Pumpkin preamp - ordered by Steen , official making thread - Page 109 - diyAudio
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Old 17th January 2008, 06:41 PM   #1081
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Lookie, lookie... who comes today...
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Old 17th January 2008, 06:42 PM   #1082
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Do I have to warry about the orientation of the 4.7 uF Caps (red and black wire) ?
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Old 17th January 2008, 06:59 PM   #1083
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Quote:
Originally posted by spavleski
Do I have to warry about the orientation of the 4.7 uF Caps (red and black wire) ?
Not really, but now that they bothered to make two colours, I suggest that the "red" goes to + or input side! Pretty tough to figure out!!
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Old 17th January 2008, 07:20 PM   #1084
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I think that "red wires" should be connected to R13 (and R18) on Pumpkin Schematic ?
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Old 17th January 2008, 07:24 PM   #1085
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Quote:
Originally posted by hershann


Pardon my poor comprehension - so you mean -ve leg of electrolytic to output of film cap and +ve leg of electrolytic to resistor which is then connected to ground. So the electrolytic is not actually parallel to the film cap at all.

Quote:
Originally posted by steenoe


Your drawing is not excactly correct! The Electrolytic cap must be in parallel with the outputcap. Said in another way; you can replace the outputcap, with the electrolytic (and add the resistor as Mr. ZM said)



Edit: And bypass the electrolytic with your faverourite filmcap ofcourse I beleive there is provided for that on the Shunty boards...

Edit Edit: I would use at least 220uF, and even that, I feel is too small. I usally go for 1000uF for headphone applications like that.
One good combo that I can recommend is 470uF Panasonic FC bypassed with a 1uF Rifa PHE426 polyprop. At least that is the best sounding "cheapo" combo that I have ever heard Using a smallish cap on the output of a Headphone amp does cut the lower octaves somewhat
In that case - it's just replacing the output cap or paralleling the output cap with an electrolytic then. Since there is already a R27/R29 (100k) shunting to ground, why is there a mention of having a 47k ohm resistor connected to ground? Is that to replace R27/R29?

Will the electrolytic cap degrade the sound somewhat when the pumpkin is used as a preamp then?

her shann
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Old 17th January 2008, 07:28 PM   #1086
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Old 17th January 2008, 07:43 PM   #1087
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Quote:
Originally posted by hershann


Pardon my poor comprehension - so you mean -ve leg of electrolytic to output of film cap and +ve leg of electrolytic to resistor which is then connected to ground. So the electrolytic is not actually parallel to the film cap at all.
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Old 17th January 2008, 07:46 PM   #1088
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Quote:
Originally posted by Variac


Yup I was trying to be clever. I know that inductance isn't important for DC so my point is that an inductive resistor is actually better in the power supply as it might (theoretically ) filter out a teeny bit noise and ripple. So part of point was that those who would blindly replace resistors with a "better" non-inductive one might be wrong...

I will never try to be "clever " again...promise...

burlesca wasn't comment of your post , in any meaning ;

as steen sez - that was clever question

I meant really on entire thread - in positive meaning ............

ou contrary to some other threads ( not just these days) this one is full of positive madness
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Old 17th January 2008, 08:09 PM   #1089
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Quote:
Originally posted by Zen Mod

Very Clever!

thanks

her shann
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Old 17th January 2008, 08:10 PM   #1090
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but "ugly"
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