Crackling in audio from AP-16+

[JackMan]

I'm getting periodic crackling coming thru the speakers from my Thriller sound track played on an AP-16+. I'm using the line level outputs connected to an amplifier. This is the same sound file and amplifier I used when the program was being run with my laptop with no issues in the sound. The file is on a Sandisk Extreme III SD card. The crackling is not very loud but it is quite noticeable. It seems to be consistant as far as when it happens which tells me there's something on the track that it's picking up but this file plays fine on my computer or an MP3 player. Any ideas?

[JonnyMac]

We actually have "anti-crackle" software in the code because of the way the Propeller works. This code was provided by Parallax and we've tested it on hundreds of files. I wish there was a way for you to get the file to me so that I could hear it for myself.

The dither is adjustable and I may be able to modify the code for you so that it handles that section; when we experienced it in the past it was usually with low frequencies, but we've tested that extensively with the player. Again, would be nice to hear what you're hearing.

[JackMan]

Now that I think about it I noticed this problem last year when I tried my Thunder and Lightning sound track on the AP-16+ but I didn't end up using it for that audio. I tried another SD card this morning and also tried using the direct speaker outputs, same result. I'll save a small portion of the Thriller track to a file and send it to your email later today.

[JackMan]

Jon, I tried several times to send a clip of the Wav file to your email but it just ain't happening with my PITA dial up. I'll have to try from another location tomorrow with high speed.  :o

[JonnyMac]

I was chatting with John B about this and he reminded me that speaker selection can affect this, in fact, I saw this last year working on the FireFall display which used an AP-16+.  The amps really want a 4-ohm load for best performance.

[JackMan]

My speakers are 8 ohm but I'm not using the onboard amps, I'm using the line level outputs with an aux amplifier. When I noticed this last year I was using the onboard amps and those speakers were 4 ohm. I emailed you a clip of the wav file this morning, let me know if you hear anything. Thanks.