Why Less Is Sometimes More, vst effects - mixing and mastering |
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Dec 16 2010, 03:36 PM
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We are very lucky that with modern daws we're able to use vsts to help mix and master our audio. There are literally hundreds, if not thousands, of vsts ranging from very good free ones to expensive specialised ones that are suitable for pro audio. A modern computer DAW is capable of hosting many on a mix bus simultaneously and so a home or project studio can essentially have an effects rack that easily rivals a pro studio in variety and number of effects.
Nonetheless what some may not be aware of is how these effects can have unwanted and unintended affects. All add distortion to the original clean signal in the sense that 'distortion' here means any alteration, good or bad, to the original signal. What I'm concerned with here is not the intended distortion caused by the vst but possible unintended issues. Some vsts are coded in a way that they add some unintended signal gain, some leave filters in place and operational even when turned off, some add cumulative high frequency signal and other unwanted artifacts, some behave in a less than ideal manner, some do a combination of some or all of these. Unintended signal gain: Caused by internal digital summing in a vst. Essentially where the output signal is made louder then the input because of summing between the wet and dry signals. On some vsts this internal digital summing occurs at a point where the increase in gain does not appear on your vst's ppl meters. If you record hot this can very easily mean that your signal is pushed in to clipping without it registering anywhere particularly if you mix post-fader. Even if you mix pre-fader it's worth remembering that most mixing DAWs are set so that the ppl only registers digital signal clipping for 4 consecutive overs: fast transients can sum up and clip without registering a clip. In the case of hardware effects it's relatively easy to measure any internal summing gain. All you need is a voltmeter which you then use to measure the incoming and outgoing signal with the gain adjustment set flat. For vsts it's not as easy as the insert point is internal to the daw. You could however use a hand held SPL meter set 1 meter away from your monitors to register any signal gain with the DAW and monitoring chain at constant volume. If you have good hearing and have your monitoring chain set at constant volume you can do this without an spl meter. Place the same track on two channels and put the vst on one channel only. Careful A/B comparison will show if there is any gain. Or failing that you could use a FFT frequency spectrum analyser that can time capture a signal and so compare before and after spectra to see if there is any gain. Filters left in place when turned 'off': Filters change the tonal and frequency balance. Most of us probably assume that when a vst is turned 'off' that it is switched entirely off and is completely out of the digital signal path. This is not the case or all vsts as some are coded in such a way as to pass through the filters, with variable results. Thus if you have a vst EQ it could still be filtering and changing your audio signal, adding gain or attenuating frequencies and so on even when turned off. If you want to check this you need to do a null test. Place your audio on one track, Copy it to a second track and put your vst in the signal chain but turned off. Process the stream and then invert the signal on one track. Mix the two together making sure you place them with sample bit accuracy. If you get anything other than a flat line at 0 you have not nulled the signal and it indicates that the vst leaves the filters in place even when turned 'off'. Cumulative high frequency and other types of noise: This occurs more with vsti, particularly romplers and samplers but can also occur with vst effects. Some generate low level unintended frequency through aliasing or post ringing. As this signal moves through the signal chain and through more and more vsts this unintended high frequency noise can accumulate to a point where it starts to become audible. Again you can see this affect on a FFT spectral analyser. Some vsts can add artifacts to a signal - pops, clicks and other odd noises. If you use a lot of vsts these need to be eliminated by editing. Some types of EQ can produce a 'pre-ring' - which is like an audible echo that precedes the sound. As the pre-ring worsens the audio can decay in to phase smearing, which is very difficult to correct. Non-ideal behaviour: Very few, if any, filter exhibits ideal behaviour. However, some are closer to ideal than others. In the case of EQ filters the further you move from ideal behaviour the more you may encounter unintended issues where you cut or increase other signal in an unintended manner: bell curves stop being symmetrical, band pass filters add gain above the cut off point and so on. Some of this can add colour and sound musical but some may not - it depends on what you are trying to achieve and your type of music. The answer to this one is experimentation and experience: try out different EQs, for example, to see what they 'sound' like and what colour, if any, they add. If it isn't what you want then leave it out of the signal path. --------------------------------------------------- Overall use vst effects and experiment but just be aware that they may be doing more than you expect even when they're turned off. If you're unsure then generally you're better off with a clean signal than an over-processed one. Less is very often more. -------------------- Get your music professionally mastered by anl AES registered Mastering Engineer. Contact me for Audio Mastering Services and Advice and visit our website www.miromastering.com
Be friends on facebook with us here. We use professional, mastering grade hardware in our mastering studo. Our hardware includes: Cranesong Avocet II Monitor Controller, Dangerous Music Liasion Insert Hardware Router, ATC SCM Pro Monitors, Lavry Black DA11, Prism Orpheus ADC/DAC, Gyratec Gyraf XIV Parallel Passive Mastering EQ, Great River MAQ 2NV Mastering EQ, Kush Clariphonic Parallel EQ Shelf, Maselec MLA-2 Mastering Compressor, API 2500 Mastering Compressor, Eventide Eclipse Reverb/Echo. |
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Dec 28 2010, 04:03 AM
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Very useful things here Tony. A bit offtopic, but I could ask. I noticed that I sometimes get short clips when I render video files, but in Vegas all is bellow odB. Could it be that the codec is amplifying audio in video? I don't use any effects in Vegas.
-------------------- - Ivan's Video Chat Lesson Notes HERE
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Dec 30 2010, 01:12 PM
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It could be Ivan. I don´t use Vegas so I can´t be 100% sure though - sorry.
What I´d suggest is doing the recordings with a little more headroom so that you peak at say -1dBFS rather than 0 and see if that stops the clipping. -------------------- Get your music professionally mastered by anl AES registered Mastering Engineer. Contact me for Audio Mastering Services and Advice and visit our website www.miromastering.com
Be friends on facebook with us here. We use professional, mastering grade hardware in our mastering studo. Our hardware includes: Cranesong Avocet II Monitor Controller, Dangerous Music Liasion Insert Hardware Router, ATC SCM Pro Monitors, Lavry Black DA11, Prism Orpheus ADC/DAC, Gyratec Gyraf XIV Parallel Passive Mastering EQ, Great River MAQ 2NV Mastering EQ, Kush Clariphonic Parallel EQ Shelf, Maselec MLA-2 Mastering Compressor, API 2500 Mastering Compressor, Eventide Eclipse Reverb/Echo. |
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Jan 6 2011, 02:54 AM
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Will try it, thanks tony.
-------------------- - Ivan's Video Chat Lesson Notes HERE
- Check out my GMC Profile and Lessons - (Please subscribe to my) YouTube Official Channel - Let's be connected through ! Facebook! :) |
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