Pumpkin preamp - ordered by Steen , official making thread - Page 347 - diyAudio
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Old 11th January 2013, 08:33 AM   #3461
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Forza Vale !

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Old 11th January 2013, 01:20 PM   #3462
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Forza Vale !

Forza Vale but also don't forget SIMONCELLI

Big boy in my memory.
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Old 11th January 2013, 01:41 PM   #3463
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Old 13th January 2013, 03:32 PM   #3464
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Default Pumpkin sturtup problem

Hi Alex! Today i have started the pumpkin and i have detected a annoying noise, i have detected from my CRO (the picture shows both channels) a hi frequency noise,but what my ears hear is more like a tone of 100 Hz square wave, strange but true!
I have to tell you that I used the molex connectors, and I think that the connections with the top of the pcb are probably not ok, so I had to make a ground bridge on below pcb, as picture shows.
I also tried to disconnect the input connector and I have to say that the noise is slightly diminished but not disappeared!
I also tell you that when i put signal it i ears the sound ok !No distortion ..but when i turn down the volume the noise is there to break my balls!
I have already set Wr1 and Wr2 and this all ok and i also add resistor for better DC offset stability(see picture).Please can you send me a diagram with the references of voltage?
Please Alex help me!
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Old 13th January 2013, 03:49 PM   #3465
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to prevent cluttering of thread , send me hires pics on e-mail

I mean - entire preamp , where I can inspect your wiring and grounding scheme
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Old 13th January 2013, 04:01 PM   #3466
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to prevent cluttering of thread , send me hires pics on e-mail

I mean - entire preamp , where I can inspect your wiring and grounding scheme
Ok Alex! I will do it tomorrow.
Thanks.
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Old 14th January 2013, 08:04 AM   #3467
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Hi Alex !Just for your information i failed to tell you that I had already tried the pumpkin before putting it in the cabinet, so.. simply connect the transformer, preamp and psu, and of course signal in and signal out, and I had already noticed that annoying background noise.
I will give you more informations in your PM.
Thanks and good morning.

Antonio
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Old 19th January 2013, 12:32 PM   #3468
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Default Pumpkin noise upgrade!

Hi Alex! Trying also the craziest things to solve the problem, I finally solved!

I removed R21 10k and it all worked out!

Then i decided to investigate and i found out that you also designed a version of Pumpkin using in place of R21 ... U1 LM336Z-5V

Pumpkin Preamp - Perfect for F4

Question... What should I do now leave everything just as it is now, or change something?

Removing R21 can involve some variation on the frequency response / stability of the circuit, or ......

I feel comfortable, listen to music and drink wine?

I hope that this discovery could also help other people in this forum!

Greetings to all.
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Old 24th January 2013, 11:01 AM   #3469
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Hi at all! I noticed that there are several differences between the schematic 1 ( that reflects the reality of my pcb) and schematic 2 .
I noticed that i reconnecting R21 but bringing R22 from 47 to 220 ohm things
got better, then I also connected the base of Q9 between D4 and D5.
But to be able to adjust the offset between -out and +out i had increase
WR1 from 47 to 220 ohm.
Now Noise is OK! (please see shematic 3)
Strangely I have a gain of 4 instead of 4.7 using R5 and R6 47K and leaving R1
and R3 10K, I also changed C1 and C2 from 5p to 10p.
I think everything I've done.
Now i need a greater extent in the high frequencies, I realized that my Pumkin
vs my Emerson is less extensive on high.
Please can you give me some advice for more extension?
I believe that pumpkin can give more.
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Old 24th January 2013, 01:46 PM   #3470
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Tony
I was working tonight (some mumbo jumbo which can be done just between day -shifts) and just arrived from trip , back home ;

I need to catch few hours of sleep

whatever - it seems you had difficulties reading Cook Book - (sorry - I'm ignorant peasant , knowing just few words of Italian , so I couldn't make Italian version ) , so you obviously messed up something , somewhere

most left schematic is last , valid one , while middle (and most right ) one are somewhere from thread , during testing and developing

whatever - it seems you solved those issues , except lack of highs , which I'm finding somewhat doubtful ; accoring to AR2's measurements - Pumpkin is some 0,5db down on 20KHz ( with highest gain setting - for F4) , but that's nothing comparing to our hearing capability , considering age

will take a look at e-mail I got this moment from you , and write what I have

now I need to nap , my eyes are already somewhere else

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Last edited by Zen Mod; 24th January 2013 at 01:49 PM.
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