[OctavianH]

6C8G is on my list but I never found some at a decent price. I think that they should be close to 6N7 because they have almost similar gain.

 

[Isaacc7]

Think I can now put my finger on what’s wrong. Listened to a wooden flute piece I have heard plenty of times before. The wood of the wooden flute was almost completely gone. I’m thinking there are some frequencies being attenuated, possibly lower midrange or several bands in the midrange. Hearing the note but not the instrument is probably a good description of the smoothness I heard. I can see how some might like this for voices but acoustic instruments just sound lifeless. Will try some other drivers but I do think it is a little weird I’ve noticed this sound issue across several tube types. Would an output tube really have this kind of problem?

 

[Isaacc7]

I had originally tried using these Sylvania 6bg6ga as a 6l6gc since they are equivalent to a 7072a. I couldn’t get a sound I liked with them and was a little worried about how far I could push the amp so I decided to go back to the normal settings. Except I didn’t lol. Once I adjusted the Ma back to normal the amp sounded better but still not right with the 6c8g. On a whim I put in the triode KTZ41. Now that’s more like it! I’ve gotten the lower midrange back and violins and that wooden flute sound much better. The bass has gotten louder but less controlled. Will actuallykeep this combo through the weekend I think.

 

[OctavianH]

It seems additional flexibility comes with additional headaches. You have what to do with that amp in the next 20 years.

 

[Isaacc7]

It seems additional flexibility comes with additional headaches. You have what to do with that amp in the next 20 years.

I see a much simpler future. I am accumulating tube combos I like and see a time when I will just rotate between them depending on what mood I’m in.

 

[OctavianH]

I see a much simpler future.

In my case I opened Pandora box: started to read about EL3/5/50/6 and Philips variants like 4654, 4689, 4694, 4699 and so on. I knew something about a part of them but I also found a lot of intersting things. Then I looked a little bit about EL509/519... And I thought I was close to the end.

 

[OctavianH]

I was telling you last week that I am in an unplanned episode related to pre-EL34 era. So I read and searched a lot regarding many tubes which I did not knew before. And this happened exactly when I gave up hope about listening to a metal base EL34. Luckily for me reading and discovering other tube types which, in my view, are related to what later became EL34 helped me find a chance to taste them. And now I can imagine, for the first time, how EL34 metal base sounds and why indeed many call them the best EL34 ever created.

So let me present you my currently output pair, Philips Miniwatt 4689 (yes, that ugly awful EL3N socket, but luckily that one works for a lot of other tube types as I have recently discovered since I put all pinouts on a table). So my old EL3N adapters will be again put to work.

But does this 4689 sound the same as 4654K I was praising last week? (which by the way, is for me the best tube I ever had the chance to listen). Honestly? NO.

(date code 52/FE5, flat ring getter)

This 4689, equivalent of EL5, sounds for me a lot more towards EL34 than 4654K which is, in the end, the equivalent of EL39. Less tight bass, more mid oriented, it's an EL34 type of sound for me but indeed, one level above in quality. It enhances all I've heard and liked on EL34 but adds more clarity and separation and so on. This has to be the sound of the metal base EL34, on a more unknown and less searched type of tube.

Are these the tubes I consider the best? NO. But they are the best EL34 I had the chance to listen and the difference is not marginal. Do I like more 4654K? YES. More linear, better bass (defined, tight, like all EL39 fans crave), incredibly detailed and with excellent separation. I have a feeling that the level of detail and separation between them is similar but the signature being more mid oriented on 4689 makes it perceived differently. However, I keep my opinion that EL39/4654K is the best I've heard.

And of course, my remarks are always related to the rest of the chain. D8000 Pro are for me a quite musical headphone and a more linear signature explores more from the bass and things I like on it. I can of course understand that people with differently tuned headphones might prefer the airier EL34 tone and choose 4689 instead. No problem, it is a very subjective hobby. I also like it from time to time but since we make a top, we need to choose.

My plans are to explore more and more on this area, but will minimal investment. I already decyphered my 2 pairs of 4654K (Mazda Bruxelles and Philips Eindhoven) and even if some claimed on different threads that they are close, well there are differences. I plan to add these and a few more to the table, listen for some months to all and then make a consolidated post regarding all. I have no idea when. Let's hope I'll do it.

PS. It's nice to read now my posts from March when I was discovering that the 4654K is not sounding as an EL34 and only the construction might be similar with the metal base versions. Indeed, at that time I was hoping to hear what I hear now with 4689 but I was discovering the Philips EL39 sound. Well, if only I was listening and believing what everyone was saying related to equivalents. We have equivalents, datasheets, factory codes. All is in front of us, but we are blind.

