Pumpkin preamp - ordered by Steen , official making thread

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#2,562
 
#2,564
hm, on the 20n5 RIFA PFE225 I can negotiate down to $55.00 plus S&H $9.90 for 50pcc and $100.00 plus S&H $14.90 for 100pcs. I'm haunted my the sound of polystyrene in RIAA filters now.. seems like a good deal, no? 20n5 is almost as large as they get in the PFE225 line it seems... not that I want to build a third phono stage... but anyways.
 
#2,565
Consider that LCR in Wales and Reliable-Cap in Cali are about the only ones left who still have polystyrene foil to manufacture such capacitors, while it lasts.

Boxed 63V types cost close to twice as much as a 160V axial counterpart from the same manufacturer.
Converted to today's price level, a 20n5 for example would be around $5 each minimum.
Epoxy resin encapsulated foil caps virtually live forever, either $1 or $1.20 a cap is a bargain if you can live with 63V, compared to RelCap RT rates.
(Wonder-C/REL RT are great caps but even the 100V type has a lousy accuracy, which limits their practical use to bypassing and with a value of up to 3uF as coupling-c imo)
 
#2,566
okay, thanks for the advice! Much appreciated.

One other pearl of wisdom I'm seeking.. what output BJTs do you favor? Things like 2SC3421/2SA1358 2SC3422/2SA1359 2SC2238/2SA968 etc. for use on a hybrid headphone amplifier? Any hard to find drek that is particularly interesting?
 
#2,568
more progress on actually casing my :Pumpkin:.. I won't be able to work on this for the next 4 weeks, as I'll be in China ... but, when I get back, I hope to put the finishing touches on it 🙂
 

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#2,569
luvdunhill said:
okay, thanks for the advice! Much appreciated.

One other pearl of wisdom I'm seeking.. what output BJTs do you favor? Things like 2SC3421/2SA1358 2SC3422/2SA1359 2SC2238/2SA968 etc. for use on a hybrid headphone amplifier? Any hard to find drek that is particularly interesting?
Click to expand...

or, in other words, recommendations do you have for this amp for a Nipponophile (i.e. 2SC/2SA preferred) 🙂

An externally hosted image should be here but it was not working when we last tested it.
 
#2,571
Depends how high you intend to bias the CCS, the range for R12+P2 is ~ 45mA-130mA.

At a low bias current level, a TO-126 wouldn't even require a heatsink.
If it were a cheapo circuit and biased at <60mA, 190MHz Phily BD135/139 would do, any other BD manufacture sucks.(see comments of Mr Creek Nikitin)
The dual triode mini a-la ECC82 at the input makes it a non-cheapo anyway, Toshiba TO-126 nicies would be 2SC2824 or 2SC3421.
Personally, i would likely try to shove a 2SC5171 through the TO-126 lead spacing holes, duh.
 
#2,572
Drawings for MITHOMAS

1/2

here is schematic , dunno did I posted it already ?

n next drawing you'll see how and where to situate input caps ;

22K resistors - just solder them on bootom of pcb - one end to jfet gate , other end to nearest gnd point
 

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#2,575
mithomas said:
Thanks ZM,
anyone know where to order those XLR jumpers Papa uses to tie pins 1 and 3 together? Is there a name for them?
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you can't find anywhere locally piece of Cu solid wire with adequate dia?

where this world is going .......

:clown:

MAKE YOUR OWN JUMPERS !

(then tell to all your friends that's last batch of jumpers from personal stash of Baron Krupp ....... )

:rofl:
 
#2,577
mithomas said:
What I have fashioned so far seem a bit ackward in real use.

I will keep working to try to please the frugal and intense ZM.:cannotbe:
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naah ....... I'm just (!!) stubborn 😉

I hate to pay for finest FiFi fog ...

been there .....

or just use two XLR cable connectors , with shorted pins 1&3 ;

these are certainly fancy , and still useful later ....

😉
 
#2,578
Zen Mod said:



naah ....... I'm just (!!) stubborn 😉

I hate to pay for finest FiFi fog ...

been there .....

or just use two XLR cable connectors , with shorted pins 1&3 ;

these are certainly fancy , and still useful later ....

😉
Click to expand...


no I am using F4 with XLR with vampire male with RCA stuck in the end, and internally shorted. Of course with Pumpie, I am not sure I want to build in RCA set for CD player, or just use a shorted homebrew XLR to RCA cable(think that's what your saying). Just thought a good jumper would do the trick, without being weird. I also assume there is no penalty for dual XLR outs here....But will re-read cookbook later.

I'm tired. Your simply an insomniac. 😴
 
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