I'll take a stab at the question...
A USB mixer has it's output designed to specifically be connected to any USB port. For example you can go
directly into your computer USB port. Behringer Xenyx X1204USB
A powered mixer is nothing more than a "regular mixer" but it has an audio power amplifier built in. Behringer
Euro-power PMP4000 800w per channel
A non powered mixer has line level output with some offering a switch for mic level outputs. Behringer Xenyx X1202
Some mixers are also available with battery power for remote usage.
For Ham Radio audio rack use and processing you need any brand or style non powered or USB mixer.
If you're not routing into a computer you can pass on the USB mixer style.
typically...microphone...noise gate...equalizer/processor.....mixer...main mix out into radio line in or mic input
The mixer will allow you to route the audio or insert reverb [minimal for the wet sound]
Often the mixer can be placed in a way where you can choose different microphones..one per channel etc
or... route your playbacks or route a telephone patch etc.
You audio chain is often delineated by the radio you're using and what your audio goals are.
Visit
WWW.W3OZ.com and/or
WWW.NU9N.com for more information in assembling an ESSB station.
In some cases a mixer is really not necessary..for example using a W2IHY 8 band equalizer and his EQ-Plus
system for one radio. In some cases depending upon the radio being used you may need a pad or the W2IHY I-Box.
Visit his website for more details. He also now offers a means to select more than one radio known as the I-Plus.
Finally visit Bob Heil's website as he offers a lot of information regarding a simple audio set up and answers questions
regarding fighting RFI and eliminating ground loops etc.
Enjoy the adventure and ignore the naysayers as this is part of the fun of ham Radio too.
When you upgrade to Extra class stop by 14.178 ...sorry your license right now does not permit
you to operate there. But listening in the peanut gallery offers you a way to glean some "stuff"
Finally to understand ESSB/eSSB known as extended ssb audio or as some call it using the little "e"
enhanced ssb audio got to
WWW.ESSB.US
John's website
WWW.NU9N.COM should answer most of your questions
Regards,
Martin KA7GKN