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-   -   Playing with hybrid amp: SRPP + MOSFET (http://www.diyaudio.com/forums/tubes-valves/202549-playing-hybrid-amp-srpp-mosfet.html)

siliconray 15th December 2011 07:32 AM

Playing with hybrid amp: SRPP + MOSFET
 
Just finished a new audio amp. It's my first hybrid design. 6N8P is used as preamplifier. 2 IRFP240 forms class A output stage. I had built more than 15 amplifiers in the past 3 years but this is the most favorite one. Althought it has 0.27% THD (1KHz, 1W, 8Ohm), much higher than the JLH amplifier (0.03%) I designed a few weeks before, but it sound sweet, and the background is dead silent. .

http://gallery.siliconray.com/var/al...G?m=1323936676

http://gallery.siliconray.com/var/re...G?m=1323936678

http://gallery.siliconray.com/var/re...g?m=1323936680

Jeffrey689 15th December 2011 07:55 AM

interesting, can you post the circuit? do you have plan to sell kits on your website?

DF96 15th December 2011 10:20 AM

Why SRPP? Unless correctly designed and loaded it can have high distortion, as you find.

Yarpen 15th December 2011 12:32 PM

It's look nice ! Can you post the schematic etc?

siliconray 15th December 2011 12:38 PM

The MOSFET has 1300pf Cg so it needs low output impedance to drive, especially when the freq is high. SRPP because the output impedance is low. I think the distortion is acceptable for a hybrid amp. I believe 50% of the distortion is cause by the mosfet. It's a design without global feedback.

Quote:

Originally Posted by DF96 (http://www.diyaudio.com/forums/showthread.php?p=2821449#post2821449)
Why SRPP? Unless correctly designed and loaded it can have high distortion, as you find.


Skorpio 15th December 2011 12:42 PM

I would suggest to use the valve for both channels and load the anodes with CCS (DN2540 cascode). Then use the low impedance output, you will get an Ro of 200-500 Ohm and good drive for the MOS-FET input...

I have done this with a 12BH7A and DN2540 CCS to drive a F4 design without the JFET input...

siliconray 15th December 2011 01:09 PM

schematic
 
1 Attachment(s)
Sure! here it is..Modified slightly from the beta version after testing.
Quote:

Originally Posted by Yarpen (http://www.diyaudio.com/forums/showthread.php?p=2821609#post2821609)
It's look nice ! Can you post the schematic etc?


Ken Newton 15th December 2011 01:23 PM

Quote:

Originally Posted by siliconray (http://www.diyaudio.com/forums/showthread.php?p=2821657#post2821657)
Sure! here it is..Modified slightly from the beta version after testing.

Perhaps I'm missing something, but that schematic doesn't appear to go to your hybrid amplifier.

Cassiel 15th December 2011 04:21 PM

Schematic?

boontiam 15th December 2011 06:04 PM

Schematic and sound this one. Tank.


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