Pumpkin preamp - ordered by Steen , official making thread

[Zen Mod]

Re: rail voltage

I have a xformer having two 0-30V AC .

I think the shunt regulator also has a important roll for the qualified sound. So, I do not want to replace it to the simple one having higher output voltage although the shunt has a big voltage drop and the voltage swing needed for F4 will be around +-20V.

But I understand that the sound quality can change by the rail V.
Choky what is your recommendation New Xformer or Change V?

In fact my F4 has 15V AC xformer. So, the rail voltage is around 18V during running. But having great sound quality. It has powerful enough. I would like to make a balaced F4 later to see what happens.

So, at this moment I want to challenge to down the rail voltage of pumpkin pre and shunt regulator also.

Let's see...........
24V can be adequate as output of shunt, so called for rail.

Too long later🙂 🙂

so - 2x30 will give ya ~ 2x40 V on caps ........... I think that we can cut this to healthy 2x28V without penalties ........ under condition that your mains voltage isn't too variable going down 😉

it's easy to change few things to accommodate that ..........

ya see that never is too late .............. 😉

 

[jkchoi]

for 30V AC xformer

R23,24 for CRC will be OK or reduce to 3E3
I don't know about OS1 300mA no idea!, pass
Q1,Q2 IRF 510 will be changed to IRF 610, or 540 (because I have it) 😀
D1-D5 ZY10 will be changed to 4X9.1V=36.4V
R7 for safety will be same, pass
D8 LED will be somwhat dimmy!!, pass
R8 68k, WR1 4k7,R9 6k8 will be changed to 24k, 2k, 4.7k because I have them and can bring ~23-30V out
R13 27k will be changed to 15k then the base of the
Q6,7 will be around 15V-17V
Q10 can be changed to 2SK246 with R19 680? for 1mA ccs and R18 22k can be changed to 15k for safety

But finally I have no BDX54(p-darligton), can I replace it to any p-type darlington with collector dissipation 60W around?

 

[jkchoi]

And for the threshold;

Will it be OK if I Oly change R20 from 27k to 15~18k? 😀😀

hehehe Give my best regards to her. 😉 😉

 

[Zen Mod]

jkchoi ....... everything is doable .........

just later tonight I'll answer you one by one (my tonight ...... now is noon )

An externally hosted image should be here but it was not working when we last tested it.

 

[lykkedk]

Hi Choky...

As you know 😀 i was fizzling around with gainsetting's / LeachAmp ... and all that !
I have ended up with gainsetting at ~ 147,5K / 6,2K = ~23x (R1, R5 / R3, R6) for giving me enough power for my setup with voltagehungry F4's.

I am having the idea to put in a serie-resistor at input R1/R3 for lowering the gain, if i will use with another amp, than F4.

Will it be a bad idea to put in e.g 4K (plus them 6,2k i have now, which will give me 10,2K on input) - this will lower the gain from ~23x to ~14,4x ??? Or must value's R1/R5 , R3/R6 follow each other if you know what i mean.

I assume this will not effect the adjustment's of the , as this only will be like replacing the attennuator i think only thing what happens is a higher resistance on input ... hope you understand what i mean!

Well i will pull in a switch to either short or add this extra resistor having the name perhaps ------> '' Pumpkin superamp , normal cheap discount's amp's 😀¨¨ switch.

Jesper.

 

[Zen Mod]

Hi Choky...

As you know 😀 i was fizzling around with gainsetting's / LeachAmp ... and all that !
I have ended up with gainsetting at ~ 147,5K / 6,2K = ~23x (R1, R5 / R3, R6) for giving me enough power for my setup with voltagehungry F4's.

I am having the idea to put in a serie-resistor at input R1/R3 for lowering the gain, if i will use with another amp, than F4.

Will it be a bad idea to put in e.g 4K (plus them 6,2k i have now, which will give me 10,2K on input) - this will lower the gain from ~23x to ~14,4x ??? Or must value's R1/R5 , R3/R6 follow each other if you know what i mean.

I assume this will not effect the adjustment's of the , as this only will be like replacing the attennuator i think only thing what happens is a higher resistance on input ... hope you understand what i mean!

Well i will pull in a switch to either short or add this extra resistor having the name perhaps ------> '' Pumpkin superamp , normal cheap discount's amp's 😀¨¨ switch.

Jesper.

you are almost as me ........ ya cheapskate, dumpster diver , ya junkyard abuser!

hehe - you'll never learn - it's easier and more convenient to make two different systems - one for each side of room ,or one for each room , than making universal huperduper gizmo

place 27k in series with 6K2 , and switch across 27K ; you don't need that amount of gain for poor leachie ......... ya wanna kill either leachie or poor cones ..........?!

 

[mpmarino]

........ ya cheapskate, dumpster diver , ya junkyard abuser!

Ya yalkin' to me??

if not, you should be!

 

[Zen Mod]

Ya yalkin' to me??

if not, you should be!

"make my day ........... punk ! "

An externally hosted image should be here but it was not working when we last tested it.

 

[mpmarino]

a little progress...

 

[mpmarino]

.

 

[lykkedk]

Very nice man... that's the most nice chassis i have seen for a long time ... congratzz.

Jesper.

 

[Blues]

Great job, Marc!

 

[mpmarino]

Thanks!

A learning experience for sure.

The top and sides are finished with a caustic soda wash and the front, rear, 'posts' and knobs are anodized. Anodizing is tricky!🙂 The parts were intended to be black! I must have tried a wrong dye. Just as well, I like silver too.

I can't even begin to say how much work it's been so far - and then to put the fire out on the pumpkin boards, which I'm sure will happen🙂

 

[Blues]

Time to update your avatar...🙂

 

[jacco vermeulen]

are anodized.

Ay, de mi.
You did the anodising yourself ?

 

[mpmarino]

Ay, de mi.

😕 My serbian is rusty.....


Yeah, I gave it a try myself. The parts are anodized .. with no color.




edit: Oh, poor me.

 

[jacco vermeulen]

Espanol, means :Oh, my goodness.
I'm ******* envious.
(thought you californicators speak a bit of spanish)

 

[mpmarino]

(thought you californicators speak a bit of spanish)

I'm 3000mi from the californicators. Not much Spanish in crunchville.

 

[jacco vermeulen]

Oopsy, wrong mark again, shoot me or make me a moderator

 

[ROVSING]

Mpmarino
Very ugly chassis - Zend it to Me for proper disposal...😉
( Haven't i read that sentence somwhere else ? ? )😀 😀