An extension of the Litmus Page but well worth a link of it's own considering its significance.

Midi Clock.  Simple in concept and mostly taken for granted its importance is often overlooked. We simply connect up, press play and enjoy the ride.

Or not.

Some clocks are better at keeping good time than others and if you use Midi Clock in your sequencing setup you need to know if your master tempo Midi Clock source really is up to the job or not.

By modifying a standard Midi cable and then connecting these to a 1/4" audio jack, Midi data pulses are converted to audio clicks which may then be recorded to any DAW software application to check timing stability.

The maths is very straight forward:-

Midi Clock runs at 24 pulses per rhythmic quarter note.

At 120 BPM this equates to 2880 Midi Clock Pulses per minute.

A DAW recording sample rate of 48 kHz captures 2,880,000 audio samples per minute.

At 120 BPM there should be exactly 1000 samples between each Midi Clock pulse when
recorded at 48 kHz.

The above screenshot shows 16 recorded Midi Clock 'pulses' as audio clicks into Sound Forge 9 (48kHz/24 bit) with precise sample markers placed at the exact front of each recorded pulse.

This screen shot is at maximum zoom showing the first marker placement at the very front of the pulse sample.

Same zoom setting but showing 2nd Marker at the same position of the pulse waveform.

The above screenshot shows two sequential markers and the exact number of samples between them.

Manufacturer: Innerclock Systems
Model Number: Sync-Gen II PRO

Recorded Midi Clock Intervals in samples - All Ports:
1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000 /1000

Maximum Midi Clock Error between any two sequential pulses = Nil Samples.

Maximum deviation away from 120 BPM/1000 sample target = Nil Samples.

Recorded Din-Sync Intervals in samples - All Ports:
1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000 /1000

Maximum Din-Sync Error between any two sequential pulses = Nil Samples.

Maximum deviation away from 120 BPM/1000 sample target = Nil Samples.

Manufacturer: Innerclock Systems
Model Number: Sync-Gen II LE

Recorded Midi Clock Intervals in samples - Midi Port Output:
1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000 /1000

Maximum Midi Clock Error between any two sequential pulses = Nil Samples.

Maximum deviation away from 120 BPM/1000 sample target = Nil Samples.

Recorded Din-Sync Intervals in samples - Din-Sync Port Output:
1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000 /1000

Maximum Din-Sync Error between any two sequential pulses = Nil Samples.

Maximum deviation away from 120 BPM/1000 sample target = Nil Samples.

Manufacturer: Akai
Model Number: MPC-3000
OS Version: Vailixi 3.50

Mansell-Labs Web - http://www.mansell-labs.com/ 

Recorded Midi Clock Intervals in samples - Port A Output:
1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000 /1000

Maximum Midi Clock Error between any two sequential pulses = Nil Samples.

Maximum deviation away from 120 BPM/1000 sample target = Nil Samples.

Manufacturer:Friend-Chip
Model Number: SRC MkI SMPTE Reading Clock
Operating System: 3.42 with MIDI Option fitted

Recorded Midi Clock Intervals in samples - Midi Clock Output:-
1000/ 1000/ 1000/ 1000/ 1000/ 998/ 1002/ 1000/ 1000/ 1000/ 1000/ 1000/ 999/ 1001/ 1000/ 1000]

Maximum Midi Clock Error between any two sequential pulses = 4 Samples (0.08ms)

Maximum deviation away from 120 BPM/1000 sample target = 2 Samples (0.04ms)

Manufacturer: Innerclock Systems
Model Number: Sync-Shift MkII

Test 1: MPC-3000 Midi Clock conversion to Din Sync:-
1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000/ 1000]

Maximum Midi Clock Error between any two sequential pulses = Nil Samples.

Maximum deviation away from 120 BPM/1000 sample target = Nil Samples.

Conversion process maximum added jitter = Nil Samples

Manufacturer: Elektron
Model Number: Machine Drum SPS-1UW MkII
Operating System: 1.50F

Test 1: Pattern Mode - Internal Sync:-
999/ 1000/ 1002/ 998/ 1000/ 1000/ 1000/ 1000/ 1000/ 1003/ 998/ 1000/ 1000/ 1003/ 997/ 1000]

Maximum Midi Clock Error between any two sequential pulses = 6 Samples (0.125ms)

Maximum deviation away from 120 BPM/1000 sample target = 3 Samples (0.063ms)