Voltage vs. current
The midi signal is sent as 0 or 1.
The midi cables sent a 5 V current that is controlled by an optocoupler.
Broadly speaking: If the current flows, the system recognizes a 0.
If there is no current floating, the signal will be processed as a 1.
Unfortunately, not all devices use the same standard – some effects analyze the current and others the voltage.
Especially the synchronization of different devices is vulnerable to misunderstandings between the diverse effects.
Although all systems use a DIN plug, they do not always proceed with the same system.
Besides a midi clock, that is controlled either by the current or by the voltage, there are also DIN-Sync and analog clocks, which are unable to collaborate with each other.
The Chase Bliss Audio effect series is a good example for this.
These devices use a current based midi clock. To collaborate with other midi effects, it needs a special current to voltage converter.
The EXH Super Pulsar is also midi clock compatible.
But it also needs a converter to work together with other midi devices.
Doepfer offers a small midi to sync converter that dependable synchronizes the Super Pulsar.
Other interesting examples are the DigiTech SDRUM and the JamMan Stereo.
Formally, they do not support midi messages but via the 3.5 mm TRS jack they are able to send and receive midi signals like start, stop and a midi clock.
To integrate these devices into your setup you only need an adapter cable with the appropriate pin assignment.
You should in general avoid stacking too many midi devices. Otherwise latencies will occur.
It is preferable to use a midi splitter and keep the single midi paths as short as possible.
Nevertheless, if you want to create a midi chain, you will get to know, that not all midi devices are compatible with each other.
Although each of them has got a midi output, it is possible that they do not lead enough current/voltage to the next device.
In this case, it is worth it, to try out different orders of the pedals.
In my setup, the Moog MF104M only works if it is placed behind a piano module.
If the midi setup works, it can be pretty helpful.
Besides the clock sync, it is also able to control the switching of the presets.
If several band members or even a sequencer are connected, many preset switches can be simplified a lot.