mpc 2000xl internal clock drift ? you decide

I noticed something very strange in mpc's timing. I would never think that it might occur.

When checking different syncing techniques for tracking my beats (midi clock, midi time code, smpte), I discovered that my mpc 2000xl has a 'original' interpretation of (for example) 95 bpm tempo, comparing to tempo of cool edit pro 2.1 or ableton live 6.

I made a test:
-recorded a metronome click of my mpc at 95 bpm, it played for over 4:30 min (no syncing during that)
-truncated the silence at the beginning of wav, so the first click was exactly at the very beginning of wav
-put this wav on the time ruler of cool edit pro 2.1 and ableton live 6 (both programs were set to 95 bpm, time rulers were set to bars + beats)
-I noticed that after 1 minute, the click of mpc was slightly after the grid of time ruler (in both programs)
-what's more, after 4 minutes, the mpc's metronome click went behind the time ruler even further, (in both programs) causing a delay/timing drift of over 40 ms

I asked one of the members of this board (mpc 2000xl owner) to record metronome click of his machine at 95 bpm, over 4:30 min long, just like I did, the same way (with no syncing) and send it to me. I asked him to do that, because he lives in the States and I'm from Europe and I wanted to have an independent source from far away.

After putting his wav on the time ruler (both programs again), I had the same results...timing drift of over 40 ms.

After these tests (I checked many combinations, including recording metronome click from mpc when it was synced to other equipment - hardware/software) I came to the conclusion, that mpc's timing is different...What's more, I stopped relying on mpc's internal clock and now I only sync my machine to software I track with.

I wonder if any of you had these problems or can share any thoughts about this issue?

I would like to point that this post refers only to 2000xl model, since I don't have any detailed experience with synchronisation in other mpc models.

i think your problem could be your harddrive this is a common problem with slower spinning harddrives they carnt take in all the information and still keep perfectly in time, it gets overworked. what is the rpm's of your harddrive? if its 7200 (most hardrives in normal home computers are) or below you should upgrade to at least 10000 rpm's for seriours recording, i too have had problems like yours with many groove box's and samplers in the past until i read up on hardrives, aparently after your sound card an monitors, a fast harddrive is just as important in a recording setup. their are a few other things/spec's your recording harddrive should have, look up harddrives for audio recording in google. hope this helps

You missed one thing.

I asked one of the members of this board (mpc 2000xl owner) to record metronome click of his machine at 95 bpm, over 4:30 min long, just like I did, the same way (with no syncing) and send it to me. I asked him to do that, because he lives in the States and I'm from Europe and I wanted to have an independent source from far away.

This excludes the possibility of a slow hard drive in my pc, which anyway was good enough to handle some serious recording so far and everything was in time. I mean recording that didin't involve mpc itself.

this is normal. every digital device has a little bit of drift when they are not synced together. try the same thing with two computers side-by-side and you will see the same phenomenon.

the reason is: the mpc derives its sense of time from the digital audio clock. that's the thing in the mpc that keeps the sampler running at 44.1khz (44,100 samples per second). since the mpc knows that the sample clock is running at 44.1khz, it can derive all other time from that (ie. 2 beats every 44,100 samples = 120bpm).

your computer works the same way, but it has a different digital audio clock inside it's own soundcard. just like two watches put on a table next to each other, they will eventually drift out of time. however, since the digital audio clocks are running at a much faster rate than a regular watch, the drift happens faster, like you saw.

this is totally normal. you can do the test with a computer and an mpc, two mpcs, two computers, whatever. stuff always drifts because the very tiny manufacturing differences are multiplied out times millions and millions of samples. the only way to fix this is to actually sync the two boxes with midi time code, midi beat clock, or SPDIF.

hope this helps! i spent a long time battling this myself, so i know where you're coming from. cheers

peter

It's weird though, that my su700 sampler passed this test excellent.
I mean, I did the same thing with it's metronome, truncated the silence at the beginning of wav and there was no drift after over 4 minutes.

It's hard to decide which interpretation of e.g. 95 bpm is more accurate, software or mpc's ?

Anyway, after these tests mpc looses the battle in syncing, imo. Slave only.

This topic was ment to be more like a tip for all users that might track everything from mpc and then put it into DAW with other tracks from this program...like I did.
I wasn't sure if anyone new about this 'issue'.
Now...I guess someone did now.

NO drift after 4 minutes at all? was the su700 connected digitally to your computer, or just with analog patch cables? either way, that's interesting!

That's the thing u know...
I recorded su700's metronome the sam way as mpc's - with no sync options, just through audio cables and trimmed the silence at the beginning.
NO drift. I'm sure about that cause I payed close attention to all the details when doing these tests.

Anybody who has 2 different machines with internal sequencers (and one of them is mpc) can do this test. I takes like 20 minutes to have wavs and compare them.

ascdi wrote:this is normal. every digital device has a little bit of drift when they are not synced together. try the same thing with two computers side-by-side and you will see the same phenomenon.

the reason is: the mpc derives its sense of time from the digital audio clock. that's the thing in the mpc that keeps the sampler running at 44.1khz (44,100 samples per second). since the mpc knows that the sample clock is running at 44.1khz, it can derive all other time from that (ie. 2 beats every 44,100 samples = 120bpm).

your computer works the same way, but it has a different digital audio clock inside it's own soundcard. just like two watches put on a table next to each other, they will eventually drift out of time. however, since the digital audio clocks are running at a much faster rate than a regular watch, the drift happens faster, like you saw.

this is totally normal. you can do the test with a computer and an mpc, two mpcs, two computers, whatever. stuff always drifts because the very tiny manufacturing differences are multiplied out times millions and millions of samples. the only way to fix this is to actually sync the two boxes with midi time code, midi beat clock, or SPDIF.

hope this helps! i spent a long time battling this myself, so i know where you're coming from. cheers

peter

Bang on the money,, every sequencer interprets bpm from either the audio cards digital sample rate clock or in the case of older software sequencers and possibly harware based sequencers its internal timing engine an internal timer if you will. Each sequncer has a resolution which is based on ppqn (pulses or parts per quater note). This DOES vary from sequencer to sequencer unless they are both being driven by the same digital sample rate clock.
Try importing a Logic audio file click track into Protools then doing a tempo map based on that click track you'll see the variation.