> I've been wondering why "audio interfaces" are so expensive. They're a minority interest. Designing good DACs is a subtle art and the engineer costs are amor

> I've been wondering why "audio interfaces" are so expensive. They're a minority interest. Designing good DACs is a subtle art and the engineer costs are amortised over small production runs. The design of the ancillary circuits (analogue preamps, headphone monitoring, phantom power, input and output protection), and mechanical design and integration are also time-consuming and tricky (=expensive) to make reliable and within design goals. And marketing costs are probably as large as engineering. You certainly could do it yourself, but the component cost is the least of your worries. You'll need a fair bit of bench gear - oscilloscope, function generator, various power supplies, DVM, ... but even that's not the problem. You need a lot of knowledge about component selection and circuit design and layout, and a lot of experience with the tools of the trade. Making something like the Presonus (but probably six or ten times as big, because I can't do an all-in-one circuit board with all those functions on it and have it work in any reasonable timeframe), getting it to a state where I would let an unknown mic or computer be plugged into it, or let someone else use it, would easily take me more than three hundred hours. If you're new to this, multiply by n (n >=3).