Guys and Gals, The APC 40 is a controller; not a sound card/audio interface. The audio interface = a way for raw MIDI/Audio data to enter the sequencer/DAW.
Consider three main things.
1. What type of connection to the machine would you like?
A. Firewire-Sustained High Speed Data Transfer Rates
B. USB-Faster than Firewire for short bursts of data transfer but slower for sustained data
flow
C. PCI(E)-Connects directly to the computer's internal bus/motherboard; some laptops
accept them through a card port-Fastest data transfer but isn't exactly plug and play.
They often require opening the computer tower and completing a hardware installation.
It's no tougher than adding RAM but still not as easy as connecting a cable from the
computer to sound card.
2. How many inputs/outputs do you need? Some soundcards have 1 in/1 out while others
have 10+ in/out. Are you recording guitar and vocals or an entire band? For most
computer based music, a card with 2 ins/2 outs and a MIDI in/out is acceptable. You can
use the audio ins for external instruments like keyboards, guitars, or turntables/mixers or
mics. I suggest at least 2 audio inputs so you can record stereo signals from things like
mixers or electronic drums. The MIDI in/out is the key to getting MIDI data into your
sequencer w/out having to draw everything on a piano roll.
3. What is your budget? Luckily. many manufacturers like M-Audio, Line 6, MOTU (Mark of the
Unicorn), and Presonus make relatively inexpensive interfaces. Even better, you can
normally find decent used gear on ebay or craigslist. For example, I have a Presonus FP10
that I got on Ebay for under $250. MSRP was around $400, I believe.
This link leads to a pretty good explanation of audio interfaces' features and benefits along with some recommendations. Some of the suggested models are a bit outdated but the manufacturers are mostly current so they should offer updated but similar models. PM me if you have any questions.