Push-pull implemented with KT88
 

Hello,
I am planning to build a push-pull KT88 based amplifier. I would like to make it operation type selectable by using a switch, so I can operate the tubes at Triode, Ultralineal or Pentode, depending on my PWR needs, and mostly for audio comparisons purposes. Fixed bias provided by extra turn on xfmr.

I could use a different tube rather than KT88, but what the h*ck, it's among the best tubes in its power rating. I haven seen some pcb boards (like pmillet's) that come very handy if testing and breadboarding, but it will be a final assembly, not an amplifier to experiment, so I will P2P it.

What is a common, high-end, not very complex schematic to use? I don't really care if it is a complex desing, but life's such, that simpler ones use to be the better ones. I don't really need to be able to select between triode, UL and pentode, that's something I am able to put in by myself :)

If you were about to build ONE, with these requirements, what proved schematic would you implement?

Thank you and best regards,
Regi

Look to the Dynaco schematics with modifications to the driver board, a ton of them floating around, for the Monoblock's look for the MKIII amps and for a stereo version the ST70. Lots of transformers from several sources and I think just an update to the driver and you will have a simple good sounding amp.

Sandy

I have had a look at that, seems quite interesting

www.triodedick.com/pdf_files_td/Bill_En.pdf

Mono Bill or Mono Bill II are later KT88 designs

don't know if its true, but I got the impression that the KT88 quality could be an issue

In addition to the Bill/Mono Bill, here are a few more:

Mullard 5-20 topology with PP KT88's:

http://www.diyaudio.com/forums/tubes...pp-blocks.html

Mullard 5-20 topology with MOSFET followers:

http://www.diyaudio.com/forums/tubes...n-mullard.html

Differential front end with MOSFET followers:

http://www.diyaudio.com/forums/tubes...c-ab2-amp.html

Why? Ain't KT88 good enough performers?

ahh, yeah, I guess they are ok
I meant, a KT88 may not be all good just because it says KT88 on the bottle ;)
hope its ok to call it a good alround performer and 'middle of the road', so to speak

I think I am going with Triode Dick's, but I can't find anything related to output transformer impedance, power and other characteristics on its website. Do you know what is used in the original design or should I just calculate it?

Link to the translated website:
Bill Part 7

monobill 2 schematic shows 5K6

OK! Thanks!