The M2 Output Stage in Class A/B, and maybe a Power WHAMMY?

setup and feeling on my very good Hifi chain and KEF R11;
Rail 23,25V and 1,55A (limit 36W/ch); 4U/400; OPA604AP; local Feedback

These are my personally feelings and not more!
compared to my F5 (also Fairchilds):

cons:
womens voices could be a little bit warmer, slightly more
slightly more texture in the very high end freq.
a lack of lower end "meat", -not punch and pressure

pros:
M2OPs is faster without any fog, any
very thrilling and a touch more decay==> so it is touch more air all around the actors
F5 is playing in a large triangle -M2OPs sounds in a bit smaller but very deep trapezoid
stage and positioning is very clear and no mixing in positioning of actors in sound

feels like: F5 is more Class A "layback"- M2OPS is more like Class AB-"lets do this"
very good punch and pressure

Thanks Patrick for this project. 😍

next: OP-amp rolling😊; got OPA627BP!! OPA551 and AD828
 
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You should try mixed feedback first.
Will give you much more control, tighter bass.
Toshiba also slightly more than Fairchild.

627 and 828 are not specified for+/-24V.
604 is probably a better choice than 551.
But have a comparison by all means.

If you want the absolutely best device, I would say 2SK1530/2SJ201.
But my taste only.


Patrick
 
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thanks for feedback --who has some 2SK1530/2SJ201 for me??🙂
topic 627, 828 --will try to make a adaptor pcb to cut off the voltage.....

also LT1793 on the way

I dont need more control---more meat means for me still more amplification in very low end- more "fatness"
 
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Thanks 🙂.
The power supply is a Micro-Audio SMPS500-CLA.
Thanks @Vunce , what's the little fan and the control board? Looks like you also used their extra capacitor boards..Did you go CRC? (I can't see the 'R', value?)

When was the decision made to put a pair of physically large lytic caps on the OPS boards? IME this is a great way to inject radiated noise from the mains transformer. Why are they needed?

That SMPSU has a secondary 12V output - could power the front end OpAmp

.. And what are the small blue/red wires for, showing at the corners of the cap boards?

Thanks all
 
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Hi. I was looking to try different amounts of mixed feedback and would appreciate some guidance on how the resistor values are chosen/calculated. In the example of applying 20db global to local, the values were 47K and 470K. Is there some in-between calculation steps that might help me understand how those amounts were arrived at?
 
Thanks @Vunce , what's the little fan and the control board? Looks like you also used their extra capacitor boards..Did you go CRC? (I can't see the 'R', value?)

When was the decision made to put a pair of physically large lytic caps on the OPS boards? IME this is a great way to inject radiated noise from the mains transformer. Why are they needed?

That SMPSU has a secondary 12V output - could power the front end OpAmp

.. And what are the small blue/red wires for, showing at the corners of the cap boards?

Thanks all

  • Noctua NF-A4X10 PWM fan
  • PWM control board with temp sensor to adjust fan speed
  • RCC (0R22, 10000uF, 10000uF) configuration for each cap board
  • Small gauge red/blue wire harnesses are power for future speaker DC protection boards
 
setup and feeling on my very good Hifi chain and KEF R11;
Rail 23,25V and 1,55A (limit 36W/ch); 4U/400; OPA604AP; local Feedback

These are my personally feelings and not more!
compared to my F5 (also Fairchilds):

cons:
womens voices could be a little bit warmer, slightly more
slightly more texture in the very high end freq.
a lack of lower end "meat", -not punch and pressure

pros:
M2OPs is faster without any fog, any
very thrilling and a touch more decay==> so it is touch more air all around the actors
F5 is playing in a large triangle -M2OPs sounds in a bit smaller but very deep trapezoid
stage and positioning is very clear and no mixing in positioning of actors in sound

feels like: F5 is more Class A "layback"- M2OPS is more like Class AB-"lets do this"
very good punch and pressure

Thanks Patrick for this project. 😍

next: OP-amp rolling😊; got OPA627BP!! OPA551 and AD828
to clarify:
this was an impression after 15 hours burn in, it could be doing better after 50 h running............report will we follow up