How to judge preamp and A/D quality on a USB audio interface?

Question

I'm looking for an audio interface for casual recording. There are things it's easy to tell from specs -- number of channels, connectors, phantom power, etc. -- but I don't know any way to tell if an audio interface actually sounds good.

I'd say the most important thing would be finding something with decent preamps and A/D converters. I'm looking at USB audio interfaces in the sub $200 dollar range, so I know the preamps won't be great, but there doesn't seem to be a good way to know if something sounds good without actually recording and hearing it. Is there any quantifiable way to know?

Answer 1

Ideally, a converter won't have any "sound". It will just transparently pass through the signal. From the spec sheet you can check things like

• dynamic range/signal to noise ratio
  • the amount of hiss that the converter will add to your recordings. 24-bit converters aren't inherently better than 16-bit. They need to actually have lower noise or the extra bits provide no information. The dynamic range spec tells you more than the bit depth.
• equivalent input noise
  • the amount of hiss the mic pre will add
• total harmonic distortion
  • distortion creates extra frequencies that weren't present in the original
• frequency response

Unfortunately, you can't always trust specs to be accurate. I've seen products with worse specs than the actual product delivers, and vice versa. Some companies are better about this than others.

Also, things like power supply noise can vary from one situation to another and won't show up in the specs.

Answer 2

I used to obsess a lot about specs, but I've shifted from buying the equipment that looks the best on paper to getting the equipment that makes me smile when I use it :-) I know it's an oversimplification, but even with specs, you make subjective decisions on what kinds of measurements to favor, or what frequency plot looks the best. In the end, all that matters is how well YOU think it works for you.

So here's my buying philosophy now: Pick a couple of audio interfaces within your budget range that looks appealing (professional reviews as well as products with many consumer reviews on e.g. Amazon are often good pointers if you don't know where to start), then borrow the equipment or buy it under a 7/14/X day return guarantee. Bring it home, make sure you have some interesting things to record lined up and see how you like the sound.

When you make test recordings, try to record the kind of things that make you think your current equipment is not up to the task.

Then buy the one that you think works best in your setup. If they all sound great, then you'll probably have a favorite in terms of ease of use or most options, etc.

Oh, and don't forget to compare with your old gear. Maybe the new gear wasn't actually what you really needed to improve your sound?