Variable sample rates 4k - 65k!

I pretty much have known the 2kxl in and out for several years now, but I just stumbled accross something I've never seen mentioned before. I was loading up a basic Akai GM drum kit and noticed that there were variable sample rates on some of the files... 22k.... 48k... 48k!?!? what the hell? It doesn't say anywhere in the specs or manual that the engine can do anything other than 44.1k.

I know that resampling allows you to resample at a lower sample rate/bit rate, but wasn't sure if it actually stored the file this way or just reduced the resolution. As it turns out, the bit rate is always 16bit, even if you resample to 12 or 8 (it just reduces the quality, not the wav file format). When you redo the sample rate, it allows you to pick anything from 4000hz to 65000hz! The file size and file format is definately reflected from these changes, so it seems it can be pretty flexible when it comes to this rate (I had assumed most hardware samplers needed set rates like 11, 22, 32, 44, 48, etc).

I know this is nothing to get excited about, but was just a little stunned to see that it had the capability to load and play these files. I guess I should assume that the sampler will only play them back with 44.1k resolution since that is the rate it is specefied at? Maybe the rest just gets aliased out? The digital out only runs at that clock speed, so I would guess so. The only thing that throws me off is; why would Akai put 48k samples in their kits if they know they will only play back at a lower (aliased) rate?

Can you change the sample rate in the sampler itself? Otherwise I think the MPC would play it back at 44.1k regardless of how may samples were taken per socond, so it would sound faster or slower.

The MPC knows the sample rate of each sample (it is stored in the wav/snd file), so it always plays it back at the correct pitch regardless of the sample's sample rate. You cannot change the sample rate of the sampler itself. If you ever record anything, it will always be at 16/44.1 to start. The resample feature lets you resample down (or up) to a different sample rate while maintaining the proper pitch. You're thinking of just playing a sample back at a different pitch (which is the same as changing the tune in the program).

The MPC 2000xl is very suspect in the whole sample/bit rate aspect.
load a couple of WAV samples into the xl convert them to different bit rates and freq.
Then take them and open them up in WaveLab, Sound Forge or Awave and look and the info.
The files haven't been totally converted to the numbers you selected.
You will generally see the correct freq but the bit rate is still 16.
Now convert a WAV file on the computer to 12-bit and try to load it into the xl and watch what message you get.
NOT 16-BIT WAV FILE

The xl does a lot of point of reference DSP to files to try a simulate property conversion.

This reminds me of the Bit Crusher effect on Logic, which simulates lower bit rates on sounds, so although your original sample is 16 bit you can make it sound as if it was 6 bit.

Naw, I'm not thinking of the pitch thing, unless changing the pitch in the MP actually changes the sample rate, rather than the playback rate, I believe the amount of samples does not change, just the speed at which they play back.

But if you have a 22.05kHz sample, it will play back at double speed in a 44.1k Machine. It's cool that the mpc adjusts for this, but I am curious about this implementation.

ntalec, I don't think you read my whole post... I already said it only uses 16 bit wav files (even if you convert to 12 or 8 ), its the sample rate that is actually effected in the file (which is what the post was about). This is because the MPC was only designed to work with 16 bit files, this is why I found it interesting that it is so flexible with sample rate (thought it was stuck at 44.1).

elmacaco, it is RESAMPLING not playing back at another pitch. Just try the resample feature, it sits there forever and actually resamples to a new sample rate, not just pitch it differently (which can easily be done in real time by changing the tune). It's real simple, wav files store the sample rate in the header so the MPC knows what the sample rate is when it loads up the sound. So it would play a 22.05 sample at half the speed so it plays correctly. Its the same thing if you open different wav file formats on your computer, it reads the headers and knows how to play them back properly. If you were to physically change the header to the wrong value, then yes, you would get a pitched effect, but thats not what I'm talking about, just the actual sampe rate.

MC SMOOTH, my whole post was just to state that what the xl does is point of reference, it just uses DSP to compensate for the variable.
As far as the xl is concerned every WAV is still 44.1k it just calculates what a different freq WAV would sound like from that reference.
For the most part it's effective for freq, but that's also what they did for the bit rate which on the other hand doesn't work.
Unlike freq bit rate relates more directly to the hardware. It would require some form of modeling to achieve the characters of flws that go along with lower resolution.

Actually the WAVs aren't all 44.1k, that was what I was saying. Try loading a 11k 16bit wav file, it will work, and takes up a quarter of the memory as the same sample at 44k in memory. This does not appear to work for different bit rates (you will not see any difference in sample size when dithering to 12 or 8 bit).

I think what you may be saying is that the sampler is always running at 44, so it technically it is always at that rate (which is why the digital out plays at that format only), and the DSP plays things back accordingly to do so. If so, I get what you're saying, I think its the case.

I had always assumed that 48k samples wouldn't work in the MPC, but found it cool that this was not the case. The real question was weather or not the MPC would play back a 44k and 48k sample any different quality wise. If it dose always play back at 44k, then you would lose the extra quality when playing back the sample normally. However, if you were to pitch the sample down (making it play slower), you would have better sample resolution, whereas with a 44k sample, if you pitch it down you start to hear the quality go down quickly. See how that would actually be of benefit to people who pitch a lot? For example playing notes (via 16 level tuning) or messing with loops and slowing them down to match a tempo. Normally when you slow a loop down more than 10% you start to hear the artifacts.

Yeah I think you are getting what I'm saying.
The xl just does the math (DSP) to say divide or multiple from the 44k point of reference to play the odd rates properly.
Would have been nice if you could change it when sampling.