed to you in the US. E-mail me at jeffreybehr(at)cox(dot)net if you're interested.

I hope you enjoy your c-j preamp; I sure love mine.
Dre, the original M8080's were indeed Mullard. The replacements, sent by CJ through one of their respected retail dealers, were not. That being said, the pre-amp has never sounded better. I cannot identify these tubes but they seem to be really good. BUT, if i could find some NOS Mullard or RCA, I would try those as well. Found a few dealers on line that seem to have passed through the audiokarma filter (a bunch of DIY guys mainly), and the prices are a little higher than for the new Genalex 12AX7 tubes, which run roughly 40 bucks each. Check this out and let me know what you think:
Jeffrey, thanks for the offer. I sent you an email.
The origional tubes in my pre were m8080's.The second set which I purchased through cj were cv4058's.These are both mullard's but with different codes.I think the m8080's are their premium grade tube.Cj apparrently bulk purchased nos cv4058 mullard's as my research and trial's have shown this to be the best tube for the classic.Let me know what tube's you are currently using.
I just bought some old records so I'll check under the hood in the morning.
Jeffrey, on the MET-1, how did you determine which tube goes with which channel? Is it something I missed in the manual?
Billimbriale, no, you didn't miss it. I suggested years ago to c-j that they include that info; apparently they're still not.

Looking at the face of the unit, the front row, left to right, is LF, RF, LR, RR. Rear row is C and SW, left-to-right.

You have one? And enjoy its sound? I LOVE mine, and it sounds even better after I replaced the front-L/R channels' coupling caps* with SoniCap Platinums (Teflon-film) and the PS small-bypasses** with Platinums and Jupiter HTs. E-mail me (address in 4th post above) if you'd like pics.

* Originally, large 'propylenes bypassed with small 'styrenes
** Originally small 'styrenes.
Dre, Here is how the tube reads, top to bottom:

Dre, just discovered this online:

6C4 tubes are available from Watford Valves of England as the Mullard CV4058 (military number) which is also known as a KQDD/K or M8080. These tubes are the best 6C4 variant that money can buy, and Conrad-Johnson uses them in their new PV-14L audiophile preamp. They told me they have never found a better 6C4 tube. They were made for Britsh military mobile radios and can really take a thrashing, as well as a minimum 10,000 hour useful life.

Looks like CJ did me right. Wondering what they recommend for the phono stage--but the genalex sound better than those electro-harmonix 12ax7's that were in there initially.
Sometimes I feel like I need two amps--one for acoustic and the other for electronic music. The CJ MF2250 has never sounded better on acoustic folk and jazz, thanks to the tube replacement in the PV-15. And it's not even the "a" version. I'm driving Dali Helicon 400's, and have a Rega DAC with a Cayin CD-t23 transport, and a VPI Scout with an ortofon 2m black. looks like i can wait a while before I upgrade my amp. Still thinking about a butler or a moscode, a VTL or a Cyber or a Rogue, or a Cary or a Cayin. lol. i just don't think a 2500a would be a significant enough upgrade for a larger living space. But right now I'm happy with this set-up in my tiny 12x11 bedroom.
Watford's "6C4/CV4058 MUL/BOX ANODE" is 15 Pounds plus shipping. Any c-j lovers up for a group buy? MAYBE the price could be lower, and shipping cost per piece surely should be lower. I'd go for maybe a halfdozen. Contact me at jeffreybehr(at)cox(dot)net if you're interested.
Hi Sabocat,I also have a cj phono.Tea2 upgraded to se.Came with Russian mullard 12ax7's.Have tried nos Siemen tubes but have gone back to mullard's.Getting back to your cj classic pre.As your origional tubes aged did you experience more tube rush in the left or right channels or was the tube rush noise even between the two.Dave.
Dre, tube rush was evenly distributed
Update--Just got my CJ MF2250 modded out by Bob and Gary over at Sound Dezign. They replaced the caps, resistors, and power supply for around $360.00, as opposed to the official CJ "A" upgrade which now runs for $650. It will be shipped out today and Bob says it sounds VERY VERY good. will probably get my PV-15 pre modded as well at some point later this year, lol.
Well, first listen, the new parts have not even begun to break in yet, and I have to say the results are outstanding. More detailed midrange, highs are silkier, and the bass is much tighter. Kudos to Bob and Gary. Anyone out there with a CJ MF2250 or 2500 send it to these guys for the upgrade and save some cash.
time for another replacement and this time I will try some cheaper nos RCA tubes just to see how they sound.

Since the last discussion, I sold my CJ mf2250 for a JWN 90w per channel tube amp, upgraded from the rega dac to a Neko, and added a mac mini to my set up.
Good evening,

Does a 6C4 fit in the CJ? as replacement tube?

and the 6C45pi&