128SP.. Different/occasional weird sound output?

I've been using 128XL on a 2500. Installed 128SP and messed around with it, but I noticed that sample playback introduced some weird digital hiss noise. Reinstalled 128XL and waited for the new update (the one released on Feb 24). I installed that and it was the same. Switched back to 128XL, then reinstalled 128SP and it seemed to disappear.. Weird.

So this is basically 3 questions:

1) Any other 2500 (or 1000?) user experience this weird digital hiss noise coming from the stereo outs/headphones?

2) Is there any conceivable reason beyond a normal bug why there should be any kind of general discrepancy between sound output from the two operating systems? This might be interesting, as I recall I think OS3 was an entirely different code base from OS2XL.

3) Or am I on crack?

Hi,
You're not on crack unfortunately
It's a known issue. It's in the FAQ.
http://www7a.biglobe.ne.jp/~mpc1000/mpc2500/faq.htm

:
Sound is distorted (OS3 & OS128XL)

A:
Since the bug of this sometimes happens, it cannot grasp a cause.
Therefore, time is required for fixation of a bug.
If DIGITAL is chosen once in the Iuput field of a record mode and it returns to ANALOG, a distortion will stop.
ANALOG => DIGITAL => ANALOG
Please stop a distortion by the above-mentioned method until it can solve a cause, although I feel sorry.
Please refer to the video of the following link.
http://www.youtube.com/watch?v=kmr_0vXqGDk (OS3)
http://www.youtube.com/watch?v=a4obwtCYt44 (OS128XL)

I guess it's an issue only with MPC2500 and also applies to 128SP now

Ok I didn't even know about this, thanks. I was about to see if I could re-create this and upload some samples with and without the effect.

I haven't had it happen yet in 128XL so I thought it might have been unique to 128SP. I'm guessing it seems to occur out of nowhere, but the solution to stop it is easy enough when it does happen. The effect might even be useful, it almost sounds like a bit reducer or something. When it occurs I could easily use it to gnarl up some synths and resample.

Does it sound like "white noise" over 8 bit sample?
On 1000 there was (fixed) smth like: when loop over a sample was too small - it was spitting out random samples of RAM with this kind of noise. But since you are in recording screen, that's seems not related, just sayin.