Pumpkin preamp - More Boring Making Thread

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#381
paulb said:
I started to look through the 64 pages of this thread. Has anybody noticed the noise to signal ratio is pretty high?
............
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well - if you look who are most frequent posters in this thread , and look for other threads where are the same most frequent posters , you'll find that these threads have same S/N ratio ............

if you think on S/N ratio of thread , not preamp's ........

(it's nice to have fun and pleasure looking at schematics , but there is some life left out of schematics world)

:devilr:
 
#383
jacco vermeulen said:
Mmm, does post 9 of the 1st page not link to the PCB selling thread ?

I can see that dviswa may have a noise issue if he's heading for unity gain, but just where did you read the SNR number ?
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Jacco,

S/N of the thread aside, which we all know is a ZM thread, doomed to OT 😀
Please explain what you meant regarding SNR vis-a-vis unity gain.

Thanks,
Dinesh
 
#384
dviswa said:


Jacco,

S/N of the thread aside, which we all know is a ZM thread, doomed to OT 😀
Please explain what you meant regarding SNR vis-a-vis unity gain.

Thanks,
Dinesh
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Jaccovitty is just playin' , as always ........

you can use that drek in unity gain ....... just rearrange (J)accordingly values of those phase lag caps in feedback net ........ observing what CRO can show you ......
 
#386
I wan't to report a very very amazing case of telepathy between Crunchville and Vienna
:wiz:

mpmarino said:
...
Shunty is beautifully ugly - she will find a home in a phono pre or a small amp - or both, and surely will do a 'terrible' job at it 😉. ...
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As marino posted these lines, at the very same time, I was asking our Master Zen :

Originally posted elsewhere by Manu
... while waiting for some caps for pumpkin, I decided to finish my ONO, I began 5 years ago... May be they will Kuscheln in same case, who knows...
BTW : Would be Shunty a good reg. for ONO ?
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He replayed almost immediately :

Originally posted elsewhere by ZenMod
... it's completelly possible to feed it with Shunty , but be prepared to double dissipation - read - double heatsinking.......
maybe smartest thing is to relocate all mosfets and darlingtons to external heatsink ...
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Isn't great?

Is it unity gain?

:clown:
Manu
 

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#388
mpmarino said:
You don't like vinyl, Choky? I thought you was a tubehead?😀

Seeing that you are awake, I have a pumpkin building question😱

pumpkin on +- 25v ?? Willit work OK?

suggested parts modifications if necessary?

I dunno if I will drive an F4🙂 but for a couple reasons it wound be convenient to lower the voltage (I'm sure you can guess at least one).

- though I'm sure it will still drive F4 🙂 fine even at less volts - if it can work.

(Has lower voltage already been discussed?? If so- sorry, I've been stickin my nose in here once per day or so lately- to poke .....wiked busy:hot: )
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me not like vinyl ...... HA!!!

it will work on +/-24 , why not ....... even without slight modification ..... if I'm not nutz completely right now ....

just toss 2 of these accus on each side , ya cheapskate!
 
#389
hershann said:
Sorry to interrupt all the intelligent discussions - and adding noise to the nice signal all of you have been generating.

Doing some calculations:
So if corner freq, F = 1/(2 x pi x R x C)
(where R = R1 X R2 / R1+R2, and R1=shunt resistor of output and R2 = input impedance of F4)
And if I use 3.3uF for C4, C5.

R = 100k x 47k / (147k) = 31973

therefore F = 1.51Hz?
So give a factor of 10 where it starts to fall off the curve - so my calculations shows that it is good for 15Hz?

Correct?

her shann
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just shoot for it , besides-you can always place nice little Wima as bypass for output caps ...... ya know these little red thingies ..... 2u2/63V

😉
 
#393
Cap Sizing

Another newbie question 😱

Most of the capacitors in the shunty and pumpkin have a range of values that can be used.

In this case - is bigger always better

:devilr:

Like other notable things :clown:


I am currently using the values in the middle for most of the caps - should I go bigger??

:whazzat:

her shann
 
#395
Beauties (Uglies) Contest

Need to ask the Beauties (Uglies) Judges in this thread.

So which of the below Uglies / Beauties will go well with the Pumpkin Carriage?

For the vaunted position of C4, C5.

And the contestants are:

1) Epcos Metallised Polyester - 10uF 100V (Blue like the boards!)

2) Arcotronics Metalliised Polypropylene - 5uF 400V 5% (Yellow!)

3) ASC Metallised Polypropylene 3.3uF 400V 10% (White and radial)

4) Jantzen Cross-cap Metallised Polypropylene 3.3uF 400V (Classy Black)

Cast your votes!

Me cheapie! Me have no money to buy the Mundorf - Silver/Gold/Platinium/Titanium/Uranium caps or the V-Cap teflons!!

her shann
 
#396
ZM,

Am I correct in that, the purpose of C10 in the Shunty is to provide a soft start? If so, I have a few 220uF in the junk box, I guess I can use them right?

Also, I am not sure if you have answered this or not. Any reason why for quite a few caps you used 15mm raster, when 5mm (0.2") raster caps are easily and cheaply available? For instance, for C12 in the shunty, holes for 0.2" could have been provided.
 
#397
dviswa said:
ZM,

Am I correct in that, the purpose of C10 in the Shunty is to provide a soft start? If so, I have a few 220uF in the junk box, I guess I can use them right?

Also, I am not sure if you have answered this or not. Any reason why for quite a few caps you used 15mm raster, when 5mm (0.2") raster caps are easily and cheaply available? For instance, for C12 in the shunty, holes for 0.2" could have been provided.
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C10 is there for better ripple rejection ; soft start - if any- is just a coincidence

C12 raster - even if Oly is strictly responsible for layout , I can tell you that I also have habit of using axial caps , so raster is more convenient

besides that ......... you can only random expect that my doings have any logical reason .......... :rofl:
 
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