I'm thinking about full JFET Babelfish based on UJN1208K depletion mode output devices. What do you think about it ? I know that bias circuit need to be changed. Maybe new external one or feed R22 from negative rail with some changes ?
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1. always post reference schematic , meaning one , from which you're referring parts designation
2. best if you introduce third PSU rail ( wimpy in current) , being neg to main neg rail
post schematic here , so we can proceed further , speaking in same terms
(later tonight; in a meantime , search for EUVL's proposal how to edit Aleph J-ish circuit , to accommodate LU JFet outputs ; trick with lower one biasing is what is important to you)
2. best if you introduce third PSU rail ( wimpy in current) , being neg to main neg rail
post schematic here , so we can proceed further , speaking in same terms
(later tonight; in a meantime , search for EUVL's proposal how to edit Aleph J-ish circuit , to accommodate LU JFet outputs ; trick with lower one biasing is what is important to you)
wrong , from many reasons
did you read what I linked in post #3
catch is in "depletion mode device" , meaning that for proper biasing UJN demands negative voltage at gate , ref. to source
also , referencing biasing voltage for upper UJN , to negative rail - is wrong from many reasons
it needs to be referenced to something in between ..... either output or gnd (matter of choice and further rethinking of output stage principle)
did you read what I linked in post #3
catch is in "depletion mode device" , meaning that for proper biasing UJN demands negative voltage at gate , ref. to source
also , referencing biasing voltage for upper UJN , to negative rail - is wrong from many reasons
it needs to be referenced to something in between ..... either output or gnd (matter of choice and further rethinking of output stage principle)
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Ok, so if I disconnect bias PS from negative rail and connect it to GND, then I will have -V at gate ref. to source in upper JFET...I think so, but I'm not sure. Sorry this is my first depletion mode circuit
An externally hosted image should be here but it was not working when we last tested it.
now - you can replace entire LM337 shebang with same combo as in F6 :resistor plus zenner across pot across cap;
just wire resistor to neg rail , instead of positive
proceed with changes in input JFet drain , see (again) what's linked in post #3 , to arrange proper biasing of lower UJN
and ... considering that we are really starting from Aleph circuit , maybe best combo should be to transfer to UJN in lower half , and to transfer to ACA -like upper half , with IRFP150 or IRFP240
Pa is lately using that approach - sorta Mi-Follower , instead of earlier Aleph CCS ...... with goal to have iteration of active CCS , while benign in nature ( not adding too much of own flawor in sound)
that way , you'll still have UJN dominant in entire picture , while lesser complication
just wire resistor to neg rail , instead of positive
proceed with changes in input JFet drain , see (again) what's linked in post #3 , to arrange proper biasing of lower UJN
and ... considering that we are really starting from Aleph circuit , maybe best combo should be to transfer to UJN in lower half , and to transfer to ACA -like upper half , with IRFP150 or IRFP240
Pa is lately using that approach - sorta Mi-Follower , instead of earlier Aleph CCS ...... with goal to have iteration of active CCS , while benign in nature ( not adding too much of own flawor in sound)
that way , you'll still have UJN dominant in entire picture , while lesser complication
Yes I knew about that combination, but I wanna go only with JFET. Ok, please take a look at this
few things ......
- you'll need either two J511 in parallel , or something different ...... needing more current there than from JFets drain
-R32,R31 ..... if you leave them , they can be start of making upper UJN as proper Aleph CCS , so time to think how to rearrange upper bias scheme and to introduce resistor from output to gate of that UJN
-delete Q8 and these two resistors ...... due to polarity at lower UJN gate , that's just a mess
- you'll need either two J511 in parallel , or something different ...... needing more current there than from JFets drain
-R32,R31 ..... if you leave them , they can be start of making upper UJN as proper Aleph CCS , so time to think how to rearrange upper bias scheme and to introduce resistor from output to gate of that UJN
-delete Q8 and these two resistors ...... due to polarity at lower UJN gate , that's just a mess
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