The Boss SD-1-4A Super Overdrive is a limited anniversary edition of the SD-1 Super Overdrive, one of the longest-running overdrive pedals in the Boss catalog. Boss released it in June 2021 to mark 40 years of continuous SD-1 production, and it was available throughout 2021 only1. Underneath the commemorative finish it is the same pedal players have used since the original came out in 19812.
What the SD-1-4A is
The 4A is one of two anniversary pedals Boss issued in 2021, alongside an MT-2 Metal Zone edition. Delicious Audio's news item on the pair said "The SD-1-4A celebrates 40 years of continuous production"15. The visual treatment is what sets it apart: Guitar.com reported that "The special anniversary edition of the Super Overdrive comes with yellow lettering and gold-capped knobs," on a black enclosure6.
Pedal of the Day, reviewing the anniversary editions in July 2021, summed up the difference from the standard SD-1 in one line5:
"it's basically the same thing: the circuit is the same, the paint job is different and the screw is vintage silver"
So a player picking up a 4A gets the standard SD-1 circuit, controls and drive character in a collectible finish. The pedal is a variant of the regular SD-1 rather than a redesign2.
The circuit and its sound
The SD-1 is an overdrive pedal8, and Pedal of the Day describes its core behavior: it "utilizes unique asymmetric clipping to replicate the feel and sound" of a driven tube amplifier, "producing a signal rich in even-order harmonics"5. Asymmetric clipping clips the positive and negative halves of the waveform by different amounts, which is what loads the signal with even-order harmonics and gives the pedal its tube-amp-like push.
The same review describes the pedal's drive range and tone control: "these mild-to-moderate drive tones have a focused midrange, perfect for using with both clean and slightly pushed amps," while "The active Tone control helps to shape the treble response, while using subtle enhancements for more low-end body as well"5. Boss positions the SD-1 as a SUPER OverDrive in its wider overdrive family, alongside pedals like the BD-2 Blues Driver, OD-3 OverDrive and SD-1W Waza Craft. For a closer look at how the SD-1 compares with its most often-mentioned rival, see the Boss SD-1 vs Ibanez TS9 comparison, and for the wider field see Overdrive Pedals.
Price and availability
| Detail | SD-1-4A anniversary edition |
|---|---|
| List price (US) | $59.99, announced May 20212 |
| Release | June 20217 |
| Availability | Throughout 2021 only1 |
| Standard SD-1 | In production 1981 to present9 |
The $59.99 figure comes from gearnews.com's coverage of the anniversary pair2, and Premier Guitar and MusicPlayers.com both carried Boss's press release stating the SD-1 and MT-2 anniversary editions "will be available in June 2021 for $59.99 and $112.99"74. Guitar.com rounded the SD-1's price to $60 in its report6.
The SD-1-4A was a 2021-only limited run. Pedal of the Day's July 2021 review warned readers to "Grab them while you can, as this limited run only goes through the end of 2021"51. The standard SD-1, by contrast, has been produced continuously since 19819.
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Questions
Is the SD-1-4A different from a regular Boss SD-1?
Only in appearance. Pedal of the Day's review put it plainly: the circuit is the same, the paint job is different, and the screw is vintage silver. The 4A marks 40 years of the SD-1 with a black enclosure, yellow lettering and gold-capped knobs, while the drive circuit, controls and asymmetric clipping carry over unchanged from the standard SD-1 Super Overdrive.
Is the Boss SD-1-4A still available?
No. Boss made the anniversary edition available throughout 2021 only, and Pedal of the Day noted in July 2021 that the limited run would go through the end of that year. The standard SD-1, by contrast, has been in production since 1981 and remains a current pedal.
How much did the Boss SD-1-4A cost?
The anniversary edition listed at $59.99 in the United States when it was announced in May 2021, with a June 2021 release. Guitar.com rounded the figure to $60 in its coverage of the anniversary pair.
What does asymmetric clipping mean on the SD-1?
Asymmetric clipping shapes the top and bottom halves of the guitar's waveform differently. Pedal of the Day describes the SD-1's asymmetric clipping as a way to replicate the feel and sound of a driven tube amplifier, producing a signal rich in even-order harmonics, which is where the pedal's characteristic overdrive character comes from.
Sources (9)
- BOSS MT-2 And SD-1 Anniversary Editions, Delicious Audio, 2021-05-20
- Boss commemorates two milestones with all black Anniversary MT2 and SD1 pedals, gearnews.com, 2021-05-20
- Boss SD-1 Super Overdrive review, Guitar World, 2026-08-17
- BOSS Releases Anniversary SD-1 Super Overdrive and MT-2 Metal Zone Pedals, MusicPlayers.com, 2021-05-20
- Boss MT-2-3A Metal Zone & SD-1-4A SUPER OverDrive Anniversary Editions, Pedal of the Day, 2021-07-20
- Boss preps anniversary edition SD-1 Super Overdrive and MT-2 Metal Zone, Guitar.com, 2021-05-20
- Boss Reissues MT-2 Metal Zone & SD-1 Super OverDrive, www.premierguitar.com, 2021-05-20
- Boss SD-1 Super Overdrive Modifications, Fromel Electronics
- TONEHOME, TONEHOME
