USB microphone

[Rochey]

My understanding is:
16 and 24 bits were chosen for processing architecture reasons, not for their initial SNR's. Original audio DSP's as we think of them these days were the Motorola 56K's - 24 bit processors. So you could process 16bit data, and still have 8 bits headroom, just in case you overflowed in your calculations etc. Registers within the device could also hold the extra overflow data.

Of course, Processors then moved to 32bit - (ADI Sharc, TI VC33 & C62x, C67x) Originally some of these processors were fixed point. So suddenly, you can improve your SNR (as ADC technology allowed us to), and still keep your mid-calculation data in the registers.

So, your data formats are pretty much set in stone - fixed bit depths which also allow for computational overflow. Your also right on your next point - even with a 120bit ADC - there are going to be 3 or 4 bits of noise.

Also, for getting more than 90dB in practice -- I think MCS is toying with some of TI's 118dB converters... It'll be interesting to see the results of his work. 100dB+ is a very attainable target these days.

I have one question for you guys in return - who do have studio's full of high end stuff. Can you really hear the difference between a 118dB converter and a 124dB converter? If the answer is "yes" - then how much is your decision biased by the frontend circuitry? How much of that is based on marketing?

Just food for thought.

Cheers

R

 

[Rossi]

Yes, under ideal circumstances you could have more than 100 dB SNR, but in actual practice you very rarely will. There is room noise when you record with micophones. And you can get a microphone's full dynamic range only on very loud sources (close to its maximum sound pressure level). On softer sources SNR will typically be significantly less than 100 dB. More often than not less than 90 dB. Additional processing will add noise, of course.

Electronic or electric instruments rarely have real SNR better than 90 dB. Older equipment may have a lot less, e.g. 80s digital synthesizers.

Still, I wish I had one of those 120 dB converters. Why? Because it would make me feel good. :green:

Hmm, I guess marketing does work