Pumpkin preamp - More Boring Making Thread - Page 51 - diyAudio
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Old 1st June 2008, 05:10 PM   #501
steenoe is offline steenoe  Denmark
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Default Re: Cook Book - few more lines

Quote:
Originally posted by Zen Mod


- In case that you are fluffy with setting absolute offset (DC voltage between plus and minus
outputs of Pumpkin ) , you'll have replicated DC on both INPUTS of Pumpkin ........ exactly
divided by ratio of feedback net .
That will result in screechy noise during volume pot turning .....
cure is simple - Papa-like ....... just include 2u2 good cap on each input leg (both + and -)
between pot and inputs ; that will block DC to reach pot .
Hehe - that cure is certainly less evil than using any kind of Servo"


regarding these caps - Holger (HB) already sez long time ago that he even will not try his without input caps .........

as usuall , Cook Book can be found HERE


[/B]
You dont need to be fluffy, to need those input caps! I am sure I have been very very carefull to do the adjustments. With "very" I do mean very, indeed. I thought the woofer cones would fly through the room, when I first started up the Pampkin Horrible experience. If you dont like things like that, install the the input-caps
I didnt find them to hurt the sound in any way, though! Funny enough. I thought it would kill the transparency of the preamp, but it didnt.

 
Old 1st June 2008, 05:49 PM   #502
steenoe is offline steenoe  Denmark
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Quote:
Originally posted by Zen Mod
Steen - I just tried for you that version ( if I'm not wrong - PD's ?) of simple 1543 DAC , feeding 22K input impedance of next stage ;


there is not enough dynamics ; sound is -sorta interesting (different than SSDac with xformers , certainly ) but just with occasional glimpse of life in it ; details are almost there , but everything is somehow flat ;

you'll always know that impedance mismatch is in case , if you have wakoo response of volume control ....... turning it up almost without normal response , and then suddenly you have enough volume ;

purely subjective described ......
Thanks a lot ZM. That pretty much matches my impression. Except that I found on top of that, the sound was Zingy and generally not pleasing at all. I have a few details I want to change. The IV resistors needs to be changed to something totally different. Like RIKEN carbon..... or some really old carbon mass resistors, you know the 1/4 watters the size of a 3-watter....


Quote:
Originally posted by housing
Look.........Look!@@@@

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
Those are really nice looking pictures Nice and sharp closeup's.
BTW I like your filmcaps, indeed

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Old 1st June 2008, 09:49 PM   #503
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by steenoe


All ya guy's are nut's I know I asked for F4 preamp, and I really like the sound of it.... Well, I will simply build the psu into a seperate case, just like the one my Pumpkin is in right now Surely, two cases dissipates double up on the heat, right? I have ordered the wood for it allready. BTW its Erocco-teak. Just hope I didnt butcher a rainforest


you'll be surprised if you make it as I wrote - with slots on both sides , on both bottom and upper plates ;

in that case - everything will stay in one box , with enough ventilation
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clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
 
Old 2nd June 2008, 05:10 PM   #504
Manu is offline Manu  Europe
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ZM : 5309 are good caps right?
Why do you need some? New project?
 
Old 2nd June 2008, 05:20 PM   #505
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Manu
ZM : 5309 are good caps right?
Why do you need some? New project?

1N5309 are sissy CCS-es needed for KSA100 duckies ;

wakoo dutchie does EU delivery of them , and - as usual - he probably made own stash in excessive numbers ( anything bellow 1000pcs is zu teuer for Jaccovitty ) ........

I have KSA100 DiyA pcbs , literally thrown in/on my head by one cwayzee SF residented Serbie ,along with AX pcbs .......

now I have obligation to make more children , just to have someone to whom I'll give all my excessive amps (which I must make) ........

besides that - already mentioned wakoo dutchie augmented my curiosity for Marantz MA24 , presenting schematic to my (always hungry ) eyes .......

there is no big enough for this ........

or is it :
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Old 4th June 2008, 08:22 PM   #506
Variac is offline Variac  United States
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MODERATOR'S NOTE

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

All of the off topic posts have been removed so it is less entertaining but possibly more useful to learn about the Pumpkin for those making it.
This edited synopsis is up to date as of June 4, 2008. There will of course be more threads posted on the original thread with the usual Off Topic posts mixed in of course, so go there to check on the latest posts, as some of them will be relevant to construction.

This is where this thread leaves off and the original thread continues:
Pumpkin preamp - ordered by Steen , official making thread

After the post #2112 nothing has been transferred to this thread.
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Last edited by Variac; 11th April 2011 at 04:46 AM.
 

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