Cloning the Famous EQD Monarch

The EQD Monarch is an out of production FET based overdrive pedal that gained a lot of popularity as a dirty boost without a lot of extra distortion or compression. It was also available as a DIY kit for many years through StewMac (and others), but while StewMac still offers many DIY effects pedal kits, the Monarch is no longer among them. I had a friend who wanted a Monarch clone - largely to allow a bandmate to leave his original unit in the studio and gig with a more easily replaceable copy - so I started doing some investigation on boards and kits available. As it turns out, the pedal is more than a bit finicky, and there were some flaws in the original design which likely led to a fair amount of frustration for both the users and the DIY community. Chuck Bones (of the PedalPCB Boneyard) did a great analysis of the circuit, suggested some modest improvements, and then took that a few steps further ultimately creating the Viceroy - a six-knob, two footswitch Monarch on steroids. Down the road, I plan to build the Viceroy, but for now I was more interested in getting a good direct clone of the Monarch working well - and across its full range.

Even though I knew I was going to make modifications, I went ahead and started with the Effects Layout Tangerine board. This board is essentially a PCB version of the etchable trace on his blog. Unfortunately the PCB now seems to be out of stock. This particular board is designed to fit either in a 125B with top mounted jacks or a 1590B with top mounted power and side mounted audio jacks. As it can fit in the smaller enclosure, it is a fairly tight board. The solder pads are all generously sized, and the through holes seem to be a bit larger in diameter than what I'm used to. This made soldering everything to the board a little different as I was initially concerned I might have issues with jumping, but everything ultimately soldered down very nicely.

Studio tech expert Steggi validating the board - with Kyle the Ankylosaurus looking on

Since I knew I was going to modify the original circuit, I went ahead and breadboarded the whole thing first just to make sure everything worked as expected with the modifications before I began soldering down components. The modifications I used are mostly detailed in the PedalPCB forum thread linked above, but I also used FuzzDog's version of the board and his circuit diagram (which was largely based on the Boneyard modifications) as a reference. I then made changes to the schematic in the Tangerine instructions to use as my reference document for the bread board and later PCB builds. Once I had the breadboard version of the pedal working correctly, I began populating the PCB itself.

For both the breadboard and PCB builds, I used all 1% metal film resistors from Yageo and KOA Speer. The build calls for a couple of 10M Ohm resistors, which to get in metal film are a bit more expensive than your average resistors, but it keeps all of the resistors the same type and tolerance. The film capacitors are a mix of WIMA and KEMET. The MLCC capacitors are from KEMET and Vishay. All of the electrolytic capacitors are Nichicon.

As you can see from the PCB, there are a few major modifications to the circuit, mostly to improve the bias path for the transistors. C9 is eliminated and replaced with a jumper. R11 - normally a 470K Ohm grounding resistor after C9 is left out entirely (no jumper!). Both C10 and C12 are replaced with 10K Ohm resistors. The PedalPCB Viceroy makes several more changes to the base circuit, but I stopped there for these initial builds. 

As I was putting resistors in slots on the PCB originally designed for capacitors, I grabbed a couple of the vertically oriented 10K Ohm resistors I still had lying around from pandemic era shortages. Not only did they fit better, but they helped me keep all of the changes to the circuit straight in my head as I was populating the boards. Another change from my normal process for building a circuit was actually building with the circuit diagram pretty much in order rather than just populating with a parts list. This allowed me to validate that each component was actually hooked up correctly. I also discovered at least one error in the silkscreen. The outline orientation of Q1for a BS170 transistor is correct on the silkscreen, but the source and drain are mislabeled. Fortunately I was able to verify the correct orientation with my multimeter on the board itself.

Once the board was populated, boxing the PCB was fairly straightforward, with a couple of minor twists. Because the LED connects directly to the main PCB as opposed to a daughter PCB, I wanted to make sure the height and orientation of all of the potentiometers and the LED was correct. Therefore rather than trying to solder the pots on first, I went ahead and put them into the enclosure along with the LED and soldered them to the board from the component side. However, the treble pot (upper left) is sandwiched between two film capacitors. I therefore had to take the board back out of the enclosure (which I often do for testing anyway) and solder Leg 2 from the other side. I went ahead and used a PedalPCB daughter board as it lines up perfectly with the Effects Layouts main board. All of the jacks are insulated with heat-shrink tubing, and as there is only one ground connection to the main PCB, I used a star ground to the input jack like I would on an AionFX board.

As you can see from the interior shot, there is more than ample room to include a battery in a 125B enclosure, but I made the decision early on to not go that route to allow more room for enclosure art! Once again the art is provided by Ukrainian artist Kate (@estelkatrin on Instagram), and our mascot is the Monoclonius. According to Wikipedia:

"Monoclonius (meaning "single sprout") is a dubious genus of herbivorous ceratopsian dinosaur found in the Late Cretaceous layers of the Judith River Formation in Montana, United States, and the uppermost rock layers of the Dinosaur Park Formation in Alberta, Canada dated to between 75 and 74.6 million years ago."

With the almost Roman sounding name, I decided to go with a Greco-Roman themed enclosure. Initially I'd tried to go with a Greek Pottery theme which would have allowed me to bring the orange of the original enclosure through, but it just didn't quite work with the dinosaur art - so the more marble / fresco version worked better.

As to the sound of the pedal, this is another one that actually surprised the heck out of me. I figured it would be a decent dirty boost, but it has a lot more range than I originally thought. The treble and bass controls aren't roll offs, they're boosts - though the treble boost appears to be stronger than the bass boost. The level gives you a very wide range of volume control, with unity coming very early in the rotation! I'm going to experiment with mine a bit more, but this one may end up on the permanent studio board!