Electro-Harmonix and Sovtex tubes

I'm a tube newbee so please forgive me if my questions are somewhat elementary.

First of all in a pre-amp what exactly do the 12at7 and the 12ax7 tubes do? I know that each type of tube has a particular function, but not exactly sure what the function of each is.

Second question, I understand that both E-H and Sovtex are both owned by the New Sensor Corp but what wondering from a sonic perspective what are differences between the E-H and Sovtex tubes (12at7 and 12ax7). At present I'm running NOS Sylvanias or NOS RCA 12at7 and Sovtex 12ax7 in my amp (Jolida SJ-502A) but down the line I thinking of getting away from NOS and going to current production stock simply because of availability (E-H/Sovtex tubes seem very available at the local music shops where I live).

Bottom line, I trying to educate myself on tubes (and it can get a little confusing).

Anyway, appreciate any comments.
Check out the following websites, they contain good information regarding every aspect of tubes/tube equipment. You might be able to find the answers there.
http://www.audioasylum.com/cgi/d.pl?audio/faq.html (scroll down to the section on tubes.

I believe E-H are hand selected Sovteks with tighter tolerance.

Here's an interesting article on how tubes work:


I use the Electro-Harmonix 12AX7 and 12AT7 tubes and really like them.
Thanks for links, I'll dig through them and see what info I can find.
I use the EH 6922 gold pins in my cj premier 16lsII pre-amp and like them very much
I don't have any experience with 12xxx tubes, but I own both the EH and Sovtek 6SN7s, and I can tell you that they are definitely not the same tube, either in construction or sound. In my Wright WLA12A the EHs are very superior to the Sovteks, and close enough to NOS tubes I've tried that I don't worry about whether the supply of NOS gets too expensive. The Sovteks sound pretty bad in comparison, grainy, constricted, no bass. If only Sovtek existed and not EH, I'd be hoarding NOS 6SN7s whenever I could.

Attached is a link to an e-bay seller who I have bought eh tubes from on several occasions. He is very reputable and trustworthy. I believe I have seen him on audiogon as well.



Thanks for the link, but I already have a good local souce for E-H and Sovek tubes.
i own eh 12ax7, 12at7, 12ay7 and 6fq7. they are the worst tubes i've ever heard. i spoke to 2 manufacturers who agree with me and refuse to use them in their products.

the only current production i liked was a chinese 12au7 in a chinese tube amp.

most eh tubes i have heard have a nasty upper midrange treble resonse.

i would love to get rid of these tubes if anyone wants them--cheap.
New Sensor is the US importer, and they name-brand these tube lines for this market. Both lines are manufactured in Russia in the Reflektor factory (as are some other brands imported by New Sensor). I'm not sure this applies in every case, but for the types I've seen that are offered in both lines, the Sovtek and EH tubes are actually physically distinct from one another. But personally, when it comes to new-manufacture miniature 9-pin, 12-volt dual-triode varieties (such as 12AX7 and 12AT7) in specific, my preference has usually been for the Yugoslovian EI make. (Also over the SED, JJ and Chinese versions I've heard.) In my experience good examples of the EI can sound almost or equally as good for less money than some of the moderately-priced varieties of NOS tubes, although not as good as the better varieties of NOS tubes (which of course can cost many times their price). But despite that they're brand new and seem acceptably durable in use, you're faced with a high percentage of noisy or otherwise sub-par tubes straight from the production runs (not saying this is unique to EI), even after the manufacturer's and/or importer's testing and QC, so it's still a good idea to deal with a reseller who'll test, grade, match and guarantee their tubes' performance, especially for high-gain preamp/phono stages. It's also often worthwhile to try some inexpensive tube-damping polymer rings with these types.
I know you don't want to hear this, but if you really want to know the difference between the EH's and Sovteks, buy a set of each and try them. It's the only real way of determining what "you" like, not what "others" may like.
For example, I personally love the EH 12ax7's. I think they are equal to if not better than most NOS including Telefunkens. Others may dissagree, that's why you have to find out for yourself!!!

Cleaneduphippy - Just posted a thread asking for input on tube upgrades for my 502B. Curious what direction you took if you don't mind sharing. Did you go with 6550s or KT88s? What mftr.?