A small nit-pick:
>The highest possible level of sound produced by audio equipment is 0 dBFS.
...is only applicable to audio equipment operating solely on digital signals. Humans don't hear digital signals, we hear pressure changes, so at some point, those digital signals need to be transformed into analog voltage signals to drive pressure transducers (loudspeakers). Those analog voltages are measured by a different reference, a standardized voltage, as opposed to the absolute max of a digital scale. Analog voltages are commonly specified in dBV or dBu (0 references of 1 volt and ~0.775 volts, respectively).
The majority of the pro audio gear I've seen interacts with analog signals. So at some point in a piece of gear that handles both analog and digital signals, you're going to have to define a reference point between your digital and analog levels. This can vary from one piece of equipment to the next. The professional audio gear worth it's salt that I've seen can handle analog signal levels of +18dBu or more. Consumer and pro-sumer audio gear have lower limits, and can vary wildly. So 0dBFS signal going into your USB audio interface might come out as a +16dBu analog signal, while the same digital signal going into a professional mixing console might come out as a +24dBu analog signal.
That's a great point. The piece was written from a very web-centric point of view. Even though I used analogue mixing desks as my jumping off point, I only really looked at decibels in a digital context.
In fact, all the digital VU meters I've looked at do account for positive values, so I definitely shouldn't have breezed over that aspect so quickly.
This varies from product to product; for example, meters in Pro Tools are labeled directly in DBFS[1]. So are Yamaha digital mixers (at least the LS9 and M7 - not sure about the newer ones).
On the other hand, the Allen & Heath GLD has its meters labeled differently, and I'm not quite sure what they're referenced to (they go up to +12). This can be a bit frustrating, since I never know how close I am to digital clipping, but in practice I aim to get everything around 0 dB on the meters and I have at least 12 dB of headroom.
Wikipedia has a neat list[2] of different analog reference levels for 0 dBFS.
...is only applicable to audio equipment operating solely on digital signals. Humans don't hear digital signals, we hear pressure changes, so at some point, those digital signals need to be transformed into analog voltage signals to drive pressure transducers (loudspeakers). Those analog voltages are measured by a different reference, a standardized voltage, as opposed to the absolute max of a digital scale. Analog voltages are commonly specified in dBV or dBu (0 references of 1 volt and ~0.775 volts, respectively).
The majority of the pro audio gear I've seen interacts with analog signals. So at some point in a piece of gear that handles both analog and digital signals, you're going to have to define a reference point between your digital and analog levels. This can vary from one piece of equipment to the next. The professional audio gear worth it's salt that I've seen can handle analog signal levels of +18dBu or more. Consumer and pro-sumer audio gear have lower limits, and can vary wildly. So 0dBFS signal going into your USB audio interface might come out as a +16dBu analog signal, while the same digital signal going into a professional mixing console might come out as a +24dBu analog signal.
Edit: Grammar and spelling