[OctavianH]

And the story of the dead Tesla 4654. This tube lost it's vacuum because I was not careful enough when removing it from adapter and touched the glass. The base got loose and started to rotate on the glass, not 180 degrees but around let's say 45 degrees. Not much, at first I said I'll glue it. Put it on the drawer and when I came back to it I realized it was too late.

Loose base made the tube loose also it's vacuum. Now, I remember I have a lot of octal tubes where the base is moving, all work fine and none of them lost vacuum because of this until now but you have to be careful not to touch the glass and always remove by dragging from the base. Here it is more complicated to do this since the base enters inside the adapter/socket of the amp for around 70% of the height. If you have bigger hands or like me you are not careful, something like this can happen. So, please be careful never to drag/touch the glass when operating such an european side contact tube. I do not really know how each side contact is tied to the internal parts and if this is a consequence of this type of base (and all with this base are prone to this) or if it was a special case only happening on this manufacturer. I will inform if I will have other unfortunate events like this, until then be careful. Even using a small screwdriver to remove the tube from the socket or adapter is not quite a solution due to the form and way these enter one into another.

 

[hpamdr]

And the story of the dead Tesla 4654. This tube lost it's vacuum because I was not careful enough when removing it from adapter and touched the glass. The base got loose and started to rotate on the glass, not 180 degrees but around let's say 45 degrees. Not much, at first I said I'll glue it. Put it on the drawer and when I came back to it I realized it was too late.



Loose base made the tube loose also it's vacuum. Now, I remember I have a lot of octal tubes where the base is moving, all work fine and none of them lost vacuum because of this until now but you have to be careful not to touch the glass and always remove by dragging from the base. Here it is more complicated to do this since the base enters inside the adapter/socket of the amp for around 70% of the height. If you have bigger hands or like me you are not careful, something like this can happen. So, please be careful never to drag/touch the glass when operating such an european side contact tube. I do not really know how each side contact is tied to the internal parts and if this is a consequence of this type of base (and all with this base are prone to this) or if it was a special case only happening on this manufacturer. I will inform if I will have other unfortunate events like this, until then be careful. Even using a small screwdriver to remove the tube from the socket or adapter is not quite a solution due to the form and way these enter one into another.

The P8A socket/base junction makes tube not as easy to remove... I have some EL3N tube with plasters. In TSF forum, some uses a specific glue recipe to make glass and tube base tight together they also add some bandage once glue is dry. Tis is in order to prevent damage when removing tube, it can also be curative. (The best is to never remove from the glass when you have a base !)

 

[OctavianH]

The P8A socket/base junction makes tube not as easy to remove...

Your remarks and my post made me reconsider a future amplifier with side contact sockets. I will go octal and use adapters. At least if needed to remove you can keep the adapters in a comfortable position and help not touching the glass. But if the socket is on an amp you cannot do this, so the risk of removing/changing a tube and damaging it it's bigger. Sad but true, it was a nice dream but it's not practical. No problem, we have the octal sockets. Replacing an adapter is also cheaper than a socket on the amplifier.

 

[OctavianH]

I think we might have an interesting Friday today, right?

And also some new clues in our war to understand from where and up to where the old Philips sound starts, where were some tubes manufactured and so on. Not answers, but clues. I put them here because maybe one day, someone will know more. Information related to this is scarce, we need to hold our ground and post relevant photos for those who will understand.

 

[OctavianH]

My interest in EBC3 was raised when I started to read the history of the Philips Red valve series written by Jacob Roschy on Radiomuseum.

Excerpt from the article:

The original series of 1936 consisted of the types EK2, EF5, EF6, EB4, EBC3, EL2, EL3, EL5, EM1, EZ2, EZ3 and EZ4.

1937 The types EBF1, EBL1, EH2 and C/EM2 appeared.

1938 The EAB1, EBF2, ECH2, EF8, EF9, EFM1, EK3, EL6, ELL1, 1882 and 1883 appeared.

1939 The ECH3 and EM4 were added.

1940 The ECH4 and ECF1 more or less completed the main development.

Some of the tubes in the list for 1936 were already usual suspects for me because I knew about them, the rest were tubes I have not dwelled too much because they were diodes, variable mu, hard to get and so on. Reading more and more about that era made me also think that many of those tube types should work without problems on my amplifier, and also that EBC3 was a rare double diode triode where the triode section has a very big potential because of the gain of 30 and 1.5W power dissipation.

So the decision was made, I want a triode from the side contact era in my amplifier on input stage, the rest was just to clarify how I can use it. Here pinwise the side contact era was again "straing-forward" because EBC3 works without problems in an EL2 adapter and I had a pair of EL2 -> 6V6 ones.

