32-bit float is the single most common reason the SP-404 MkII throws “Unsupported File.” Here’s why it fails, whether converting costs you any quality, and how to fix a whole pack.
32-bit float is a high-headroom sample format used by DAWs and most modern sample packs (Splice included) because it’s forgiving during production, it can hold levels well past 0 dBFS without clipping. But it is a different format from the 16-bit integer audio the SP-404 MkII expects.
The SP-404 MkII’s direct SD-card import reads only 16-bit linear PCM (WAV/AIFF/MP3). A 32-bit float file isn’t “too high quality” for it. It’s simply a format the SD-card importer doesn’t parse, so you get “Unsupported File” with no hint as to why.
No, not in any way that matters here. The SP-404 MkII runs internally at 16-bit / 48 kHz and conforms every import to that rate and depth anyway. So a 32-bit float file is going to become 16-bit on the device no matter what. Converting first just makes it import cleanly. 16-bit still gives roughly 96 dB of dynamic range, far more than a sampler and its monitoring will ever expose.
| Bit depth | 16-bit integer (from 32-bit float) |
| Codec | Linear PCM WAV |
| Sample rate | 48 kHz (or 44.1 kHz) |
| Channels | Mono / stereo preserved |
By hand: in a DAW, set the export bit depth to 16-bit and render each file, or script ffmpeg -i in.wav -c:a pcm_s16le -ar 48000 out.wav. Both work, both are
tedious across hundreds of samples.
The fast way: It’s 404, yo! takes the whole folder at once, converts every 32-bit float (and 24-bit) file to 16-bit, resamples odd rates, and leaves already-compatible files untouched, folder structure preserved, fully offline.
Related: Why the SP-404 says “Unsupported File” · FLAC to WAV for the SP-404