Thank you very much for all the feedback about the last post and consequential survey that some of you have replied, much appreciated.
Following on what was being discussed in the last post, the feedback I’ve got from the survey had me thinking about the possibility of how to address the issues that my questions raised as well as your replies.
The two most important concerns that came up when using MIDI comms are Packet Loss and Hardware stop functioning at all. Let me address them separately.
When I say Packet Loss, I mean when your devices are sending MIDI commands and the receiver gear is not acknowledging or responding to them 100% of the time. Quite frustrating actually, especially if you are on stage trying to change the clock or your guitar pedal board patchbay. The issue could be in the transmitter, receiver on in between, and it cam be quite painful to find an intermittent fault.
So, lets break this down into the following scenarios for tests need to be done to the system as a whole to find the fault.
Yes I know it is the lamest of the excuses but you should check it first before going to the trouble of the next round of fault finding.
The power supply (PSU) is the most important module in the system as it delivers clean uninterrupted power to the MIDI transmitter and receiver. If the PSU is found to be the culprit, the issue should disappear instantly.
So, how to find a fault in PSU? With a voltage meter, start by measuring the voltage at the output of the PSU. If the PSU says it should output constant +9V DC, then your meter should not move more than 5% within that value. There is always a percentage of error due to component variations, temperature and output load. Measure again when devices are communicating and if power is getting to all devices with no exception; again the meter should read same value. If so far you haven’t found the issue, you may need to get hold of a piece of lab equipment called Oscilloscope, this will enable you to “see” the PSU output voltage signal on a screen instead of just having its magnitude measured and presented in numbers. The scope screen should show a straight line when devices are communicating. There may be very small fluctuations but this is allowed within the 5% error I wrote above. If you see big deeps or peaks in the wave while MIDI packets flow, then there is an issue with the PSU or it may be something harder to overcome: EMI electromagnetic interference.
EMI – Electromagnetic Interference
Everything works in the studio but when you go out to stage it behaves erratically? then EMI may be the thing. Conducted through cables and PSU and being received from radiation.
EMI is something that we can’t run away from, especially in this day and age with so much wireless communications and heavy electric power consumption everywhere, but there are ways to mitigate the problem.
In my previous post I proposed to used a good quality cable with narrow tight metallic shielding to help to block all external EMI. The shielding should be connected to the Ground pin on the transmitter side only. And last but not least, if shielding doesn’t mitigate completely the issue, get a toroidal ferrite core and wind the MIDI cable 3-5 turns.
If none of these solve the problems you are having, then more aggressive measures have to be taken. Please read next post to find out how we will solve this.