I tested on a larger number of EL12N and EL12-375 on a NEUBERGER-RPM370 (tube tester) and could not actually find any difference when measuring at 425V. The tubes themselves look exactly the same physically, so I doubt that this is just a different designation of a completely identical tube. I am thinking of the EL12 / 375 produced in the "Mühlhausen tube factory" and not the old "Telefunkem" production.
I am quite sure that all original EL12's and derivatives were produced exclusively at the TELEFUNKEN Berlin or Ulm plants, as were the EL156's, regardless of what has been stamped on them.
Of course the EL12/375 also will run at 425 volts for some time, but surely not as long as EL12 Spez.'s or EL12N's. Tuber are far more tolerant w.r.t. neglecting their ratings, but will show reduced lifetime in case of that.
Maybe the EL12 Spez.'s and EL12N's internal insulators are of better quality that can't be recognized by visual inspection?
Best regards!
Of course the EL12/375 also will run at 425 volts for some time, but surely not as long as EL12 Spez.'s or EL12N's. Tuber are far more tolerant w.r.t. neglecting their ratings, but will show reduced lifetime in case of that.
Maybe the EL12 Spez.'s and EL12N's internal insulators are of better quality that can't be recognized by visual inspection?
Best regards!
Experience tells me that it is not a problem in insulators because they do not determine the difference in power supply of ~ 50V, but rather whether the G2 can withstand that higher voltage or not! The problem is that it is very close to the heating plate, so with its own heating, the temperature of G2 rises so much that there is a secondary emission of electrons, overheating, and eventually self-destruction. Such a phenomenon is usually prevented by applying a thin layer of gold galvanically to G2, which has a small tendency towards secondary electron emission, or simply moving G2 away from the anode. In this case, G2 does not move away from the plate because it would make a tube with completely different characteristics, but with EL12N the second grid G2 is made more resistant to secondary emission and thus suitable for higher voltage supply.
I compared by measuring (Neuberger-RPM370 tube tester) a pair of EL12-325 (I don’t currently have an EL12-375 with me because I built them into a guitar amp I last made) with a pair of EL12N.
Even EL12-325 does not show any traces of instability at Ua = Ug2 = 425V, and G2 shows no traces of overheating, current increase and secondary emission even after ~ 1 hour at Ia ~ 40mA (Pa ~ 17W) which is quite on the limit of maximum allowed possibilities for EL12N as well! The G2 current was very stable and ranged between Ig2 ~ 3.9mA and Ig2 ~ 4mA.
I can’t say with certainty that all the EL12s produced in the “Mühlhausen tube factory” are actually EL12N, but they certainly speak in favor of durability and build quality.
No difference can be seen in the pictures between the EL12N and the EL12-325, except of course in the print on the glass.
Even EL12-325 does not show any traces of instability at Ua = Ug2 = 425V, and G2 shows no traces of overheating, current increase and secondary emission even after ~ 1 hour at Ia ~ 40mA (Pa ~ 17W) which is quite on the limit of maximum allowed possibilities for EL12N as well! The G2 current was very stable and ranged between Ig2 ~ 3.9mA and Ig2 ~ 4mA.
I can’t say with certainty that all the EL12s produced in the “Mühlhausen tube factory” are actually EL12N, but they certainly speak in favor of durability and build quality.
No difference can be seen in the pictures between the EL12N and the EL12-325, except of course in the print on the glass.
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Well, my EL12n arrived and I've been doing some listening. I'm using it in triode as a driver for 300b outputs. It's set up with a big NP Acoustic amorphous core plate choke, 180H, and Russian teflon FT-2 coupling caps. I have around 20mA going through it, a-k around 160v. Bias around 4v, no cathode bypass. It's clearly a good valve, no doubt about that, and well worth the relatively cheap price from European dealers who seem to have quite a few of them.
So - listening impressions. Sound is clear, clean and has plenty of details. Tonality is neutral - not warm/euphonic like a 26 DHT but not flat/lean either. Right in the middle, I keep returning to "neutral" which seems to describe this tube well. I'd say it is quite involving to listen to, it holds the attention. Strings are particularly good - resonant but still smooth, quite lifelike. It's not lush on vocals like a 26. Vocals are cooler - not so warm and forward, but not flat or boring. Again, natural and neutral. This is all exactly what I'd say about the teflon FT-2 caps I use - very detailed, neutral, clean. The sound could probably be warmed up a little with boutique paper in oil coupling caps if this were desired.
I've only done some basic comparisons, but I think I'd say I prefer listening to this in triode as a driver, rather than EL84 or 6V6. It was also more involving than an E80L I tried which was in many ways very nice and better than an EL84, but had a slightly cooler presentation.
I'll leave this in my system for a while. Listening to Meistersinger/Solti as I write and enjoying the sound. It's good on classical music. Natural and very easy to listen to. I have no idea if tubes burn in - these were straight out of the box. So altogether a positive recommendation - I like it. The EL12n in hifi is a definite "yes".
So - listening impressions. Sound is clear, clean and has plenty of details. Tonality is neutral - not warm/euphonic like a 26 DHT but not flat/lean either. Right in the middle, I keep returning to "neutral" which seems to describe this tube well. I'd say it is quite involving to listen to, it holds the attention. Strings are particularly good - resonant but still smooth, quite lifelike. It's not lush on vocals like a 26. Vocals are cooler - not so warm and forward, but not flat or boring. Again, natural and neutral. This is all exactly what I'd say about the teflon FT-2 caps I use - very detailed, neutral, clean. The sound could probably be warmed up a little with boutique paper in oil coupling caps if this were desired.
