Source follower in a DC-coupled pp amp?

rongon · 9th January 2012, 07:10 PM

I want to add MOSFET source followers between the phase splitter/driver LTP and the output tubes of my 2-stage DC-coupled 2A3 PP amp. I figured it with cathode followers, and it looked pretty easy to do. Here it is in a similar fashion, but with MOSFET's.

Did I do that right? I suspect there's more to it than that...

I figured on about 160V dropped across the current sinks below the FET's sources. About 20V drain to source. 10mA is enough?

--

Gluca · 9th January 2012, 11:06 PM

Hey ... would you mind telling more about that choke on the 6N6P?

Tks

rongon · 10th January 2012, 01:47 AM

Well... It's actually a push-pull OPT designed for EL84's in pentode. I'm just using the primary as a center-tapped choke, as the plate load for the 6N6P. I figure it has enough inductance for that use, and measurements bear that out. The amp passes pretty decent sine waves well below 20 Hz at 6 watts RMS out.

A purpose-designed split load choke like the Tango TC-160-15W would be better, I'm sure.

But I was hoping to hear from someone about using the MOSFET's that way...

--

9th January 2012, 07:10 PM	#1
rongon diyAudio Member Join Date: Jul 2009 Location: Across the river from Rip's big old tree...	Source follower in a DC-coupled pp amp? I want to add MOSFET source followers between the phase splitter/driver LTP and the output tubes of my 2-stage DC-coupled 2A3 PP amp. I figured it with cathode followers, and it looked pretty easy to do. Here it is in a similar fashion, but with MOSFET's. Did I do that right? I suspect there's more to it than that... I figured on about 160V dropped across the current sinks below the FET's sources. About 20V drain to source. 10mA is enough? --

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9th January 2012, 11:06 PM	#2
Gluca tarmac ripper diyAudio Member Join Date: Nov 2004 Location: Back to Italy	Hey ... would you mind telling more about that choke on the 6N6P? Tks

10th January 2012, 01:47 AM	#3
rongon diyAudio Member Join Date: Jul 2009 Location: Across the river from Rip's big old tree...	Well... It's actually a push-pull OPT designed for EL84's in pentode. I'm just using the primary as a center-tapped choke, as the plate load for the 6N6P. I figure it has enough inductance for that use, and measurements bear that out. The amp passes pretty decent sine waves well below 20 Hz at 6 watts RMS out. A purpose-designed split load choke like the Tango TC-160-15W would be better, I'm sure. But I was hoping to hear from someone about using the MOSFET's that way... --

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