I've got some Focusrite gear, although a bit upper range. I was curious about their low-end stuff, and there we go!
What's interesting is that the Focusrite Scarlett Solo is a good example, IMO, of a good design while saving cost wherever it makes sense and still get pretty decent performance. A few things:
- The microphone preamp is just made from discrete opamps (low noise ones, though, not crap stuff, but still, to get better performance, you'd usually use some integrated instrumentation amp instead for XLR input, which is differential.) They still manage to get something good enough for the ADC. And, as you noted, they still implement an RFI/EMI filter. (I'll just add that it is more than wise and XLR mic preamps without such filters are probably pretty rare even on low-cost gear. Due to having to support pretty high gain for some microphones, not adding an RFI/EMI filter is a recipe for having a very noisy output);
- They used a single-chip codec (ADC+DAC) from Cirrus. Performance is not too shabby, but clearly not top-of-the-range stuff. It's still a relatively cheap Codec. But it does the job here;
- If I saw it right, they used simple opamps for the headphones amplifier? Whereas that works reasonably well, that's not the best you can do;
- They used a XMOS chip for USB interfacing (+ control of various internal stuff). That's an interesting choice. I'm pretty sure they must use XMOS chips in most of their USB audio interfaces. That's actually a sound choice (no pun intended), as XMOS provided an USB Audio 2.0 implementation that is fully compliant and robust. Implementing that yourself on some random general-purpose MCU with USB HS is a recipe for longer dev time than planned, various bugs and incompatibilities in the field (yeah, getting it right is not trivial), etc. There a few dedicated USB Audio 2.0 dedicated interface ICs out there (usually handling ADCs/DACs through I2S), that you can find in various USB audio interfaces, but they are less flexible (an example is the CM6631A from CMedia). XMOS chips can be used to implement the full USB audio stack with ready to use libaries, and then you can implement whatever else you like to drive various parts of your board with it. Whereas they may have been able to shave off a couple dollars by using a cheap MCU + a CM6631A, or even a mid-range MCU alone supporting USB 2.0 HS, this choice of XMOS, that they again likely use in their other USB products, allows them to handle fewer parts over their whole range of products, and also allows them a lot of code reuse, so this looks wise to me.
All in all, they have used the cheapest parts they could reasonably use without compromising on quality, at least for this range of products.
Except for the aluminum case for the Rode, I'd say that the Focusrite all in all is better designed with fewer "exotic" parts, and connectors look much better as well. Wonder what your opinion is on that?
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