ZapPulse 2.2 SE noise/intereference issue

Mario KS

Member
2016-03-05 10:53 am
Hi guys and girls (but I'm guessing mostly guys...),

Having at bit of a noise issue with my first amp kit build. It has been unused for the past 5-6 years, but previously it was working hard as a student home party amplifier with no big issues. I brought it back and would like to use it again in my stereo setup.

It starts fine and doesn't blow up, which is a good start! But after a few seconds there is some heavy white noise in both channels - clearly audible at 1-2 meters away.

After fiddling around, I noticed that there seems to be a huge effect of touching the input cables, sqeezing them, or worst case: touching the non-connected cable screen (!)

I also noticed that the ferrite coils are getting quite warm after some use, borderline uncomfortable to touch (not heat from FETs).

What the h* is going on?

Video illustrating the issue:
https://www.youtube.com/watch?v=IaoBVW7zOMA

The only difference I can think of from before, when it was working fine, and now, when there's noise, is that it was connected to unearthed mains before, and now in our new house, it's connected to earthed mains.

Noise appears both with source connected and playing, and with phono cables disconnected.

Ingredients:
LC-audio soft start
Sjöström DC-filter (tested with and without)
Toroid 500 VA 2x50 V
35 A bridge rect.
2x 15000 µF 100V Rifa
10-15 cm cable from rail to modules

Ubalanced input, shielded microphone cable
Speaker output cable, shield connected to chassis ground

all help appreciated!
Mario
-Norway

[picture shows an older setup than video]
 

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jlithen

Member
2009-11-20 8:57 pm
Vaasa
Your modules look familiar in some way :D
Did you replace the caps with black gates?
What was the capacitance of the original caps?

I have no noise issues with them, but everything is totally ungrounded for this first test :)

Actually I must say sound is pretty awesome to be class-D, very soft and deep.

I guess there is capacitive coupling between signal and unconnected screen...so if you add interference to the screen with your hand then it may also be added to the signal.

And the ferrite cores do get warm...they usually do :)
 

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Mario KS

Member
2016-03-05 10:53 am
Your modules look familiar in some way :D
Did you replace the caps with black gates?
What was the capacitance of the original caps?

I have no noise issues with them, but everything is totally ungrounded for this first test :)

Actually I must say sound is pretty awesome to be class-D, very soft and deep.

I guess there is capacitive coupling between signal and unconnected screen...so if you add interference to the screen with your hand then it may also be added to the signal.

And the ferrite cores do get warm...they usually do :)

LOL!

I am happy that you are satisfied with them! The black gates were original for the Special Edition.

I since moved on to some eBay class D modules, which blew up one of my irreplaceable speaker elements.

Now I have bought a Pavel Dudek gainclone pcb and a bunch of components to solder. Project for next winter.