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Can anyone suggest a portable, 6-input mixer that will be compatible with my laptop? I understand some come with Bluetooth, but I’m thinking to stay with USB if that makes sense.

Avoid Bluetooth. Way too much latency.

Nearly every interface introduced since 2020 supports Fast USB 2 — you are looking for this as it is capable of near zero latency. USB-C is a pipe, not a protocol and adapter cables are available if the one you like doesn't match your PC — see my above post.

There are three basic types. 1) Most interfaces nowadays do not have mixers. Your analog Ins have corresponding USB Outs with 1,3,5,7 hard L and 2, 4, 6, 8 hard R. MOTU M2/4/6 and the M•Audio AIR series and many, many others are like this. The mixing is done in your DAW and you hear it over the USB Ins. Most have an I/O Mix knob so that you can hear both while tracking.

2) Another type has a hardware mixer built in. The Mackie ProFX mixers are 6–33 channels In but only 2 Out and 4 In over USB. If you look at these, get gen 3 or 4 as the older ones do not support Fast USB 2. One nice advantage is that these have hardware effects built in. I have a couple but only use them for live performance where I am recording off the board. I made a number of recordings with these but, the second I wanted the keyboard to play stereo on 1/2 while I tracked on 3... well, that doesn't work when you have only 2 Out over USB.

3) The third type is a hybrid with a mixer you set up in the box or through an app. MOTU 828 and the upper end Scarlett are well known. As good as they are, the setup in CueMix or the Focusrite app gets in the way. Fast USB 2 doesn't really require this unless you insist on tracking with effects which I don't. With Scarlett, you want gen 3 & 4 as they have lower latency than the older ones, same as Mackie.

I have many Fast USB 2 interfaces from MOTU, Zoom, Mackie, M•Audio and Neumann. My go-to is the M•Audio AIR 192|14 which is in the (1) category. Not only can it track 8 channels simultaneously but it has 4 mic/instrument preamps on CombiJacks + 2 Instrument Ins + 2 Line Ins + 2 headphone outs + MIDI. You can hook it up to anything including an iPad—which I have done. I also like that M•Audio has telephone support as does Mackie and MOTU.

The AIR 192}14 is a bit over $300 new but used can be had under $200 on Reverb. M•Audio also has 1, 2 & 4 channel versions but plugging a stereo keyboard into 5/6 while tracking 3 singers on 1–3 and a guitar on 4 plus a synth in 7/8 simultaneously is very nice.

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