Hi, I uploaded the Example Playback sketch for this library. http://highlowtech.org/?p=1963
There is a square wave output on Pin 11, at approximately 50kHz. When I connect a small amplifier and speaker to the pin via a blocking capacitor, there is some variation in a high pitch whine noise, at about the same repeating rate of the expected sample repeat rate. I put the same playback code into the loop() as well as setup(), to be able to continuously monitor the output without having to reset. I tried a simple filter of 470 ohm in series with output and 0.1 microfarad after that to ground. Square wave is showing on scope as a much lower amplitude triangle wave. So the filter is working. Still no audio output to the amplifier. Amplifier is working fine with another source.
An Arduino Promini is using the same Atmega328 as an Uno. There shouldn't be an issue?