Red Bear MKE60

[Chuck H]

Bob,
I only have two 12AX7WA here, so this does not say much really, but compared side by side with 6N2P-EVs, these two perform quite different. A lot less gain and a bit(...a NOTICEABLE bit, that is) noisier.
Maybe Sovtek used part of the original tooling, but different materials. Or the substitute filament wire makes all the difference.
There is still plenty of old stock available - even the EV-variety, I'd just order a dozen or so and have a lifetime-supply for the amp. No need btw to use -EV throughout the amp, you won't notice a difference if you put in a bog standard 6N2P as the PI, for example.

The way you've worded this post and your sentence structure leaves me entirely unclear about what tube, between the two mentioned, you are making statements about. Which tube is lower gain? Which tube is noisier?

[Cpt. Fixit]

My apologies, Chuck, if this was unclear:
I wanted to say that my two 12AX7WA were noisier a had less gain on tap than the 6N2P-EV I compared them to.

Wrt. to the original question:
The 6P3 biases and perfoms exactly like any other 5881.

Toby

[Chuck H]

Not to get off topic, but I've had many noisy Sovtek 12ax7wa's AND wc's. They also have a pronounced top end roll off even though the specs don't show it in the capacitance figures. This may be where the lower gain perception comes from. Just plain bad tubes. And OEM in a lot of factory amps!?!

[g1]

Not to get off topic, but I've had many noisy Sovtek 12ax7wa's AND wc's. They also have a pronounced top end roll off even though the specs don't show it in the capacitance figures. This may be where the lower gain perception comes from. Just plain bad tubes. And OEM in a lot of factory amps!?!

Well, since we are already OT (thanks Chuck ), if memory serves, the 12AX7WB Sovtek's were originally marketed as "higher gain". Unfortunately, what that meant was that the WA's were really "low gain", and the WB's were being compared to that.
Attached is a comparison test of current 12AX7's from Amplified parts website, the WA are down at the bottom. The noise spec seems to be referring to "tap test" or microphonics.

[bob p]

Attached is a comparison test of current 12AX7's from Amplified parts website, the WA are down at the bottom. The noise spec seems to be referring to "tap test" or microphonics.

Do you seriously expect to get away with saying that Amplified Parts / AES / CE Dist tests their tubes for microphonics? That's going to be a tough sell around here...

[g1]

Do you seriously expect to get away with saying that Amplified Parts / AES / CE Dist tests their tubes for microphonics? That's going to be a tough sell around here...

I know you know I didn't say or mean that! (thanks to your smiley). Appreciate the humour though. And love the new avatar, is that a russkie space dog? I don't see CCCP on it anywhere....

[defaced]

my understanding is that that amp was originally supposed to have 6N2P-EV in it, not the tubes that the OP mentioned.

Russian tube, Russian alphabet. 6H2N is Russian, when translated to English it becomes 6N2P. Russian alphabet - Wikipedia, the free encyclopedia

Funny I notice this post today. I stumbled upon the amp last night when looking for schematics of high gain Russian amps. They seem to have a pretty devout following.

[bob p]

And love the new avatar, is that a russkie space dog? I don't see CCCP on it anywhere....

No he's an American Space Dog. The only thing Russian in this thread is the tubes.

[g1]

No he's an American Space Dog.

I was going to say "no such puppy" but it appears I may have been mistaken.


Apologies to Lowell for thread hijack.

[Chuck H]

Let me help to get the thread back on track... If it were "MY" project "I" would rewire it for 12ax7's. My reasoning on matters like this is simply that the amp should sound and perform the same using 12ax7's and they're readily available with much less confusion. The 12ax7 as a "guitar amp" tube is known by all. It's easier for me and the customer now and in the long run. I don't know if the rusky power tube specified has a different pinout from the standard guitar amp power tubes, but I would make any changes there too and use the nearest 6l6 type for the same reasons. The only reason I wouldn't make these changes would be a customer request to keep the original tube types. In which case I would do some brief research and immediately order the tubes.

[lowell]

My thoughts exactly being that the responses here indicate no noticeable difference in tone. I had already ordered these tubes from Triode Electronics so at this point I'll see how they perform and if they suck or are microphonic I'll suggest the rewire.

[km6xz]

Well, not quite. A 6H2N does not exist, it is not part of the nomenclature here. A 6Н2П-е and a 6Н2П exist as do 6Н1П. They are good quality dual triodes that are probably what is being discussed. They are different in characteristics than a 12AX7 besides the obvious 6 volt heater. The translation would be 6N2P-e and 6N1P. The "P" just means glass envelope 19-22.5mm across. The E sometimes seen tacked onto the end is an Enhanced mechanical stability for a minimum life of 5,000 hours at rated parameters. The do not have a "B" at the end, which is the Russian letter with the sound of "Vee". A Russian Б is the sound of the English B

Anyway, change them if you wish but they will not sound the same. The Red Bear and First Mig-100's sounded really good because of the controlled breakup in the preamp, sort of like having a built in compressor. The reason being the 6Н1П had two different characteristics that, one being the internal shielding but the one used to good effect in those amps was the fact that it is a remote cutoff triode, meaning the mu varied with bias. Drive it hard in cathode bias and the gain changed. It will have different "touch".

There is another characteristic, both these tubes are much more rugged than the junk that is coming out of the Reflector plant now with the dozen New Sensor names painted on. If you ever feel the need to replace a 6Н1[2]П it will not be because it failed or became microphonic. The curves are closer to a 6DJ8 than 12AX7. They are cheap, about $1.50 here which is why I like them. I probably have a hundred of them, all older new stock. I built a small balanced compressor with them that works really nice and pleasant using their remote cutoff characteristic, more like a 6BQ7. The internal shield not only isolates the sections but adds rigidity. Every one I have tested on my curve tracer is very well balanced between sections.

[km6xz]

Not really. The 6П3с lower plate dissipation then than a 5881 but about the same mu. Think of it as a super 6V6. The 6П3с-е is similar to a ruggedized 5881, very reliable and tough. Blues and Jazz players like them a lot but they are not as high Mu as later 6L6's so hard rockers tend not to care for them, even though they will outlast any current 6L6 in modern amps. Buying those surplus is what got Groove Tube and New Sensor into the tube business. They normally have the wafer base but some later versions had the conventional 6L6 base.

[Chuck H]

Damn Stan! You sold me!!!