PS2. 4689 has lower ratings than EL34, will not work as a 1:1 replacement in some situations. But in my headphone amp I am a lot below them anyway. (Va max 375V, EL34 was around 700-800V)

 

[Isaacc7]

Turns out I had been testing the Sylvania 6bg6ga in ultralinear, not the triode I had thought I was in. They are now singing along nicely. I switched my preamp tubes to the GEC b36 (from 14n7) and am using Brimar 13d1 input tubes. This is a much better overall combo than I‘ve heard with the Sylvanias before.

 

[OctavianH]

Even if I do not have any experience with ultralinear mode, from all your tries and experiments I realize I would, most probably, prefer triode mode, if I would be able to use both modes on my amp.

 

[Isaacc7]

Even if I do not have any experience with ultralinear mode, from all your tries and experiments I realize I would, most probably, prefer triode mode, if I would be able to use both modes on my amp.

The sound quality of ultralinear will vary dramatically with the tube and the amp Not to mention the speakers.You could argue that switching between triode, pentode, and ultralinear means that talking about a tube’s sound doesn’t make much sense. Both triode and ultralinear modes are forms of feedback that dramatically change the tube’s parameters. Triode is the most forgiving of all of them in that the distortion is the lowest. Triode mode is essentially a tube with 100% local feedback whereas ultralinear feedback goes through the transformer and is a percentage of the b+, usually 40% or so. I get a chuckle when pentodes wired as triodes are advertised as zero feedback. Maybe they don’t have global feedback but there is plenty of local feedback.

 

[Isaacc7]

Switched from the 3d21 to c3m inputs. Woooooo. There is a vividness to the midrange now. Guess it is a bit more forward than before but there is mire detail and the lower midrange is much more solid. Strings in sitars and and sarods are ringing out as well as nylon string guitars. Will coast with this combo a bit. Don’t think I’ll futz much more with the Sylvania 6bg6, think this combo will go down as the one to beat for this tube.

Next up will be the 6aq5 output tube. When I originally contacted Tomas I was thinking of an amp only made for the lower output tubes like the 6aq5, 6v6, 6k6, etc. The option to go with higher power tubes was offered and I took him up on it. A weird consequence is that I might not be able to run the 6aq5 optimally because at 250v I can’t go any higher than 30ma bias current. They really should be run at 35ma. We’ll see how they sound. I will be a bit disappointed if I can’t get good sound out of them but I have plenty of other good sounding tubes to console me lol.

 

[Isaacc7]

First experiment with the 6aq5 didn't start out auspiciously. First off, those tiny little pins always make me worry about bending them. Prefer the bigger pins in bigger tubes. Speaking of which, they are tiny! Look kind of ridiculous really IMO.

Anyway, popped in some Brimar 6aq5 in along with some TS BGRP and... Wow, super clear and natural sounding! Almost eerily present. But, almost no bass. Sigh. I knew I couldn't run them at the ideal settings but this is nuts. I like the sound but it's tough to love without bass. On a whim I dropped in the closest other driver tubes I had, the TS 6c8g. First of all, the sight of the driver tubes dwarfing the output tube is comical. More importantly, I now have bass! Really nice sound though I admit I don't want to think about spending all that money on the amp for just 4 watts output lol.

 

[OctavianH]

I also had some problems with my 6AT6 experiments. I had some hum and the sound was not right with them at 2.5mA. I guess I was pushing them too much or gain of the combo was too high. I stored them for a later try. In the meantime my rolling activities are paused. I am only enjoying music.

4689 made me to forget wanting to try any other EL34. No, thanks, I am fine. These are doing right everything which different EL34 were doing wrong and are exactly the sound you dream to obtain when thinking about EL34. The black or brown base just cannot compete. I will keep them for collection, stored. I cannot listen to them anymore. The synergy with the ITT/Lorenz E88CC is exceptional (for both 4689 or 4654K), so I kept this on input for several days without every need to change something.

I was afraid to make this statement, but in the end these forums need people to contribute with honest opinions, otherwise they would become useless. The power of the community comes from each individual who shares experiences and findings. After discovering 4689, which for me have the perfect EL34 sound, even if these are not EL34 in terms of ratings only somehow related as signature, and after my very interesting and successful experiments with small pentodes I came to the conclusion that if I would start again with Eternity I would not go again towards standard non metal base EL34. Nope. I would go towards EL85 or EL82 for a fraction of the price and then search for a pair of a metal base equivalent. The small ones are very cheap and for me are providing 75%-80% the same experience. And for a fraction of the cost you can buy from more manufacturers and types and play with gain and so on. You save money and you get more. But of course, none of these or normal EL34 can touch the metal base ones. Those are in a different league, in terms of sound but also sturdiness and build quality. Built like a tank, solid, extremely good sound. Gone are the days of EL11 or grey glass KT66 where you had to glue several times those bases and so on. I have 2 pairs of grey glass KT66 and one of them has a tube with glued base, worked for 1 month, then reglued because it started to fell again, now crackless, the other pair I do not touch for obvious reasons. On my pairs of metal base I never had any hum or crack on anything. Rock solid. It's true that these are hard to find but still, if you dig a little bit and find some equivalents or rebrands you can still be in the game for a decent price/performance ratio (well, honestly performance is so high that even maybe 100 EUR / piece is for me a bargain - I know what I said about 20 EUR / piece as a maximum, these are an exception).