I said some time ago that the investigation of the side contact era needs basically 2 adapters, one with Anode on top and the other with Grid on top. Almost, if not, all the tube types have first 4 pins standard and only the top cap and pins 5-8 might slightly differ. So I started and measured 2 of these Philips EBC3 with date codes 52/KYL. 5 according to my knowledge indicates a factory of Philips located in Eindhoven, Holland. Looking at the tubes I found out that these remind me of the first type of 4654 I have listened, that one with the "whirlwind" spacer on top.

So all I had to do is measure. These bias on 180V/4mA with around -3.3V grid voltage. Then things went straight.

Soundwise I am in evaluation but I can say 2 things even at this point: the sound is an idea more wet and the additional gain of the triode vs my EBL1/EL3N pentodes is beneficial. Sounds more dynamic and airy. This helps because one of my problems with EL50 was that it sounded very low distorted and sometimes dry. In terms of bass I feel these are thinner sounding than EL3N but still have the rich signature of Philips. Of course, take this with a grain of salt, we are in testing phase. All in all, I am a happy puppy that I put a triode on input stage and went more to my way of pairing and still not going out of the red series tubes.

More will come about this, also some evaluation of ECH3 but for that one I need to document more and make some other tests before putting on the amp. Another thing I have a feeling would work is to put directly the EL2->6V6 adapters on the 6J5 sockets because EBC3 has no Grid 2 therefore I think should work without converting with 6V6 -> 6J5 adapters. But there is a catch here related to my amplifier, because I wanted to use natively 6N7 on 6J5 slots Tomas wired pins 3+6 and 4+5 and this means if I put directly EL2->6V6 adapter on the 6J5 slot, I'll have -3.3V (Grid 1) on the unused pin 7 of the EBC3. Not a big problem in my view but I prefer to be cautious. Of course, never do on your amp what I do and buy dedicated adapters if you want to use these, side contact tubes anyway make problems when removed often from adapters. I've done this only to be able to advance faster in my research. And of course, only my amp has this special 6N7/6J5 special wiring (well, except the other Eternity but that user is much more advanced than me and he knows for sure what to do and not to do).

 

[OctavianH]

These are indeed very beautiful, you have to see them with your own eyes to make them justice.

I tried to make a photo from the top to show similar "whirlwinds" and that all 4 tubes look close in construction but the big top caps of EBC3 mask everything. Whirlwinds looking similar make me think that the outputs might be also made in the "5" factory. But this is not sure. I've seen similar spacers on some old early EL32 production. EL32 is an EL2 with a different base, so many old EL32 and EL2 are somehow looking similar and sounding... I did not have time to check and they are not my focus, but I assume the same. Many of those EL32 were sold as Mullard, but I was unsure if indeed they were produced in the UK. Now I see other tubes built the same which are sold as Philips made in Holland.

 

[triod750]

The journey is almost endless and it is much easier to come up with questions than answers. Makes life more interesting, less boring.

 

[OctavianH]

But we have one more thing to do before the weekend. To prove a point. THIS IS ONLY FOR DEMONSTRATION, NEVER TRY THIS ON YOUR OWN AMP. This was a higher risk experiment so I took bigger caution. What we want to do? I'll tell you, to put the ECH3 triode hexode made by Mullard in Blackburn in input stage of Eternity, but again without a dedicated adapter. Of course, something nobody should do except he understands exactly what is he doing. This is the Mullard ECH3:

Made in Great Britain and now they are right. This is a Mullard. But first let's understand a little bit what we are doing here. I will use the EL2 adapter towards 6V6 put on top of 6V6 to 6J5 and put ECH3 on 6J5 slots. Here there is no question that we will need the triode strapping one under the EL2 adapter because here ECH3 has a Grid 2. Let's see how all these grids are looking in the datasheet:

Now that we know this, let's look at the pinouts:

In the EL2 adapter, all which is green is 1:1, so we are fine, the anode of the triode is yellow because it will be floating, but we do not care about the triode right? We want the hexode here because the triode has too lower ratings anyway. So the only problem I see is that we will leave the Grid 3 floating. This is normally tied to Cathode. But after some experiments on the tube tester, I would say we can try to put ECH3 at 180V/4mA with the hexode triode strapped and Grid 3 floating, just for demonstration purposes. Bias was around -9.6V grid.

Soundwise, well this is a Mullard, sounded muffled and veiled compared with the Philips EBC3 and the gain was also lower. I felt it's somehow distorted but it might be only burn in or that this hexode does not like to stay at 4mA. I have no idea, my experiente with hexodes is 0 and this was a reason I documented myself for this crazyness. But works and sounds acceptable, I will not say good. I will investigate more how others are straping hexodes and what's the point with these variable mu frequency changers. I have a feeling some guys around used hexodes in a similar way but maybe they strapped them better. If anyone know what's going on if you let Grid 3 floating let me know, seems rock solid here and works. But the sound was below what I want for a Friday evening, it was veiled and more that I was remembering the british tubes are. Maybe my scenario was not optimal to obtain something from this tube.

