More about current consumption

The technical specifications for our products in pedal format (Torpedo C.A.B. and Le Preamp series) include a voltage and current value. To understand how they work, let's first talk about power supplies.


Power supplies are voltage sources, which means they supply a voltage. A 9V power supply will always supply 9V, no matter what you connect to it. On the other hand, the current can change freely. Consider this : when nothing is connected to a 9V power supply, the voltage is 9V, but the current is zero, because there is nothing the current can flow into. As soon as you connect a pedal to the power supply, current begins to flow, and the value of the current actually depends on the pedal (how much does the pedals require), not the power supply.

Every power supply has a limit however, some maximal amount of current that, if exceeded, will cause the power supply to overheat, go into protection, fail, or even be destroyed. The actual result depends on how well the power suplpy is designed, but the bottom line is : this value should not be exceeded.


What this means from the pedal's perspective is:

  • the voltage value of the power supply should exactly match the voltage required by the pedal
  • the current value of the power supply should be equal or higher than the current required by the pedal.

If you connect several pedals to the same power supply, you should add the current requirements of all the pedals. This sum should be equal or less than what the power supply can output.


Now to go into more details about all this:


If you know a little about electronics, or if you are a little bit curious and maybe made a current measurement on your pedal, you may know that a pedal rarely actually draws the exact current that it says it requires. This is because current is highly dependent on many factors that vary, sometimes widly, like ambiant temperature, or the fact that the exact values of the components can't be controlled to an infinite precision. In particular, tubes are known for varying largely, and if some tubes are sorted, only a few caracteristics are actually selected (usually gain), while the others remain unmeasured (like heater current, which has no effect on audio). And when it comes to digital products, any firmware change can have a sligth effect on current draw, which is virtually impredictable.


How all this is taken into account may differ among manufacturers. Here is how it goes for us here at Two notes Audio Engineering:


Indicated current draws are indeed always a little higher than current draws measured in real situation. This is because we always take into account the worst case scenario : every function used at maximum power, every input and output connected, extreme temperature, small variations of the values of every electronic component, and so on. The final step of this is to round up, which of has the advantage of presenting a nice and simple figure, but is also a safety margin.

Also, the manufacturer of the power supply may or may not include a safety margin. Our safety margin also takes that into account, in some respect.

All of this insures that, if you respect the current draw indicated on our products, you will never have a problem.

So does this mean you can actually power your Two notes product with less current than indicated ? Maybe using a 400mA power supply while Le Clean requires 500mA ? Well, the short answer is obviously "no, you shouldn't", but let's say it like this :

You can always try to bite the margin, and because it is a margin, maybe everything will be fine. But maybe at some point it won't, because these margins are not here for no reason. So it's basically up to you to use caution and common sense. We can insure that if you keep the margins, everything will be fine, but we can't insure anything if you bite them. It might work, but you'll have to test it to be sure. And even then, it might work one day and stop working the next day. Or it might work 1 hour and fail the next hour. Or it can work at home, but not on stage. Or it can work on a fresh day but not on a sunny day.

So if you want to try, our advice is: you can, but keep in mind that it may not work, and it may destroy the power supply. Even if it does, keep in mind it may not work in every situation. Maybe monitor the temperature of the power supply, and stop if it begins to get really hot. Definitively keep the original power supply somewhere, as a backup, and if something doesn't work as expected, don't insist, and use the original power supply instead.