I even tried to mess with AC coupling and bandwidth limiter, I gave a 440Hz audio input to the projector - I can hear it well in output - but I cannot detect it on pin 18. Now, this is just an audio signal, I'd expect levels and bandwidth to be fairly simple to see on a scope, I'm not exactly debugging DDR memory chips. Note I did not use the analog ground (pins 13,14), as my scope is not floating and I want to exercise caution. Kind of surprisingly, I get some sort of noisy waveform that matches the input on pin 19, that is the feedback channel, connected to the input through at least a resistor and a capacitor (in the picture, see pins 5 and 6 for the left channel). However, I expected to see a signal when putting the scope probe on pin 18 - instead I get a (noisy?) fixed 2VDC. In the following image, my setup, with the area where the chip lives highlighted in a circle. With the probe on pins 23.26 I see this wave that changes according to the input, and I can hear it while being played.
I connected my oscilloscope (ground to chassis) and (for example) I can see the "PWM" speaker output. Note: I wasn't able to find a schematic of this board, so I have to try to guess how it works.įrom the datasheet it looks like this chip takes a line level input and outputs an amplified audio signal. I opened up the projector and backtracked the integrated speakers wires to a chip that is a MAX9736A, a class D audio amplifier, conveniently located on top of the mainboard. I am aware of that solution but I do not wish to go that way. This particular projector has internal speakers but does not have an audio out and - as I have built my own external audio amplifier - I wanted to modify it and extract audio from the projector.Īt this moment, I am NOT considering an HDMI audio splitter. I am exploring the mainboard of an Epson 3010 projector.
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