Colorless writings, part 13 – The Power

I just noticed something. It’s been exactly one year since i started the current reincarnation of this blog. Since 19th of july 2013, i’ve written 144 posts. Eleven and thirteen bi-monthly. This post marks 13th Colorless Writing, which also mens that i’ve written my reviews/analysis on 130 pedals so far. To be honest, i’m not sure if can keep the pace as i may run out of pedals to write about at some point. Maybe a little less per month should suffice… Anyway. I’d like to thank you, all my readers. Thank you. Now let’s get over this crap and talk about Power!

Powering up the pedals are we?

Yup. It’s been a while since i started to read Denton J. Dalley’s book called Electronics for guitarists. The first edition is up on the web for grabs, but i didn’t know that at the time i bought myself a paperback version of the book’s second edition. The first edidion has most of the information, but second has over 200 pages more and it’s been updated on many subjects. Not to mention there’s a foreword by Billy Zoom. This book is highly recommended reading by the way.  The book starts out by saying a thing or two about the power. In our modern world we get our electricity through our wall sockets and what we get is a alternating current electricity. AC has a lot advantages when we need to transfer that power from power plant to our houses, rehearsal studios and clubs we gig at. The loss is a lot lower than what it would be to transfer DC current. To be exact, the DC would be real pain to move if we need to have more than fifty meters between the supply and the user. So what does this all have to do with our gear? Well. Everything from amplifiers to your pedals require direct current to work. Only thing that’s AC in our gear is the guitar’s (or bass’) signal itself (and some parts of our amplifiers, but i’ll disregared that for now). And that DC we’re hoping to use should be as stable as possible.

I’m not about to go too deep in AC power part, but think of a straight line where that line is zero volts. Now picture a sine wave going up and down that line, upper half reaching +120 volts and lower half -120 volts (that’s for us europeans). That’s what the AC coming from your wall socket looks like in theory. There are different phases to it, usually three, but the one is enough for our examples. Now, we need to turn that power in to a stable DC source for our pedals.

There are basically at least two things we need to do that. First, the transformer. What that does is it drops the voltage down and bounces the bottom half of the sine wave we discussed a second ago to the upper half, making the upper half a DC source. Let’s assume that this transformer is something we may find in standard 9V wall wart power supply. That’ll make the DC voltage appear on the line, but the dropping the voltage to something like 13-15 volts. Since the AC looked like a sine wave on that line, pushing the bottom part to top part doesn’t make it stable 13-15 volts. Sine wave stays in the equation, it’s simply pushed between zero and 13-15 volts instead of being where it was – between zero/minus and zero/plus. Due to sine wave looking like it does, there are bound to be lower voltages on along the line with our DC we got out of the transformer. For example, the new DC voltage could vary from +12 to +16 volts after the transformer.

And that’s called the ripple effect?

Exactly. Now, if we were to push that DC voltage to our pedals, we’d notice a high noise floor, hum or even loud oscillations and and other unwanted noises on some pedals. All these issues are usually generated by unstable, unregulated DC source. The second thing we need for a DC supply is a regulator. Regulators like 7809 are designed to take slighty higher voltage than their output and levelling the ripples. These regulators also need a few filter capacitors to function right. Since in this case we want regulated 9V DC output, the input for the regulator needs to be at least 12V. That’s why we used the transformer above to generate unregulated 13-15 voltage. The regulator cannot up the voltage, so if you feed the 9V regulator only 7 to 9 volts, you won’t be getting out nine, but a lot lower reading. It will need that 12V to fuction properly.

And next i’d like to take a look at the filter capacitors. The regulator usually wants some form of ripple filtering before its input and after its output. Let’s say that out wall wart in this case has 47µF caps at those positions. We may still have some ripples left, as even the best transformers and regulators are subject to what we feed them. Not all wall sockets offer neat and perfect sine wave. There will be variances. This is why we want and need to have power filtering in our pedals too.

Well. Maybe not for every single pedal, but most. Some wild fuzzes are better to be left without additional filtering as their features may be downsized by too stable DC source. But for non-dirt effects, the extra filtering is wanted. Looking at the filter, the idea is to place a capacitor between the supply and the ground. This will push the AC leftover ripples to the ground leaving cleaner DC voltage for the pedal. Mathematically thinking, the capacitor should be BIG to have a sufficient effect. That’s why you’ll find 1000µF and even 2200µF capacitors in some pedals.

But how does the unregulated power source affect the pedals?

Think of this like if you were powering your pedal with lab power suply that has voltage setting on a knob. Then you wiggle the voltage control between eight and ten volts as fast as you can. This will affect the operation of all your semiconductors. With fast and uncontrolled changes in operating conditions, the operational amplifiers can’t function properly. Same goes with your transistors. As supply and reference voltage changes, so change the operating conditions. And as the ripples come out at the same frequency as your wall socket pushes the AC out, you’ll have ~60Hz hum at the pedal’s output. In some extreme cases the ripple will result in even worse situations, like oscillations. But if we take one tiny 100pF cap and onebigger 220µF cap between the supply and the ground, that will send most of the inconsistencies in your DC voltage to ground.

There are a lot of different manufacturers offering their solution on how to power up your pedals. Some of those are well designed and offer very stable DC for your use. Some others.. Not so much. If your pedals sound like crap with lots of extra noises on their character, you should point your eyes to the power supply first. Even if it’s made by one of the biggest names in the business, it doesn’t mean that it will be the best choice for you and your chosen pedals. There is only one completely stable DC power source. And that’s a battery. But you can get a well regulated wall wart power supply that will serve you for 10 years easy – for the same price as you would need to spend on three batteries. Which is why i recommend using a good, regulated, stable powersource that turns the wall socket AC to the DC voltage you need.

Leave a Reply