As written in articles past, I’ve christened Tim Escobedo as the “godfather” of DIY, when in reality, he’s more like Sonny Corleone—the eldest son of Vito Corleone, the actual Godfather. In the annals of guitar effects history, Jack Orman is Vito, and his DIY projects are circuits you can’t refuse.
And I mean that very literally—Orman’s craft has been copied and re-copied among boutiquers since the word was used to describe pedal builders. His webpage—musique.com—has been bookmarked on every pedal tinkerer’s computer since launching in the days of web 1.0. The page contains original circuits designed by the man himself, as well as treasure troves of knowledge from which any pedalsmith can learn at least one thing they didn’t know already. Schematics flow freely on the page, and one such is what I consider to be among the best clean boosts ever made.
Copyrighted in 2001, the AMZ MOSFET Booster beats the pants off almost any booster on the market with minimal parts. Unlike most pedals of its time, it uses a Zener diode, which isn’t found in almost any other pedal even to this day. Whether or not that diode contains all the proverbial magic isn’t exactly the point, but rather that innovation led to the MOSFET booster, and the result is a low-parts-count monster of a boost.
Because the circuit is relatively simple, I will take this time to instruct you how to build pedals in a 1590A enclosure, also known as “mini enclosures.” It’s an art unto itself in the effects world, and cramming a DIY effect into such an enclosure without the benefit of surface-mount boards and pots is often an endeavor. Luckily, the MOSFET booster fits perfectly, and you will soon see, because you will be building one.
But first, let me hit you with that disclaimer:
Neither I, nor Tone Report Weekly bears any responsibility for any kind of personal or property damage that may occur as a result of the instructions provided herein. Legal mumbo-jumbo aside, we ask that readers be familiar with a soldering iron and its accompanying safety procedures before trying anything listed here. Furthermore, if you fire the pedal up and it does not work, it will need troubleshooting. Assuming the components are not damaged, the pedal will work. I built this very unit according to these instructions and it fired up, first shot, so I know the instructions are correct.
Ok, now let’s do this thing! Here’s what you’ll need:
1x 47pF ceramic
1x 2.2nF film (0.0022uF, the original calls for 1nF/0.001uF, but I like the sound of the 2.2nF better)
1x 100nF film (0.1uF)
1x 10uF electrolytic
1x 100uF electrolytic
1x BS170 MOSFET
1x 9.1v Zener diode (part numbers vary, mine is 1n4739A)
1x 3-pin transistor socket (buy SIP socket and break off three pins)
1x piece of Veroboard (stripboard) cut to the specs in the diagram
This is a short one, so let’s go! Before we continue, though, in a 1590A enclosure, compactness is key. Be sure to keep wire lengths as short as possible, and I will offer some tips here and there that slightly deviate from standard procedure.
Insert resistors and diodes, bend leads out, then solder and clip. Save the leads for later.
Use one of the leads to form the sole jumper wire, then solder it in. Insert the transistor socket, then place a flat object on top and flip the board over. Solder in the socket.
Insert the caps, bend leads outward and solder. Mind the polarity of the electrolytic caps.
Attach the wires, keeping them as short as possible relative to their destination. I used a bit of double-sided foam tape to mount the board directly to the pot. Again, keep wires short, we have limited space in the enclosure.
That’s it! Now let’s build the enclosure!
The old adage “measure twice, cut once” needs to be modified for the DIY set when it comes to 1590As. We will change that to “measure thrice, cut once” because accuracy is critical. If you’re using a pre-drilled enclosure, you’re in the clear, but take care if you drill your own.
2x ¼” mono input and output jacks. Lumberg jacks are the best for this, but anything low-profile is critical
1x 3PDT latching footswitch
1x LED; you can use whichever size you want but I recommend 3mm
1x LED bezel of the same size
1x knob of your choice, but make sure it won’t hang over the edges for aesthetic purposes
1x DC power jack
Resistor for the LED (I used 4.7k)
Mount the switch, LED in bezel, and all jacks. Again, space is critical.
Wire the LED’s negative leg to lug 1 on the switch, and attach a component lead between lugs 4 and 9. Solder lug 4.
This is where we ground the pedal. Attach a wire to lugs 2 and 6, then attach that to the nearest ground point—the sleeve lug on either jack or the DC jack’s negative lug. Soldering as you go, attach wires to all these points, leaving the last point unsoldered for now.
Connect the input and output jack tip lugs to their appropriate spots on the switch—input to lug 9 and output to lug 8.
Solder the resistor to the LED’s positive lug, and then attach the other end of the resistor to one of the power lugs on the DC jack. DO NOT solder yet.
Your pot has a metal tab on it that prohibits it from being mounted properly. Remove it with pliers and insert the pot and board. Attach the loose wires to their destinations, including the power (thread power wire through both positive lugs, one of which is shared with the LED resistor and solder them both), ground (attach to previously unsoldered ground lug), Gain 3 wire (to any ground point) and circuit inputs and outputs (lugs 5 and 7, respectively).
So, what does it sound like?
It’s definitely one of those pedals that you may never turn off. It brings out all your guitar’s natural “flavors,” if you will, and I can see hollow and semi-hollow players especially fond of the circuit. It also seems to get cleaner the higher you turn it up, which is somewhat of a rarity. Even with the knob on zero, it sits around unity gain and thickens the whole mix. Here’s Andy giving it a whirl on a couple of his amps.
Until next time, up the irons!