I'll try not using the ac adapter and I'll pick up some batteries instead for the recording. In a way I like the noise because It makes it sound so raw, but I just don't want it to catch fire as I'm playing lol.

My bet is this. Sounds like a power problem.

circuitbend it.

Sounds like it could be the AC adapter you're using isn't providing the right voltage or amps, or low batteries if the unit has them (not familiar with the Casio SA 21). I used to have that "crackle" at the end of the note on my old portatone keyboard when the batteries were getting low.

Not sure if this is what you're describing?

"The sounds of this instrument are made from low resolution samples and thus partly have quite funny timbres. There is a reverb in most percussive and many other sounds, that was likely added to hide the aliasing noise of the low sample resolution and to sound differently than Yamaha."

I am getting a really sandy harsh sound when I play my Casio SA 21. It's like the samples are airy and like flute like, and they always crackle when the note ends. Could anyone help me with advice on fixing this/?

Also one more question, I want to buy something from usbgear.com
does anyone know if this is safe site?
Cheers and thank you guys for your time!
-4BP