Zoom H2 4 channel hack

So the Zoom arrived in April, 2009. After 7 years without ever using the microphones, it was time to do the deed. All you need is to replace the microphones with RCA connectors. The gain switch set to low is the same as line level. It worked perfectly when taking input from a computer sound card, but had serious noise when recording the microphone preamp. Turning off the gain on the preamp made the noise go away. The line input didn't have the noise. The Zoom had fixed 2k resistors supplying phantom power to the RCA connectors, but pulling out a resistor didn't matter. The Zoom & preamp had independent power supplies on different grounds. The source of the noise remanes a mystery.


More importantly, it was impossible to monitor audio from a computer & microphone without some way of having independent monitoring volume for the 4 channels. Otherwise, the computer would have to be recorded at a very low level. The 4 channel experiment was dead.


The computer outputs TOSLINK, so it should be recorded by sniffing a digital signal. Another STM32 running the CP33 recording firmware would have to be hooked up to the point in the amplifier when the audio was in I2S format.