Pumpkin preamp - ordered by Steen , official making thread

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#1,553
jazz said:
Hi

as ordered schematic with voltage measurements.

grtz
Joris

edit: sk170 GR (sorry junkbox)
Click to expand...


in that case - R7 and R8 increase to 1k3

goal is to have no more than 3 to 3,5mA through each GR 2SKs

you have problem with led string - which needs 5mA for proper operation

if you can't set R24 for needed 5mA through R23,R25,Q11,R24,led string chain......... than use plain bjt critter instead of Q11 - C up,B down , 130- 140 ohms as R24 - between E and B ; that way you must have ~ 5mA through biasing chain

regarding 3mA through each side of LTP .......... increase R22 to 140~150 E
 
#1,555
Hi Zen Mod,

Thanks for the advice. Ok gr version takes to much conversion, wanna stay close to your circuit.

For now I'll just double fets, with extra 1-10R in source should provide current sharing and hence compliance with 7 ma per halve of LTP right? Is just to get to grips with the circuit and setting procedures. I'll figure out how to get ccs in led bias string to behave.

I'll see if i can order j309 somehow. local shops say they don't know them, but farnell has em.

thanks
Joris

ps ccs in bias string is using 10x trimmer for r24, i figured the changes would require something like that.
 
#1,556
jazz said:
Hi Zen Mod,

Thanks for the advice. Ok gr version takes to much conversion, wanna stay close to your circuit.

For now I'll just double fets, with extra 1-10R in source should provide current sharing and hence compliance with 7 ma per halve of LTP right? Is just to get to grips with the circuit and setting procedures. I'll figure out how to get ccs in led bias string to behave.

I'll see if i can order j309 somehow. local shops say they don't know them, but farnell has em.

thanks
Joris

ps ccs in bias string is using 10x trimmer for r24, i figured the changes would require something like that.
Click to expand...


🙂

I have no objection .......

anyway - I choose J309/310 because is :

- dirt cheap
- widely available
- more than good enough for purpose
 
#1,557
jacco vermeulen said:


Eeer,

me no steppin inside no pyramid, only Beaubourg one.
And the milk lady had a strange nose.

I is currently playing role of Matthias from the Omega Man , hiding in the bathroom with dark sunshades till nightfall.
Click to expand...


ya cerazy duthie ......... :rofl:

so - job is done , and you can read what I scribble ....... ?

good :clown:

hehe - better Omega Man than Pinball Wizz

be good , and take care of these sunshades
 
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