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1. Noone said that the anti-imaging filter was literally built into the DAC package. 2. The analog reconstruction filter doesn’t need ideal stopband rejection.

1. Noone said that the anti-imaging filter was literally built into the DAC package. 2. The analog reconstruction filter doesn’t need ideal stopband rejection. An oversampling DAC [0] pushes the image frequencies far beyond the passband, so a gentle analog filter is sufficient to suppress it to the noise floor. 3. Noone said anything about mathematically perfect reproduction. Of course there is quantization noise. Of course there is clock jitter. And so on. But the cumulative effect of these is still way below the detectability threshold of the human ear. And the noise floor of a digital system is still way lower than what’s achievable with an analog one. [0] https://www.analog.com/media/en/training-seminars/tutorials/mt-017.pdf https://www.analog.com/media/en/training-seminars/tutorials/...

pja 4y ago
Yeah, you can‘t just ignore the analogue circuitry that you’re expected to put in place around the bare DAC. It’s part of the design!
ChrisLomont 4y ago
You: "Noone said anything about mathematically perfect reproduction." Also you: "thereby getting back the original smooth waveform". I don't think you're using the word "original" correctly. And now we agree - the reproduction is not perfect. That is exactly what I wrote to begin with. >Noone said that the anti-imaging filter was literally built into the DAC package. That's right - I did not write that, so don't imply I did. I demonstrated that the DAC chip does not do it, then demonstrated that any possible outside filter cannot do it. This is counter to your claim, but matches what I originally wrote. >And the noise floor of a digital system is still way lower than what’s achievable with an analog one. Not true - both can be run easily down to thermal background radiation noise floor, then both need things like liquid cooling and other techniques if you want to go below (physics experiments run into this stuff and have to push both digital and analog signal noise floors vastly below probably any audio systems). There is no inherent noise floor for either system.
- pja 4y ago
  > There is no inherent noise floor for either system. This is silly. Every system has a current noise floor based on whatever the thermodynamics of the system are. If you can push the artifacts of your output below that then they will be indistinguishable from the noise. That’s the point.
  - ChrisLomont 4y ago
    >This is silly. Every system has a current noise floor based on whatever the thermodynamics of the system are. Each fixed system has a noise floor, but there is no noise floor forced on all systems. You can design a system to have as low of a noise floor as you desire, digital or analog. Physics experiments routinely do it to detect extremely rare events. As to thermo, it's almost like you ignored that I already wrote this, which I repeat: "both can be run easily down to thermal background radiation noise floor, then both need things like liquid cooling and other techniques if you want to go below". In common audio, thermal noise is often the biggest component of the noise floor in a system. Hence the point to cool them. There is no floor except zero if you want to engineer such a system. And it works for analog and digital. >If you can push the artifacts of your output below that then they will be indistinguishable from the noise. Nope, you can signal below the noise floor using many techniques, such as spread spectrum techniques. This is used routinely for military and other covert operations. As usual, this is even Wikipedia level knowledge: "Signals that are below the noise floor can be detected by using different techniques of spread spectrum communications, where signal of a particular information bandwidth is deliberately spread in the frequency domain resulting in a signal with a wider occupied bandwidth." [1] Heck, even everyday GPS signals are vastly below the noise floor, yet we use those signals all the time with cheap hardware. "The strength of received GPS signal transmitted from a satellite to the ground users is about −157 dBm below the noise floor of −138.5 dBm" [2]. This is all common knowledge among people doing even basic signal processing. Tons of everyday tech signals below their respective noise floors. It's not a rare thing to do. You make many claims that are not true. So, as to your claim that "the noise floor of a digital system is still way lower than what’s achievable with an analog one" - have a citation in a paper stating this? Have a theorem in a textbook? I'd like to see why you make this claim. [1] https://en.wikipedia.org/wiki/Noise_floor https://en.wikipedia.org/wiki/Noise_floor [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292143/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292143/

pja 4y ago

Yeah, you can‘t just ignore the analogue circuitry that you’re expected to put in place around the bare DAC. It’s part of the design!

ChrisLomont 4y ago

You: "Noone said anything about mathematically perfect reproduction." Also you: "thereby getting back the original smooth waveform". I don't think you're using the word "original" correctly. And now we agree - the reproduction is not perfect. That is exactly what I wrote to begin with. >Noone said that the anti-imaging filter was literally built into the DAC package. That's right - I did not write that, so don't imply I did. I demonstrated that the DAC chip does not do it, then demonstrated that any possible outside filter cannot do it. This is counter to your claim, but matches what I originally wrote. >And the noise floor of a digital system is still way lower than what’s achievable with an analog one. Not true - both can be run easily down to thermal background radiation noise floor, then both need things like liquid cooling and other techniques if you want to go below (physics experiments run into this stuff and have to push both digital and analog signal noise floors vastly below probably any audio systems). There is no inherent noise floor for either system.

pja 4y ago
> There is no inherent noise floor for either system. This is silly. Every system has a current noise floor based on whatever the thermodynamics of the system are. If you can push the artifacts of your output below that then they will be indistinguishable from the noise. That’s the point.
- ChrisLomont 4y ago
  >This is silly. Every system has a current noise floor based on whatever the thermodynamics of the system are. Each fixed system has a noise floor, but there is no noise floor forced on all systems. You can design a system to have as low of a noise floor as you desire, digital or analog. Physics experiments routinely do it to detect extremely rare events. As to thermo, it's almost like you ignored that I already wrote this, which I repeat: "both can be run easily down to thermal background radiation noise floor, then both need things like liquid cooling and other techniques if you want to go below". In common audio, thermal noise is often the biggest component of the noise floor in a system. Hence the point to cool them. There is no floor except zero if you want to engineer such a system. And it works for analog and digital. >If you can push the artifacts of your output below that then they will be indistinguishable from the noise. Nope, you can signal below the noise floor using many techniques, such as spread spectrum techniques. This is used routinely for military and other covert operations. As usual, this is even Wikipedia level knowledge: "Signals that are below the noise floor can be detected by using different techniques of spread spectrum communications, where signal of a particular information bandwidth is deliberately spread in the frequency domain resulting in a signal with a wider occupied bandwidth." [1] Heck, even everyday GPS signals are vastly below the noise floor, yet we use those signals all the time with cheap hardware. "The strength of received GPS signal transmitted from a satellite to the ground users is about −157 dBm below the noise floor of −138.5 dBm" [2]. This is all common knowledge among people doing even basic signal processing. Tons of everyday tech signals below their respective noise floors. It's not a rare thing to do. You make many claims that are not true. So, as to your claim that "the noise floor of a digital system is still way lower than what’s achievable with an analog one" - have a citation in a paper stating this? Have a theorem in a textbook? I'd like to see why you make this claim. [1] https://en.wikipedia.org/wiki/Noise_floor https://en.wikipedia.org/wiki/Noise_floor [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292143/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292143/