Pumpkin preamp - ordered by Steen , official making thread

Jump to Latest
#3,321
10y said:
Hi,

finally tested my two pumpkie board one by one with music in a balanced out setting first with Up ampli ( test failed because speakers protection is always activated even if diff. offset is around 1-2-mV after caps) and after in an unbalanced output setting with my aleph 30.

In this configuration sound is present but is covered by a very loud noise like hum that seems a ground loop effect.

1)All current and voltage tests are ok.

2)Tryed to distance boards from trasfos without effect.

3) Wired all input and output as usual in my others pre hum-free.

4) Rca ground are isolated from chassis.

5)Changin' simple wire with coax wire don't produces variations on the noise level.

6)tryed boards with ugs-low voltage supply: always noise.


This pre is a very challenge for me but with your help I will win on it.😕

Ciao,

Anto
Click to expand...

I did like the Pumpkin, but Newbies just need to be aware that this is a project for experienced audio DIYers.
 
#3,322
KatieandDad said:
I've sold them now, they're off to America.

As I said, Zen Mod did state that it might be a component mis-match but no-one at the time could offer any advice.

I'm a systems engineer. To me one 0.1uF cap is the same as another until you so called "experts" tell me otherwise.

I'm now playing with my B1, which works absolutely perfectly, just trying to "Brighten" it up a bit.

We are currently at the stage of playing with the 10uF output caps. I've got all manner of caps here from Mundorfs to Chinese Audiocaps.

I'm getting a lot of suggestions which is VERY VERY useful.
Click to expand...

If your going to post here with the intent to troubleshoot, your effort should at least be authentic.
 
#3,323
KatieandDad said:
be aware that this is a project for experienced audio DIYers.
Click to expand...

Definitely.
Good luck with the next one, Andy&Stephen.

For less experienced ones ;
- Buy new current production parts.
- Make sure you solder right, reflow if in doubt.

Oldies carry the risk of having aged, or belong to a bad batch. This is true in particular with semis, some part vendors buy up off-spec transistors to flog them off to sillies. Was common practice in pre-bay times, is now.
Cold solder joints can lead to oscillations, depending on factors such as part location, value, bandwidth.
Construction flaws can be the cause of problems, and in most cases are.
 
Last edited:
#3,324
Hi,

resolved hum problems on one channel with a new in-out ground wiring. Now my

pumpkins sings dead silent on my altec system.

Tomorrow will work on the other channel and will post other pics.

Thanks to ZM and Jimbo51 for their great helps.

Anto
 
#3,327
jacco vermeulen said:
Definitely.
Good luck with the next one, Andy&Stephen.

For less experienced ones ;
- Buy new current production parts.
- Make sure you solder right, reflow if in doubt.

Oldies carry the risk of having aged, or belong to a bad batch. This is true in particular with semis, some part vendors buy up off-spec transistors to flog them off to sillies. Was common practice in pre-bay times, is now.
Cold solder joints can lead to oscillations, depending on factors such as part location, value, bandwidth.
Construction flaws can be the cause of problems, and in most cases are.
Click to expand...

Tanks jacco will bear this in mind when I get the PCB.

Would you know if maighty Zen got same more?
 
#3,331
Hi,

almost the happy end of my pumpkin andy shunty adventure.🙂

The two channels now work perfectly.🙂

Next step is PS Lightspeed Attenuator to put in the right

empty space.

After will try a LL1540, bought some years ago,to bal the

unbal DAC output.

Anto
 

Attachments

  • 1.jpg
    1.jpg
    599.3 KB · Views: 366
  • 2.jpg
    2.jpg
    430 KB · Views: 345
#3,335
10y said:
Hi,

almost the happy end of my pumpkin andy shunty adventure.🙂

The two channels now work perfectly.🙂

Next step is PS Lightspeed Attenuator to put in the right

empty space.

After will try a LL1540, bought some years ago,to bal the

unbal DAC output.

Anto
Click to expand...

Where have you guys found the smaller heatsinks of the PSU? that's exactly what i'm looking for, but i haven't found anywhere!
 
You must log in or register to reply here.
Top Bottom