Babelfish M2/SEF amp

[Zen Mod]

Babelfish M2/SEF amp (yup , S means Schade)

Another funny pair , for your fun , amusement and joy

First remark - it's easy to convert your existing M2 to SEF amp ..... see yourself

Anyway , to start with Babelfish M2 - practically nothing new under the Sun , everything you're going to see it is familiar ; so , that one was trivial to make and test.

Practically - same approach as with Babelfish M25/SissySIT , sans Halls in rails ; difference vs. Papa's M2 are:

- tiny buggers (2SK2145BL) input JFet buffer , or T092 Toshibas , or any decent T092 N channel JFets ; xconductance conduct how many are going to be used

- with this pcb , one can use Edcor or Jensen or Cinemag Iron ; all well known candidates

- for all tests Iq set at 1A8 , while Papa's original was more sissy in that department

 

[Zen Mod]

Babelfish M2, hard facts, 8R load

each pic is having own capture , so ...

Edcor 600:15k used , in all tests

25W graph missing - my EMU1212 based setup is not having enough cojones for that , was lazy to add gain block

Papa's original THD graph for comparison

 

[Zen Mod]

Babelfish M2, hard facts, 4R load

as titled

 

[Zen Mod]

Now more fun one - SEF amp

SEF , as short for Schade Enhanced Follower ;

refer to Papa's DEF amp for idea ...... while entire world is grasping for Symmetry , Mithrandir is deliberately seeking Asymmetry ...... from various reasons



same pcb , same everything , difference vs. Babelfish M2 - circled in red

 

[Zen Mod]

SEF amp, hard facts, 8R load

as titled

 

[Zen Mod]

SEF amp, hard facts, 4R load

as titled

 

[Zen Mod]

SEF amp , Sugar iteration

When you err, err mellower you can

difference being just Schade resistor value - 6K2 instead of 3K3 , as in previous- so called SEF Final

 

[Zen Mod]

SEF Sugar amp, hard facts, 8R load

as titled

 

[Zen Mod]

SEF Sugar amp, hard facts, 4R load

as titled

 

[Zen Mod]

Catch 22 , as if there is ever need to claim existence of one

SEF Sugar iteration , same applies to SEF Final but in much lesser degree - is not Ruthless Party Behemoth ....... from simple fact - when being asked to reproduce substantial level of sine wave for prolonged time , simple biasing mechanismus can't cope , and result is decreasing standing current

of course , regular music isn't sine wave , nor DC , but don't say I didn't warn you

SEF Sugar working in 4R load will suffer most , same with 8R load will suffer less

SEF FInal working in 4R will suffer much less , same working in 8R load will suffer even less

Babelfish M2 is same as regular M2 in that department , but be warned that even these two aren't blameless ....... but we all know what's difference between decent FW format amp and RPB ; if you want one - go buy PL Beastie

as comparison with SEF Sugar - attached measurements of EAR 859 ; as always - ignore weed generally (not just on graphs ) , ignore everything left of 1K

 

[Zen Mod]

few funny pics more

as titled

 

[indra1]

Suspecting positive D2 phase, perhaps you want to confirm with DiAna?

 

[Zen Mod]

can't - got EMU1212 with one channel fishy , so not able to make any test asking for dual channel

choice is simple - put everything aside and repair EMU , or have fun with new toys and ignore that channel

need to invest some time to resort to QA400 I got few months ago , but sorta hesitating.... either manual is lacking in some areas or thingy (software) isn't made to cover all that

I know later one (410?) can work in conjunction with other software , but this one is sorta orphaned

edit: SEF FInal sim sshot attached

 

[indra1]

DefiSit has the SIT on the N side and has neg phase D2. I suspect the Schade R (R16) should be on the N side for neg phase.

 

[Zen Mod]

you're certainly right, as usual

.....output node arrangement , when we flip that and position of Schade-d mosfet , THD raise up for some 6db or so , what I measured in vivo , few days ago , to check what sim predicted

dunno , probably xconductances , I mean difference between N and P are culprit

it's easy to flip speaker phase , anyway

 

[indra1]

Allrighty.

 

[Zen Mod]

is it so scary?

 

[Zen Mod]

no one yet tried converting his M2 to SEF ?



it's easy - inserting just one resistor and moving LS output wire to other place , with some slight readjust ....

 

[Ylab]

Well.. I want to try it ! But noob questions : what kind of difference in sound quality can we expect between the original and sef? And : the mod to sef is ok on the original schematic too? I know there’s no big difference between your’s and original but asking anyway to be sure.

Hubert

 

[Zen Mod]

OK , I'll post tonight original schm with edit to SEF

you can expect little more sugar and - what's most important , you can set it to your own liking, simply trying few values for one tiny resistor