My MOSFET amplifier designed for music.

Mooly · 10th March 2008, 11:05 AM

Hi, Well after having seen all the amazing projects and designs you guys have come up with I thought I would share my design on these pages. First and foremost this was designed for music reproduction in a domestic setting and without wanting to "hijack" another current thread, YES amplifiers do sound different, that is why I spent so much time in the development of this one. This amp is without doubt "musical" in all the best sense of that term, it's ability to recreate a believable soundstage is absolutely compelling. If anyone is interested in what it looks like and further details there are some piccys in the "Post your solid state pics here" forum. (About post 283) The thinking behind this project draws on the work of the late John Linsley Hood whose designs and thinking I much admired.
Regards Karl

Mooly · 10th March 2008, 11:08 AM

This is the Preamp in outline form (I am only just getting to grips with a PCB Software package) all the original work was hand drawn. The series /shunt switching works brilliantly and give total isolation between inputs. Even with something ridiculous like a 10volt peak/peak squarewave as an input, there is no audible breakthrough even with volume on max.

Tube_Dude · 10th March 2008, 02:50 PM

Hi, Mooly

You don't need R24 and R23...

darkfenriz · 10th March 2008, 03:24 PM

Quote:

Originally posted by Tube_Dude
Hi, Mooly

You don't need R24 and R23...

... and C3

Tube_Dude · 10th March 2008, 03:39 PM

Quote:

Originally posted by darkfenriz

... and C3

Hi Darkfenriz, how are you?

I agree , the servo is "in charge" of taking care of the offset...

Anyway, C3 in the schematic is with the polarity inverted...

Mooly · 10th March 2008, 06:32 PM

Hi Tube_Dude, you know, I wondered that at the time, my reason for including them was to provide more? if thats the right word isolation for the MOSFET's . They do reduce efficiency though. I would like to develop this design further, possibly running the front end (Up to Q3 and Q5) on a higher rail with shunt regulation (Power supply rejection is one area that could be improved).
Darkfenriz, wish I could do away with the electrolytic in the feedback arm, as you say the servo is in charge, but the base voltage of Q1 is around -6volts, so C3 is unfortunately needed (polarity is correct on circuit with about 5 volts across it) . That's the price you pay for using a single ended input stage but one that's well worth it. The TL071 works fine with only a single negative rail in this application, many other Op-Amps won't and would need + & - supply.
Thanks for the input
Karl

jerome69 · 10th March 2008, 07:02 PM

Hello Karl,

Very good !

Regards.

darkfenriz · 10th March 2008, 07:54 PM

I'm fine, Jorge
Just a little overworked, underpaid, bored and lazy last days.
How are you?

darkfenriz · 10th March 2008, 07:57 PM

Molly
the -6V on Q1 base will go up closer to zero if you remove the capacitor, like -1.5V or so...

mikefromaus · 11th March 2008, 08:00 AM

OK now we need someone to design a PCB

.
I have tried designing a few using ExpressPCB but it seems to end up a mess!
I have many of the 2sk1058/j162 waiting for something like this!!

10th March 2008, 02:50 PM	#3
Tube_Dude diyAudio Member Join Date: Mar 2002 Location: Aveiro-Portugal	Hi, Mooly You don't need R24 and R23... __________________ Jorge

11th March 2008, 08:00 AM	#10
mikefromaus diyAudio Member Join Date: Dec 2007	nice OK now we need someone to design a PCB . I have tried designing a few using ExpressPCB but it seems to end up a mess! I have many of the 2sk1058/j162 waiting for something like this!!

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10th March 2008, 06:32 PM	#6
Mooly diyAudio Member Join Date: Sep 2007	Hi Tube_Dude, you know, I wondered that at the time, my reason for including them was to provide more? if thats the right word isolation for the MOSFET's . They do reduce efficiency though. I would like to develop this design further, possibly running the front end (Up to Q3 and Q5) on a higher rail with shunt regulation (Power supply rejection is one area that could be improved). Darkfenriz, wish I could do away with the electrolytic in the feedback arm, as you say the servo is in charge, but the base voltage of Q1 is around -6volts, so C3 is unfortunately needed (polarity is correct on circuit with about 5 volts across it) . That's the price you pay for using a single ended input stage but one that's well worth it. The TL071 works fine with only a single negative rail in this application, many other Op-Amps won't and would need + & - supply. Thanks for the input Karl

10th March 2008, 07:02 PM	#7
jerome69 diyAudio Member Join Date: Feb 2008 Location: Lyon	Hello Karl, Very good ! Regards.

10th March 2008, 07:54 PM	#8
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	I'm fine, Jorge Just a little overworked, underpaid, bored and lazy last days. How are you?

10th March 2008, 07:57 PM	#9
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	Molly the -6V on Q1 base will go up closer to zero if you remove the capacitor, like -1.5V or so...

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