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

[CeeVee]

completed and naked.....

[CeeVee]

Doing what it was made for.....playing sweet music.....thanks again ZM for this HOT amp

[Zen Mod]

Fugly!

[ozzy]

Zen,probao sam First Watt F5 na mojim sirokopojasnim ribonima ( seceno na 400 Hz , 97 Db/Spl ) zvuci sjajno ali malo suvo na srednjem opsegu.Interesuje me teoretski , iako imam B J2 PCB ( a nisu jos kompletirane ) dali B J2 moze da ponudi dovoljno struje shodnoCurrent Source Amplifiers and Sensitive / Full-Range Drivers sto je predocio Pass.Sve ide preko mecovanog trafoa 8 Oma na 0,3 OmaIli treba da se napravi pa vidi.

[Zen Mod]

bitan deo odgovora - J2 zvuci prirodnije od F5 u srednjim i visokimostalo je irelevantno , ako imas interstage

[grau.]

bitan deo odgovora - J2 zvuci prirodnije od F5 u srednjim i visokimostalo je irelevantno , ako imas interstage

jel si slusao u ameriki ili ima neka zrtva ovde koja je to skockala?

[Zen Mod]

jel si slusao u ameriki ili ima neka zrtva ovde koja je to skockala?

sto da slusam u Ameriki kad sam ja skockao ovde pored moje vec legendarne auditivne memorije , F5 i Babelfish J2 sam bas direktno poredio i to i na nezahtevnim i na zahtevnim zvucnicima ....... naravno - visoke rezolucije :buehehe:Nisam nesto trosio limited time u 'merikama za bilo kakve komparativne ujdurme , ali se taj zakljucak moze preneti i iz Papinog i iz Vladinog iskustva .Vlada ima ime za Babelfish J2 - The Amp:rofl:

[ozzy]

Zen,sve je jasnoVeliko hvala

[generg]

Hi everybody, :respect:some news about BJ2....inspired by the SIT discussion and driving the SIT with a CCS i learned a bit more about Mu and CCS, really only a bit....but that does not avoid experimenting.....in the original BJ2 constellation the last recomendation for the resistors around the both Semisouth here in the thread for the source resistor of the upper Semisouth was 2x0,68Ohm parallel or 3x1Ohm. For the drain resistor of the lower SS 2x1 Ohm parallel and 2x0,47 Ohm for the source resistor of the lower SemiS.In this constellation both Semis contribute to the gain and wattage, so you can get 25W at 8 Ohm...Inspired by Nelsons comment on his SITs, that he wanted them speaking "more with one voice" I wanted to reduce the contribution of the upper Semisouth to a degree forming "nearly" a CCS.(I drive Lowther and Tone Tubby (96db) so I do not really need 25W, the half wattage could be sufficient......)I decided to change the arrangement of the drain and source resistors.......1. no source resistor any more for the lower Semisouth........2. but I took the "free" 2x0,47 Ohm and combined them with the 2x1 Ohm in series so I got about 0,75Ohm and put this combined resistors no more at the drain of the lower SemiS, but at the source of the upper SemiS!3. and of course the the former source resistors of the upper SemiS 2x0,68 Ohm (or 3x1 Ohm) got now the new drain resistor of the lower SemiS.result: less wattage but sounds lovely and more panoramique... :guitarplayer: :guitarplayer:of course it is now near to F2J, but you have the opto bias regulation and no cap at the output!really lovely.....if you have a Bj2 running (hello B300!) try it and report if I am wrong......

[Zen Mod]

nice to read you herecan you please just sketch that arrangement ( without rest of circ ) ;I'm not sure that I'm following youin case that you don't have time ( Tai Chi etc. hehe) for shrinking usual Generg's sketch , just send it to me

[generg]

I tried to paint my best.....and Zen Mod correct me If I am wrong with my assumptions, I feel strong today.......I do not want people trying something completely wrong....

[Sipi]

.... more panoramique... :guitarplayer: ....

YEEAH ! :punk:Zum Wohl

[generg]

Hi Sipi, I knew I could count on you when panoramique sound is in the air.......... Now we only need your Genius to change the feedbackloop to make a triode out of our pentode Semisouth to open another game....

[generg]

Of course I meant SP300b and not 300B.......

[Sipi]

Hi Generg,What can I say? I just love panoramique... :DI'm guilty of not following the thread thoroughly so it's not clear to me what device are we talking about - SIT, power JFET (SJEP...) ?SITs should be triode-ish by birth, and power JFETs could be converted easily enough...

[Zen Mod]

Generg and Sipi - regarding Shade of SSluths -just a quickie , don't have more time now :

http://www.diyaudio....tml#post2955803

in short - there is no need

[Sipi]

I see that pwla0516 examined the bottom part (murky presentation in the datasheet) of the output characteristic of the SJDP device.So triodish it is - in the region of interest...

[generg]

Hi Generg,What can I say? I just love panoramique... :DI'm guilty of not following the thread thoroughly so it's not clear to me what device are we talking about - SIT, power JFET (SJEP...) ?SITs should be triode-ish by birth, and power JFETs could be converted easily enough...

Hi Sipi,It is the SJEP R100 in a mullowerconstellation and I really would be very interested to try out the sound difference between the lower SS driven pentode like (at the moment) and triode like! Do you need data of the present feedback loop to change the characteristic?

[generg]

But may be the SJEP120r100 is also triodish in the region of 1-2A .....So I ask myself why did Nelson develop his own SIT?

[Sipi]

According to datasheet SJEP exhibits somewhat different behaviour compared to SJDP, so I suppose that something can be done towards your idea (although I don't know what your present, working, schematics looks like).If there is a benefit in using the Schade approach (needs to be confirmed), it should be done with composite device (low power JFET at input plus SJEP, both locked in the Schade loop) because big parasitic capacitance of SJEP will force us to use small value resistors in the local feedback which leads to small Rin, etc...Anyhow, there is some work needed to asses the problem and to evaluate possible solutions. Right now I don't have neither SJEPs, nor the time to play with them...

[Sipi]

But may be the SJEP120r100 is also triodish in the region of 1-2A ........

Yes, but only when Vds is very small - like LU1014 in F3

[Zen Mod]

But may be the SJEP120r100 is also triodish in the region of 1-2A .......

yes , it is - difference between R100 and R085 is , say , negligible in our field of use .edit - just found that , in a hurry , I mixed SJEP and SJDP .......... when I wrote negligible - I meant on SJEP's , while SJDP are somewhat different :rofl:anyway - you dissmantled source resistor in lower SS source ; with adequate value of resistor (as everything - compromise between one and another goal - load line or xconductance/gain) you'll have more leaned load lines on graph .......... so more triodish

So I ask myself why did Nelson develop his own SIT?

to have strictly triodish with still needed xconductance ( without need to alter load lines with resistor or something else )