WRECK STYLE WITH PENTODE PREAMP

[RCGPNY1]

Has anyone ever tried going into unkown territory and build a Wreck style amp with a pentode(EF86 or 5879) preamp?

[10thTx]

I think the main issue would be the tone stack after the pentode.

IF I were to try something like that, I'd be tempted to use a mosfet CF after an 5879 and then a traditional Trainwreck tone stack off the CF. However, I have NO idea how that would sound and how far off from a Trainwreck tone that would be?
With respect, 10thtx

[KellyBass]

A while back, I built a rocket with an EF86 circuit that could be mixed into the normal circuit via a volume control. If I recall, i piped it into the PI. It was similar to a DC30 arrangement...only I was forced to choose a single cap as opposed to the DC30 array. I didn't have enough space. It sounded great! As you might expect, the low end was incredible, and the distortion characteristic was unique. Being able to mix the two signals together was great. If i did it again, I would definitely do the cap array for extra flexibility.

[RCGPNY1]

After owning a Divided by 13 RSA 23 which has a 5879, I really liked the "click" channel with its 6 pos. bright switch-odd but wonderful sounding amp...sorry I sold it. 23 watts out of a pair of KT88's !!!!
But what 23 watts they were. Anyway I have a feeling Id like to have a regular and a pentode channel and use an external a/b box to switch between or combine them

[10thTx]

Just an idea. Not sure what it would sound like? Could be relay switched.

I am thinking that the cathode cap on the next gain stage may need to be simultaneously relay switched from 22uf to something lower more like 5uf when using the 5879?

You obviously could use a triode as a CF although the mosfet CF works great in this position.

With respect, 10thtx

[KellyBass]

That Divided by 13 amp sounds amazing! I think that I would regret selling it as well!

Switchable "real" pentode/triode with a CF? Sounds like an interesting project. Maybe in a simple SE amp to start. But, with a KT88!...just in case.

[KellyBass]

I didn't see your schematic before my last post 10thTx. That's cool!

[didit]

Or use a combo small signal pentode+triode tube designed for RF (TV etc) such as ECF80/6BL8. The pentode for gain and the triode as CF. Worked in Dynaco hifi designs as voltage gain plus cathodyne PI driver swinging a pair of EL34. Has more than enough to push a tone stack. Will require some fiddling with passive values to get the right gain + drive characteristics.

And quality NOS (eg. Mullard or similar) are remarkable affordable.

Best ... Ian