These ports are usually (but not always) colored blue to differentiate them from older, slower USB 2.0 ports. If you've been paying attention to the ports on new PC and Mac desktops and laptops, you'll see that just about all of them come with 'new, faster' USB 3.0 ports.

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The power source (relevant to the voltage drop numbers) was a Dell plugged into its preferred 20V upstream power supply. This test was run with two microphones plugged in: An Aston Origin on the first input, and a Movo LV8-C on the second. On the other hand, if your laptop tops out at the 'high-power device' profile, you might have trouble. The USB 2.0 battery charging extension allows on a standard USB-A port if your laptop supports this extension - or you upgrade to a laptop with USB 3.0 support that supports the 4.5W 'high-power SuperSpeed' profile - you'll be more than fine. Going from no use of phantom power at all to phantom power on one input, we have an increase in power usage of about 0.26W adding the second input, that increases by an additional 0.17W and whether we're actively recording or just monitoring appears to have no impact on power draw.

Actively recording both inputs with phantom power on: ~0.65A 4.93V (~3.20W).

Running with phantom power turned on for both inputs: ~0.65A 4.94V (~3.22W).

Running with phantom power turned on for one input: ~0.62A 4.95V (~3.05W).

Running without phantom power turned on on either input: ~0.56A 4.96V (~2.79W).

Note that while I rounded the amperage and voltage numbers to two decimal points, the wattage numbers are based on the full instantaneous measurements. These are instantanious snapshots - if we wanted more solid numbers we'd want to actually record usage change over time, but eyeballing the numbers, they look pretty stable. To go into the specifics for this hardware, I own a SSL 2+ and a USB-C power meter, so I'm able to produce actual measurements of the power draw with and without phantom power turned on. Others have described the theoretical basis - that one can convert to a higher voltage with a corresponding drop in amperage.

Usb 2 vs usb 3 audio imnterfaces