Pumpkin preamp - More Boring Making Thread

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Zen Mod

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hershann said:



Anything needed to be changed on Shunty if I use a 36v-0-36v transformer? Found a 72VCT 50VA transformer that is much smaller than the 250VA 84VCT I found earlier - but I guess 50VA might be too anemic.

I do not need that much gain planning on 5 or 7 - so a lower max voltage swing does not matter.

Still looking for suggestions for good source of EI transformers - only sinker is that I am going to need 240V primary.

her shann
Click to expand...

for Shunty:


change one of zenners (in D1 - D5 string) for 4V7 , so - you'll have ~ 40V after Q2

set (with WR1 ) output voltage to 30V

in case that you can go so low - increase R9 to 7K5

same procedure for negative side of Shunty

you'll be fine even with 50VA , just look is it too warm .......... in case that these 50VA aren't real ;)
 
jacco vermeulen

jacco vermeulen

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Zhe-Modski should be spanked for making me thread kiddy M3.
The tie-strap thing is kind of fun once you get the hang of it, and so Blue
 

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steenoe

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jacco vermeulen said:


Each Yamster should be terminated (minus some pianos and the V-Max)
Even the most basic models contain gourmand items, we is the recycle bunch.

Pretty lights, the heatsink/plate of the shunty must be a hotpants.
Eh, LLcoolø is first taking it out, and then putting it back in ?
Click to expand...

Jacco-man, ya too sharp:D Yep the plate will be changed, when the Pumpkin enters its final home. Look at Rovsings picture of the LL heatsinks:D.

Okay seriously; my AX's were warm, so was the Pumpkin after adjustment. Plugged it in and ...... sound :D :D
Sound is very good! I have no idea what ZM did to the J310's, but the sound is crisp, delicate, liquid and very, very much in control! I never build a better preamp, considering all aspects.
The X'ed-CCS'ed CC'ed BosoZ might be a tad more warm in the sound, but it lacks the pinpointed soundstage and extreme details of the topend!! Soundstage is absolutely bang on....
The soundstage is very open, both in width and depth.
I bet its the Shunty thats on play!! I remember to have heard the same sort of openness with the NS10 on shunt's!!

:)
 
Zen Mod

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jacco vermeulen said:
Q : which commercial pre-amps have shunt regulation ?

Me think a heatsink above 3C/W for the Shuntee is a hot cat on a tin roof.
OK in open air, with a cover on top Iznogood for the lytics.
Maybe if Rovsing keeps them high enuff.
Click to expand...


don't forget that LL is cheapskate and he is feeding Shunties with 2x12Vac ...... heaven knws - Pumpylimpie is certainly starving , with negative-negative voltages :rofl: ....... countin' that Shunty have own losses of ~ 10V , each side .......

so - he doesn't need 'sinks ,at all ......... :devilr:
 
H

hershann

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Zen Mod said:



ya dumb dutchie ;

that means that Steen is in rotten shape - too much hangin' with Metaldanske, lately ;)

he isn't powered Pumpylipi at all ......... that's more like 2x0Vac .........

so - he need warmers for poor critters , not sinks .....
Click to expand...


Talking about starving pumpkins - since I'm going to use the 72VCT transformer and aiming for +/-30V after shunty - is there any other adverse effect on pumpkin other than the reduced max voltage swing?

The F4 is max +/-23v anyway? {ah that's 46v pp, and pumpkin is only 30vpp if single ended.?}
Anyway not going to need that much gain since my speakers are 93db/w in a really small room.

her shann
 
steenoe

steenoe

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jacco vermeulen said:
Q : which commercial pre-amps have shunt regulation ?

Me think a heatsink above 3C/W for the Shuntee is a hot cat on a tin roof.
OK in open air, with a cover on top Iznogood for the lytics.
Maybe if Rovsing keeps them high enuff.
Click to expand...

The heatsinks get really warm. A few ventilation holes in the pcb would help in that respect. Just in case my crazy man, ZM, is gonna do a second run of boards;) Raising the heatsinks to add a little airflow underneath will also help, ofcourse.
Running only 72VCT like me, helps too;)

Steen (with 2 dedicated preamps, specifically designed for him:D )
How cool does it get?
 

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Zen Mod

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jacco vermeulen said:
The super-shunty is Mr Stax Noro's brainchild.
Stax Ca-X,CA-Y, SRA-14S preamplifiers, DA-100 power amp, other stuff.

+ sheetdump of valve junk
Click to expand...


Mr. Noro's shunt reg is example of elegancy , not as Shunty .......... :rofl:


this - last one - Shunty - is certainly more versatile ( with changing just few resistor values) and plain overkill .....

valve junk was ........ waaaaay before Mr. Noro's sand trap ......

anyway - give me OA2 , keep Noro or Shunty for your self ;

any time

:clown:
 
Zen Mod

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Manu said:
Having problem deciphering last posts, I don't know if this thread is the right one.:D

Maître Jacques says : If you halve value of before-reg- caps you should twice the value of dedicated Rs.
So if C15, C16 is 1000u so R21, R23, must be 10R?

Maître Zen says let it unchanged (sorry if I not recall right)?

What should Mallarmé do?


Mebbe my Pumpking Ashanti will play music this WE
Hehe.

manu
Click to expand...

if you use plain metal film , for which I never know - are they 0W25 , or 0W4 - then put 2E2 , not 4E7 as in schematic and parts list ............ whatever amount of uF you have in first caps .

if you use plain carbons , you can leave 0W25 jobies here , but do not increase them ........
 
Manu

Manu

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Thanky,
I asked because I wan't to use 1000uF/100V for the first 2, because of higher voltage after Dagnall, then 2200uF/63V as in Schematic.
I didn't found anything else than carbon 4E7
Hope it is not isnogoud.

Hehe, me Tarzan very excited to soon playing Zique with pumpkin.

manu
 
jacco vermeulen

jacco vermeulen

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Manu,

i use two 18.7 Ohm resistors in parallel, soldered on both sides of the board.
And they are 0.6W metalfilm, total power handling 1.2 Watt.
Halving the electrolytic values halves the inrush loading, doubling the R values again halves it.
At a cost ; Twice the dissipation, Twice the voltage drop.

A major upside is the lower temperature of the resistors :
-by spreading the heat across two resistors
-by soldering the second one on the pcb bottom side
-because higher powered resistors have a lower temperature at the same load.

70mA through 18.7 Ohms is <0.1W dissipation, <1/6th of their max power capability.
 

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Zen Mod

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steenoe said:


We are crossposting:D I cant think of anything about the pampkin to wish for. Except for the vent holes I mentioned earlier!
The Pumpkin is playing steadily for 2 days now, it sounds just like the silky smooth thing that I like...!!! 2 days here is at least 23 hours a day!! :) He-he....
Click to expand...


well ....... there is just no place for these holes .......... besides that - ya know the rule - don't use force - use bigger hammer ........

so - just use bigger 'sinks ......... :rofl:

I likeeee that ya likeeeee ;)

seems that Lykkkk isn't so wackoooo , except that he just doesn't know for new dimension - with Shuntys ......

I'm curios what AR2 can tell , after implementing proper PSU .......

regarding Babbie - currentising it ....... naah ......... but - if you want - we can try that , even if few tech facts are against .......
 
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