Pumpkin preamp - ordered by Steen , official making thread

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#2,803
hm... dear Zen Mod,

I suppose I have to change the value of R7 at least and I think because you recommend a 470 Ohm resistor to load shunty for test that shunty is programmed for 36V/470ohm =76 mA per rail, two rails about 150 mA.

Aleph P 1.7 demands about 70mA per channel at 60V, two channels 140mA. This is only a the half of pumpkin correct? Correction necessary?

have a nice afternoon!
 
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#2,806
generg said:
Hi Zen Mod,

I measured the current of one channel, about 70 mA at 60V, with another PSU!
Click to expand...

so - please refresh my memory - you are going to use Shunty for P1.7 , using Shunty's negative output as GND for P1.7 , Shunty's positive output as positive supply leg for P1.7 , and omitting Shunty's GND on P1.7 side ?

that way - you can use Shunty as is , because you'll have 2x36V=72Vdc on output ( well in working range for P1.7) and programmed current in Shunty is perfect for mating it with P1.7

so - as scribed in Cook Book :
Then you see CCS part of shunt reg , made with Q2,Q3 and few surrounding
parts ; same as with main CCS in Pumpkin -current is set with Ube voltage of Q3/ R7
, and that's 0V65/4E7 = ~140mA ....... so - that CCS is trying all the time to push
140mA through everything after him ,and that's nothing else than Pumpkin's positive
halve , in paralel with shunt part of shunt reg ;
In all shunt reg- load combos , most natural way of current sharing is when
you have same currents through load and shunt element of reg .... it be that element is
active , or passive , or combination of both .
Click to expand...

refer to Shunty schematic in Cook Book

be aware that I'm counting that you'll use one Shunty per one P1.7 channel .

just one question : why you are trying P1.7 now ?
 
#2,807
O.K. Zen Mod I thanks you for the clarification!

I am afraid the answer is, I cannot stop building things! I am infected!

I had already the boards for P 1.7 before I build pumpkin and I was simply curious how P 1.7 sounds. Different, also very pleasant, it has a very broad stage, the difficulties are the caps, they change the sound completely. So I am happy I can use pumpkin with caps only in the output.

yes I use one shunty per channel.

..... but please let us suppose I needed just the half of current, what should I change?

thanks for your patience.....
 
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#2,810
generg said:
so simple, wonderfull, all looked so complexe behind this point Q3 and R7 so I supposed more changes.

what is your newest solid state project? Updating J2? I hope!!!:mafioso:

:cheers:
Click to expand...

I'm glad that I helped you 😀

Babelfish J2 (not a clone of J2 , but another ZM's Drek inspired with J2 ) is finished on paper , and it will be tested in a week or so , when I invent the time needed for that ;
anyway - I'll not post it here , because I promised my self to not do so .

Seems that Papa isn't too happy about Babelfishing J2 (that's my impression , at least ) , so - even if I wrote few times here in words my vision of Bab. J2 , I would not post my schm ......... at least 'till someone else do the same

besides that ...... we (my , my self , an eye :rofl: ...... and spavleski ..... and Juma ) are working on some additional circs for spavleski's Primare CD31 ; I made xformer I/V conversion for gadget , Juma made beautiful simple SUSY stage , but with few caps in line ........ and spavleski urge me to make superduper UGS stage with subatomicohm output impedance and rock solid offsets .......

so - life is good and interesting , evn if I'm living in small town in country which is always in deep drek (read - either war , or transition :rofl: )

I have at least 5 different "projects" in every moment ....... not counting speaker projects ..... Sonido , Lorenz , EV 12TRXB , Iskra + 811B ........

correction - life is more than good and interesting - life is fun !
 
#2,816
hi Zen Mod, 😛

Why all your new layouts have again these lights looking like Navigational light for ufos! :radar:

I am sure in real life you wanted to be captain.:hphones:
 

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#2,817
generg said:
hi Zen Mod, 😛

Why all your new layouts have again these lights looking like Navigational light for ufos! :radar:

I am sure in real life you wanted to be captain.:hphones:
Click to expand...

reason is probably pretty simple - recently I have no enough time for playin' with real singing devices - Toobz ...... besides my everyday job - repairing electronics , I have a bunch of demanding friends , which resulted in dozens of napkin sketches ...... majority of them are filled with these little critters for sissies :rofl: , while real parts are dreaming in my drawers ....

so - I decided that every sketch must have two dozens of green leds :clown:

'nuff scientific reason ?

:cheers:

( no - I didn't (like Papa does ) bought drekload of green leds :devily: )
 
#2,820
sorry mate, had wrong color stuck in my head.
That reason is more insightful into the bigger picture of cool looking, quiet diodes, that can light up your preamp, (or pretend amp) the more 'naked' it is. And naked is good for ventilation as we know. And since ZM's stuff runs HOT, it needs to be naked..
ya know.
Good morning from across the oil slicked pond. Namaste'
 
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