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Babelfish ᄅſ

Seeing some stones turned lately , I simply couldn't resist Babelfishing urge......

Though , as I already did some mild Babelfishing of our dear and beloved J2 , logically that this time I needed to do something ...... completely different :beach:

due to constant demand and popularity mainly on Far and less Far East , schematic of original FW J2 is still generally unknown or - better said - none of circulating DIY schematics weren't blessed by Mighty Pa (pleonasm here , Pa is Mighty by 42)

few things we all know , and these few things are good and plenty enough for basic postulates of variation of Jazz Standard smile.gif

Basic premises :

1. possibility of incorporating less critical ( for acquire) JFets for input LTP, by choice and must possible use of 1+1 , or 2+2 in same ;

2. possibility of incorporating various output devices , of lesser and bigger rarity and/or price

2a. possibility to avoid tearfully matched parts (outputs and other ) , while still easy settable both output offset and OS Iq in broad range of values

I got it all ........ how:

1.easy peasy - use N channel JFets (choice is waste!) , lead them (currents) back to lower output gate via simple and effective current mirror ..... put few cascodes here and there to pet both JFets and fine CM parts (tiny JFets are always grateful for that, but high beta small BJTs like that too) ....... and while we are there - why not using fine emiter follower between CM final end and lower output's gate .......

2. OK - trimpot in front of lower output's gate is trivial ; second part is feeding Optocoupler with CCS , with some current spare , and routing the same in loop around ( in parallel practically) said optocoupler , so we can set Iq of upper mosfet with ease and in broad range

2a.partly already covered above , just to add that output devices can be plain old IRFP150 , same as any boutique part you already have , value of Ugs is irrelevant - easily covered with change of ,say, two resistors

'nuff talking , time for schm (read notes on left side):



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then yesterday and today I put it in T-Bed , and did some final tweaking of some values

for start , they're equipped with 1+1 Toshiba 2SK170BL in FE , Iq set at 10mA (5mA per tiny) and pair of goodoldsturdy IRFP150 are in OS



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power-on and power-off behavior is same polite and nice and gorgeous as ZM Might itself , so there is no any surprise :rofl:

now some measurements ....... being lazy and impatient , I didn't use recently acquired Quantasylum ( older , SE one ) but my old funny interface box and EMU1212 in PC , software is ARTA

Iq set at 1A8 , rails more or less exactly 25Vdc

first set of measurements at 8R load ; each graph is titled at bottom ; as always with my T-Bed and test setup - ignore everything left of 1K ...... plastic box for interface , old and crummy PSU incorporated in T-Bed blahblah








Babelfish J2 IRFP Freq. response 8R load.png

Babelfish J2 25W 8R IRFP.png

Babelfish J2 10W 8R IRFP.png

Babelfish J2 20W 8R IRFP.png

Babelfish J2 1W 8R IRFP.png

Babelfish J2 5W 8R IRFP.png

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so , set of measurements at 4R load , same Iq and rails as for previous test

btw. I decided that clipping is at 1% THD , and that's exactly at 21W9 ...... though - it was tricky to set level pot to exact value (THD rising rapidly at that level!!) pretty good , if you ask Mighty Moi






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that's it , practically , for today

tomorrow , I hope - same tests with 2+2 2SK2145BL in LTP , LTP current programmed to 5mA per tiny (20mA overall) , so it'll be nice and cozy 50mW for each

will up a little current through EF , to be closer to 20mA than 15mA ........

after that will most probably leave 2SK2145BL in situ ( not crazy enough to remove them ) and try same battery of test with SJEP120R100whatever in lower output position .... will leave mighty IRFP150 in position of upper one ( mu or what-follower) , can't see what Semisouth could do better in same role ....

ZM , Happy Camper this evening :Viannen_loungelizard:

edit: Shade game not promptly ; first need to evaluate this one in long term listening test , to be able to value Shade after ..... I know it'll measure worse , but it could happen that my ears are happier with worse

after all , I'm listening regularly one of crappiest amps by measurements and enjoying immensely

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eto, ovaj nema ono ckupo gvozdje i nema one ckupe current sense chips i nema one ckupe tokine




sinko,ovaj sinko - imas li ti ostali hardware ...... to uvek kosta isto .......

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Ma to za u arhivu. Začas mi ćune da se napakuje Babel, ako duša ište. Obećo sam sebi, jerbo sam prodo onog.

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as I promised (to my self , in first place ) , today I did change pair of 2SK170BL in input LTP position , for 2+2 pcs of 2SK2145BL

previous idea was to up LTP current from 10mA to 20mA , resulting in healthy 50mW per tiny bugger , but later decided to try Papa's approach , of doubling input JFets , while Iq keeping at same level as for single pair

that way - due to increased combined xconductance , OLG is rising , and without change of NFB network , NFB is rising , so we can expect lower level of THD

is it good thing or not - sound wise , who cares ...... I have all the time left to humanity to try that ...... later :smesna:



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now the real stuff ...... I mean - hard data

(observe how I finally switched two cells On , so removed confusing unnecessary part of graph :)  )

each graph is having title in bottom

so , THD indeed goes down , comparing to yesterdays measurements , with pair of Toshiba 2SK170BL in FE

load 8R

Babelfish J2 Piccolo JFets 1W 8R IRFP.png

Babelfish J2 Piccolo JFets 5W 8R IRFP.png

Babelfish J2 Piccolo JFets 10W 8R IRFP.png

Babelfish J2 Piccolo JFets 20W 8R IRFP.png

Babelfish J2 Piccolo JFets 25W 8R IRFP.png

Babelfish J2 Piccolo JFets 8R IRFP Freq. response.png

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