Discrete Distortion +

I've seen a few people playing around with discrete opamps in classic circuits, and thought I'd give it a go with one of my favorite circuits, the classic MXR Distortion + (or DOD 250, etc.). The typical 741 opamp has been replaced with Joe Davisson's Diode-Compression Opamp. The 6.8k resistor in the bottom left corner of the board may need to be adjusted till the collector of Q3 is around 4.5v. I haven't tested this, but it should work.

MXR Custom Badass Modified OD

Here's another one I was surprised I hadn't drawn up before. Like the Custom Badass '78 Distortion, it's also based on an old Boss pedal—the SD-1. (Or I guess you could say it's a modified version of the Zakk Wylde Overdrive, but that's based on the SD-1... Either way, it's definitely been modified with the added 100Hz control and the Bump switch. Here's the schematic for reference. Should fit nicely in a 1590B.

MXR Micro Chorus

The originals used a now nearly unobtainable SAD512D chip, but the wizards on FSB converted it to work with an MN3007. Now that those are also hard to get a hold of, I've laid this out for an MN 3207–which is almost the same as the 3007, just with a slightly different pinout for power and ground. But if you want to use a 3007, I've included a daughter board that will let you use it (it will also work to use a 3207 in place of a 3007). This will best fit in a 125B and the schematic can be found here.

MXR Commande Sustain

Here's one from MXR you probably haven't heard of before. It was apart of their Commande line of plastic boxed effects from the late 80s. They aren't highly regarded because of the plastic, but the circuits were pretty well designed. The circuit in question today is a better design than the DynaComp, offering less distortion and more sustain. It does have a little less compression range than the DynaComp, but also less noise. (And really, who needs that much squish? haha) Couldn't find a demo of this one, but the schematic and discussion can be found here on FSB.

MXR Custom Badass '78 Distortion

I've wanted to draw this one up for a while. It's a fantastic clone/variation of the  Boss DS-1 Distortion. I had one for a while and loved it, but ended up selling it to fund some other stuff. But I'm definitely adding this one to the pile. You can sub a TL072 or JRC4558 in place of the TLC2262 if you need to.

MXR Distortion II

This one was kind of a sleeper. No where near as popular as MXR's Distortion +,  the Distortion II was quite a bit more complicated and ran off a 15v supply, complete with a built power cord . This layout is a bit modified from the original, and can be run off a normal pedal power supply (+9/18v). Originals also tend to be very bass heavy, so I've included a few mods to tame the low end. You might be able to fit in a 1590B, but a 125B will have a bit more room.

MXR Distortion III

Here's the MXR Distortion III. It's pretty similar to the MXR ZW-44, which itself is a Boss SD-2 clone. The main difference is hard clipping in the Distortion III instead of soft clipping in the ZW-44/SD-2. Originals use an MC33178P dual opamp, but try a JRC4558 or TL072.

MXR Noise Gate

Got a request for this one. The schematics that come up with a Google search are all wrong apparently, but it looks like the good people on FSB have figured things out. Here's a link the the discussion and the latest schematic (which this layout is based on) is on page 5. I based this layout on the original layout from MXR, using 2, single op amps. Early versions used the 741 chip, but you can use TL061 or 71s if you want.

The Drivestortion Project

I really enjoyed making the Big Muff Project file a couple months ago and thought it would be fun to make a similar project based on the MXR Distortion +/DOD OD250 circuit (in an attempt to combine the 2 names I call this project the Drivestortion). This circuit was also cloned by other pedal manufacturers (apparently this was the Timmy of the 70s), so the project provides component values for a couple of these as well. Let's start with the schematic:

This is the basic circuit for several versions of the DOD OD250, the MXR Distortion +, the Ross Distortion, and the DeArmond Square Wave, just to name a few. The only difference between all these is differing component values (and sometimes not even that). The component names from the above schematic follow those in the layout drawing below.

For a full BOM for 6 different versions of this circuit, download the linked file below. In addition to the BOM, it contains scaled transfers for etching your own circuit board and a scaled drilling template for building the effect into a Hammond 1590B enclosure.

