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
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
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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power-on and power-off behavior is same polite and nice and gorgeous as ZM Might itself , so there is no any surprise 
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
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
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you're not going to confuse me ..... I will post everything what I intended
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 .......
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
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
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
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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I've been waiting to see the details, super fugly
I would be interested in your impression with both IRF & SJEP.
Will you scratch that itch?
I would be interested in your impression with both IRF & SJEP.
Will you scratch that itch?
as I said , Semisouth in bottom is on schedule in next few days , but on top - not likely
I'm more than familiar with how J2 is singing , so no need to evaluate that again , even if this one is having lower THD than original (both now and in case of Semisouths in output) - there is same THD spectra ........ and all of my speakers are so easy to drive , thus difference in THD would sneak unnoticed anyway
I know that Pa is successfully using battery of some gizmo ( shunt resistors or what) , adding it to his Tanns , so he can evaluate amplifiers of various power levels , same as presenting easier or heavier load to amp , while listening to direct result on Tanns ...... however , that type of test is ......... too much work for poor ZM ....... I'm content with plain "pleasure first" long term testing , as Papa Sigfried used to say
I'm more than familiar with how J2 is singing , so no need to evaluate that again , even if this one is having lower THD than original (both now and in case of Semisouths in output) - there is same THD spectra ........ and all of my speakers are so easy to drive , thus difference in THD would sneak unnoticed anyway
I know that Pa is successfully using battery of some gizmo ( shunt resistors or what) , adding it to his Tanns , so he can evaluate amplifiers of various power levels , same as presenting easier or heavier load to amp , while listening to direct result on Tanns ...... however , that type of test is ......... too much work for poor ZM ....... I'm content with plain "pleasure first" long term testing , as Papa Sigfried used to say
I forgot to say tnx!
...... Using the 2SK2145BL has much appeal
certainly
as being proven in Iron Pumpkins , SissySIT and Babelfish M25 , I'm expecting nothing lesser performance here
besides , I know for one major manufacturer , using them in phono section/preamp
besides besides - they're of current Toshiba production , hope will stay that ...... and I've just got 1K of them
