Many here have jumped onto the M2 band wagen, but few have paid attention to the opto-biased output stage in detail.
We have, for example, discussed the use of different MOSFET pairs.
https://www.diyaudio.com/community/threads/complementary-power-mosfets.378024/post-6889027
Nelson has previously dropped some hints that it works well also in Class A/B.
But how ?
This is an attempt to analyse precisely that, using LT Spice simulations.
It is a waste, IMHO, not to use this clever OPS design in more applications.
For example, how about in a WHAMMY Power amp ?
Patrick
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Only an attempt to encourage people to understand how things work,
rather than just blindly copy and paste.
Patrick
rather than just blindly copy and paste.
Patrick
I think I recall reading in Nelson's thread "Official M2 Schematic," that he said his intended purpose of the three 1N4148 diodes was to give a smoother recovery from output voltage clipping when driving normal 8 ohm loads. The Pchannel side has a different number of diodes than the Nchannel side, intentionally.
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If any part of my analysis is in error, I am sure Nelson will care to put it right.
Cheers,
Patrick
Cheers,
Patrick
Assuming Nelson would agree, and someone has a serious interest :
I shall make available the Gerber of the above PCB with an integrated DIP8 opamp powered by the same supply.
So then you can build a WHAMMY power amp and start playing with opamp and MOSFET types.
But Nelson has to approve first.
Patrick
I shall make available the Gerber of the above PCB with an integrated DIP8 opamp powered by the same supply.
So then you can build a WHAMMY power amp and start playing with opamp and MOSFET types.
But Nelson has to approve first.
Patrick
Patrick,
Although I can not (yet) fully appreciate the subtleties of the circuits, your posts and findings always give me a lot to consider and to learn.
Thanks for sharing!
What opamp tp choose from other than OPA551 for a power WHAMMY ?
For +/-24V rails, OPA604 is well known.
ADA4098 will just make +/-25V.
Above +/-25V, choice is rather limited.
I found ADA4700, which is quite similar to OPA55x but can go as high as +/-50V.
Other candidates -- LTC2057HV, and perhaps ADA4522.
Patrick
For +/-24V rails, OPA604 is well known.
ADA4098 will just make +/-25V.
Above +/-25V, choice is rather limited.
I found ADA4700, which is quite similar to OPA55x but can go as high as +/-50V.
Other candidates -- LTC2057HV, and perhaps ADA4522.
Patrick
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The M2 OPS is a complmentary push-pull MOSFET output buffer.
The original M2 has a JFET frontend with no global feedback.
So, for me, a fitting discrete frontend is either an all-FET VAS with no global feedback, e.g our own HAGS :
https://www.diyaudio.com/community/...a-zgf-headphone-amplifier.225577/post-3395149
or if it has to come from Pass, an F5-Pre (single ended version).
But a power WHAMMY is an easy starting point.
Cheers,
Patrick
The original M2 has a JFET frontend with no global feedback.
So, for me, a fitting discrete frontend is either an all-FET VAS with no global feedback, e.g our own HAGS :
https://www.diyaudio.com/community/...a-zgf-headphone-amplifier.225577/post-3395149
or if it has to come from Pass, an F5-Pre (single ended version).
But a power WHAMMY is an easy starting point.
Cheers,
Patrick
Recently there is an IXTH26P20P that seems to complement IRFP250 close enough with somewhat not so painful pricing. 🙂
An experienced power amp builder has kindly promised to do Alpha Test.
Opamp has differential inputs.
Patrick
Opamp has differential inputs.
Patrick
Since Mark mentioned a discrete frontend in post #10, maybe it's good to show an example.
Not fully optimised yet, but in principle it works.
But one at a time.
Patrick
Not fully optimised yet, but in principle it works.
But one at a time.
Patrick
Not toasted.
Just some no-name resistors of the right value I have lying around.
Good enough for alpha test.
Patrick
Just some no-name resistors of the right value I have lying around.
Good enough for alpha test.
Patrick
I was asked to post a schematics for the opamp front-end power amp.
This is still pending alpha test, so draft only. Not proven.
Patrick
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This is still pending alpha test, so draft only. Not proven.
Patrick
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