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The Balance Of Power

No sooner had I opened a new file to write this leader column, aimed squarely at the annoyance of external power supplies, than I received an email from one of our long-time readers asking if he could submit a Sounding Off piece in favour of them. His argument was that by getting all those nasty little transformers away from the rest of the audio gear, there’s less chance of hum pickup. Up to a point that is perfectly true, and in fact I have no beef with properly designed external power supplies, but, sadly, some of the nastier ones actually inject interference back into the mains supply.

Paul WhiteWhile some manufacturers do indeed decide to use properly designed external power supplies to improve technical performance, a great many others use consumer PSUs because they are cheap and because it simplifies the process of getting new designs approved for sale in different countries. Unfortunately, I’m told there are regulations that prevent the equipment designers from building in a storage compartment to hold said external power supply in such a way that it can be connected up via a regular IEC mains cable to keep the thing from getting lost or damaged. In addition to the prospect of loss or damage, there’s also the irritation factor when you plug one of these wall-wart PSUs into your mains power reel and find that it obstructs the socket opposite so you can’t use it.

Fitting those familiar little coaxial power sockets to effects pedals is fair enough, as anybody serious about using them live will have them mounted on a pedalboard and run them from a dedicated multi-output power supply. However, using consumer-grade wall-wart power supplies to power multi-effect pedal processors, vocal processors, guitar processors, personal monitors and even keyboards is just asking for problems in a live sound situation. I was prompted to write about the subject following a spate of local musicians bringing things to me for repair.

The use of thin cables means that the inevitable continued flexing eventually breaks the cable or splits the insulation where the cable joins the plug or where it enters the power supply. I’ve had to fix or replace lots of those. But that’s not the worst thing, as the push-in connectors often get trodden on or knocked, breaking the socket (or worse still the circuit board) on the piece of gear they are powering. I’ve seen this happen twice on a gigging keyboard and just this week I repaired a guitar multi-effects floor unit that had suffered the same fate. Then there are the odd disasters where somebody damages a piece of gear by plugging in the wrong power supply. The least the manufacturers could do is provide a stick-on label to put on the included PSU to tell you which piece of equipment it belongs to.

We can’t reasonably expect manufacturers to stop using external power supplies, but I would encourage them to have versions made up for them using heavier and more resilient cable plus proper locking metal connectors that put the stress on the equipment chassis, not on the circuit board. Just shipping a consumer PSU with an otherwise professional piece of equipment does nobody any favours and I make no apology for pointing this out where appropriate in my reviews.