[OctavianH]

In place of 6L6 in your DAC, you should give a try to 6M6 tubes (if you can find them) it is a direct replacement of EL3N / EL11 with EL34, 6L6 pinout

Do not spend money on useless expensive tubes. 6M6 or EL3(N) are already known and this is the reason they should be avoided. I had excellent results with EBL1 which is a double diode pentode, but the pentode is electrically equivalent to EL3. Actually the RT branded I got from France are superior to the WIRAG EL3N all are using. Slimmer and less dry sounding, better extension on highs. It's true you will need to make a pact with the devil and start using adapters for european side contact socket but well... nothing is for free. When you will discover how good quality old european pentodes sound on UltraSonic amps, you will not be able to listen to something else. EL3 is a small baby and this is why it never really got me, but I have rediscovered it on input when I started to listen to the bigger boys in the family like EL6, EL50 (4654) or EL51. And after you get the adapters you will see that many pinouts are similar so in fact you need 2 types of adapters (with top anode and top control grid) and only make some smart wiring inside to allow usage of more types than one.

Let's see what Radiomuseum says about EBL1:

The EBL1 is an EL3 extended by two signal diodes. It was used in simple superhets without audio pre stage where the output section was directly driven from the diode detector, or in sets where the audio pre stage was combined with the IF stage (6F7, ECF1, ECH4) or with the tuning eye (EFM1, C/EM2) or also used in the 3-diode-circuit combined with the EBC3. [J.R.27Mar2003]

Later edit:
I'll explain a little bit the trick with the pinouts taking a screenshot from my plans for my future amp.

1) top cap control Grid adapters - can work for EL2/EBL1/EF* tubes with some careful wiring
2) top cap Anode adapters - can work for non top cap tubes and also for anode wired top cap ones with some smart wiring.

The key is to identify similarities and to reuse not used pins from a pinout to enable other type (in case of 2) you can put anode on pin 8 and also top cap).

Of course, you need to know a little bit how pinouts and adapters work and also to verify.

Golden rule: Never take as good what others advise and ALWAYS double check.

Similar things and tricks are also available for loctal adapters, basically with 2-3 types you can use anything. LOL

 

[hpamdr]

Golden rule: Never take as good what others advise and ALWAYS double check.

It is even easier if you have a measuring device (like duovac) to get an idea of the bias voltage, pinout, ..... before inserting in your amp.

 

[OctavianH]

It is even easier if you have a measuring device (like duovac) to get an idea of the bias voltage, pinout, ..... before inserting in your amp.

I used DuoVac to determine needed grid bias for a specific tube where I could not find triode graphs. But I never tried to determine unknown pinout with it (not sure if it is possible).

 

[hpamdr]

I used DuoVac to determine needed grid bias for a specific tube where I could not find triode graphs. But I never tried to determine unknown pinout with it (not sure if it is possible).

In fact you cannot determine pinout but at least verify that your adapter is correctly wired before damaging the amp...

 

[OctavianH]

In fact you cannot determine pinout but at least verify that your adapter is correctly wired before damaging the amp...

I verify all my adapters via a multimeter for continuity (attention, I also measure resistance, because if it does not beep might be a resistor connected for strapping). After that I make a table in my notes for each adapter. After that I make the test on the tester and then if all works well I move to the amplifier. Of course, might be fine just to test on the tester but in my case I use adapters for several types not only the one it was built for and then I need more control and safety checks.

 

[Isaacc7]

Amp factor of cv4062 is 10 in single triode mode, this is half of single triode of 6SN7 (20). If you strap 6SN7 to have 2 triode in // the amp factor remain the same but Internal resistance is halved and noise is halved. One 6SN7 tube for a balanced chanel..

Right. I usually have a single dual triode per channel as drivers in my amp. When I use pentodes for input I have to use 2 of them in triode mode.

 

[ARCXENOS]

It's true you will need to make a pact with the devil and start using adapters for european side contact socket

May I ask who makes those? Deyan?

I got a couple of side contact stuff in my inventory that I hope to use someday

 

[Isaacc7]

Had to switch out of the Raytheon 12j5wgt. They had a super smooth response but the bass was indeed lacking. Plus, everything sounded strained and reserved. Have put the Miliwatt branded b36 in and seems to be a good compromise so far.

I have noticed some intermittent noise on the right side. At first i thought it was the b36 since they were the new thing. But I’m getting the noise with the preamp off. SO that means I’m getting noise out of at least one of 4 tubes. Probably the cv4062. It only comes up once in a while so I’m going to let it ride.

