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Old 13th January 2017, 09:05 PM   #1
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Default Cathode follower interstage power amp

I quarrel with a concept of a pentode SE power amp being driven by a cathode follower (and using a pentode input tube). Would it make sense to install an interstage between the cathode follower and the power tube (10K:40K)?

How about circuit stability problems for the feedback loop, if it includes the interstage trans?
Do I have to experience more probs than benefits with that design vs. a straight cathode follower driven output pentode?
I thought it could have much sonic benefits.

Sorry, but Im unable to simulate the circuit on a PC.
Many thanks in advance.
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Old 14th January 2017, 02:01 AM   #2
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Location: Oregon
Why wouldn't you link the pentode input stage to the pentode power stage directly? Pentode power tubes are usually easy to drive. The interstage transformer would make a dog's breakfast out of any attempt at global NFB, and you're going to need feedback around the pentode output section at least, if you want reasonably low output impedance.
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Old 14th January 2017, 06:54 AM   #3
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With a cathode follower between the preamp stage and the power amp, there's really no reason to have an interstage transformer. The low impedance output of the CF should be perfect to drive the power stage grid.

Sent from my LG G2 with CM13 using Tapatalk
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Old 15th January 2017, 01:25 AM   #4
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Many thanks for your answers, messieurs.
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