Effects Layouts' Drivestortion Project

MXR ZW-44 Berzerker Overdrive

Got a request for Zakk Wylde's signature overdrive from MXR. It's essentially Boss SD-1 Super Overdrive without the buffers. Original units have MC33178P, but socket and experiment with dual op-amps. You can use right angle PCB pots to mount them on the board from the solder-side.

Wampler Distortion Plus Mods

A while back Brian Wampler shared a bunch of mods to the classic MXR Distortion Plus circuit in Premiere Guitar magazine. It adds a tone control, a switchable soft clipping stage, a compression switch, and a bass boost switch.

MXR DynaComp

Here's the classic DynaComp compressor from MXR. This frequently cloned and copied effect has been an industry standard since it was introduced in the 70s. It uses the CA3080 IC, which can be a bit expensive and/or difficult to source as it is a rather obsolete chip. It might be a good idea to use tantalum capacitors in the place of the 1µ electrolytic caps for noise purposes. You can mount the pots directly to the board using either long leg right angle PCB pots or these more normal ones.

MXR Script Phase 90

The Script version of the Phase 90 is probably the holy grail of phase shifters and was the first effect released by MXR in 1973. It's probably most famous for helping create Eddie Van Halen's brown sound on the first 2 Van Halen albums. It was designed before dual op amps were really affordable, so it used 6 op amps, in addition to 4 JFETs and a PNP silicon transistor. I've wanted to do a layout for the Phase 90 for a while, but all those op amps intimidated me, so I held off till a request for it came in. I used the original MXR board as a starting point. I ended up with 2 jumpers, but original units had a 150k resistor spanning over half the board (going from the base of Q5 to pin 6 of IC5).

One of the weird things about this layout is how the JFETs are oriented. The drain and source pads are further apart than the source and gate pads because the ground fill has to go between those gaps, and this quirk is evident on the original board from MXR. I would imagine 2N5457s would work if you can't get ahold of the original 2N5952s, and a 2N3906 can be swapped for the 2N4125 if necessary. Also, if you're not a fan 741 chips, a TL061 or 071 should work fine.

MXR Micro Amp

The Micro Amp is a classic clean boost circuit first introduced by MXR in the late 70s. It's a great option if you need to stomp on something for solos. Pretty simple op-amp design that should fit nicely in a 1590a.

MXR Phase 45

I've seen a lot of different PCB layouts online for this effect, but all of them had at least one jumper on the board. Jumpers aren't the end of the world, but I know for me, if I'm going to go to all the trouble of etching a PCB, I don't want to mess with jumpers. This layout is jumper-free and will still fit in a 1590B type enclosure.

MXR released the Phase 45 along side the more famous Phase 90 in 1975. The name comes from the number of degrees of the phase shift it's capable of. Some say it's similar in sound to a UniVibe and can be modded into being more of a vibe pedal.

The original units used 2N5952 for the FETs (make sure you match them by the way), but others can be used. I listed 2N5457 in the layout because they're what I have on hand. MPF102, J201, or 2N5458s could also be used. Really, any FET with the DSG pinout.

If you want, you can hardwire the C500k pot to the top of the board, though I would suggest using a long leg PCB mount pot (like these) and mounting it above the component side of the board (like this).

DOD Overdrive 250 Grey Spec

Here's the grey spec DOD Overdrive 250 that fits in a 1590a enclosure. You could also build a yellow spec 250 or the MXR Distortion + with this layout. Just compare the schematics and value swaps.

MXR Distortion +

The classic '70s overdrive by MXR, and is essentially the same as the DOD 250 and Ross Distortion. I designed the layout to have onboard pots, to alleviate some offboard wiring. It also has the LED resistor on the board, again to reduce offboard wiring a bit.

It'll fit perfectly in a 1590B enclosure. Might be a good idea to socket the diodes. The original had germanium diodes, but silicon diodes or LEDs will sound good as well (just different).