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Old 29th August 2011, 04:09 PM   #1
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Question KT88 Push Pull Amp using transistor driver stage

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
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Old 29th August 2011, 04:51 PM   #2
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This may get your juices going.
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Old 29th August 2011, 05:45 PM   #3
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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
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Old 29th August 2011, 06:29 PM   #4
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Originally Posted by richwalters View Post
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.
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Old 29th August 2011, 07:45 PM   #5
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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
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Old 29th August 2011, 07:51 PM   #6
poynton is offline poynton  United Kingdom
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There was a "wireless world" article re: using theLindseyHood class a as driver stages for KT88



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Old 30th August 2011, 02:42 AM   #7
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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
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Old 30th August 2011, 03:15 AM   #8
BudP is offline BudP  United States
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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
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Old 30th August 2011, 03:41 AM   #9
limono is offline limono  United States
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Isn't Audio Research doing this for years? (at least 30 I think)
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Old 30th August 2011, 05:18 AM   #10
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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.
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