I've been playing with the PAM8403 amp. I built a small mono speaker as a children's project and thought it would be sensible to parallel the two output channels for more current capability (yes the advantage of this depends on load impedance and voltage rail).
At first I put some 0.22R resistors in line with each output and tied them together. This is standard for a class-AB amp with the resistors helping to balance the current from each output. When I increased the volume the amp cut out to protect itself.
A bit of reading revealed that the spread-spectrum output uses an independent randomised modulator for each channel. That means the switching carrier for each output channel is not matched, even when you link the inputs to the same source. When the outputs signals are not perfectly matched the outputs try to drive each other which ain't good.
The solution is simple - add LC filtering on the outputs before tying the channels together. The inductor (33uH) / capacitor (220nF) filters out the switching carrier allowing the outputs to work together. Just thought I would share this as I found a few others on the interwebs trying to do the same. Hope this helps.
At first I put some 0.22R resistors in line with each output and tied them together. This is standard for a class-AB amp with the resistors helping to balance the current from each output. When I increased the volume the amp cut out to protect itself.
A bit of reading revealed that the spread-spectrum output uses an independent randomised modulator for each channel. That means the switching carrier for each output channel is not matched, even when you link the inputs to the same source. When the outputs signals are not perfectly matched the outputs try to drive each other which ain't good.
The solution is simple - add LC filtering on the outputs before tying the channels together. The inductor (33uH) / capacitor (220nF) filters out the switching carrier allowing the outputs to work together. Just thought I would share this as I found a few others on the interwebs trying to do the same. Hope this helps.
An externally hosted image should be here but it was not working when we last tested it.
Thanks for this - just what I've been looking for! But sadly the link to the image is broken. I'm hoping the image is the schematic, in which case, any chance you could post a working link? Thanks in advance.