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]
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]
Attachments
Your modules look familiar in some way 
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
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
Attachments
The ZapPulse 2.x are known to have some noise at the output.
You can upgrade the modules to "low noise" version, according to the instructions from LC Audio. See this link at the bottom: L C Audio Technology / Need-2-Know Info
It is shown for a 2.3 but as I remember, it is also possible to do the upgrade on a 2.2.
You can upgrade the modules to "low noise" version, according to the instructions from LC Audio. See this link at the bottom: L C Audio Technology / Need-2-Know Info
It is shown for a 2.3 but as I remember, it is also possible to do the upgrade on a 2.2.
Your modules look familiar in some way
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.
Oooops, sorry to hear that!
Which particular ebay Class D module, and what exactly happened?
It was the LJM L25D, similar (or identical) to this: NEW LJM L25D Power Amplifier Kit AMP DIY (Include 2 Channel Boards) J163-5 | eBay
Issue was already known, apparently: http://www.diyaudio.com/forums/class-d/191739-my-design-l20d-irs2092-irfi4020h-200w8r-94.html#post4652024
The transistors IRFB4020 with batch number WIQU were defective and were overheating. Rotten bit of luck.
Issue was already known, apparently: http://www.diyaudio.com/forums/class-d/191739-my-design-l20d-irs2092-irfi4020h-200w8r-94.html#post4652024
The transistors IRFB4020 with batch number WIQU were defective and were overheating. Rotten bit of luck.
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