Timing Issues in MIDI Slave Mode

After much testing I can confirm that there are timing issues when the 500 is in MIDI Slave mode. It is readily apparent when using any type of swing quantize - once in 'slave' mode the feel changes and in some cases using lower swing values (<60%), the swing disappears entirely.

Out of slave mode - just recording free into a DAW, the 500 shows rock-solid timing with very little variation from beat to beat - a testament to Roger Linn's original software. However, there appears to be a tempo difference of about .13 between the 500 and most software - e.g a 100bpm sequence would measure at 99.87 in Logic or ProTools - this deviation is very consistent across various tempos. No idea why this is so, but it does ring a faint bell in the back of my mind...

Anyway, the only workaround seems to be to increase the bpm in the MPC by .1 and dump all tracks "free" using a click at the start to line them back up. A lot of work, but worth it IMO.

Can't say if the problem is with the MPC or to do with USB MIDI. Tested using Logic 8 and ProTools 7.4 on a Mac iBook G4 with OS X 10.4.11. MIDI via Edirol PCR-50. MPC OS v 1.13

After some more testing I emailed Akai on this - no reply so far.


From another thread:

Just tested my MPC 500 with some interesting results. Using Innerclock's methodology and testing over 8 bars, the 500 is remarkably consistent with generally only about 1 - 2 samples drift. I say "generally" because there is the occasional 33 sample dip usually on the last quarter-note in about 2 bars out of 8. Where this occurs is not consistent - I'll have to test some more.

The other issue is that at 120bpm, the 500's quarters are 22081 samples apart - in other words not 120bpm - more 119.84 to be exact. I had noticed this before because on my system the 500 is useless in MIDI clock mode - the feel disappears completely. So I've been dumping beats free and editing them after. Testing using the above method revealed that the performance in MIDI clock mode to be pretty ropey - up to 64 samples drift. This may be a quirk on my system (MIDI via USB/OS X/EDIROL PCR).

If Akai could solve or fix that bpm mystery I would be very happy...

http://www.mpc-forums.com/viewtopic.php?t=89624&start=30