Pumpkin preamp - More Boring Making Thread

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Synopsis of Pumpkin preamp - ordered by Steen , official making thread

EDITOR'S NOTE

This thread is a subset of is a synopsis of the thread: "Pumpkin preamp - ordered by Steen , official making thread"

http://www.diyaudio.com/forums/showthread.php?s=&threadid=118994

I have removed all of the off topic posts so it is less entertaining but possibly more useful to learn about the Pumpkin

Variac

END EDITOR'S NOTE
_________________________________________________________

well ...... seems ages ago ,buried in some obscure DiyA Pass thread , after few quickie (on back of napkin) modifications of XYWZwhatever BOSOZ , my budy Lucky Luke (AKA steen) , demanded one little preamp with balls ....

few posts later , LL have some ideas about topology, perfectly good for me , just because I'm good at paper (napkin) and hand calc almost as he is good in making amps ........

little later - I already have some quickie quickie drawn , but somewhat flipped in regard to LL's idea,with added output stage(s) etc.

main reason why I flipped it is because I feel ( well - I rarely think,anyway) that's smart to use some non-audio-fancy-schmanzy Jfet , which is easy to find in near tobacco store, with all other parts .....

well - result is here (lookie lookie schmtc)

crazy process of :Pumpkin: delivery is also crazy documented in THIS
thread .........

I can just say tnx to entire OFF TOPIC MOB , just because they make my life miserable with regular questions "will it drive F4 " etc . :devilr:

anyway ......... for first post is 'nuff


schematic:
(next post -The Shunty)...........
 

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:Pumpkin: setup in my livingroom... Swinging so easily 40v with 1,8 on input !!!

Thank's for all the help ZenMod... Maybee it will be a while before finishing it up...

I made a :Pumpkin: from scratch, designing my pcb (clumsy i know) myself... but the thing is playing really nice, not to mention very relaxing too. All diy'ers, which life depend's on the F4, really should consider the :Pumpkin: to drive it wild an mad...

ZenMod :devilr: :devilr: :devilr: nice weekend...

Jesper.
 

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crazy danske was fast almost as his country man LL :clown:

lykkedk earned his right to post piccies of his own :Pumpkin: because he is first who actually made non-prototype version ..........

first official pair of main :Pumpkin: boards are happily arrived at first BAF in history....... we'll hear more about Smashing and Barking :Pumpkin: tomorrow......


well- steen ordered :Pumpkin:, but he didn't count on my everlasting love for shunt regs .
as result of that love there is The Shunty ........ simply - proper reg for any eeny weeny preamp ........

my friend Oly (AKA Vangelis on DiyA) is responsible for stunning pcbs for both :Pumpkin: and Shunty ; btw. "The Shunty" is his name for that simple reg . you'll see pcb piccies in later posts.

he is also responsible for keeping me in sane boundaries ; well - almost keeping me ;)

when I drew series reg, in front of already drawn and tested shunt part of now existing Shunty, his only (and last ) comment was "that's pure demonstration of force....... why you need that ?" :clown:

I also wanna say many tnx to Off Topic Mob , which constantly make my life miserable with repetitive questions as "will it drive F4?" etc .......... :devilr:

anyway - this was (is) open source project ......... my intention to make decent preamp for regular DiyA members, without braking leg and arm to find obscuremadeofpreputium audio parts (read - toshiba 3 or 7 legged fuses) ...

both schematics are here ; I intend to sell pcbs along with matched crucial parts , in several levels ........ just main boards with parts, just Shunty with few important parts (if they exist at all) , complete package, main boards with just one Shunty ( if you are bean counter) etc.

to cut a story..........

here is The Shunty schematic:
 

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Hi ...

ZenMod, when you tell to place voltmeter, at outerpin of C4 / C5, you mean at the point, where R13 meets C4(-out) , and where R18 meets C5 (+out) right ? - seem's a little hard to understand 100% (at least for me ;)). Well my pumpkin have been playing for several week now., but i will recheck the adjustment's when i somehow in future get chance to put it in box :)

C4 / C5 is the 10uF outputcap's you're meaning in the assembly-instruction's right ???

Jesper.
 
lykkedk said:
Hi ...

ZenMod, when you tell to place voltmeter, at outerpin of C4 / C5, you mean at the point, where R13 meets C4(-out) , and where R18 meets C5 (+out) right ? - seem's a little hard to understand 100% (at least for me ;)). Well my pumpkin have been playing for several week now., but i will recheck the adjustment's when i somehow in future get chance to put it in box :)

C4 / C5 is the 10uF outputcap's you're meaning in the assembly-instruction's right ???

Jesper.

let me see ........

