Is this why the VAS transformer is normally needed?
In the above diagram is the LM329 reg adjustment leg attached to R6 & R7, not clear to my eyes. Is BD139 /140 not a better option?
Thanks
The way of DIY Audio seems to be to talk in riddles
https://www.analog.com/media/en/technical-documentation/data-sheets/129329fd.pdf
The 3 pins are clearly shown on page 6, although one of which isn't used
https://www.analog.com/media/en/technical-documentation/data-sheets/129329fd.pdf
The 3 pins are clearly shown on page 6, although one of which isn't used
Last edited:
diyAudio members drive the M2 output stage with a transformer, because that's what Nelson Pass did in the original design
Official M2 Schematic (link)
and some people feel "if it's good enough for Nelson Pass then it's good enough for me", while others think "there must be something sonically wonderful about that transformer or else Nelson Pass wouldn't have used it. So I will assume the sound improves when the transformer is in place, therefore it's a good idea for me to use it too".
Official M2 Schematic (link)
and some people feel "if it's good enough for Nelson Pass then it's good enough for me", while others think "there must be something sonically wonderful about that transformer or else Nelson Pass wouldn't have used it. So I will assume the sound improves when the transformer is in place, therefore it's a good idea for me to use it too".
As Mark J is indicating, the sound of the M2(x) is intimately dependent on the use of the Edcor signal transformer. An Edcor driven by an OPA551 sounds wonderful and tonally well balanced.
And the M2x requires careful construction to avoid those smaller transformers from picking up hum from the main power transformer(s). Trade-offs…
And the M2x requires careful construction to avoid those smaller transformers from picking up hum from the main power transformer(s). Trade-offs…
It does describe the project, although not properly. The title should say something like : 'An investigation into running the M2OPS in class A/B'.
Seems like there are very few on this thread with English as their first language
The amp that has grown out of this study needs a new name. It's not just an M2OPS as VAS has been added in the form of various OpAmps and local + global feedback implemented (which is not mixed).
Good luck / Happy listening all, I'm off to further fettle my LuDEF
Seems like there are very few on this thread with English as their first language
The amp that has grown out of this study needs a new name. It's not just an M2OPS as VAS has been added in the form of various OpAmps and local + global feedback implemented (which is not mixed).
Good luck / Happy listening all, I'm off to further fettle my LuDEF
Mark, you are wrong about people using a transformer because Mr Pass did, I like diy because it affords me the opportunity to try different topologies and hear for myself what it sounds like. I really appreciate projects like this because it is different, Patrick is competent so I know it will work and it won’t break the bank to give it a try and see how it sounds, as far as the name goes who cares, Schitt Audio is a funky name and they seem to be doing pretty well.
Bill
Bill
There are lots of fun ways to tweak the M2 available to DIY enthusiasts. I have tried reducing the Source resistors to 1% precision 0.45 Ohm and boosting the current through the optocoupler with positive listening results.
As with other Pass designed amps, the M2 may also benefit from increasing the bias current through though output Mosfets. My tweaks did this as well.
As with other Pass designed amps, the M2 may also benefit from increasing the bias current through though output Mosfets. My tweaks did this as well.