Teenage Engineering adds USB audio and longer samples to EP-133 KO II

Teenage Engineering’s OS 2.5 update for the EP-133 KO II landed on June 24 and added USB audio recording and monitoring, reverse sample playback, adjustable sample-rate recording, longer mono samples, equal-length auto-chop, a faster keys-and-scales shortcut and improved timestretching. The biggest shift is practical: the KO II can now take audio over USB, which moves it closer to a compact production hub than a simple sketchpad for beats and loops.

Teenage Engineering now describes the EP-133 KO II as a 128 MB sampler and composer. It sells for $329 and includes a built-in mic and speaker, USB-C power, sync in and out, MIDI in and out, and 4x AAA battery operation. The company’s own specs list a sampling frequency of 46 kHz at 16-bit. With OS 2.5, the maximum mono sample length rose from 20 seconds to 40 seconds, a meaningful jump for longer vocal phrases, guitar parts or field recordings that used to need tighter trimming.

That extra room matters most when the box is used as a living-room sampler or onstage sketch machine. Longer mono capture gives bedroom producers more freedom to grab a full phrase without worrying about running out of time, while USB audio recording and monitoring make it easier to sample from a laptop, phone or other gear without extra hardware. The new adjustable sample-rate recording also opens the door to deliberate degradation, giving the KO II more lo-fi character when clean audio is not the goal.

The update also fits a broader firmware cadence around the EP line. Teenage Engineering launched the EP-133 KO II on November 22, 2023 as the follow-up to the PO-33 K.O!, which the company calls its “world’s most sold sampler.” The PO-33 offers up to 40 seconds of sample memory, a benchmark the EP-133 had now matched on mono recordings after OS 2.5. Teenage Engineering’s update history shows OS 2.0.2 arrived on September 30, 2025 with workflow and stability improvements, and the newer release continued that pattern of adding features instead of treating the hardware as finished.

The result is a sampler that now punches more convincingly above its price. The KO II still keeps the pocket-sized, battery-powered appeal that made it easy to carry, but OS 2.5 made it materially better at the one thing many players want most: getting sound in, mangling it quickly and getting it back out with as little friction as possible.