Of course, what I said is a personal subjective opinion and might also not be a good advice for everyone or every amplifier. In my case, Eternity keeps these at 20mA/200V so the fact that the EL34 goes higher is irelevant. Small pentodes with max 250V or around were perfectly fine for me. Of course, guys with bigger guns need to pay more, to have those types with higher ratings and so on. Pity for them. Also for those who need quads.

PS. For a small headphone amp, if the ratings allow it, I would not go either for EL84. For me EL83 was perfect and same feeling and EL803 from Telefunken was a revelation. So, I would continue on this area for more gain.

 

[Isaacc7]

I also had some problems with my 6AT6 experiments. I had some hum and the sound was not right with them at 2.5mA. I guess I was pushing them too much or gain of the combo was too high. I stored them for a later try. In the meantime my rolling activities are paused. I am only enjoying music.



4689 made me to forget wanting to try any other EL34. No, thanks, I am fine. These are doing right everything which different EL34 were doing wrong and are exactly the sound you dream to obtain when thinking about EL34. The black or brown base just cannot compete. I will keep them for collection, stored. I cannot listen to them anymore. The synergy with the ITT/Lorenz E88CC is exceptional (for both 4689 or 4654K), so I kept this on input for several days without every need to change something.

I was afraid to make this statement, but in the end these forums need people to contribute with honest opinions, otherwise they would become useless. The power of the community comes from each individual who shares experiences and findings. After discovering 4689, which for me have the perfect EL34 sound, even if these are not EL34 in terms of ratings only somehow related as signature, and after my very interesting and successful experiments with small pentodes I came to the conclusion that if I would start again with Eternity I would not go again towards standard non metal base EL34. Nope. I would go towards EL85 or EL82 for a fraction of the price and then search for a pair of a metal base equivalent. The small ones are very cheap and for me are providing 75%-80% the same experience. And for a fraction of the cost you can buy from more manufacturers and types and play with gain and so on. You save money and you get more. But of course, none of these or normal EL34 can touch the metal base ones. Those are in a different league, in terms of sound but also sturdiness and build quality. Built like a tank, solid, extremely good sound. Gone are the days of EL11 or grey glass KT66 where you had to glue several times those bases and so on. I have 2 pairs of grey glass KT66 and one of them has a tube with glued base, worked for 1 month, then reglued because it started to fell again, now crackless, the other pair I do not touch for obvious reasons. On my pairs of metal base I never had any hum or crack on anything. Rock solid. It's true that these are hard to find but still, if you dig a little bit and find some equivalents or rebrands you can still be in the game for a decent price/performance ratio (well, honestly performance is so high that even maybe 100 EUR / piece is for me a bargain - I know what I said about 20 EUR / piece as a maximum, these are an exception).

Of course, what I said is a personal subjective opinion and might also not be a good advice for everyone or every amplifier. In my case, Eternity keeps these at 20mA/200V so the fact that the EL34 goes higher is irelevant. Small pentodes with max 250V or around were perfectly fine for me. Of course, guys with bigger guns need to pay more, to have those types with higher ratings and so on. Pity for them. Also for those who need quads.

PS. For a small headphone amp, if the ratings allow it, I would not go either for EL84. For me EL83 was perfect and same feeling and EL803 from Telefunken was a revelation. So, I would continue on this area for more gain.

Have you ever looked into el90/6aq5? They are still fairly inexpensive, some of them are downright cheap. The expensive American ones are around $25. I've seen the Brimar and Thompson ones going for $10 or so. I'm impressed with the Brimar so far.

 

[OctavianH]

Have you ever looked into el90/6aq5?

I looked into them but never decided to go this path. I know they are the successor of 6V6 and those never sounded very good in Eternity. I think they are too soft for this kind of neutral tuned amplifier. I always preferred EL34/807/EL39. But your idea is good, because I always wanted to try some Mazda / Fivre 6V6 and if I can do this via EL90/6AQ5 at a fraction of the cost why not? But the 1M$ question is: How close are EL90/6AQ5 sounding to 6V6? Can you check that? Do you have 6V6 or something to see if these go towards a similar sound signature? I looked on the graphs and they even bias the same around -15V in my case.

Anyway I sold my 6V6 and kept only a pair of Sylvania straight grey glass (GT/G). Never regreted it, at least on this amp. I had some Brimar and Westinghouse and Sylvania was a quad, so I sold 2 of them only. I do not remember if I had others than these.

By the way have you tried EL95? It seems to work with the same adapter as EL90.