C4 and C5 from Pumpkin schematics ;
outer pins - physically outer on pcb , far left and far right side ......

I'm clearer now?

:D
 
C4 and C5 from Pumpkin schematics ;
outer pins - physically outer on pcb , far left and far right side ......

Yes Yes :D I know, i thought it over today, and see what you mean, regarding the placement of the output cap's...

I have attached a schematic, with 3 grey spots on, pointing on the meassuring point's, are they located the right places on schm. ???

Jesper.
 

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lykkedk said:


Yes Yes :D I know, i thought it over today, and see what you mean, regarding the placement of the output cap's...

I have attached a schematic, with 3 grey spots on, pointing on the meassuring point's, are they located the right places on schm. ???

Jesper.


grey spots are on spot ;)
 
Good ZenMod.... Then things will work for dummies (ahh like me ???) :D too !!!

Btw... I use a 10k stereo alps pot on input, you somewhere in the past mentioned something about what's fit your'e source best... Well i donno what impedance my DDDAC / PearlPhono have, so do you have any good suggestion, for an allround pot... meaning values both for stereo + eventually an balanced one. Maybee this could interest someone else too :D ... Anyway, keep up good work ...

Damn... i haven't got much time listning to dreky... and finishing up thing's - Right now i am designing an inputselector, with 3 unbal RCA input's + 1 balanced input + balanced/unbalanced switch for output, for futureproof - all along with a switch, where you can switch between two toslink input's... All that must go into dreky :Pumpkin: too.

I was inspired to make this myself, looking at twistedpears darwin-input-selector btw:.. But this is way O.T. sry for that.

Jesper.
 
lykkedk said:
Good ZenMod.... Then things will work for dummies (ahh like me ???) :D too !!!

Btw... I use a 10k stereo alps pot on input, you somewhere in the past mentioned something about what's fit your'e source best... Well i donno what impedance my DDDAC / PearlPhono have, so do you have any good suggestion, for an allround pot... meaning values both for stereo + eventually an balanced one. Maybee this could interest someone else too :D ... Anyway, keep up good work ...

well - did you saw AR2's solution - two Black Widows (AKA Blue Velvets ;) ) , each stereo 50K pot ?
one per channel, so you have in same time balance too ....
that variant is both marked as good and also as bad , depending which personal preference is in question.....
anyway - 4 channel ALPS aren't so expensive - I think somewhere in range of 40 Euro ............... look HERE ..... that's my friend from Geek toob forum ......

I presume that you don't want Magura San to make eeeny weeeny attenuator for you , except if you have spare room just for them :devilr:

in any case - it's better to use as low attenuator value as you can, considering output impedances of your sources ; if sources are happy with 10K pot - then use 10K pot ; anyway Pumpkin is made with input impedance in that range ( remember value of resistors in both J310's gates )

Damn... i haven't got much time listning to dreky... and finishing up thing's - Right now i am designing an inputselector, with 3 unbal RCA input's + 1 balanced input + balanced/unbalanced switch for output, for futureproof - all along with a switch, where you can switch between two toslink input's... All that must go into dreky :Pumpkin: too.

I was inspired to make this myself, looking at twistedpears darwin-input-selector btw:.. But this is way O.T. sry for that.

Jesper.


my advice , and you know that I'm always willing for at least one :clown: is - use 4 channel volume pot , use only XLR connectors on input and also on output , use mini relays for input selector ( one double Takamisawa per channel input , so - when rely is not in use , both signal rails are grounded .

then - if you need to use nonbalanced source, just short gnd and minus leg ditto in cable XLR of that source

clear enough ?
I'm not sure ........ sometimes is hard to force my Engrish to follow what I want :clown:
 
clear enough ?

yeah, I think so... Your Engrish is better than you think :)

Ya know... I've been toying with the idea of building a separate input select/attenuator module with remote volume. Sort of what someone might build as a passive 'pre amp'( I always wondered how you could have a passive preamp?) Fully balanced input to output using whatever good components I have in the drawer. This would simply go between the sources and the pre. The actual pre would just be a box with 1 in and 1 out. Nice n' easy.


Why? you ask?
Maybe you didn't ask why- but I'll tell you anyway. Whenever I build a preamp circuit I'm finding that the most difficult part is the in selector and the attenuator - partswise. Also, it's hard to compare circuits because I never end up with the same type of attenuator. In doing this I would never have to scrape for an attenuator or input selector again - just keep using the same one.

Whadya think?
 
mpmarino said:


..................
Ya know... I've been toying with the idea of building a separate input select/attenuator module with remote volume..................

Whadya think?



"....cunning plan......"

:clown:

( Babelfish 2SJ74 are matched and packed ; post office tomorrow ....today........ now is 05:27 local time ;) )
 
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