Simple 2 stage PP fet amplifier

vuki · 5th April 2006, 03:16 PM

I made simple 2 stage push-pull amplifier. It sounds quite nice and measurements are not so bad too.
More about it at http://www.moxtone.com/s2s.htm .

hacknet · 5th April 2006, 04:01 PM

im surprised at how the jfets can drive the gate capacitance of the hexfets.

CBS240 · 5th April 2006, 04:52 PM

yes there ought to be a driver stage in there somewhere. Also, wouldn't you want to drive the fets with a higher voltage PS than is on the drains for source follower to get rail to rail operation.

vuki · 5th April 2006, 05:36 PM

Please, take a closer look at the schematic and measurements.
That's not a source follower on output - output stage has voltage&current gain!

darkfenriz · 5th April 2006, 06:40 PM

Do you run output stage in class A ?
How is PSRR ?

Upupa Epops · 5th April 2006, 07:00 PM

Voltage gain ? Really ?

vuki · 5th April 2006, 07:09 PM

@darkfenriz
Ic of output hexfets is 200mA
I don't know PSRR, but with 350mVpp at output PS there is only noise on speaker output and absolutely no hum&noise to be heard on 94dB/W/m sensitive Tannoys.

@Upupa Epops
Voltage gain. Really.

mlloyd1 · 5th April 2006, 07:15 PM

sounds like you're trying to say this is a bit of a hafler transnova clone. my croatian is REALLY bad :-(

never seen it done without using lateral MOSFETs at output.

mlloyd1

Quote:

Originally posted by vuki
Please, take a closer look at the schematic and measurements.
That's not a source follower on output - output stage has voltage&current gain!

vuki · 5th April 2006, 07:22 PM

@mlloyd
Yes, something like that. Jim Strickland is mentioned in the text as you have maybe seen. It works nice with hexfets, but maybe it would sound even better with lfets?

moamps · 5th April 2006, 07:22 PM

Quote:

Originally posted by Upupa Epops
Voltage gain ? Really ?

Some background reading:
http://www.tubecad.com/2004/blog0006.htm

5th April 2006, 04:52 PM	#3
CBS240 diyAudio Member Join Date: Aug 2005 Location: K-town	yes there ought to be a driver stage in there somewhere. Also, wouldn't you want to drive the fets with a higher voltage PS than is on the drains for source follower to get rail to rail operation. __________________ All the trouble I've ever been in started out as fun......

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5th April 2006, 04:01 PM	#2
hacknet diyAudio Member Join Date: Nov 2002 Location: sg	im surprised at how the jfets can drive the gate capacitance of the hexfets.

5th April 2006, 05:36 PM	#4
vuki diyAudio Member Join Date: Jun 2002 Location: zagreb, croatia	Please, take a closer look at the schematic and measurements. That's not a source follower on output - output stage has voltage&current gain!

5th April 2006, 06:40 PM	#5
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	Do you run output stage in class A ? How is PSRR ?

5th April 2006, 07:00 PM	#6
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Voltage gain ? Really ?

5th April 2006, 07:09 PM	#7
vuki diyAudio Member Join Date: Jun 2002 Location: zagreb, croatia	@darkfenriz Ic of output hexfets is 200mA I don't know PSRR, but with 350mVpp at output PS there is only noise on speaker output and absolutely no hum&noise to be heard on 94dB/W/m sensitive Tannoys. @Upupa Epops Voltage gain. Really.

5th April 2006, 07:22 PM	#9
vuki diyAudio Member Join Date: Jun 2002 Location: zagreb, croatia	@mlloyd Yes, something like that. Jim Strickland is mentioned in the text as you have maybe seen. It works nice with hexfets, but maybe it would sound even better with lfets?

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