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-   -   Genalex VS Mullard 12AT7 & 12AX7's HUGE DIFF? (http://www.diyaudio.com/forums/tubes-valves/183651-genalex-vs-mullard-12at7-12ax7s-huge-diff.html)

cabsvrt 21st February 2011 08:09 PM

Genalex VS Mullard 12AT7 & 12AX7's HUGE DIFF?
 
Need to get some new tubes for my VTL 5.5PH Preamp. It uses 6-12AT7's and 6-12AX7's and there is a huge price difference between the Genalex tubes and the Mullards. I am looking at new production tubes at Tubestore.com and I don't know what the sonic differences would be in the VTL. Any comments or suggestions?

SY 21st February 2011 08:20 PM

Did you look at JJ? Best 12AT7/ECC81 of any I tested (including "real" Genalex and Mullard). The 12AX7 seems to be excellent as well, but not as much of a night and day improvement over other types.

Oh, yes, and they're cheap.

rknize 21st February 2011 08:52 PM

The "Genelex" 12AT7 looks like the old EH version...the one with long plates (both are from New Sensor). I have a pair of the older EH tubes. They work fine, but bias a bit colder than a normal 12AT7. I haven't tried the newer short plate EH version. Frankly, I don't know what to make of New Sensor's marketing techniques with these "re-issues".

The Mullard 12AT7s that you see around for $30 are real NOS Mullards. They work well and should last a long time. Same with the JAN Philips tubes that you see around.

I have a bunch of JJ ECC81s and am finding they they are all getting weak after a few 100 hours in two different amps. They are cheap and measure well, so buy them by the dozen I guess. I'm not alone is noticing this with JJ's small tubes, though not a lot of other people have reported noticing it.

I don't know what to say about the 12AX7. They are popular in guitar amps and so there is a plethora of them and a lot of guitar-oriented opinions about them. In terms of noise, the Sovtek 12AX7LPS (New Sensor) was one of the best for a while. That is what I used in my one amp that uses this type. The "Mullard" and "Genelex" reissues look to have the same long plate structure as these and so I suspect they are similar. New Sensor has a short plate version marketed as an EH. I have one of these too, but it lives in its box. I didn't like it for some reason and can't remember why.

JJ has a long and short plate version too. The long plate looks more like a typical NOS tube while the short plate has a frame grid construction. I have one of the latter, but have never used it that I can recall. I think I meant to stick it in a guitar amp.

Anyway, my two cents for what it is worth!

SY 21st February 2011 08:59 PM

FWIW, the ones I've tested/used are the short plate variety- they look a lot like ECC88. Five years in the prototype RLD amp and no problem. I built three more for a friend and all the original tubes are still going strong after four years.

Wavebourn 21st February 2011 09:04 PM

JJ proudly keeps former Tesla design and manufacturing culture, their tubes are very good.

http://farm1.static.flickr.com/194/4...d04e4ba6_o.jpg

DF96 21st February 2011 09:07 PM

In theory a frame grid ought to be a good way to build a linear high mu valve, so this may be why SY finds the JJ valves good. However, it is not clear to me whether the JJs are genuine frame grids or merely something which leans in that direction.

rknize 21st February 2011 09:29 PM

Quote:

Originally Posted by SY (Post 2477804)
FWIW, the ones I've tested/used are the short plate variety- they look a lot like ECC88. Five years in the prototype RLD amp and no problem. I built three more for a friend and all the original tubes are still going strong after four years.

Maybe I got a bad batch then, I dunno. I have two that are in one of the same amps that those still measure OK. I know I got them separately as I got them with reasonably-matched sections, but they are also newer. They are in the phase splitter positions in a VTA-70 board. The input section was the one that was weak. I replaced it with another JJ, but haven't checked it since. Maybe I'll do that and report back to my old thread. George has all my weak/cold 12AT7s at the moment....

Salas 21st February 2011 09:32 PM

I have old CVC on my amp that are rebranded CV4024 Mullard. Short plates with that sandwiched copper visible on the plate wings. I remember I had exchanged EH, Brimar NOS, RFT, 6201 JAN, I am not sure if I put JJ there also back when I was rolling. Its a phase splitter with a BJT cascode CCS for its tail, so it was running same current with all and AC balance was good with all. For some reason, maybe its synergy, I settled for CV4024. Was coming across smoother and more meaty than the others. Anecdotal I know, just a story.

cabsvrt 21st February 2011 09:39 PM

VTL tends to frown on tube rolling, so there is not much info out there. All I know is it was going to be $633 for a Genalex full set or $145 for Mullards, both asking for matched sections. That's a HUGE difference in price!

Salas 21st February 2011 09:54 PM

Don't know about that Genalex reissue, but the Mullard CV4024 original had served well my amp. I had a new 12AY7 EH gone hissy in 100h and I replaced it on that amp (had GE 6072A also, those EH are even cleaner to me) but the CV4024 Mullards never did anything odd in years of use. Mine they heater flash at turn on BTW.


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