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| quote: | | am i correct in thinking that the difference in sound quality is not that noticeable between 48khz and 96khz at 24-bit recording? should i just continue ripping my vinyl at the 48khz setting? |
its sort of hard to explain since i need to explain the difference between digital copies of analogue sound sources.
if you look at a sine wave that is generated from analogue (i.e. from an analogue monosynth) it is a continous wave.
a digial copy of that would look for the vertical height of the sine wave and take loads and loads of snapshots of it over time to build up that sine wave in discrete intervals.
the horizontal distance between each dot is determined by the sample rate. obviously, the higher the sample rate, the more snapshots are taken in the same time, and the more continous it is horizontally and the more accurate it is to the original analogue source.
the vertical distance between each discrete sample is the bit depth. the manner in which an analogue sound source is 'digitised' is called quantisation.
to cut a potentially very long story short, there is a noticeable difference between a 96,000hz recording and a 48,000hz recording. at least, its audible in my productions. this is all digital at 24 bit/96 khz - nothing i use is analogue. more than likely, all your vinyl is actually a digital recording put back onto an analogue playback medium. there cant be a record released in the past 5 to 10 years that doesnt have a single analogue to digital conversion. most productions are in 24/96 at every stage before being dithered down to 16/44.1 for cd, although some arent. to keep things simple, its best to keep everything in 24/96 throughout to cover for any eventuality. unless you need to put your mixes onto CD in which case you still need to keep everything at 24/96 up until the very last stage where you dither it down to PCM wave. but that would take another thread to explain how to do that.
a 48,000hz recording has a theoretical frequency range of 0 to 24,000hz. therefore, why would you need to record in 24/96 you say? the limit of human hearing is only about 20 to 20,000hz to 22,000hz! this is adequately covered!
you are of course correct. however, downsampling a 24 bit, 96,000hz sound source to 24 bit, 44,100hz will introduce quantisation error.
because, you now have half the horizontal discrete samples to express the same sound signal. this results in very very low level cyclical noise in your recording. most people wont have a clue what to listen for, and it is difficult at normal listening levels but once you notice it, it can be quite evident and it can be annoying. the more samples and bits you throw away, the more evident the noise is although it is very small at this bitrate/sample rate.
interesting fact: bitcrushing effects are basically distortion effects that achieve their result by truncating bitrates to the point where the audible signal just becomes a mush of quantisation noise. its fairly unpleasant sounding.
but back on topic. the obvious solution then, is to keep everything in 24/96. ideally the resulting mix would be burned to dvd-audio since it can playback at 24/96. if not, then it needs to be dithered down to 16 bit/44.1khz PCM wave in order to be burned to CD. you can simply render the result to PCM wave but of course, you would simply be truncating the bitrate as well as the samplerate, introducing more quantisation error.
to hide this quantisation error, you need to use a filter process called dithering before you truncate a 24/96 recording to 16/44.1
there is a thread in the production forum on doing this - ill try to find it and link to it here. dithering is something you attempt at your own risk since if done wrong, can easily make your recording sound worse than if it were not dithered at all. it is essentially a process in which you add very low level random noise to your recording to cover up the very low level cyclical noise caused by quantisation error.
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bear in mind that this is absolute audiophile stuff. my sister doesnt know what quantisation noise is, what it sounds like at high amplitude and can find no perceivable difference between a 192kbps mp3 and a 24/96 wave recording. for 99% of the human race (the remaining 1% being audiophiles, engineers, producers and so forth) alot of this is practically a non issue.
but if you are going to make it your demo cd in an official capacity...thus representative of the work you do - i am a firm believer that whatever you are doing, you should always endevour to make it absolutely the best it can possibly be.
dithering is something that i would leave to a qualified engineer to do though unless you know what you are doing and want to give it a go - an engineer however will more likely be in possession of the right tools whereas you probably are not - they will have a very good set of ears, a very very good set of monitors that very few mortals can afford, and a range of dithering alogrythms which they know how to use.
if your demo release is pretty serious then it may even be worthwhile to get a professional engineer to do this for you although i expect to do an entire cd's worth of material, the cost would be high. hope this helped in some way. or at the very least, proved interesting.
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can you recommend about this stuff. it seems pretty interesting.
