- Jan 1, 2019
- São Paulo, Brazil
Nothing wrong with this, it all would work. I've done something similar to show a few sigma delta DACs are in fact putting out an accurate signal to the 23rd bit and not far off the 24th bit. Even though I don't have any gear with 24 bits of resolution. What I did was feed the digitally reduced signal to the DAC, and feed it into a microphone preamp with 60 db of gain. The microphone preamps analog circuit will amplify noise along with signal while adding very little of its own noise. So having boosted the signal well above the noise floor of my ADC I take the recorded result and reduce it digitally until the test signal is back at its original low value. This pushes the noise floor of the DAC (which I amplified above the noise floor of my ADC) down proportionally. This lets me recreate the signal and with FFT gain actually accurately measure signals down near -150 db even though I don't have any gear with that low a noise level themselves. This is what they have done in the above described setup only using better gear than I have.Their website before home page printed below.
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Well -200 db with a 1 meg FFT is only -143 db for the full bandwidth. So almost 24 bit. And remember in the diagram of the measurement gear setup they were using a 22 bit ADC (plus analog gain to push noise above the noise floor of the ADC).Wow...
-200dB Measurement System Noise.
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That's beyond 32bit.
This is really a shame given their price! as a poor working class I can't afford their dac but this is like Ferrari claiming their car can do 0-60 if tyre have no grip limit! R2R are known to be measuring worse than DS dacs, and I believe those who would buy one at this price don't need them to cheat like this and will pay with a properly measured result with say 90-100db SNRHere is a measurement of the March Audio DAC I did. Signal is -60 db. Only a 128 k FFT. The line of noise would drop another 9 db if it were 1 meg FFT putting it close to -170 db. And if I used the method MSB used I'd state this DAC has about 148 dbFS of dynamic range. With a 1 meg FFT I might also lower that by a few more db.
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Are there any link to the MSB results for a quick comparison?Today someone asked me about the MSB measurement result.To explain this problem, I partially reproduced the measurement.
According to the measurement block diagram released by MSB, they use -30dbFS signal and -60db DAC attenuation, then use a +70db LNA to amplify the measurement, and shift the vertical axis to keep the signal level at -90db.At the same time, it is known that the MSB uses 1MFFT.
The following is the measurement result when I use a DAC that is less than 300 US dollars, without LNA, and directly use 1MFFT:
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