DHT driver for triode wired SE EL84, 6V6 or EL34

[tizman]

Three years later than the last bunch of posts, so I'll update. In this time I've committed entirely to high gain output tubes in triode mode in my SE amps. These have been:
EL38 - previously my choice, still good but I now prefer others
E80L in PSE - these surprised me - very clean and detailed, better than EL84 types, mu=20 in triode. Certainly a contender
EL12n - poor man's EL12 still cheap in Europe for new tubes. A very good sound
EL12 - just a little bit better than EL12n but now rare and prices have gone through the roof so not a contender any more.

So in view of the above I've made an amp with linked sockets for both EL12n and E80L. Both freely available in Europe.

Driver stage has alternated between 26, 46, 47 and 10Y. All better than 2P29L, 4P1L or 112A. 10Y now also rare and high prices, and I've finally settled on the 26. Plenty of stocks and It sounds very good indeed in filament bias with a resistor load. Resistor needs to be 39K or more so B+ around 350V. For hum purposes, put a grounded aluminium tube over the 26s. The synergy is very good between the warm and liquid sounding 26 and the neutral and clean EL12n or E80L.

So there we have it for a tried and tested combination which is simple, very good value and has the DHT sound in spades. Just 2 stages so very direct and detailed sound. I'm happy and all my 300bs, 2a3s and 6C4Cs are back in the cupboard. Putting the DHT first in the chain really works - it's a true DHT sound and I love it, especially on vocals and piano, but tone is good all round especially on acoustic instruments. I'm not going back to 300b/2a3 with high gain indirectly heated tubes. That was a cul-de-sac for me, never liked any of the driver tubes the way I love DHTs.

Andy: Thanks for the update! Once I finish my never ending 45/46 build, I am going to revisit the DHT to triode strapped pentode configuration. A reasonably priced DHT front end followed by a reasonably priced triode strapped pentode power section has worked for you, and you have already tried far more configurations than I’ll likely ever get to. In my case, I’ll use a 26 to a 7868, as I have a bunch of both on hand. My 30 to EL84 amp sounds good, but was not properly optimized to kill microphonics, and the use of a steel chassis caused issues with magnetics, both the power and filament transformers, inducing noise into the circuit through the chassis. That amp still sounds good, and taught me not to use steel, and to use a separate chassis for the Coleman regulator and power supply. Thanks again for the update!

 

[andyjevans]

7868 should work fine. Much more common your side of the Atlantic. I tend to use European tubes, though the 26 is a welcome exception. There's nothing quite like it. It was the first DHT I ever tried back around 2009 and my jaw dropped when I heard the sound of it. Always in filament bias with Rod Coleman regs.