KT88 Push Pull Amp using transistor driver stage

[shumgary]

Hi,

I am wondering is it possible to use transistor at Phase-Splitter/Driver stage while push pull output stage using power tube such as KT88/KT90?

Is there any existing design/schematic for this configuration on Internet?

Thanks in advance.

Gary

 

[HollowState]

This may get your juices going.

 

[richwalters]

Considering the output tranny is the limiting bandwidth item; If one has paid a fortune for a fantastic performing specimen, then is there justification for using sand in the earlier stages ? I think not.

richy

 

[HollowState]

If one has paid a fortune for a fantastic performing specimen, then is there justification for using sand in the earlier stages?

Agreed, and it's not something I would do myself. With the possible exception of a FET follower between the driver and output. But shumgary asked, unless he meant just the driver portion.

 

[Globulator]

Agreed, and it's not something I would do myself. With the possible exception of a FET follower between the driver and output. But shumgary asked, unless he meant just the driver portion.

I could understand a follower too, very useful to drive a triode grid in fact.
God forbid anyone using bipolars for amplification and then mashing it all up with a big dose of NFB (including the transformer for Pete's sake!). It's all so wrong on so many levels

 

[poynton]

There was a "wireless world" article re: using theLindseyHood class a as driver stages for KT88



.

 

[shumgary]

Hi All,

Thanks all your replies.

Yes, it is exactly what I am exploring. But after review the schematic, I do agree it will be much simpler to use tube driver stage instead of sand.

Gary

 

[BudP]

If you use an interstage transformer you can get away with mixing sand and fire. The sound will be everything you hoped for from utilizing the sand to drop noise and distortion and increase power supply ripple rejection. I have a push pull solid state to SE tube amp near the start of Frankenstein's and a SE power tube driver to push pull solid state Frankenstein up and running. All you loose is the noise and distortion. Neither of these are my design and the SE to PP is from the hands of Rene' Jaeger. This next one comes from Gary Pimm, filtered through Rene'.

As you can guess, I am not a proficient amp designer or builder, I just design extremely high performance audio transformers.... and they are insanely expensive too, or at least these here are.

Bud

 

[limono]

Isn't Audio Research doing this for years? (at least 30 I think)

 

[HollowState]

If you use an interstage transformer you can get away with mixing sand and fire.

I'm curious to know why one needs an interstage transformer to use transistors and tubes together. There's nothing to "get away" with. It would make the merging a little simpler, but wa-a-ay more expensive. Not really an equitable trade in my book. Perhaps you just like transformers too much.

 

[BudP]

Of course I do, I make my living designing and mfg them.... so transformers rule. Everyone should have a treasure box full of them! And give me their other worthless gold treasure while getting them!!!!

Does allow you to isolate stages though and then it is possible to treat each stage as it deserves, thinking about what Lynn Olson has to say for this.

Bud

 

[richwalters]

Perhaps you just like transformers too much.

Agreed..I'm addicted too...In 1970 I earned my higher degree in physics...Magnetics unfortunately for many seems too much for todays lot to understand. It's the best thing ever for cleaning up signals and not much has changed from those early days except applied simulation and perhaps a dab of exotic metals thrown in... The Laws of physics don't change.

richy