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You'll have to modify the Audio library to use DAC1 for AudioOutputAnalog in place of DAC0 in
hardware/teensy/avr/libraries/Audio/output_dac.cpp

Good Luck

if you need stereo output through DAC0 and DAC1, i don't think you can do analogRead() on A22 or A21. It might work with mono output (DAC0) and using A22 rather than A21 for analogRead(). For mono...

So we don't have to guess what your sketch is doing, obey the forum rule above:
Forum Rule: Always post complete source code & details to reproduce any issue!

The audio lib is probably...

This works for me on T3.6

void setup() {
analogReadResolution(12);
analogWriteResolution(12);
}

void loop() {
for (int i = 0; i < 4095; i += 64) {
analogWrite(A22, i);