Please can someone help with this? I have searched this forum and the web, but find very little about using the Teensy audio capability with speakers.

I've got my Teensy 3.2 + audio board happily playing the SDTEST.WAV files, or my own .WAV file, from the SD card, and I can listen via the headphone jack.
However, I can't seem to persuade it to output anything to my amp via the DAC output. There is some hiss from the speaker, but no signal.

Hardware:
Teensy 3.2
Audio board
Adafruit PAM8302A
8ohm Visaton speaker (what I happened to have)

I have connected A+ on the amp to A14/DAC, and A- to GND.
I am powering both from 4AA LiFe batteries via a Polulu step-down 5V regulator.
GND is common throughout.

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

AudioPlaySdWav           playWav1;     
AudioOutputAnalog        dac1;           
AudioConnection          patchCord1(playWav1, 0, dac1, 0);
AudioControlSGTL5000     sgtl5000_1;     

#define SDCARD_CS_PIN    10
#define SDCARD_MOSI_PIN  7
#define SDCARD_SCK_PIN   14

void setup() {
  Serial.begin(9600);

  AudioMemory(8);

  sgtl5000_1.enable();
  sgtl5000_1.volume(0.4);

  SPI.setMOSI(SDCARD_MOSI_PIN);
  SPI.setSCK(SDCARD_SCK_PIN);
  if (!(SD.begin(SDCARD_CS_PIN))) {
    while (1) {
      Serial.println("Unable to access the SD card");
      delay(500);
    }
  }
}

void playFile(const char *filename)
{
//  Serial.print("Playing file: ");
//  Serial.println(filename);

  playWav1.play(filename);

  // A brief delay for the library read WAV info
  delay(5);

  while (playWav1.isPlaying()) {
  }
}

void loop() {
  playFile("LAPWING.WAV");  
  while(true); 
  }