Pumpkin preamp - ordered by Steen , official making thread - Page 111 - diyAudio
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Old 18th January 2008, 03:15 PM   #1101
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Thinking of putting together the Opus balanced DAC (as described in the Digital section of the forum) to feed the pumpkin.

Can the Pumpkin accept a common mode DC of 2.5V? I am wondering if I can omit the DC coupling caps at the DAC output to improve its sound.

The pumpkin has output caps - thus will block any DC from going to the power amp - but will the DC itself damage the preamp?

her shann
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Old 18th January 2008, 03:17 PM   #1102
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Originally posted by Zen Mod
but I'll not make any fuss if someone publish his own variant ......... [/B]

I dub ye the .................. The Squash, with his trusty side-kick power supply The Gourd!
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Old 18th January 2008, 05:11 PM   #1103
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Quote:
Originally posted by hershann
Thinking of putting together the Opus balanced DAC (as described in the Digital section of the forum) to feed the pumpkin.

Can the Pumpkin accept a common mode DC of 2.5V? I am wondering if I can omit the DC coupling caps at the DAC output to improve its sound.

The pumpkin has output caps - thus will block any DC from going to the power amp - but will the DC itself damage the preamp?

her shann

nope ; you can't do that - from two reasons - you have attenuator ( pot ) on input which is based on ground ; even in case that you use shunt attenuator (between two inputs , without connection to gnd) , gates are still leaned/based on gnd

after universal Headphone preamp , you now need voltage convertor .......

you can't have anything .

put xformer on output of your DAC
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Old 18th January 2008, 05:12 PM   #1104
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Quote:
Originally posted by luvdunhill



I dub ye the .................. The Squash, with his trusty side-kick power supply The Gourd!

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Old 18th January 2008, 05:19 PM   #1105
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Quote:
Originally posted by Zen Mod



nope ; you can't do that - from two reasons - you have attenuator ( pot ) on input which is based on ground ; even in case that you use shunt attenuator (between two inputs , without connection to gnd) , gates are still leaned/based on gnd

after universal Headphone preamp , you now need voltage convertor .......

you can't have anything .

put xformer on output of your DAC

We are GREEDY boys - 1 Pumpkin to rule (do) them all!
I'll just use the coupling caps on the output of the DAC then before feeding the Pumpkin.

her shann
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Old 18th January 2008, 06:46 PM   #1106
DaveM is offline DaveM  United States
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No The Gourd!! follow the Gourd!!
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Old 18th January 2008, 07:01 PM   #1107
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Add some beads, a handle, and you don't even need to plug it in anymore for sound.
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Old 18th January 2008, 09:44 PM   #1108
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this is right place to post this:
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Old 19th January 2008, 04:18 AM   #1109
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Cookbook says EI transformer is preferred - I supposed due to better noise characteristics and ability to withstand DC etc.

For my Pumpkin the transformer is going to be mounted near the front panel and the audio circuit right at the back (the pot probably actuated via an extension rod).

So should I go for the old EI transformer 250VA, 42VCT x2 (pic 1) or the toroidal transformer 600VA 90VCT (pic 2). They are similar in price - with the EI at $20 and toroidal at $29.5.

BTW how easy is it to shield the EI's stray magnetic field?

her shann
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Old 19th January 2008, 04:35 AM   #1110
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Toroidal Transformer

her shann
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