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Dan Lavry · 3rd July 2009

Hello Wado,

You said:

"For instance, if I recorded a guitar to 12-bit digital, I'd have to keep the level pretty high in order to sound acceptible. That's due to the distortion being so high at lower levels".

I say:

Yes of course. If you drop the level of a 12 bit converter to around 70dB below FS, you end up with almost square waves. The errors are no longer just random noise, they are signal dependent and are rather bad sounding. That is because the steps are too big in relation to a low level signal.

But there is some relationship between dynamic range and the distortions you are talking about. In order to get a huge dynamic range, the steps must be very small, so one can go for lower level signals before the quantization errors will sound that bad. With 8 bits, you drop the level to 1/256 of full scale (around -50dBFS) and the signal is either between 2 quantization levels (you hear nothing) or is crossing a single quantization up and down (horrible sounding).

But with say 20 bits, you drop the signal by 50dB from full scale, and you still have around 4096 quantization levels (12 bits) to play with.

I agree that there is more to the story then the size of a quantization step, but dynamic range is importent, to a point. Personally, I would not touch a converter with less then 100dB noise floor.

You said:

"Of course, but there inlies a problem because the definitions are a bit blurry where this comes to play. For instance, I have some microphones that are +-3dB 10Hz to 25KHz or so. Now if you record those though my preamp with 50KHz +-1dB, that bandwidth is preserved. Comming back off of tape, the playback maybe -3dB at 20KHz but I can see on an FFT that there's valid information going clear up to the limits of my testing ability on 96KHz converters... "

I say:

The definition of bandwidth is the points where the power drops to 1/2 of the usable range. The ear is not an FFT. I can have an FFT show me energy spikes at 1MHz, and I will never hear 1MHz.

Devices are not "brick wall" so the frequency response has a slop to it. But you can add the responses of various device (for a dB scale vs, frequency plot), and the sum is the outcome. So if your mic is at say -3dB at 20KHz, and your tape is at -.001dB at 20KHz, the overall is -3.001dB. Say your 20KHz mic has a slop such that at 25Khz you are down by 10dB, and your tape perfect at 20KHz (0dB at that point). The outcome is -(10+0) = -10dB. You can not get better response then the lowest device.

Given that we do not hear much above 20KHz, and certainly not anywhere near 44.1KHz, using 88.2KHz sample rate is more then enough for all times. Given that we can reconstruct EVERYTHING we can hear by sampling at 88.2KHz and even lower, we will never need higher sampling rates.

People with cameras do not care about capturing non visible light, because such wavelength do not impact what we see. I do not know why folks that insist on using 192KHz are not insisting on video gear and camera that can record and display infra red, utlra violate, and why not X rays.... Making such a camera would bring about all sorts of compromises, performance trade offs and costs for no good reason. Same with 192KHz for audio.

We found out long ago that humans require around 20KHz. That is why the old hi fidelity was specified for 20-20KHz. It was an ear driven decision, and it was based on research. People that claim that we hear higher, should have an iron clad, repeatable proof that such is the case. Once such claim is proven, and the hearing range is QUANTIFIED (such as 20KH, 22KHz or 30KHz or whatever), then it is time to consider recording such a range.

An argument that one day we may find out that we can hear higher, does not cut it. Why not argue that one day we may figure out that we can see X rays, and all cameras should accomodate such a range? We do have research about hearing range and visable range and the research stands until such time that it is found to be wrong, which is not particularly likely.

I do not understand the fascination with what we can not hear, other then marketing forces that try to sell you new gear, which WAS the driving force behind 192KHz! I am glad it mostly died down. I did what I could to stir audio back to a more sensible range 44.1-96KHz, and it did take some serious effort to make it go away.

Regards
Dan Lavry

Regards
Dan Lavry

3rd July 2009	#57
Dan Lavry Gear addict Joined: May 2005 Posts: 437	Hello Wado, You said: "For instance, if I recorded a guitar to 12-bit digital, I'd have to keep the level pretty high in order to sound acceptible. That's due to the distortion being so high at lower levels". I say: Yes of course. If you drop the level of a 12 bit converter to around 70dB below FS, you end up with almost square waves. The errors are no longer just random noise, they are signal dependent and are rather bad sounding. That is because the steps are too big in relation to a low level signal. But there is some relationship between dynamic range and the distortions you are talking about. In order to get a huge dynamic range, the steps must be very small, so one can go for lower level signals before the quantization errors will sound that bad. With 8 bits, you drop the level to 1/256 of full scale (around -50dBFS) and the signal is either between 2 quantization levels (you hear nothing) or is crossing a single quantization up and down (horrible sounding). But with say 20 bits, you drop the signal by 50dB from full scale, and you still have around 4096 quantization levels (12 bits) to play with. I agree that there is more to the story then the size of a quantization step, but dynamic range is importent, to a point. Personally, I would not touch a converter with less then 100dB noise floor. You said: "Of course, but there inlies a problem because the definitions are a bit blurry where this comes to play. For instance, I have some microphones that are +-3dB 10Hz to 25KHz or so. Now if you record those though my preamp with 50KHz +-1dB, that bandwidth is preserved. Comming back off of tape, the playback maybe -3dB at 20KHz but I can see on an FFT that there's valid information going clear up to the limits of my testing ability on 96KHz converters... " I say: The definition of bandwidth is the points where the power drops to 1/2 of the usable range. The ear is not an FFT. I can have an FFT show me energy spikes at 1MHz, and I will never hear 1MHz. Devices are not "brick wall" so the frequency response has a slop to it. But you can add the responses of various device (for a dB scale vs, frequency plot), and the sum is the outcome. So if your mic is at say -3dB at 20KHz, and your tape is at -.001dB at 20KHz, the overall is -3.001dB. Say your 20KHz mic has a slop such that at 25Khz you are down by 10dB, and your tape perfect at 20KHz (0dB at that point). The outcome is -(10+0) = -10dB. You can not get better response then the lowest device. Given that we do not hear much above 20KHz, and certainly not anywhere near 44.1KHz, using 88.2KHz sample rate is more then enough for all times. Given that we can reconstruct EVERYTHING we can hear by sampling at 88.2KHz and even lower, we will never need higher sampling rates. People with cameras do not care about capturing non visible light, because such wavelength do not impact what we see. I do not know why folks that insist on using 192KHz are not insisting on video gear and camera that can record and display infra red, utlra violate, and why not X rays.... Making such a camera would bring about all sorts of compromises, performance trade offs and costs for no good reason. Same with 192KHz for audio. We found out long ago that humans require around 20KHz. That is why the old hi fidelity was specified for 20-20KHz. It was an ear driven decision, and it was based on research. People that claim that we hear higher, should have an iron clad, repeatable proof that such is the case. Once such claim is proven, and the hearing range is QUANTIFIED (such as 20KH, 22KHz or 30KHz or whatever), then it is time to consider recording such a range. An argument that one day we may find out that we can hear higher, does not cut it. Why not argue that one day we may figure out that we can see X rays, and all cameras should accomodate such a range? We do have research about hearing range and visable range and the research stands until such time that it is found to be wrong, which is not particularly likely. I do not understand the fascination with what we can not hear, other then marketing forces that try to sell you new gear, which WAS the driving force behind 192KHz! I am glad it mostly died down. I did what I could to stir audio back to a more sensible range 44.1-96KHz, and it did take some serious effort to make it go away. Regards Dan Lavry Regards Dan Lavry