 

[OctavianH]

May I ask who makes those? Deyan?

Mine are made by Deyan, but you can also find in China for example this one.

I got a couple of side contact stuff in my inventory that I hope to use someday

Be careful, adapters usually break at many removal/insertions. So indeed, 2 adapters might be fine for many types, the downside is that the socket itself is of low quality. More than this, these tubes do not really have a solid base to grab when removing from adapter, so you might have to pull/touch the glass and so on. As I said, careful. I hate that socket but unfortunately those are the best tubes ever made.

 

[hpamdr]

Mine are made by Deyan, but you can also find in China for example this one.

Be careful, adapters usually break at many removal/insertions. So indeed, 2 adapters might be fine for many types, the downside is that the socket itself is of low quality. More than this, these tubes do not really have a solid base to grab when removing from adapter, so you might have to pull/touch the glass and so on. As I said, careful. I hate that socket but unfortunately those are the best tubes ever made.

@Deyan is building great adapter, nice looking, top quality and you can disuss with him in HeadFi to optimize tube/socket usage. I've also used in the past chinese adapters and got some faulty ones specially small one using adapter board and crappy socket... I'm now building mine when i have time and get good base/socket in China or from old rusian stock for 7/9 pin socket or GU50 ceramic ones. (Final result is audibly OK but much more ugly than Deyan ).
If you have in your device not so good socket, using adapter and/or rolling tube too much can lead to loose connections. Jut pay attention from time to time that each pin is individually secure and if not use a micro screewdriver to inch a little the connectors.

 

[OctavianH]

I went today for a full Tesla setup. Tesla 4654 with Tesla 12AX7. Surprisingly it sounds good.

I was never very impressed about high gain 12AX7 or 808 tubes, I felt that in their case rising the gain you loose some tube flavour and go into a more sterile and energetic area where you miss the point of these tube amps. This was the reason I was almost all the times focused on 12AT7 or 6SL7. This combo has not changed my opinion but I have to say this is how I imagine a "modern" tube sound. Tight, precise, fast and less flavoured. Not for every day use, but a good point of view.

 

[ARCXENOS]

Mine are made by Deyan, but you can also find in China for example this one.

Be careful, adapters usually break at many removal/insertions. So indeed, 2 adapters might be fine for many types, the downside is that the socket itself is of low quality. More than this, these tubes do not really have a solid base to grab when removing from adapter, so you might have to pull/touch the glass and so on. As I said, careful. I hate that socket but unfortunately those are the best tubes ever made.

Ah, I was interested in the AL4 and their ilk sometime back, but yeah I agree they really need some loving care.

I was actually thinking of the European B5 side contacts, I think no one made them publicly?

 

[hpamdr]

The Eternity design is very clean and is not pushing too much the tubbey sound as rectifier and girator as very precise and fast...
This is why with high gain in output like the 4654 is not the best combo. For me the good match fo 12AX7WB is the GU50 (the tube combo for SS lover )
I like a lot 6N7G or mullard NR73/ECC31 in place of 6J5 (I have internally strapped socket in my eternity) with EL39 which have almost same electrical spec as 4654...

I'll explain a little bit the trick with the pinouts taking a screenshot from my plans for my future amp.

Have you found a builder in Europe ?

 

[OctavianH]

Ah, I was interested in the AL4 and their ilk sometime back, but yeah I agree they really need some loving care.

4V tubes. Very nice.

I was actually thinking of the European B5 side contacts, I think no one made them publicly?

If I understand correctly, this is the B5 socket:

This is something totally different than the P8A side contact I use. I have no idea about adapters for these.

 

[OctavianH]

Have you found a builder in Europe ?

In Europe not, but after reading this I think I might give a try with 1101 Audio. I would incorporate some of those ideas in a build with P8A sockets for 6.3V/4V old european pentodes. I think it will be something revolutionary. I find interesting the concept of "servo-biasing".

I will explain why. During my experiments I realized that some tubes do not perform optimally at a fixed anode voltage. Usually tube amp builders choose a decently low value for the plate voltage which will let you use safely mostly all tube types. This does not mean you will optimally use those. I would like to try some of these old pentodes at different voltages, for example tubular newer versions which allow higher plate voltage or currents to bias higher while older pentodes with more restricted ratings to bias safely lower. In this way I think we could achieve the "sweet spot" for each of them and use them properly.

I was lucky to obtain so good results here with 4654 and the rest of the family but I am sure I can do more.