generg

good news...after half an hour the optocoupling device tracks the current precisely and offset is stable around 1mV plus minus 5mVeven at 1,4 A and 6 times o,25 Ohm!@tea-bag: good luck and I hope the sound will change in the direction you want!

we will find the holy grail......

sorry Zen Mod, I was amused by the communication structure between you, sp300b and tea-bag , it was a sort of comedy......

hear the laughter that no one can hear..............

no he is working hard.......... Last Active: 13 minutes agoCurrently:Viewing Topic: SemiSouth power Jfets

sp300b are you sure? Less current is astonishing and the tracking or the optocoupler with these low values? .....

please sp300b a little tiny mini description what changed to your earsI will hear again with your values.

Very nice book better than the power amplifier book from Douglas Self that I had! Ten points for Serbia!

We do what we can and you do what you can.....Together we are crazy.....

thank you Zen Mod, I will observe the tracking over a longer time and look if it stays stable ....... next days! it´s a changing bazar....... if it would only be easier to keep the sound in memory.......

I managed to install the second pair of SemiS, and don´t ask how it sounds, I am too exhausted...... now all other things of life, no more electronics........

hm, hm dear brothers in Babelfisch J2 :Viannen_loungelizard: :Viannen_loungelizard: :Viannen_loungelizard: on the way to a fish with two pairs of SemiS I could not resist testing the possibility of doubling the number of drain and source resistors so that a value of 0,235 Ohm results. With the method Zen showed I reduced the voltage over the new drain resistors to 0,35V, giving in the sum 1,4 A, that we suppose Nelson uses. (did I do maths correct?)R26 was 100 Ohm, to get the lower current...... the sound seems to have a bit more body and more crazy details what tea-bag called "dirty sound", the same ability I always admired with Pumpkin!But I have to say the resistors put over the originals are other type ..... sound influence?I compared strictly with Aleph 3 only mono, one channel changing. I choose Aleph 3 because he has much body, may be too much (9610 mosfet bloom).The sound of BabelJ2 had, before the changes, always more room around the box and always the better highs, but voices ( Ella and Louis) sounded better with aleph3, more chest, more dynamics. After the changes I have the feeling Babelfish articulates better, has more resolution, still not the chest Aleph 3 has, but a quality in forming the shades of voices that competes the "chest".You all know the seduction of the new, and the disillusion some days later, but I hope my impression persists the next days ....... I can encourage try the lower resistor values and 1,4 A. I am eager to hear your impressions!

hi Zen Mod, I am ready to implement the second pair of SemiS, but I have to reduce the current first I have now 0,91V over the drain resistor and the R25 is at minimum position. I want to get less current let´s say 1,4 A per pair. the problem is I cannot lower the current because of minimum position already. Should I change R 26 in what direction to get less current?

thanks Zen Mod

it is really difficult ...... I never heard the original FW J2, but for me and my damned Thiel speakers ( I like them nevertheless) the highs of Babel J2 were perfect, the bass was overwhelming and the sound "panoramic" (ha,ha) .....and the only thing I wanted was softer medium area, hearing that J2 had so wonderful medium area. that means I can share the wish of AR2 to have a little bit more medium bass or what were his words? that shows how dependent all the impressions are of the rest of the chain. Dear Zen Mod it would be very nice of you could give us some hints how to tune sound in your opinion in one or other direction. Like you did when developing pumpkin. and don´t forget your name is program: Zen Mod and we all want to MODMODMODMODMODMDO till we get ZENZENZENZEN..... best for you

I invited Mikael .......

When tazzz made his FW J2 conehttp://www.diyaudio.com/forums/pass-labs/151909-firstwatt-j2-53.htmlI changed a few mails with him. He tried to be closer to Nelsons circuit, but he stated"Thanks for your description. I have not played with the gate stoppers but simply put 47ohms resistor there I changed the current running through my voltage source tough for the upper jfet and that changed things considerably! Its still warming up as Im writing this but I can hear how much sweeter the top end is now... remarkable really. If you still want to play with your amplifier look up the articles about impedance multiplier at tubecad.com. There you will see that the upper pair of current sense resistors should take into account the transconductance of the upper Jfet and hence one should be made slightly smaller to compensate for the this and set the ratios right, than the other three resistors."I think some of you will understand the last part, not me......

Yippeeh, tea-bag you did it! Happy to hear all worked finally. what did you mean by the second part of this sentence I did not quite understand it "t's certainly reminiscent of the J2 at BAF09, and unlike the F2 and other SemiSouth contraptions with Aleph current source. Those devices have more upper mid - high clarity to it. More time will tell. "I know you have many experience with many many amplifiers, so I want to understand what you said....I am a little bit slow at the moment I will try to double the output devices and choose a higher current I´ll report end of the week

Nevertheless in the second moment I am irritated, I cannot use this circuit as a balanced input with unbalanced out? And when I use the input balanced I have o db ?

Thanks Impuls for solving the riddle for me .... I was irritated by the C in the word "?CInput"

and the original text

Hi dear Zen Mod,I try to use the Borbely super buffer with Babelfish J2. And in the description is mentioned the possibility to get 0db or 6db amplification.But the pdf has a formatting problem there are ? in a black field. He writes "?Cinp is left open" what could he mean?I add both the text and the circuit, thanks for help.......

Oh there are very special semiconductors I must scratch together and I am waiting for some DalesAnd first priority the next week is babel shark with two pairs of SemiS, when I can get the current lower, my sinks cannot manage 4A.....Your shark works fine, which gate stopper did you use?I had the idea papa took the 22 Ohm in F1 only because the input impedance is so low, but I am not really competent......

and the sourcehttp://www.semisouth.com/application/SiC_Vertical_JFETs_Operated_at_Temperatures_Greater_than_300C_HiTEC04_Merrett.pdflook at side 2 there is a model

Its from Ak4396 diyaudio forumhttp://www.diyaudio.com/forums/pass-labs/151909-firstwatt-j2-49.html