As soon as palmerr23's new 8x8 channel Teensy audio hardware was available h4yn0nnym0u5e, author of the Teensy Multi-TDM driver, grabbed the Open Hardware files and had a batch of boards built. 

Next to a stacked pair of the  new audio boards, which deliver 16x16 channels 'out of the box' h4yn0nnym0u5e added another 6 stacked boards and an extra multiplexer chip to enable eight boards producing a total of 64 inputs and 64 outputs.

The toll for this was 770mA of USB current draw and 22% of the Teensy's CPU capacity to produce and transmit individually generated sine waves to each channel. Changing to less intensive triangle wave generators reduced the CPU load to only 5%!