I wanted EBC3 back, but this time I wanted to get rid of the unnecessary 6V6->6J5 adapters since EBC3 has no Grid 2. Before doing this I wanted to check on the tube tester if the special wiring of my 6J5 sockets to allow 6N7 natively with triodes in parallel will make problems, since Grid 1 (-3.2V) will go to the unused pin 7 in EBC3. No problem on the tester, nothing fishy. So I am good to go.

Now I deserve a beer, or at least a glass of wine, time to listen to some music.

Remember, do not do this at home, you might damage your amp. This was a technical demonstration, to prove myself that hexodes work well triode strapped and that at lower currents even a G3 floating will not damage or bring the tube unstable. What I have done was after months of study and reading, do not try it and use dedicated adapters!

 

[OctavianH]

An some "behind the scenes" photos of today's experiments. EBC3 on the tester tried directly on a simulated 6J5 socket with special wiring.

Eternity with ECH3, voltmeter and all prepared, if something happens we stop immediately. Triode strapped Hexode sound on the way to us.

And all for the glory of this small red tiny triode:

We were discussing yesterday about this bloody socket, try to remove EBC3 from it without touching the glass. LOL

And last photo for the fans of Italy. One of the EBC3 from the quad has different date coding, almost deleted, I investigate it but internally looks similar. I love the flag and Philips Italia markings.

 

[triod750]

Little red rooster...

 

[OctavianH]

What to do next? Ah, there's plenty. EBC3 is here to stay, the sound is very nice, an idea on the brighter side but very transparent. From time to time I have a feeling that because it's transparent it leaves more from the EL50 sound to be heard and all goes an idea towards a brighter neutral sound. I have a feeling EBC3 would benefit more from more musical tubes like for example EL6 or EL51. This remains to be checked one day.

ECH3 worked fine even if it were not the best conditions and made me gain trust that the variable mu pentodes, hexodes and so on when strapped as triodes can work and sound decent in an audio amplifier. In the end, as Isaac said, these have to behave as a triode when strapped so I guess there is a path to follow in this area. EBF1 and EBF2 seem interesting tubes. Also EF6, this one is praised by many about it's graphs as triode. Even Thomas Mayer spoke about it here. Mu of 36? 1W? Hmm, if I'll find some cheap one I'll try but I am reluctant because of one thing. I have a feeling all these pentodes strapped as triodes have close electrical characteristics and will sound close or the same. So it will be like EL50, 3 construction types and all sound the same. And then EL3 -> EL6 -> EL50 are somehow in the same style with some differences based on gain and going to a bigger one you just increase the zoom on the scene. So I am unsure if it really makes sense to follow one specific model instead of just buying the cheapest one you find and you'll be fine.

And now some tube magic as some call. Mostly all these pentodes/triodes dwell in the 0.2->0.3A area with the heaters. Without any technical explanations I observed that a tube has more bass if the heater current rating is bigger. So even if I go towards some of these, I will not fix my problem of wanting more bass in input stage. I remember when I asked Tomas (from Ultrasonic not to be confused with the other guy with the blog) about heaters rating related to sound quality he told me "no relation, just more efficient tubes". Well, efficient tubes do not like bass or what? Maybe Thomas Mayer will build such a tube which is efficient and has enough bass but then he'll ask me 3000 EUR for it. LOL

 

[OctavianH]

And why not, let's present also our failures. This tube is a Fivre 6K7G:

I got a pair from a guy in a bigger order and planned to use it in my 6J7 -> 6J5 adapters I never used until now (because forgot to check 6J7 prices before ordering them LOL) and compare how close a 6K7 strapped is to a 6C5 both from Fivre and both same style of base/glass/plate... Before getting them I check the datasheet and I had no idea why I thought "ah this is a kind of 6J7". Found even some 6J7 triode graphs here on this loadline calculator. All seemed fine, until today when I measured them. I had to go up to -20V for 180V/4mA! So I cannot use these in my amplifier and what's funny is that the 6J7 needs -6V for the same current. So "a kind of 6J7", right? We'll store this for a possible other amp or usage scenario. At least they look nice.

 

[triod750]

Maybe Thomas Mayer will build such a tube which is efficient and has enough bass

Custom made tubes to elevate custom made amps? Next level and we are heading there

 

[OctavianH]

Custom made tubes to elevate custom made amps? Next level and we are heading there

Only a pair of custom elf ears is missing.

 

[hpamdr]

Only a pair of custom elf ears is missing.

No just a pair of elves to follow a custom purse full of gold