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Babelfish M25 R.2/SET amp

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Yup, improved iteration of previously made Babelfish M25

Who remembers - 'twas bstrdzd FW M2 with implementation of XA25 main trick - Square Law arrangement of OS mosfets, in simpler words - mosfets in OS put to work without source resistors

Result - looooow THD of OS, but main difference being broader A Class envelope , most prominent in context of 4R load - where regular M2 is KlunK!ing around 12-13W, while B. M25 doing the same around 40W ...... rest to max being KlunK!

This pcb made for easy implementation of Schade arrangement for one OS mosfet, arbitrary chosen to do that with lower one, even if that is making some problems with choice of small mosfet for source follower/level shifter ....... I need one with lower Ugs treshold ( it adds to Schaded mosfet Igs) , and P channel small mosfets with that are scarce, somewhat

Anyway, find enclosed both schmtcs, full one ( all parts on pcb populated) for SET (Schade Enhanced Thingie) and second - few parts omitted - for Babelfish M25 R.2

note - slight tweaks of THD Spectra, for one's Golden Ears, possible with change of output mosfets - down one can use either IRFP9140 or 9240, up can go IRFP240 or 150

about that later

reminder - extensive ( if crude) explanation of biasing mechanismus posted in LuDEF thread , posts #32-#37, LuDEF

Today - all files for Babelfish M25 R.2 ; anyway - read captions - each file is properly named and have caption

Babelfish M25 R.2 schematic.png


SET schm.png

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How it sounds?

Bloody, Jolly good - as your regular M2 ....... Berserked 

on eeeny speakers ( not demanding anything from amp) - maybe just little cleaner; if you have speakers, you not even thinking being adequate for 25W A Class amp, this is A Class amp to change your thinking

Have few ( of previous incarnation - Hall chips in biasing mech.) driving Dynaudio Contours, one is driving Guy tall Triangles with trio of 8" woofers per side

Hope tomorrow to post same files for SET amp

observe that I implemented 2 veeeery secret tricks, how to make amp muchmuch better than schm itself is promissing - I've put one strategically placed Blue LED (Papa's trick) and Cinemags put to sing are my Uncle Bubba Bob's .... so World is my Oyster  



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10 minutes ago, Mikorist said:

Mere unimeri :sarcastic_hand::hyper:

nista ja ne merim, samo na uvce se podesava


1 minute ago, zerowaf said:

Oš kasti, da spojim na njega poklopac od limene kante za smeće da bi i to prosviralo?   :D


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lepo što je sve na istoj bazi pa uz malo pažljivog planiranja pre izrade moglo bi se čak napraviti i svičabilno između M25 i SET uz naravno ponovno biasovanje

čak kad se ima slobodnih par sati može da se prepravi u Old Soul ili Sissy, uz malo više vratolomija i u LuDEF

lepo, lepo :crazyrocker::clapping::worship:

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-Honey, I Shrunk the Kids!
...... no, wrong movie.....
-Honey, I Shrunk the SITs!
.....no, there is no such movie....
-Honey, I created a Monster!
.....no, there is no such movie....
-Honey, I am The Monster!
...that's the movie which must exist!



SET schm.png

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name of the game was to create SIT amp for Greedy Boyz Hordes ......

naah, I don't care for Hordes, I have all the fun :Viannen_loungelizard:

logical thing would be to put emulated SIT in same position as in DEFiSIT/SissySIT, which is positive rail; from some reasons I tried in simulations to put it down (lower rail), then realized that that approach is resulting in difficulties - choice of small P channel mosfets for Source follower/level shifter, having low threshold Ugs is much smaller than counterparts in N polarity

however, me being stubborn as I am, stayed with P channel .......

SF Ugs is important, beacuse it is additive to feed point of Schaded mosfet, which in this case we have as -3V8 (ref to output) , then Ugs of TP2640, so resulting biasing voltage at TP2640 gate is around -5V4, ref to output

in same time , Ugs of upper mosfet is +4V42, which means that resistances from rails to adjacent gates are still pretty symmetrical

one of interesting things - of all lately seen amps, only this one is having same current distribution of output parts as real DEFiSIT is having - up to clipping point of more active part, parts are working in antiphase , fighting each other..... and only at and after clipping, lesser acting part ( one with lesser xconductance) is helping other one

see attached - graph from sim, but confirmed in vivo....... though, easier to post this than capturing scope screen ..... counting on fact that I have a scope from Lee De Forest time, but before triode invention 

sim shown from output sine of around 20Vpp @ 8R load

biggest sine - upper mosfet current
smaller sine - current through load
smallest sine - Schaded mosfet current

Current distribution.png

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