Pass JFET Power Amplifier

Status
Not open for further replies.
Jump to Latest
#423
Samuel Jayaraj said:
Choky, you are indeed the man of the hour!!

Where are you?
Click to expand...


here I am,baby-sitting after all day in workshop...😉


lemme see:

164 is too wimpy
165 is Vmos (according to ECA TDV)
176 is also Mos fet

ok-you have 310,and his max. current is OK for J LTP,but I'm little suspicious with max 25V for Uds......
mebbe even two pieces of 2SJ174,also with "just" 25V Uds.........?!???? .... that seems too risky...


any J-fet with 10mA Ids and 30V Uds is probably OK
I was crying at loud for 2SJ109V iteration (max current capability) ,almost forgetting maximal dissipation -200mW for all three:GR,BL and V.....


anyway-if you can stay bellow +/- 25V (say twice 22 ?) you can use Jfet with 25V max Uds....





look at Shuro in Germany-they have 2SJ109BL....and at least one place on east (Japan,Taiwan...I can't remember right now-try some googlin'...)
I live in pretty small town (even if it's ancient) ,so money transfer to outer world is major PITA; I hope that things are something easier for ya 😉


or flip entire Aleph,so you can use some N channel Jfets-they are easier to find,and with mucho balllllssss :clown:

further:

even with 109-you absolutely must stay at twice 25V limit,just counting on possible +10% mains variations....

In Babbelfish J (even Babbelfish J is not mine- it's Papa's - again! ) left half of 109 ,with twice 25V, have some 21-22V Uds; right half have even more-some 25V ! that's pretty close to puff.......but -I can't see any other way to make it; maybe-if NP ever let us see right schmtc of Aleph J.....
but-where is fun,if not in researching ........ 😉

use cap multi if you want ; from my experience-for stereo you must have at least 120.000UF in plain CRC (say 33.000-fat R - 33.000 , all that twice).

Papa sez numerous times what are most important factors for choosing output mosfets ; U, I ,P and input capacitance (not to mention few other parameters );
in this case,I can't see why you shouldn't use 260;
460 is not good-Rds-on is waaaay too big.....
use two pairs of IRF540....they must be dirt cheap everywhere......
.
 
#424
addendum:

in case of two (single) Jfets in LTP- they MUST be thermally coupled
they must be tight matched (if possible-in situ) and probably you'll must use some 3,3 to 4,7UF in series with 22K feedback resistor (I like to say-DC gekoppelt 😉 )


for Fostex-es ....you can make Mini Aleph J-say wih Iq of 1 to 2A (what you like) and -say- twice 15 to 20 V.......
I suspect that your donuts are not so hard to unwound few turns,or even to rewound entire secs .......

in that case choice of LTP Jfets isn't critical,so you can use J310......

this days I'll beg,kill,and rape donkey for few matched 174 or 310 or ,God forbidden, 2SJ109-s...........😉
Shuro is ,I hope , close enough....... ;(

10W of A muscless is pleeeeeeeeeeeeeeenty......

:devilr:
 
#425
Choky, from what you say, it appears that J111 is a better candidate. I have 3 pieces at hand and can order for more either from RS or Farnell. What do you say?

Since you mentioned the Mini-Aleph, don't the JFET Alephs sound better in the mids/highs than the former? I suspect they do!?
 
#428
Samuel Jayaraj said:
Choky, from what you say, it appears that J111 is a better candidate. I have 3 pieces at hand and can order for more either from RS or Farnell. What do you say?

Since you mentioned the Mini-Aleph, don't the JFET Alephs sound better in the mids/highs than the former? I suspect they do!?
Click to expand...

Samuel
j111 is,according to ECA etc. ,is N Jfet
you can use it only if you make upside down Aleph J (P channels for outputs etc....)

I mentioned Mini Aleph J (with JFETS on input)

mini is still Aleph-just scaled down with current and voltage...


as I say- you can make Mini J 0with just decreased voltage...say 2x 20 V,and you then have much broader choice for input Jfets....

I tried mine mono Babbelfish also as Mini- with 1A Iq and 2x15V



all combinations are possible with voltage and current and number of output devices.....that's brilliant in that design-you can make wall with your bricks,but solidity is still there...


Mark
-I made it,in fact just one channel and just breadbord,but it works
http://www.diyaudio.com/forums/showthread.php?postid=845666#post845666


my friend Oly is now dedicated to PCBs (and he's good in that);

I have 800VA donut (and another for KSA ),caps,Oak for case,sinks,vents etc......

as soon I have PCBs on my bench,I'll make it

btw -did you forget me-with your generous offer?:apathic:
 
#434
massimo said:
But you need "V"....
I'm probably getting a couple of "V" in few weeks..... 😉
Click to expand...


like I said in one of my last posts-you don't need "V",just because dissipation is limiting factor ;
with almost 25V of Ugs in Aleph J, I can't think of more than 7mA through one jFet (half of 109) ,just because Pmax is 200mW.........so "V" iteration is ,say,welcome ,but not so necessary in Babbelfish LTP....
conclusion: "BL" is adequate and "V" is just more than adequate 😉
 
#440
Mr. Pass,

I have a question about your Zv9. You state that all resistors are 1/4 watt unless otherwise noted. The question deals with R18, a 0.47 ohm resistor. Please excuse my ignorance, but is that a 1/4 watt resistor also?
Thanks
Bruce
 
Status
Not open for further replies.
Top Bottom