trinityamps.com

Thanks for the reply. That makes sense. I'd like to try EL34's at some point. Is there a big difference in tonality between them and the KT66's ?

I'll have to see if my amp has that tap available as I bought it already built. Are there any procedures printed up for the EL34 option anywhere, does anyone know ?

You can read this thread and it should help you. But if your OT is older and it doesn’t have the 3.5 k taps than you cannot use EL34 tubes. If the wires are there they will be blue with a white stripe and brown with a white stripe stowed

Thanks mate...I'll take a look when I get home from work. I guess if I really wanted to I could order a new OT ?! If that's my only option that is.

Yes you could do that.i don’t play My son does I was the one that built it. He has played 6V6, KT66 and the EL34S in it. I can ask him about the tonal
Differences and post it later tonight
Mark

Yep, it has the original OT in it. If you can let me know about the EL34's when you get some time, that would be appreciated.

Thanks, Martin

The el 34s in my opinion are the best in it, you can easily get a nice lead tone without a boost or anything which is something the kt66 and 6V6 did well with but the 34s were stronger. Definitely felt more 70’s rock ish with the 34s, similar in gain to 70s marshalls but a different feel and more note definition.

Here are some pages out of the build manual. The extra taps are the later OT. Not sure when Stephen changed it.
Mark

Looks like a new OT is on the cards provided it's not too crazy a cost. Will drop them a line for a price . Thanks for doing this Mark. I really appreciate you taking the time.

Martin

Your welcome, we really like the amp and it was a blast to build.. I have some pictures in another thread “Triwatt build from Texas”. Check it out if you haven’t. I’ve subscribed so if you have questions I’ll see it
Enjoy the amp
Mark

Thanks Mark. I've had it for a few months now, just haven't had the time to fix some small annoying issues but everything's running as it should now.
Just made myself a combo cab this weekend. Almost finished the build. Should be complete this weekend.

The OT has supported EL34 for just a year now. Seemed logical to add even more flexibility.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I'm trying to decide whether to swap out my speaker first or go for the EL34's and change the OT. Looks like we'll have some shows in the next month or two , if the contracts come through it will help with the funding !

Output transformer ordered !

Excellent, I’ll be here if you need help
Mark

So just to confirm, for EL34 operation, @rotorcraft230, looks like you found success by:

• Putting the bias switch in the KT66 position (to remove the Zener diode, and keep the plate voltage higher)
• Completely removing R44 (620k)
• Changing R43 from 180k to 220k
• Using the 3k5 transformer taps (brown/white + blue/white)

This is a bit different that what was suggested by the builder's guide, which says that only R44/620k would need to be increased to 1M. (Also interesting is the schematic says "alt 910k" for the R44/620k resistor.)

I've been wanting to do this for a while now, but keep putting it off. I just need to order some resistors.

Thanks!