Playing with hybrid amp: SRPP + MOSFET

siliconray · 15th December 2011, 07:32 AM

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. .

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

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

Sure! here it is..Modified slightly from the beta version after testing.

Quote:

Originally Posted by Yarpen

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

Ken Newton · 01:25 PM

Quote:

Originally Posted by siliconray

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.

15th December 2011, 07:32 AM	#1
siliconray diyAudio Member Join Date: Sep 2011	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. . __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

15th December 2011, 04:21 PM	#9
Cassiel diyAudio Member Join Date: Sep 2004 Location: Madrid	Schematic? __________________ Good sound comes and goes.

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15th December 2011, 07:55 AM	#2
Jeffrey689 Banned Join Date: Oct 2011	interesting, can you post the circuit? do you have plan to sell kits on your website?

15th December 2011, 10:20 AM	#3
DF96 diyAudio Member Join Date: May 2007	Why SRPP? Unless correctly designed and loaded it can have high distortion, as you find.

15th December 2011, 12:32 PM	#4
Yarpen diyAudio Member Join Date: Sep 2004 Location: Poland	It's look nice ! Can you post the schematic etc?

15th December 2011, 12:42 PM	#6
Skorpio diyAudio Member Join Date: Mar 2004 Location: Denmark	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...

15th December 2011, 06:04 PM	#10
boontiam diyAudio Member Join Date: Nov 2011 Location: thailand	Schematic and sound this one. Tank.

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