Tearing into a Morley Mini-Volume

In my quest to create my ideal portable pedalboard I've decided a Morley Mini Volume pedal is perfect for adding volume functionality to the finished product. The idea is to just use the circuitry in a new enclosure so as to avoid unnecessary routing and cabling. I had lofty goals of completing some projects for work and on our house today, but unfortunately I feel like I'm about to die, so I'll do something that requires less effort and decipher the schematic. First thing's first, tear it apart:

It's a very simply constructed pedal. It's not even a fully enclosed box or cast aluminum or steel as many are, but rather a formed piece of sheet steel with a bottom cover. Four screws hold the bottom in place. After removing the screws it's easiest to remove the battery cover and reach inside to pull the base off. It's a very tight fit, so it takes more force than I was initially comfortable with, but nothing broke, so I was good.

The wide open space of an optical volume pedal. From the factory 

it featured a foam battery holder and 9V terminal. I tore them 

out the first time I opened it since I always power it with a 

9VDC power supply. 

The next step is to remove the outer nuts from the in/out jacks and the nuts that hold the pcb in place. A socket or wrench for both are necessary unless you're too lazy to walk across the room to the workbench so you just grab a pair of pliers and go to town. That works too. Then with a little bit of finesse and some prying on the case you can remove the entire PCB in one piece. 

Evidently in order to save money on production costs Morley uses the same board for all their mini pedals. They offer a volume/wah combo, as well as a dedicated wah. This PCB has two sets of LED/photovoltaic sensor combos, although only one is in use. Once I discovered this I started formulating how to incorporate a switch onto the body of the new enclosure that would allow me to switch between acoustic and electric volume. Basically in position 1 the acoustic would be full volume while the electric is controlled through the top bank of LED/photovoltaic sensor, and in position 2 the electric would be at 0 volume while the acoustic is controlled by the lower bank of LED/photovoltaic sensor. This will allow me to start at 0 volume on both signals, fade the acoustic in to full volume, hit the switch, and then have the electric. If I decide to have the option of fading the electric in I will need another switch that would mute it while I move the pedal back to the 0 position, then reengaged the signal and fade up. I'm not sure that's an option I'll want to use because of the amount of space needed to add two more switches on the final enclosure. Regardless of what I decide, there are two sets of LEDs:

 They shine through these slots and illuminate the photovoltaic sensors. A lot of reviewers online complain that this pedal is either all on or all off. This is because of the design of the holes. They're shaped similar to a hammer, a long skinny 'handle' and a large open 'head. When the 'head is in front of the LED, all the light is allowed through, where the 'handle' section limits the amount of light. I'm thinking that this could be remedied by tapering the opening more and then adding a small piece of translucent tape. I'm not unpleased with the control of the unit, so I will not mess with any of it unless I find myself frustrated with it, or am really, really bored one day.

The circuitry of the volume pedal is insanely simple. Below left is the top (pedal side) of the board, and below right is the bottom side:

In it's simplest explanation, the LED is constantly powered by either battery or a 9VDC power supply (when the pedal is powered on, through the switching input jack). The ground is common for both input and output jacks, as well as the LEDs. The tip (hot) side of the input jack runs to one side of the photovoltaic sensor while the tip of the output runs to the other. The amount of light that reaches the sensors adjusts the amount of signal that passes through from 0-100%. As I said earlier, the second pair of LED/sensor is unused. Here is the schematic I drew up to help get it all clear in my mind:

Now don't focus too much on the wildly beautiful hand drawings that make up this little beauty, because you'll miss out on all the wealth of information it has to offer. What it lacks in complexity it makes up in simple straight forward information. If you'll notice that I've already noted where I intend to steal the signal to send to and and receive from the iRig Stomp. This was originally penned when I intended to just house the guts from the iRig in the enclosure of the Morley. Since I intend to house it all in one enclosure, there will be no need to grab the signal from the input of the Morley since I will simply rout straight from the input jack of the enclosure to the iRig, and then from the output of the iRig to the side of the jumper leading to the sensor. The only reason I will use the jumper is simply because it will be easier to solder there than elsewhere. If I decide to add the switching option for the acoustic signal I will just jumper on the in/out to the bottom photovoltaic sensor and use either a 3PDT or 4PDT switch to handle the signal routing.

Hopefully the coming weeks as I mull over the final product I'll be able to find a few more ideas/shortcuts to make the whole thing work a little better or more polished. Anyway, this is a teardown and reverse engineering of a very simple little volume pedal. I'm hoping that you'll find the confidence/desire to tear into some of your stuff and make it a little more perfect for you...