Official M2 schematic

[Cinco]

@Cinco

I noticed your using dBFS for spectrum scaling in ARTA...is there a reason. I've always used dBV.

Oh, I never thought about changing the scaling. Next time I do some spectrum measurements I'll explore that option.

Thanks for pointing that out Kevin.

 

[generg]

Hi Cinco, and you cannot work with asio4all?

https://www.asio4all.org/

 

[Cinco]

I tried asio4all too. Maybe I gave up too soon tinkering with that generic driver.

Ah computers, you can't live with them and you can't live without them... kind of like women.

 

[juanitox]

In my M2 clone, I added a 1R3 ohm resisitors in parallel with the original 0R47 source resistors to lower them to 0R345.
I simply removed them from the R2 positions and zeroed the output offset to try favoring the P-ch. It raised H2 to about the same level as H3 as seen in the measured spectrum.
I like the sound, more relaxed and spacious was my impression. I'll leave it like this for a while.
I need to get a twin-T notch filter built to look at the residual distortion in real time.

Cinco

something my dumb brain don't understand , do you set R2 to 0R and R1 to 0.35 ?

 

[Cinco]

something my dumb brain don't understand , do you set R2 to 0R and R1 to 0.35 ?

Oops... source resistors in Nelson's M2 schematic are R13 and R14 (see first post in thread).

So the mod is:

R13 = 0.47
R14 = 0.345 (1.3 paralleled with 0.47)

My Q1 is 2SK1530 and Q2 is 2SJ201

See post #3544 for my simulation schematic where source Rs are R1 and R2.

 

[juanitox]

So the mod is:

R13 = 0.47
R14 = 0.345 (1.3 paralleled with 0.47)

thanks i will try it has i have some 5W 0.33R left..

 

[Vunce]

Cinco,
Have you tried IRFP mosfets before the Toshiba’s? Just wondering if the Shiba’s are a noticeable difference?
Thanks.

 

[juanitox]

so i 'v done the easy 5min mod , DC offset put to 0 . it is not night and day but a subtle change in the tone more tubey you can call it , as i don't have distorsion meter all i can say is that it rounded a little the crisp berrylium tweeter that i have or blurr it a little if you want . fun to try but don't know yet if i will keep it ( i use stock IRFP92140 and 2SJ74 2KS70 front end

 

[Cinco]

Cinco,
Have you tried IRFP mosfets before the Toshiba’s? Just wondering if the Shiba’s are a noticeable difference?
Thanks.

No, just built with the Toshibas. Couldn't get any Harris IRFP240 at the time and Fairchild, like in stock Firstwatt, unavailable/obsolete too. I could get the Toshibas though.

The nice thing about these Toshibas is the bigger TO-263 package and read good things about them.

Probably very subtle differenes since these are in common drain mode.

 

[Vunce]

Thanks Cinco.
Mine has Harris semi’s installed already, but I have the larger Toshiba’s also in my stash. When time allows I will try the R14 mod.

 

[Zen Mod]

from top of my head, if you left upper one slower/lower xconductance ( leaving 0R47 up, decreasing lower source resistor), you'll end up with dominant 2nd, neg phase

same scenario as with DEFiSIT

 

[juanitox]

make the ZM shade M2 mod this afternoon and i like it very much even if it cost me a lot to say that knowing who is the author

 

[Zen Mod]

 

[flocchini]

I should try the Schade mod to my Toshiba version.
I have done "stock" M2, Schaded stock M2 and Toshiba version - can't remember why I did not take the Toshiba to the next level. I, myself ,clearly favored Schaded stock over stock

Stock is the IRFP version with Harris 9240.

 

[Vunce]

Looks like there will be more tweaking to the ‘ole M2 to be done. Flocchini’s mention of Schaded M2 got me going and I found ZM’s info on what to cut and stitch during surgery. Nice!

 

[codyt]

Looks like there will be more tweaking to the ‘ole M2 to be done. Flocchini’s mention of Schaded M2 got me going and I found ZM’s info on what to cut and stitch during surgery. Nice!

Vunce, do you have a link you could share for the schade operation steps? My interneting game is off today…

 

[flocchini]

Cody
check this out
https://www.diyaudio.com/community/threads/babelfish-m2-sef-amp.346819/

 

[Vunce]

Yup, that it! Specifically post#23
Since building ra7’s SCG preamp, I’m liking this Schade thing. I’m always late to the game though…

 

[codyt]

Thanks guys!

 

[Cinco]

Hmm... the Schade mod, I'll look into that... when the weather is cooler, we're going through a heat wave here in Texas.

I haven't turned on my M2 in a while. 140W and 104°F don't go well together.