I've only done some basic comparisons, but I think I'd say I prefer listening to this in triode as a driver, rather than EL84 or 6V6. It was also more involving than an E80L I tried which was in many ways very nice and better than an EL84, but had a slightly cooler presentation.
I'll leave this in my system for a while. Listening to Meistersinger/Solti as I write and enjoying the sound. It's good on classical music. Natural and very easy to listen to. I have no idea if tubes burn in - these were straight out of the box. So altogether a positive recommendation - I like it. The EL12n in hifi is a definite "yes".
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What amplification do you arrive at with these settings? How well does it present the low bass register compared to EL84 on 20mA?
Mu is listed at 18, EL84 is 20. Deep bass is there, though not out of balance with the rest of the frequency spectrum - this is from a listening point of view. I'm unable to take measurements.
I did some measurements some time back using sinewave with the EL12N. Gain is flat (@18x) from 15Hz to 25kHz .
Loaded with 150H plate choke. Can't remember the plate voltage (200v?) but anode current was 25mA (current
limit by the plate choke).
I've a couple of EL12N and all having consistent measurement results from tube to tube.
Observed the EL12N from RSD, RFT and Siemens are all having the same construction.
Loaded with 150H plate choke. Can't remember the plate voltage (200v?) but anode current was 25mA (current
limit by the plate choke).
I've a couple of EL12N and all having consistent measurement results from tube to tube.
Observed the EL12N from RSD, RFT and Siemens are all having the same construction.
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After using 2a3 outputs for a while I'm going to go back to the EL12n and drive it with a 2P29L just in an experimental amp. I tried the 2P29L as a driver for the 2a3 and while the gain was too low, it was enough to hear that this was a pretty special DHT driver. For an output stage with more gain the overall sound will surely be interesting. I call this the "Inverted DHT Amp" since the DHT is in the input, not the output which we usually see. Dissipation is 18W so should make an OK SE Triode amp, a little more power than a 2a3. I could try it with 3.5K or 5K OPTs. Ri in triode is supposed to be 1.1K and S is 15 so good gain. Curves look like EL12. I have a set of red curves for the EL12n, not sure where they came from. The EL12n is still available new in Europe, e.g. from BTB in Germany or Conrad in Sweden.
I'm just getting ready for an EL12n PP build in triode. I've noted that 325V should be perfectly safe on the anode so shooting for around that or a bit less. I also noted that the data says separate cathode resistors in PP. Each cathode resistor looks to be around 160-180R for around -10v bias and 60mA. Looks like cathode bypass caps needed. OPT is 6.6K PP.
Idea is to use a 2P29L or 112A into a 6N1P concertina as input.
Idea is to use a 2P29L or 112A into a 6N1P concertina as input.
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EL12N playing with diy converters. The amp sockets are octal and I play 6L6, 807 and tried F2a too.
Output transformers are Nickle permalloy and handwound.
Power supply is 5U4G tube rectified and quasi monoblock based on Graetz Bridge connecting concept. 6N2P at driver stage.
I'm surprised you need a 6N2P with the EL12n. I'm using a 26 in a 2 stage amp. See the 26 preamp thread. Plenty of gain in triode with the EL12n.
Here's a EL12n SE amplifier with the 26 input stage. All works nicely. I had a pair of LL1682/50 to use up but a pair of LL1664 would be more conventional.
Builders using valves with Y8A bases, where do you get your valve sockets from?
Do you ever use CT style rectifiers (AZ1 for instance)? If so do you have a source for them too? I had some Chinese ones which would not release the valve.
I am hoping to start a project with ECL11 at some point, and have lots of nice CT rectifiers on hand.
Do you ever use CT style rectifiers (AZ1 for instance)? If so do you have a source for them too? I had some Chinese ones which would not release the valve.
I am hoping to start a project with ECL11 at some point, and have lots of nice CT rectifiers on hand.
Do you ever use CT style rectifiers (AZ1 for instance)? If so do you have a source for them too? I had some Chinese ones which would not release the valve.>>
Those Chinese side contact sockets are a disgrace. They plain DO NOT WORK. Don't EVER buy them. They will destroy your precious tubes. I binned every one I had. Rubbish.
You absolutely need NOS sockets. Try in Europe.
Those Chinese side contact sockets are a disgrace. They plain DO NOT WORK. Don't EVER buy them. They will destroy your precious tubes. I binned every one I had. Rubbish.
You absolutely need NOS sockets. Try in Europe.
Broke guiding pin of my EL12N exposing the glass.
Since I bought quite a few sockets, have to use them. The thin gold (?) plated pins are also a disgrace. Have to use a small screwdriver (minus) to release my tubes. Will try to loosen the pins and see if that helps. Moreover the plastic (described as Bakelite) is cheap quality.
Such fine tubes and so poor sockets… Finding nos is very hard and sometimes as expensive or priced even more than the tube cost itself.
Since I bought quite a few sockets, have to use them. The thin gold (?) plated pins are also a disgrace. Have to use a small screwdriver (minus) to release my tubes. Will try to loosen the pins and see if that helps. Moreover the plastic (described as Bakelite) is cheap quality.
Such fine tubes and so poor sockets… Finding nos is very hard and sometimes as expensive or priced even more than the tube cost itself.
There are some options here at Ask Jan First ... not sure if those side contact bases are NOS, but they have salvaged Y8A for sale (OOS?)