Thanks, Jim, good to know. Funny thing is that I have a few dozen of those, all of which are clearly the same, all of which have different countries of origin printed on them.
I'm surprised at the high failure rate of JJ ECC83- the ECC81s I've used (perpahs 20 or so to date) have been 100% good.
I'm surprised at the high failure rate of JJ ECC83- the ECC81s I've used (perpahs 20 or so to date) have been 100% good.
How about 6N2P-EV ? I just recently found a very nice cheap bulk source, and I think could be worth looking into.. anyone did any testing of these?
The more important question is what are you going to do with them? SE gain stages or LTP phase splitter? With or without NFB? What's the input impedance? This being a high gain type will produce a substantial Cmiller, and needs a lower driving impedance than lower gain triodes.
The inclusion of NFB will help make the performance much less dependent on the characteristics of the active device. "Tube rolling" really makes sense in designs that run purely open loop.
The best type would be that with the highest reliability and lowest microphonics.
This is nonsense, at least it is these days. If the ECC83/12AX7 doesn't sound good for Hi-Fi, it isn't because of the type, but rather the bad designs based around it. The main problem here is that this type drives up the u-Factor by driving up plate resistance. It's some 90K with this type. However, since it's still a triode, it likes a light plate load: at the very least, 180K, and higher would be better. Most designs don't have the necessary voltage reserve, and tend to operate into steep loadlines. No triode sounds good for Hi-Fi operated that way.
These days, solid state comes to the rescue, and you can replace the passive plate load resistor with a CCS and operate the plate into a very high load resistance that will make for much less distortion. Used properly, there's nothing wrong with this type.
6N2P-EV are very good tubes, but they are not exactly pin to pin compatible. You'll have to rewire the heater connections. Otherwise, they are very cheap alternatives to 12AX7, with a very pleasant sound. Fitted with very long life cathode, they will last really longer than common 12AX7s.
What about this tube? Any one use itn
Reissue Mullard 12AX7 ECC83 pre-amp tubes @ $15.00 ea. | eBay
Some people say that Tungsram ECC83 are very good,
Reissue Mullard 12AX7 ECC83 pre-amp tubes @ $15.00 ea. | eBay
Some people say that Tungsram ECC83 are very good,
My gripe with the 12AX7 is due to it's inconsistency of manufacture. Getting high mu means a VERY fine pitch grid, which is hard to wind accurately and in a repeatable fashion from unit to unit. Minor pitch or tension variations will alter the plate curves and make the tube less linear. This happens in all tubes, but the coarser the grid pitch the less variation it causes. A related issue is microphonics; as a rule, the higher the mu the more susceptible it is to microphonics. Remember the Ei 12AX7s that were smooth plate Tele look-alikes? I actually sorted through a bunch of these years ago and got some real gems. They measured VERY good on the curve tracer and were very well matched between sections. The problem was that they were almost uselessly microphonic. I put a few of them to use, but most are still rattling around in one of my tube caches. They were absolutely useless in guitar amps..... unless you were looking for a very special effect 😛
The 12AX7 IS a good sounding tube if you get a decent sample and load it right. For me, I prefer running a 5751 or 12AT7 which isn't quite as finicky. I try not to build stuff that needs that much single stage gain, although my current project has forced me to go to 5751s rather than the med-mu triodes I started with. Still, the results are looking promising
The 12AX7 IS a good sounding tube if you get a decent sample and load it right. For me, I prefer running a 5751 or 12AT7 which isn't quite as finicky. I try not to build stuff that needs that much single stage gain, although my current project has forced me to go to 5751s rather than the med-mu triodes I started with. Still, the results are looking promising
just add my .02c here:
The 'best' of the vintage stuff - Amperex, Mullard Blackburn, RCA Blackplates (50s), and Telefunken (various years).
For low budget, I don't mind the Shuguang 12AX7C9, the JJs, or the Sovtek 12AX7LPS.
My friends are really into tube rolling and will tailor the sound of their system, getting different results depending on the brand, year, and component being used. Personally I find it all rather OCD!
The 'best' of the vintage stuff - Amperex, Mullard Blackburn, RCA Blackplates (50s), and Telefunken (various years).
For low budget, I don't mind the Shuguang 12AX7C9, the JJs, or the Sovtek 12AX7LPS.
My friends are really into tube rolling and will tailor the sound of their system, getting different results depending on the brand, year, and component being used. Personally I find it all rather OCD!
I would be worried about Miller capacitance. Would a 25K input resistor (grid to ground) be low enough to get decent HF response?
Depends on what's driving it- some stages are fine with a load that low, some aren't. If you drive the grid of a 12AX7 with a nice, low source impedance, the Miller effect is not much to worry about, independent of the size of the grid leak.
One more 12AX7 trick- don't let the grid swing positive of more than -1V or so or you'll see some grid current distortion.
One more 12AX7 trick- don't let the grid swing positive of more than -1V or so or you'll see some grid current distortion.
I can only speak from my experiance with my amp, speakers, ears... In my Yaqin MC-100b, I really like the JJ- ECC803 long plate. I tried shuguangs, EHs and Sovtecs. In that paticular amp, there just seemed to be frequencies that the Sovtec and Shuguang could not produce, the EHs sounded kinda lifeless, though they came from ebay with no lables, so they may have been bad. The Yaqin is pretty picky about tubes. I have tried these 4 in other amps and not really been able to tell the differance. Just my 2 cents.
Yeah, they were made on old Philips equipment and tooling. They had the seam in the top of the bottle that led up to the evacuation nipple. Decent tubes if you culled out the crap. I didn't mean to imply that they were like smooth plate Tele's, only that the plate structure looked similar.
Hi,
Minus 1V is still a negative voltage, SY....?
I guess you guys aren't familiar with 12AX7 equivalents made the same way a 6DJ8 is made?
Ciao, 😉
Minus 1V is still a negative voltage, SY....?
I guess you guys aren't familiar with 12AX7 equivalents made the same way a 6DJ8 is made?
Ciao, 😉
Hi,
If there ever were any smooth plate TFK ECC83s then I must confess I never, ever came across any of those in Europe.
That should tell you something about how industry operated in the seventies... 😀
Ciao, 😉
If there ever were any smooth plate TFK ECC83s then I must confess I never, ever came across any of those in Europe.
That should tell you something about how industry operated in the seventies... 😀
Ciao, 😉
Yes, it is. That's why it's a "trick" rather than "common sense."
See the discussion above about the JJ, which looks startlingly like an ECC88.
Nothing to do with Jim,but can anyone check a tube and guarantee it will prove more reliable than another ?......except microphony 🙂
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They say smooth plate Telefunken with the diamond mark on the bottom of glass were made in Germany.
Same with ribbed plates and diamond mark.
Other "Telefunkens" were made by Ei,RFT and possibly others.
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