One important thing to note is these do not have balanced XLR outputs. They instead come with an unbalanced 3.5mm stereo output, suggesting that Sound Devices had DSLR shooters in mind when they designed this.
If you’re trying to decide between the two, here’re the main differences I’ve seen:
- MixPre-6 gives you the option to do 192kHz sample rate, on top of the 44.1, 48 and 96kHz sample rates that the MixPre-3 also does.
- Mixpre-6 allows you to have 1/4″ inputs also, which are more commonly found on music instruments.
- MixPre-6 gives you 8 tracks (stereo mix + 6 ISOs), while the MixPre-3 gives you 5 tracks (stereo mix + 3 ISOs).
Which to get?
Personally, since I already have the Sound Devices 633, I would primarily be using this unit as an XLR adapter for my Panasonic Lumix mirrorless camera. Given that I would seldom need more than 3 inputs, I would choose the MixPre-3 for its smaller and lighter build.
If you’re hoping to use the unit both in a one-woman-band shooting situation with a DSLR camera and in a two-person-crew situation where you have a sound mixer operating this device, I would suggest choosing the MixPre-6 for the additional inputs. That said, I’d also suggest checking out this post where I compare the Zoom F8 with the Sound Devices MixPre-6, before you make your decision.