In Reply to: don't record hot in digital posted by Joe Murphy Jr on March 24, 2012 at 21:07:33:
If a DAC clips when playing a digital file that is unclipped it is, to put it simply, improperly designed. Either there was insufficient headroom in the analog circuitry (BAD) or insufficient headroom in the digital signal processing (WORSE). Designers do this because they are either (a) incompetent or (b) dishonest. One can get better measured signal to noise ratio by building in more gain to the upsampling routines inside the DAC (or DAC chip if this is done in the chip). Since many idiots buy equipment based on published S/N specifications rather than sound, there is economic pressure on designers to cheat.
It's pretty black and white if the DSP in a DAC clips while doing upsampling, as this creates distortion up and down the F scale due to aliasing, with horrible result. It's not so horrible (or necessarily obvious) when the clipping takes place in the analog circuitry as this creates harmonics up the F scale. If one suspects a DAC of clipping then one can put the digital file through a digital volume reduction. With most players this can be done without creating a new file, e.g. using a digital volume control built into the player.
It is helpful to be able to hear and recognize the difference between digital and analog clipping while making transfers. On one occasion I was transferring a "hot" metal cassette tape and heard clipping, so I reduced the input level to my converter. It turns out that the problem wasn't the converter clipping, it was the output stage in my tape deck that was clipping on the very hot tape. It was necessary to turn down the output volume control on the cassette deck to avoid this distortion and turn the gain back up in the ADC to get good digital levels. This kind of gain-staging problem is typical of consumer setups or improperly set up professional equipment.
To get the best possible results with one's equipment one needs two skills: an understanding of how the equipment and how to use it within its limitations and the ability to hear and reject various distortions created by misbehaving or abused equipment. Without both of these skills and incredible diligence motivated by love of music one will not get consistently good results as it only takes one slight screw-up to ruin an otherwise good recording. (At least when doing transfers one can go back and redo them, unlike live recording.)
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
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Follow Ups
- RE: don't record hot in digital - Tony Lauck 10:04:35 03/25/12 (2)
- RE: don't record hot in digital - tom.dennehy 22:10:39 03/25/12 (1)
- RE: don't record hot in digital - Tony Lauck 07:46:43 03/26/12 (0)