Adding some info, I have a 250 kHz sinewave on the output. I think that my cutoff frequency is too high. Adding more capatance in parallel to the 680nF, lowers the measured voltage on the 250kHz. I have no caps to test if the noise is gone once I damp the 250kHz. Might this be the problem?
These caps are of very decent quality. I do not think Wima's will help with my design error. I think I will need to push the HF block fequency to the 24 kHz region. More tests are to come. Currently it's playing quite well, aside from the noise.
Class d is layout and decoupling critical.
Decoupling off b+ to b-, b+ to gnd and b- to gnd should be as close as possible.
Decoupling off b+ to b-, b+ to gnd and b- to gnd should be as close as possible.
The output filter never gets rid of this completely. Its not a problem as the speaker will reject it anyway.
I have heard of people adding a second output filter, I didnt bother.
Be careful adding more capacitance as this will cut off the higher audio frequencies.
How long are the leads from the power supply to the pcb ?
I had trouble with a class d test rig I had that had 4 inch leads to the pcb.
The amps clicked like mad until I shortened the leads right down.
I had trouble with a class d test rig I had that had 4 inch leads to the pcb.
The amps clicked like mad until I shortened the leads right down.
Did you build the amp too ? If so, what's your experience ? Does it work out of the box or did you have to modify it ?
I didn't know this topic had new posts. After altering the pre-set gain to it's minimum all problems were gone. I did this by breaking the connection of the gainpins. This left the gain pins floating which turned out to set the gain to it's minimum of 20 dB.
Today I will try to redesign the PCB.
Today I will try to redesign the PCB.
Use the smallest case size X7R SMD MLCC capacitors for decoupling class D, the least parasitic inductance the better.
A lot of EMC information regarding switched designs can be found on this thread:
http://www.diyaudio.com/forums/power-supplies/193705-switcher-emc-design.html
A lot of EMC information regarding switched designs can be found on this thread:
http://www.diyaudio.com/forums/power-supplies/193705-switcher-emc-design.html
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