A CASE STUDY IN MXR CASE HISTORY: WHICH POWERPLAY FITS YOUR VINTAGE PEDAL?

The lore of 1970s guitar pedals is a beautiful mess — part history, part folklore, part faded memory. This is our attempt to bring some clarity to one of the most common questions we get at SmallAxe Music.

POT Codes Are a Great Start — But They're Not the Whole Story

If you've been around vintage pedals for any length of time, you know about potentiometer (POT) codes. Stamped on the back of the pots inside your pedal, these codes can tell you the manufacturer and the date the component was made — often within a few weeks. With a few caveats about mismatched parts, POT codes are mostly a tried-and-true method for dating your MXR.

But here's the thing: knowing when your pedal was made doesn't automatically tell you what case it's in — and that's exactly what matters when you're buying a PowerPlay adapter. Two pedals from the same year can have completely different case specs. And that's where things get interesting — and confusing.

Chapter 1: The Bud Box Era — Where It All Began

The earliest MXR pedals weren't housed in MXR stamped cases at all. They lived in off-the-shelf Bud Box enclosures — standard aluminum project boxes that MXR used before branding its own cases with MXR Innovations and an ID number.

These Bud Box pedals are script logo only — if you have a script logo MXR in a Bud Box, you're holding a piece of early MXR history. (My vintage MXR Noise Gate is a Bud Box but it been modded previously.)

👉 PowerPlay for this case: PowerPlay MXR 1970s Script Logo Bud Box & MXR Case 101-2004-1

Chapter 2: MXR Innovations 101-2004-1 — Same Spec as the Bud Box

MXR eventually moved into their own enclosure: the MXR Innovations 101-2004-1. This case shares the same specifications as the Bud Box — same dimensions, same fitment. These are functionally interchangeable from a PowerPlay standpoint.

Like the Bud Box, the 101-2004-1 appears on script logo versions of MXR pedals. However, not all script logo pedals use this case — the later 101-2004-2 can also wear a script logo. If you're unsure which case you have, checking your backplate’s internal engraving info is the most reliable way to confirm.

👉 PowerPlay for this case: PowerPlay MXR 1970s Script Logo Bud Box & MXR Case 101-2004-1

Chapter 3: The 101-2004-2 — The Shape-Shift Nobody Warned You About

At some point — sometime in 1977 but perhaps the exact date is, fittingly, lost to the haze of 1970s rock and roll — MXR introduced its MXR Innovations 101-2004-2 case. This is a different spec from the Bud Box and the 101-2004-1.

Importantly, the 101-2004-2 can appear on both the last of the script logo pedals as well as block logo pedals — so don't assume that a script logo automatically means you have the earlier case. A pedal that looks earlier could easily be wearing a later case. 

👉 PowerPlay for this case: PowerPlay MXR Vintage Late 1970s Block and Script Logo

Chapter 4: The 101-2004 (No Suffix) — The Mystery of '79 (ish)

Just when you thought you had it figured out, MXR introduced what might be the most confusing chapter of all.

By 1979, (at least according to my own ‘79 MXR Dyna Comp) backplates on MXR pedals were engraved with simply: MXR Innovations 101-2004 — no "-1", no "-2", no suffix at all. These are all block logo pedals, and notably, its case specs match the 101-2004-2, so the same PowerPlay applies. Why not use “-3” to continue the series? Hey, man, it was the ‘70s!

👉 PowerPlay for this case: PowerPlay MXR Vintage Late 1970s Block and Script Logo

The Trap: Why the '74 Reissue Phase 90 Fools Everyone

This is another one that catches people often — and honestly, it makes sense that it does.

The Dunlop MXR '74 Vintage Script Phase 90 reissue (CSP026) is a beautiful pedal. It is a modern pedal meant to evoke a vintage classic. It looks the part. It feels the part. And if you're buying a PowerPlay for what you believe is a true vintage '74 Phase 90 reissue, your instinct might be to grab the Bud Box / 101-2004-1 adapter.

Don't.

The CSP026 reissue uses a case with specs that match the 101-2004-2 and 101-2004 — not the original Bud Box. A true vintage 1974 MXR would have been a Bud Box, yes. But the reissue is a different animal dressed in vintage clothes.

This is a common source of confusion we see from PowerPlay customers, and it's completely understandable. The pedal is called a '74 reissue. It looks like a '74. But the case is not '74 spec.

👉 PowerPlay for the CSP026 Reissue: PowerPlay MXR '74 Vintage Phase 90 (CSP026) Script Logo Reissue

The Quick Reference Guide

A Final Note on Vintage Lore

The history of 1970s MXR pedals is, to put it charitably, hazy. Production records are incomplete. Transition dates are approximate. Sometimes pedals may have used parts or components from earlier years or anything else that was laying around the shop. Memories of the era — however fondly held — have been filtered through decades of magazine articles, forum posts, and stories told at guitar shows by people who may or may not have been there.

We've done our best to document what we know from firsthand experience with these cases (mostly trial and error on our part lol) but if you're ever unsure, don't hesitate to reach out. A photo of your backplate engraving goes a long way.

Ready to find your PowerPlay? Browse the full collection: PowerPlay No Drill 9V Vintage Pedal Adapters