DC-coupling line out from Teensy Audio Board

B

Borogove

New member
I'm working on a hybrid monophonic synthesizer using the Teensy 3.5 and Teensy Audio Board to produce the oscillator waveform and control signals, which then go to an analog filter and VCA.

I had intended to use one of the two channels of the audio board to produce control voltage for the analog filter cutoff, but I have realized the line outs are AC-coupled and thus unsuitable for relatively slow-changing CV.

I'm considering just removing the AC-coupling caps from my audio board. It looks like the row of 4 passives between the SGTL5000 and the line in/out header are the coupling caps for the inputs and outputs; would there be any particular problem just removing those and replacing them with jumper wires?

The SGTL5000 datasheet implies the headphone outs are DC-coupled, so that might be an alternative as well.
 
I use ADAU1701 to try some voltage controlled thing. It works well in my experiment.
On other experiment,
I tried to connect ADAU1701 to teensy and it works with Teensy as slave.
ADAU1701 cheap board was used with teensy 4.0.
 
I've been running experiments with PJRC PT8211 audio board (stereo I2S 16-bit DAC) replacing the output capacitors with shorting wires. It works beautifully. Good results from DC up to 500 ksamples/second.

The results are good enough to allow us to move toward an affordable test bench for our 64-channel data acquisition system.
 
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