SemiSouth power Jfets .......... FW J2

[Zen Mod]

anyway - be happy - input Jfets are still pentode-like ........ so nothing wrong with proper pentode even in output :roflyou remember - M2 isn't so bad amp , even with plain Mosfets in source follower configuration

[generg]

O.K. thank you both for your explanations and hints.......! :)and I am afraid my cd-player is also pentode like so I have no chance......... :Pmaybe one point is important, the Mufollower is normally more push pull than single ended.....

[Zen Mod]

Gyou don't need these two 0R68 resitorsjust bridge them ( short) and re-set Iq and offsetthat way you'll have even less Mu

[generg]

Gyou don't need these two 0R68 resitorsjust bridge them ( short) and re-set Iq and offsetthat way you'll have even less Mu

every suggestion welcomeI will try and hear....

[Zen Mod]

as always - you're more than welcome

[generg]

as always - you're more than welcome

Gyou don't need these two 0R68 resitorsjust bridge them ( short) and re-set Iq and offsetthat way you'll have even less Mu

o.k. I bridged the 0R68 resistors and ....now in my system the sound gets even more precise but a bit too hard and less "panoramique"so I returned to the former constellation..incredible what o.34 Ohm changes.......!next tries come......

[Zen Mod]

[ozzy]

10mm za MF (15mm za R32)23mm za 3Wto su sve dimenzije direktno iz lib , s tim sto sam maltene sve korigovao velicinu padspcb je 80x110

Od Tea-bega kupio Semisouth-e ,hvala na podrsciZoran

[Zen Mod]

sluzimo narodu !

[generg]

update for all BJ2 fans and builders....

I occupied over 6 weeks with the sound of my BJ2 compared to an original FW J2........

it was a hard time...... I tried all.........................................................................................!

I even ordered a pair of R125 because the FW J2 had them, from a guy at Miami, but,

no the input was the place!

To make it very short............................ to come near to 80% of the lovely sound of J2 original.......

I had to take one pair of 2SJ109 in the input. ( I know it is a compromise)

Every try to set in, even very closely matched quadrupels of J74, and not so closely matched two 2SJ109 in parallel,

(I spend some money to buy them in Germany and I had to sent back some because they were sold defect.....)

................gave a more muddy sound.

So if you want to experiment with your BJ2 and you still have a pair of good old 2SJ109 give it a try.

After six weeks it is a happy day today!

[Zen Mod]

:cheers:

[Mikorist]

[generg]

:cheers:

I wish you could hear it!

[generg]

Just for fun I changed today the one 2SJ109 BL in the BJ2 to a pair of closely matched 9610. (from diytech 0,01V), Zm will laugh, "change your lousy BJ2 back to an Aleph 3"My intention was to drive them with the 20mA the two 2SJ109 or four J74 get normally, and I was eager to hear if the much higher transconductance would do something to the sound.sound is (as often remarked) darker, a bit more punch in the lower bass, but much, much less detailed and airy than the J-Jfets.So back to one 2SJ109 per channel again.....Can anybody comment if going to 15mA with one 2SJ109 device would be to much, Euvl did even heatsinking the 2SJ109 in former times when they were still more in use....

[Zen Mod]

Babelfish J2 or "origigi" J2 schematic ?by 15mA you mean setting CCS in tail to 15mA , so 7,5mA per side ?

[Sipi]

....Can anybody comment if going to 15mA with one 2SJ109 device would be to much...

Depends on Idss of each JFET inside j109. If you set the Id higher than Idss you'll put JFET in dangerous zone where Ig starts to flow and JFET starts to act differently. Don't go over 90% of Idss - or your panorama will be lost, and JFETs will follow....

[generg]

Babelfish J2 or "origigi" J2 schematic ?by 15mA you mean setting CCS in tail to 15mA , so 7,5mA per side ?

yes 7,5mA per side.....and I confess "origigi"

[generg]

Depends on Idss of each JFET inside j109. If you set the Id higher than Idss you'll put JFET in dangerous zone where Ig starts to flow and JFET starts to act differently. Don't go over 90% of Idss - or your panorama will be lost, and JFETs will follow....

thanks Sipi for valuable hints.... and I take care of the panorama! :oke:and I will give the 2j313 a try instead of old 9610

[Zen Mod]

yes 7,5mA per side.....and I confess "origigi"

Sipi already tell yain case that you have some 2SJ109V , it will be possible , but non cascoded origigi is still nono , regarding dissipation in that caseyou can always use J271 ( matched ) , thinkin' about Idss and Vgs ratio , but dissipation is still issue even with themno free sonic lunchbe sure that you really hear as difference between your's and Pa's iterationI know what he would say .........

[generg]

Sipi already tell yain case that you have some 2SJ109V , it will be possible , but non cascoded origigi is still nono , regarding dissipation in that caseyou can always use J271 ( matched ) , thinkin' about Idss and Vgs ratio , but dissipation is still issue even with themno free sonic lunchbe sure that you really hear as difference between your's and Pa's iterationI know what he would say .........

Pa is of course in the sweet spot......me not....thanks Zen Mod

[Sipi]

... and I will give the 2j313 a try instead of old 9610

I doubt that it will be an upgrade at such a low current, but you can give it a try...If we were talking about 300-600mA than you would clearly hear the difference, but as input devices - Ich glaube nicht...

[generg]

I doubt that it will be an upgrade at such a low current, but you can give it a try...If we were talking about 300-600mA than you would clearly hear the difference, but as input devices - Ich glaube nicht...

Danke!