Hi, I recently upgraded from Teensyduino 1.51 to 1.52 in order to switch a project over from the Teensy 4.0 to the 4.1. The project uses the Audio library with the PT8211 DAC. In doing so corrupted any and all audio with a harsh modulating tone around 347Hz on both the 4.0 and 4.1. The issue persists whether I use AudioOutputPT8211 or AudioOutputPT8211_2.

The following code (and attached circuit image) is a minimal example that reproduces the problem using the latest Teensyduino standalone (Arduino 1.8.12, Teensyduino 1.52). This one starts with the harsh 347Hz modulation as mentioned, but after a second or so syncs the sine wave with the 347Hz modulation, producing the waveform shown on the scope image. Reverting back to Teensyduino 1.51 fixes the issue.

The other DAC breakout I have lying around is the Adafruit UDA1334, and I was able to get it working under Teensyduino 1.52 using AudioOutputI2S2 without the modulating tone issue.

Please let me know if there is a workaround or a fix planned, as I would simplify my project to use the 4.1 with the PT8211 over the 4.0 or the UDA1334. Many thanks!

Code:
#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>
#include <MIDI.h>

AudioSynthWaveform osc;  
AudioOutputPT8211_2 out;

AudioConnection out_l(osc, 0, out, 0);
AudioConnection out_r(osc, 0, out, 1);

void setup() {
  AudioMemory(4);
  osc.begin(1.0, 440.0, WAVEFORM_SINE);
}

void loop() {

}
Click image for larger version. 

Name:	IMG_1764_.jpg 
Views:	1 
Size:	140.7 KB 
ID:	20722
Click image for larger version. 

Name:	IMG_1766_.jpg 
Views:	4 
Size:	167.7 KB 
ID:	20723