EP-133 K.O. II Update Adds USB Audio, Reverse & Arpeggiator

TL;DR: Teenage Engineering just dropped a major firmware update (OS 2.5) for the EP-133 K.O. II that finally adds USB audio, sample reverse, an arpeggiator, and new sample rates. They also quietly released a hardware refresh with 128 MB of memory (double the original), and CME is shipping a dedicated Bluetooth MIDI adapter for the K.O. II. It’s a good time to own this little orange box — or to finally cave and buy one.

• EP-133 K.O. II OS 2.5 adds USB audio streaming and sampling, sample reverse, an arpeggiator, new lo-fi sample rates (26.25 and 32 kHz), and an Equal Length Autochop mode.
• A new hardware revision of the K.O. II ships with 128 MB of sample memory — twice the original — and is available for pre-order now.
• The EP-40 Riddim and EP-1320 Medieval also get firmware updates: the Riddim gets most of the K.O. II’s new features, while the Medieval gets USB audio.
• CME’s WIDI K.O. II adapter brings Bluetooth 5 MIDI to the K.O. II with sub-3ms latency and 20m range, priced at $39 during pre-order (until Oct 31, 2025).

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Firmware OS 2.5: USB Audio and the Missing Reverse Button

Let’s start with the update that makes you wonder why it took this long: the EP-133 K.O. II can now play samples in reverse. Yes, reverse. The feature every sampler had since the early ’90s. But we at Noxal aren’t here to mock — we’re here to celebrate that Teenage Engineering finally listened. Reverse is in. And honestly, for a device built around mangling sounds on the fly, its absence was a glaring omission. Now it’s there, and the glitch-loving community can finally sleep at night.

But the real headline is USB audio. You can now plug the K.O. II into a computer or smartphone via USB-C and send stereo audio both ways. Sampling over USB works too, which means you can grab sounds directly from your DAW or YouTube without fumbling with a 3.5 mm cable. This makes the K.O. II a much more viable studio tool — and a far better travel companion. New sample rate options (26.25 and 32 kHz) let you lean into lo-fi grit or save memory, and mono samples now stretch to 40 seconds. There’s also an arpeggiator that works in Keys mode with Oneshot and Legato samples — hold the Hold button, hit a few pads, and let the machine do the arpeggiating. It’s not a full-on synth arp, but it’s enough to add motion to your beats.

The Equal Length Autochop mode is a subtle but welcome addition. Previously, Autochop split samples by transients — great for drum breaks, less great for melodic loops. Now you can force equal-length slices, which makes chopping pads or ambient textures far more predictable. The timestretch algorithm has also been optimized. I’ll believe it when I hear it, but Teenage Engineering has a decent track record with these incremental polish updates.

128 MB Hardware Refresh: Twice the Memory, Still Tiny

If you’ve been holding out on buying a K.O. II, Teenage Engineering just gave you a reason to pull the trigger: a hardware revision with 128 MB of sample memory. That’s double the original 64 MB. Now, before you scoff and point at your Digitakt II or MPC One — yes, 128 MB is still laughably small by modern standards. But here’s the thing: the K.O. II was never about sample libraries. It’s about grabbing a sound, chopping it, and moving on. Too much memory breeds indecision. I have 50 GB of samples on my hard drive, and I still use the same three kick drums. The K.O. II forces you to commit. That’s a feature, not a bug.

Still, 128 MB is a meaningful upgrade. If you’re sampling on the fly at a live show or building a set from scratch in a coffee shop (we’ve all done it), having room for 40-second mono samples across more slots is genuinely useful. The new hardware version is available for pre-order now and should ship within a week. If you already own the original 64 MB version, there’s no upgrade path — you’ll have to buy a new unit. That stings, but Teenage Engineering has never been big on backwards compatibility when money is on the table.

CME WIDI K.O. II: Wireless MIDI for the Portable Sampler

CME, the company that made wireless MIDI almost respectable, has released a dedicated WIDI adapter for the K.O. II. It plugs directly into the sampler’s MIDI jacks, matches the orange-and-grey aesthetic, and is powered via MIDI. No batteries, no dongles dangling from the side — just a clean, flush adapter that turns the K.O. II into a Bluetooth MIDI device. Latency is rated at sub-3 ms, range is about 20 meters, and it supports Bluetooth 5. It works with macOS, Windows, Linux, iOS, and Android, and can connect to other WIDI-equipped devices or your DAW wirelessly.

This is the kind of accessory the K.O. II always deserved. The sampler’s portable nature is somewhat undermined by the need for a MIDI cable. Slap this on, pair it with an OP-XY or a laptop, and you’ve got a truly wireless sketchpad. The pre-order price is $39 (€39 / £34) until October 31, 2025, after which it jumps to $59. Shipping starts November 1. If you own a K.O. II and have ever tripped over a MIDI cable at a gig, this is a no-brainer.

Who Should Care — and Who Should Walk Away

The OS 2.5 update is free, so every K.O. II owner should download it immediately. USB audio alone is worth the price of admission — it transforms the sampler from a fun toy into a legit studio tool. The reverse function and arpeggiator are gravy. If you’ve been on the fence, the 128 MB hardware refresh makes the K.O. II a more compelling purchase, especially if you value immediacy over sample-count flexing. The CME WIDI adapter is a niche but excellent accessory for live performers or anyone who hates cables (which should be everyone).

Who should skip this? People who need deep sample manipulation, multi-track sequencing, or a screen larger than a postage stamp. The K.O. II is still a quirky, knob-heavy groovebox with a learning curve shaped like a cliff. It’s not for everyone. But for those who crave tactile, immediate sampling with a side of Swedish design, this is the best the K.O. II has ever been. And we haven’t even mentioned the Medieval update — yes, the EP-1320 Medieval gets USB audio too. Your lute samples are now USB-ready.

I’d write more, but my coffee’s gone cold and the K.O. II is now sampling the sound of me sighing through USB. Priorities.