A question for Bob or anyone, ST35, SCA35 or any EL84 based amp to triode mode.

For an El84 would you remove the green or green white wire from pin #9, insulate.

Then put 100 ohm resistor from pin #9 to pin #7?

If this is correct then to add a ultralinear to triode switch you would.

Remove green or green white wire from pin#9 of each tube and solder to separate poles of DPDT switch on the same end.

Solder wire from pin #9 to center pole of DPDT switch.

Solder 100 ohm from pin #7 to DPDT switch opposite end from green or green white wire.

All wiring to and from switch side must be to same tube.

Also I once had a MKIV which I triode, did not work. Was wired correct. Asked a guy about it, he thought it may be osculating at radio frequency, suggested 220 ohms. It worked fine. Is this common?

Thanks Bob!!!

I have very efficient speakers that can do with only 10w. Also I have been designing speakers for 30 years & would be Bi or t
Triamping with a triode strapped EL84 amp.

Anyone else if you do this tell us your results.

Sorry to bump a two year old thread, but I'll be trying this soon with the ST35 I'm currently building: http://www.diyaudioblog.com/2011/06/customized-dynaco-st35-kit.html

Has anyone actually added this functionality to their ST35 yet? I almost always prefer my ST-70 in triode mode, seems a little more warm with perhaps a bit more midrange bloom.

Here's a photo of my Dynaco ST35 with Triode switches. Thanks for the insight Bob, this old post came in handy The rest of the amp and build notes are here: http://www.diyaudioblog.com/2011/06/customized-dynaco-st35-kit.html

I actually found that the speakers that I have connected, a very small pair of Tektons with 4" full-range Fostex drivers, sounded better in ultra-linear mode, perhaps they needed that extra little bit of drive. But at least I'll always have the option now

Thanks very much for the kind words Bob. I hope one day when $$ permits I'll be able to put together a set of those hot looking M125 monoblocks you've just rolled out Keep up the great work!

Bryan,
just curious where you got those special sockets you used on your ST35 build?

The Teflon sockets I found on that auction site. You can also find similar ones at PartsConnexion and WooAudio, those two vendors also selling the corresponding PCBs.