SS 120R085 Depletion Mode Jfet

[flg]

Refrenced to something Buzzforb eluded to earlier, I found this:
"You can drop the JFET into the Aleph circuit, it's just that I
found the mu follower to operate a little better with the lower
Vgs. Not a big deal. You can easily adapt the board in any case
with the npn as the voltage reference." N.P.

 

[flg]

ZM, I thought we were trying to do a simple Pass like design with all N devices?

 

[Zen Mod]

ZM, you mind putting the cute little AC signals in appropriate places so ican get my head around this thing.

same way as in pretty well known Aleph input stage

look at pic .

regarding SE magic - that's hogwash ;

good amp is good amp

SE or not - much more important issue is type of speakers/room , in combination with amp in question

 

[Zen Mod]

ZM, I thought we were trying to do a simple Pass like design with all N devices?

don't ask me - I just wrote what I thought , then buzz buzzes me to sketch

besides that - you know that I'm talented only for over-complicating Papa's ideas

edit:

disclaimer : whenever you see sketch made by Mighty ZM - don't be so sure it's working .....

 

[buzzforb]

same way as in pretty well known Aleph input stage

look at pic .

regarding SE magic - that's hogwash ;

good amp is good amp

SE or not - much more important issue is type of speakers/room , in combination with amp in question

THanks for the cute signal thingies! As for speakers, recently been reading OB thread which you had something to do with. Probably doing something similar for next speaker. BA will probably have some help in this area as well.

Why do you like Bipolars so much?

 

[Zen Mod]

.....
Why do you like Bipolars so much?

who sez that

point is just that sometimes Vbe is more predictable than Vgs

 

[flg]

... As for speakers, recently been reading OB thread which you had something to do with. Probably doing something similar for next speaker...

What a coincidence? Me too! But there are many. And some real good tech pages too. There are also OBs and Dipoles!
John K, Linkwitz, Stigeric, MJK, Rudolf, and many others. Personally I'm a line array lover and I'm working towards a semi Dipole/OB line array. I've always been a box guy so this will be my first OB configuration. Did you se the "Fin" recently published project thread. Very good work by Cuibono. Amazing actually

 

[buzzforb]

Please, no more suggestions. Can't you see that already I have enough of a problem. BTW, I was reading in the speaker forum.......

 

[buzzforb]

FYI, I am looking at using the 12" Tone tubby in my OB. Seems to be getting a lot of good air.

 

[buzzforb]

same way as in pretty well known Aleph input stage

look at pic .

regarding SE magic - that's hogwash ;

good amp is good amp

SE or not - much more important issue is type of speakers/room , in combination with amp in question

So, just like in the aleph cs, the .66V is divided by resistor to set bias. You are just using two bipolars instead of bi/mos combo?

 

[Zen Mod]

input LTP current is set by CCS ( that one drawn as circle with arrow)

resistors in emiters of bjts are there to set needed ratio of currents through adjacent verticals of Current Mirror

so - that way you can have greater current through right half of current mirror than through left .

me likeee more current

 

[Zen Mod]

FYI, I am looking at using the 12" Tone tubby in my OB. Seems to be getting a lot of good air.

see what Generg wrote in Pub - he's using Tubby

 

[buzzforb]

input LTP current is set by CCS ( that one drawn as circle with arrow)

resistors in emiters of bjts are there to set needed ratio of currents through adjacent verticals of Current Mirror

so - that way you can have greater current through right half of current mirror than through left .

me likeee more current

Thanks for the explantion. Missed the cs at bottom of LTP. Too busy looking at all those bipolars.

Is bipolar at top of LTP providing only V gain, being common base? Top pair of bipolars in cs to bottom pair which form cascoded source follower. I need to look up current mirrors. My head hurts. Where's my De Lite schematic, I need to rest.

 

[Zen Mod]

well - that's just mishmash - rough sketch

it can be simplified , or complicated further ; it even doesn't contain important part instead that resistor in middle - it needs proper voltage "accordion" for that right part of current mirror .

be aware that I don't have formal education in electronic ;result is that I'm sometimes overenthusiastic ........ at least as long I check things in reality

dunno - toobz are simpler that these multilegged fuses

 

[buzzforb]

How much should I budget for burnt, three legged reality Seems like more everyday. I'll practice on cheap mosfets before playing with real toys.

 

[Zen Mod]

naah - I didn't meant on smoke - I'm too old, clever & xperienced for that

I meant just on , say , slightly wrong concepts

edit :

I knew that there was a "slight" omission ........

 

[buzzforb]

Is there a disadvatage to having a different transistor type for the ccs? For example, having an IRF240 as cs with SS on the bottom. Are ther thermal issues that would affect performance?

 

[Zen Mod]

plain CCS or Aleph (like) CCS ?

 

[buzzforb]

Either? I realize that using R085 as CS is difficult, so whether mu follower or Aleph, I will have to use something else. Just didn't know advantages or disadvantages. As FLG said, Pass suggested in J2 article that Mu follwer was better for use with R100'S over Aleph, but SS with ALeph isn't really new design.

 

[Zen Mod]

seems that , for serious conversation , one ( or we ) need to decide which part(s) and which concept to use

depletion or enhanced , Aleph CCS or ( as Papa sez ) Mu Follower ......

some of these are mutually exclusive , or just too complicated to realize .

if going for Aleph -like input stage - why using depletion output , and need for additionall small CCS and helper (more) negative leg ....