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Wife took my Zoom 2 recorder

Sampling pipe organs and turning them into something you can play in Hauptwerk.
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davidgarner16

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Re: 1-bit recording.

PostThu Apr 09, 2009 1:54 am

NicholasA wrote:I've read some articles on this technology and I would be willing to state that most of it is hype. It claims to reduce that amount of filtering needed to process, but that simply doesn't make sense from a mathematical perspected... I am sure that I've read before that 1 bit recording also generates more high-frequency noise that traditional ADC's - I will search around for the article that I read and post it (but you can clearly see it in Paul's picture as well for the 1-bit example... that is certainly not a signal).

All I can do is present some numbers:
A 24-bit ADC sampling at 192000 gives an effective bit rate of 4.608 million bits per second.
A 1-bit ADC sampling at 2.8 samples/second gives an effective bit rate of 2.8 million bits per second.

I certainly know which one I would pick.


I don't think it is hype. It is almost certain that the Zoom will also use 1-bit A/D conversion, as well as the Korg. This is standard for audio products these days - the performance of 1-bit A/D's is just so much better as the requirements on the filter that you need before conversion are so much lower than with "traditional" ADC's (known as Nyquist-rate).

The difference is that the Korg outputs the raw "bitstream" that comes out of of the 1-bit ADC, whereas the Zoom first converts it to a 24-bit PCM code. It is this conversion process, known as the "decimation filter" which I think the Korg hype is referring to when it says it needs "less filtering".

Decimation filters are complex and quite an art ... and there is no point in putting your bitstream through one if you don't have to. And if all you want to do is to re-create the original analog signal (in an amplifier for example), it is very easy to do with the original bitstream. So, why not just send that? The bit-rates are comparable. That is what even mainstream consumer audio products are doing nowadays, and of course you have the SACD's which are just recording the raw bitstream.

By the way, the bit-rates don't really tell you much about the audio quality - working out the signal-to-noise ratio (which is all that matters for audio) is quite mathematical and, in the case of 1-bit A/D's, depends on the so-called "order" of the A/D.

David (who designs 1-bit A/D converters for a living)
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