You'll notice that the Raspberry Pi 400 doesn't have the same 3.5mm audio port as the Raspberry Pi 4.
This means you won't be able to connect traditional headphones or 3.5mm wired speaker units to the keyboard, however, there are many options for getting sound out of your Pi400:
HDMI Audio - The Pi 400 will pass audio through the HDMI cable, so if your TV/monitor has speakers, you can listen to audio from them (or use a splitter to extract the audio).
Bluetooth Speakers - The Pi 400 includes a Bluetooth connection, which will allow you to connect most Bluetooth speakers to the keyboard for playing audio. We have our very own Bluetooth speaker here!
USB Audio Adapter - These adapters plug straight into your Pi 400 and allow you to connect headphones or another device via a 3.5mm jack cable. You can grab one here.
USB DAC - Similar to the option above but offering much greater audio quality, our NanoSound USB DAC simply plugs into a USB port and offers RCA outputs for connecting to a speaker system line-in. It also has an amplified headphone port.
USB Speakers - Some speakers use just a single USB connection for both audio and power. A good example of this is our Mini USB speaker set.
GPIO Audio Card - We now stock a dedicated GPIO audio card for the Raspberry Pi 400, the DACberry 400, for the best in Pi 400 audio quality. It includes a 3.5mm jack to run out to a set of speakers.