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

[Zen Mod]

lucky bstrdzI'm stuck with plain ol' F4:dash1:

[Zen Mod]

Vlado - sp300b is interested ( and I'm asking just because he's busy all day long ) - can you make direct comparison of sound of FW J2 and your Babelfish J2 , considering all differences - you heard FW at Papa's , while you are listening yours at your place .....

we already have Tea Bag's opinion - " The BJ-2 sounds a lot like I remember the FW J2 sounding like at Burning Amp 2009 "

tnx

[zika]

lucky bstrdzI'm stuck with plain ol' F4:dash1:

And I'm on both of Your sides...

[Tea-Bag]

Vlad has had opportinity to hear the FW J2 for longer periods than the two tracks that I heard with it. So dont take my opinion seriously at all. And I think the speakers there may have played a big part in it.Some other words to describe it. Organic, dark, dynamic (unexpected). The soundstage sounds a bit less precise than F5. More atmospheric and wider and deep soundstage than F5. It is not dry sounding. It sounds 'dirty' compared to F5 or F2J 'clean'More tone than F5, and tone is darker than F2J, and Aleph type with R100. I think Generg could make a comparison here with the latter as well.Keep in mind, I plan on using 100R gates, and adding in other LED or Diode into Vref to bring up Drain voltage on 2SJ's Changing the diode sounds easier. . This may change things for better or worse.

[sp300b]

Vlad has had opportinity to hear the FW J2 for longer periods than the two tracks that I heard with it. So dont take my opinion seriously at all. And I think the speakers there may have played a big part in it.Some other words to describe it. Organic, dark, dynamic (unexpected). The soundstage sounds a bit less precise than F5. More atmospheric and wider and deep soundstage than F5. It is not dry sounding. It sounds 'dirty' compared to F5 or F2J 'clean'More tone than F5, and tone is darker than F2J, and Aleph type with R100. I think Generg could make a comparison here with the latter as well.Keep in mind, I plan on using 100R gates, and adding in other LED or Diode into Vref to bring up Drain voltage on 2SJ's Changing the diode sounds easier. . This may change things for better or worse.

Tea-Bag ...just for curiosity..You are talking about F2 J with SS, not BJ2 - correct ?

[Sipi]

Tea-Bag ...just for curiosity..You are talking about F2 J with SS, not BJ2 - correct ?

Of course - he said "atmospheric", BJ2 is "panoramic"...

[generg]

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......

[sp300b]

Of course - he said "atmospheric", BJ2 is "panoramic"...

Juma...juma...better tell me Your opinion about this shunt

[sp300b]

I think some of you will understand the last part, not me......

generg, would you mind Inviting him to come here and share his experience - We are welcoming him

[Zen Mod]

Juma...juma...better tell me Your opinion about this shunt

take money and run type

[generg]

I invited Mikael .......

[Sipi]

Juma...juma...better tell me Your opinion about this shunt

Nece raditi lose... Sa'ranili su gomilu delova gde ne treba,a na dva mesta ima manjak - al' to je komercijalni, potpisani uredjaj, ne bih da se dublje brkam u to...

[sp300b]

I invited Mikael .......

Very good. At first glance, seems that idea is to have Upper JFet biased with larger current and to use lower resistor in his sourse. Not exacty clear at this stage to me

[Zen Mod]

nope - he meant changing value(s) of middle resistors in output stagewe have 2x0R5 in series ......changing them - you are changing modulation of upper half of totem poleit is impossible to have unequal currents through output vertical . except if you make another path for equalizing currents in that pole

[sp300b]

nope - he meant changing value(s) of middle resistors in output stagewe have 2x0R5 in series ......changing them - you are changing modulation of upper half of totem pole

You mean, for example to put one 0,22 and other 0,78 for example instead of 0,5 and 0,5 ? What about offset ?

[Zen Mod]

You mean, for example to put one 0,22 and other 0,78 for example instead of 0,5 and 0,5 ? What about offset ?

you have diff input stage to servo thatno difference in thatjust one thing - I'm pretty satisfied with Babelfish J2 as is now ........ just need to make it in box , one day .....

[sp300b]

you have diff input stage to servo thatno difference in that

Ok - LTP - zero - clear, but it is not possible to have let's say 2,4 A in upper Jfet, and 1,5A in lower Jfet in our schematic - correct ?- if we imagine schematic without speaker connected....

[Zen Mod]

Ok - LTP - zero - clear, but it is not possible to have let's say 2,4 A in upper Jfet, and 1,5A in lower Jfet in our schematic - correct ?- if we imagine schematic without speaker connected....

seems that your thinking apparatus is these dayz in ZM mode :rofl:we must include path where we can direct 900mA of differencebut - not in speaker , please :rofl:so - this isn't modern Pass SUSY amp , with introduced additional SE bias

[sp300b]

seems that your thinking apparatus is these dayz in ZM mode :rofl:we must include path where we can direct 900mA ....... but - not in speaker , please

So, how it's possible....I also think it's not possible in our schematic...

[generg]

just one thing - I'm pretty satisfied with Babelfish J2 as is now ........ just need to make it in box , one day .....

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

[Zen Mod]

@sp300b:

why should that be possible ?

it is , but I can't see why - put either power resistor from output to negative PSU leg , or CCS

that way - with introducing additional current path - you can diss-balance currents through output pair

[Zen Mod]

......

you can try to change ratio of these resistors between lower and upper SS outputsnow they're 0R5 and 0R5increase upper/decrease lower (in same amount) - more local degeneration of upper SS - comparing to output node - where is - important - tied feedback netincrease lower/decrease upper (in same amount) - less local degenaration .......dunno what results - sound wise - can be ......