Pumpkin preamp - ordered by Steen , official making thread

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#101
Re: Sweep me off....

steenoe said:
Guys, you are bored..... Here is something to have you listen up..
Since this thread has my name printed on it, I thought that you might want to see one of my fav. flies:::🙂 he-he Here ya go, take a look at the sweeping flow, that this fly has........Makes you want to throw it into thew current...... I am sold, Greame is, the question is, are you???? Yep, I dressed it......;-)

Steen🙂
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:worship:

:worship:

:worship:

:worship:

:worship:

:worship:
 
#103
lykkedk said:
ZenMod, I know that you can't remember the open loop gain / close loop gain, of the circuit, but is it possible that it can be explained howto calculate it.

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lykkkkkgreedydanske

it's hard to please everyone ;

with phono section as that - you can't have all ;

I told you before - you can't go near OLG without sacrifices , just beacuse everything is matter of compromises ;

near OLG , you loose both freq extremes ( not that both are necessary)

what you also loose is amount of X feedback ;

anyway - it's up to you to choose what's best for your ears

in your boots - I'll toss both :Pumpkin: and F4 ( as a gift to Magura , just because he doesn't have them :devilr: ) and make one nice toob system ...........

:clown:

anyway - for test - desolder feedback resistors and measure OLG at 1KHz ; you can measure also OLG at 20Hz and 20KHz , while you are at it . I'm sorta short in time , because it will take few mnths that I make my own :Pumpkin: ; all I have in this moment is just one populated Shunty pcb.

let us know what results are :smash:

regarding calcs - I remember that my calcs aren't very near measured ; I'm primary toob guy - used to graphs and rulers ,along with calculator ; there must be something I missed for OLG calculus .... those dreky mnfctrrs of 3-7 legged fuses make so small and useless graphs :clown:
 
#104
dviswa said:
ZM, anybody,

C4/C5 & C11/C12 are the output caps, I know you have said use your fav. But, I do not have a "fav". I am thinking of using
Black Gate N 47mfd 50V available in partsconnexion for $10, bypassed with 1mfd Vishay MKP 416-420 available on Digikey for a buck.

Why 47mfd? Well, my pumpkin will also be doing double duty of a headphone amp. I thought a larger cap will help with lower impedance cans. Or is this not a good idea?

What do you guys think of this choice? Any other suggestions?

Thanks,
Dinesh
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Dinesh ;

you package ( + 😉 ) , along with others is packed and ready to sending ;

I just kissed closed doors of post office today ;

seems to me that you found your fave caps 😉

just go for it .

somewhere - in one of my useless OT threads - I mention that I tried :Pumpkin: with cans - with stock (4uF) output caps , cans's impedance was ...... both channels in parallel - so must be no more than 50 ohms........

to cut a ... sound was pretty decent , no flabbyness ....... blabla

think about decreasing output resistors to ~ 22E , from 47 as they are now ;

if needed - we can later try something simple - increasing Iq in output stage(s)

don't forget to take cans off the head , if BG's need little burning in :clown:
 
#113
Zen Mod said:

you package ( + 😉 ) , along with others is packed and ready to sending ;
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Thanks a lot.

Zen Mod said:
seems to me that you found your fave caps 😉 just go for it .
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Thanks, I will.

Zen Mod said:
somewhere - in one of my useless OT threads - I mention that I tried :Pumpkin: with cans - with stock (4uF) output caps , cans's impedance was ...... both channels in parallel - so must be no more than 50 ohms........

to cut a ... sound was pretty decent , no flabbyness ....... blabla

think about decreasing output resistors to ~ 22E , from 47 as they are now ;
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OK, anything else I should be changing?

Zen Mod said:
if needed - we can later try something simple - increasing Iq in output stage(s)

don't forget to take cans off the head , if BG's need little burning in :clown:
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I was wondering about it too. Let's say I want to double the Iq, what values should I be considering?
 
#114
dviswa said:

............

Let's say I want to double the Iq, what values should I be considering?
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roughly speaking .........


halving all mosfet source resistors ;

so - R11 & R16 to 15~18E , R12/R26 & R17/R28 to 330//240E (all that in Pumpkin)


so - that also need changes in Shunty - besides xformer capable to give ~ 82Vct/800mA minimum for stereo , all heatsinks twice thermally capable ( that applicable for Pumpkin too ) and decreasing R7/R7a to 2E4 (Shunty)


in that case you'll double present current hunger :clown: of Pumpkin/Shunty combo , which is ~140mA/channel

so - you'll have preamp drawing 82V x 0,28A x 2 =46VA ......

more than some hifi DrekMKXX SE^2 amps

:devilr:
 
#115
anyway - it's up to you to choose what's best for your ears
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This is not a problem... no difference between soundsonics of 10xgain and 20xgain

Actually, i am not having trouble, with the gain anymore, it was just an idea i have, that maybee someone else was gainhungry like me 😀 too ! ... I allready adjusted the gain to my need's... I see ofcause that the phono-pre, can't be playing as loud as i would like it to, with a gain of 20x, but it's good enough for now.

I realise, that this is not the right place to ask, about howto calculate such thing's as X-feedback OLG, CLG... etc... seem's that anyone else but me, understand's this. 🙁

I am going to study these technicue's in future... regarding gain/loop etc... that i don't understand quite well... And maybee (can't promise) i will try the meassuring ZenMod suggested.

Anyway, in next few day's.... sneakpreview of my :Pumpkin:inputselector :bigeyes: :bigeyes:

Greeadylykkedk.... yes i am 😀

Jesper.
 
#119
vitalstates said:
I wonder...did steen ever get caught with his flies undone???

the real question, choky OLD chap....my F4 sings with my squeezebox and I can only get the volume up half way....this means that thinking about pumpkin is idling away the time for no good reason???

Ed:cannotbe:
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well........ you have schematics , cookbook, few hysteric threads for easy reading for fun ....... what are you waiting?

😉
 
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