I'm an idiot. I put a filter into v54 to get rid of frequencies below 300 Hz and above 3000 Hz. However, I hard coded it with the wrong sample rate, which meant it was actually getting rid of frequencies below 408 Hz. I didn't catch it in testing because I wasn't testing with low frequency tones. Sorry for the foul up, a corrected v54a is now posted.
Andy
Andy, if it is any consolation, I am sure that you are the only one on this forum that thinks you are an idiot!
Keep up the awesome work.