Pumpkin preamp - ordered by Steen , official making thread

[Zen Mod]

no problem

decrease R19(a) accordingly - to have around 5mA through

if unsure - put 100R and measure voltage across it

 

[noSmoking]

Hi Zen,
Are shunty boards available? or point me to a link to order.
Thanks,
NS

 

[Zen Mod]

will send PM

 

[noSmoking]

Hi Zen,
Did you send PM ?
NS

 

[Zen Mod]

sorry , had stuffed PM box

done some cleaning and I'm gonna write

 

[noSmoking]

hi Zen,
No worries take your time,lol. Would you point me to where this DC fix is ? I have built the pumpkin from your layouts,Waiting on a few Parts,lol. and what I'm going to do to power it,lol.
Thanks,
NS

 

[Zen Mod]

DC fix is still waiting ...... pretty much finished in LTSpice , but also pretty much not so simple .....

main reason for that issue being on back of list is fact that Pa's ( how dare he !? ) is also having caps ...... everywhere

, however good sounding it is , was just innuendo to next thing ;

that thing , not existing in this Universe , sometimes called as Ultrasymmetry ......



just chill - caps aren't harmful on that sole position

 

[wengtech]

hi ZM,
i have one pcs talema 2x55v 2x0.73A
can i use for stereo (2channel) pumpkin shunty ?

here the pic:


how to connect properly with the stereo pumpkin.?

thanks.

 

[Zen Mod]

connect black+yellow , to establish center tap for 110V secondary ; confirm proper phasing connecting it to mains and measuring 110V across outer taps (red , orange)

if there is zero V , rotate one secondary

then connect CT to gnd on Shunty input side , outer taps to AC points

make bridges to same points on second Shunty

be sure to make proper ventilation in case , same as proper voltage ratings of caps on input side of Shunty (prior to Q2,Q2a) .... which means 110% x (55 x 1,41)

take care that Q2 , Q2a are heatsinked enough ...... and it's wise to use Irf610/9610 in their position

 

[wengtech]

my record is:
- it is save giving 110v into this shunty
- 2x0.73A is adequate for 2ch pumpkin+shunty
- using 9610+610 with larger heatsink
- caps prior to Q2 Q2a should be 100v minimum

So basically I am ready to fire on my pumpkin i guest.

Thanks again ZM.

 

[wengtech]

why EI Xformer is preferable than Toroidal
in case of this pumpkin-shunty?

 

[Zen Mod]

not critical in any way or sense but , generally , toroidal xformer will transfer greater amount of dirt from mains

using EI , there is less mains pollution to fight

 

[wengtech]

Hi ZM,
Is that enough matching bc556 and bc546
Through digital multimeter, only by seeing the hFE ???

Are there any accurate matching techniques for this transistors?

 

[Zen Mod]

Hfe matching is good enough

 

[wengtech]

Ok thanks.

 

[wengtech]

hi ZM,
i am going to matching the J309
what is the best Idss value for this pumpkin to work best?

thanks.

 

[Zen Mod]

they're having relatively high Idss ..... but if you really have them in quantity needed for that , try to find pairs with 10mA Idss

if not , just match them

or put 2SK170BL

 

[wengtech]

Okay I see.
Ah yes I forgot something, about the 10uf caps
I am planning to use solen.
Do you think solen caps have a direction?
Is it the S logo for in or out?

Thanks.

 

[Zen Mod]

dunno

gimme exact type

however , at these voltages , I'm not sure that inner/outer foil thing can make any difference

 

[wengtech]

Like this one...

Just curious...