Q Can I feed 16-bit digital audio into a 24-bit digital device via S/PDIF?

Sound Advice : Mixing



Hugh Robjohns



Can I link the S/PDIF out of my Boss DR-880 to the S/PDIF input of my Focusrite Scarlett 8i6 audio interface and get good results? The DR-880 output is at 16-bit resolution but the Focusrite’s S/PDIF input operates at 24-bit. Do I have to match the bit rate [or ‘word length’] as well as the sample rate? Both units are set to 44.1kHz. When I make this connection, I have nothing at all showing in my Focusrite Scarlett’s Mix Control software: nothing shows in the metering at all, no matter what the output level is.



If a device, such as this Boss DR-880, can only output 16-bit digital audio over S/PDIF, you can still hook it up to a modern 24-bit audio interface — but the interface must slave to the other device’s clock signal.If a device, such as this Boss DR-880, can only output 16-bit digital audio over S/PDIF, you can still hook it up to a modern 24-bit audio interface — but the interface must slave to the other device’s clock signal.



SOS Forum post



SOS Technical Editor Hugh Robjohns replies: Yes, you can. The S/PDIF interface format always carries 24 bits of audio data and the 16-bit signal from the DR-880 is automatically padded out with zeros (effectively) in the bottom eight bits. That’s definitely not the problem.



Having the same sample rate is important, but digital equipment can only have one clock source. Everything else must slave to that, so a common cause for an apparent lack of input signal is when the interface is running from its internal clock rather than slaved to the incoming signal. In this situation, the external input is non-synchronous with the interface’s internal clock and thus unusable. Make sure that the 8i6 is configured to slave to the external input from the DR-880, which becomes the wordclock master for your interface/computer. Other possibilities include a ground loop between the two devices, or insufficient signal level from the source. Digital ground loops don’t cause audible hums but often result in glitchy or non-functioning connections, while a poor-quality or overly long S/PDIF cable can degrade the signal level substantially, rendering it unusable. If available, an optical S/PDIF connection would avoid ground loops completely, as would an in-line digital transformer in a coaxial connection. Another reason could be incompatible channel-status bits, but although that is much harder to resolve it is also extremely rare!  

Published in SOS October 2015

Q Can you coach a vocalist to sound more ‘breathy’?

Sound Advice : Recording



Mike Senior



I’m working on an acoustic track and would like my vocalist to sing backing vocals in a more ‘breathy’ way — in other words, as per Messrs Gibb, although not in quite such a high register! Are you able to offer some vocal coaching tips that I can ask him to try?



What a singer hears in his headphones can affect how he delivers his vocal part — and that’s something you can use to your advantage.What a singer hears in his headphones can affect how he delivers his vocal part — and that’s something you can use to your advantage.



SOS Forum post



SOS contributor Mike Senior replies: If he’s having trouble shifting into a breathy delivery style, it might help for him to think ‘whispering’ while singing. This doesn’t necessarily mean singing as quietly as possible, because it’s possible to sing breathily at a reasonable level, in much the same way a speech actor can ‘stage whisper’. To state the blindingly obvious, though, it does require more breath to sing like this, so the singer may well need to rethink his breathing patterns to allow for more frequent lung refills. In addition, you can help from an engineering perspective by giving the singer a bit more vocal level than normal in his cans. This serves a dual purpose: he can hear what he’s singing without having to move out of ‘breathiness mode’; and he’ll be discouraged from opening up too much in terms of level (which is likely to reduce the breathiness) because it’ll otherwise feel over-obtrusive in his foldback mix  

Published in SOS September 2015

Adam Blackstone meets the Korg Kronos!

Q Why do my power supplies spark when first plugged in?

Sound Advice : Recording


Hugh Robjohns



I have three laptops in the house, all of which produce various sparks and flashes at the mains end when plugged into the wall. It’s always bothered me —in terms both of health and of the safety of my computers and audio gear. Can this be ‘right’ or is there a problem with the power supplies, or even my mains supply?



SOS Forum post



Switched-mode power supplies can cause large inrushes of current when power is first switched on. By plugging them into the wall socket before you switch on the mains supply, you’ll at least prevent the scarily visible sparks, even if they’re probably happening behind the scenes!Switched-mode power supplies can cause large inrushes of current when power is first switched on. By plugging them into the wall socket before you switch on the mains supply, you’ll at least prevent the scarily visible sparks, even if they’re probably happening behind the scenes!



SOS Technical Editor Hugh Robjohns replies: Switched-mode power supplies, like those ‘line lumps’ used on laptops (and almost everything else, including plenty of audio processors) usually have a pretty heavy in-rush current when first exposed to the mains supply. The magnitude of the in-rush depends on the design and power rating of the SMPS, but a 24V / 10A supply could easily pull 30 Amps or more for a fraction of a second — hence the sparks. It’s quite common to see and, sadly, is even considered normal. The sparks act as RF interference generators, inducing transient clicks on poorly shielded audio equipment and often imposing a brief voltage pulse in the local mains earth wiring, which can cause glitches in susceptible digital equipment of all kinds!



If you plug in with the socket switched off and then switch on at the wall, at least you won’t see the sparks any more (although they are probably still there across the switch terminals), but I’ve known some el-cheapo knock-off wall-socket switches become welded closed because of excessive in-rush currents!  

Published in SOS September 2015

KORG ALL ACCESS: Stanton Moore on the Korg Wavedrum

Korg Pa3X Professional Arranger Workstation - Official Product Introduction

Q Why would I want to bounce out mixes for referencing?

Sound Advice : Mixing




Mike Senior



While dedicated plug-ins such as Melda's MCompare, Sample Magic's Magic AB and Meterplugs' Perception all, in slightly different ways, provide useful means of making comparisons on the fly, they're probably best used as a complement to -- rather than a substitute for -- bouncing out and referencing your mixes in the traditional way.While dedicated plug-ins such as Melda's MCompare, Sample Magic's Magic AB and Meterplugs' Perception all, in slightly different ways, provide useful means of making comparisons on the fly, they're probably best used as a complement to -- rather than a substitute for -- bouncing out and referencing your mixes in the traditional way.



In May’s Mix Rescue, Mike Senior talks about how he bounced out a mix any number of times to compare it to his references. I understand the purpose of referencing, but what I don’t understand is why he bounced out the mix. Why not use something like Magic AB? Wouldn’t that be easier and faster? It would be possible to put Magic AB on the master bus and have everything in the mix feeding into a pre-master bus (which then went to the master bus) so that you could adjust EQ and stuff on the pre-master to tweak it into line with the references. No? I can see just the one advantage of doing it his way — you’d have a series of bounces that you could compare to see if you were tweaking in the right direction.



SOS Forum post



SOS contributor Mike Senior replies: This is an interesting question that I’ve been asked on a number of occasions, but I’m not sure I’ve ever written down my answer to it before! I realise that it’s perfectly possible to compare a mix in progress with commercial releases using something like Magic AB, Melda MCompare, or Meterplugs Perception — or indeed just using a multi-channel switcher plug-in within Reaper, which is my own normal method. However, I do still prefer to bounce out my mix as a WAV for referencing purposes most of the time, for several reasons — although not, funnily enough, for the reason you suggested!



Q Why would I want to bounce out mixes for referencing?



Q Why would I want to bounce out mixes for referencing?On a practical level, I like the flexibility the DAW offers in terms of editing out and looping the most relevant pieces of each reference track, and the way it lets me easily adjust the time offset between my mix file and each reference track, something that I’ve not found as straightforward in the referencing plug-ins. I also often experiment during referencing to see what impact loudness processing might have on my mix, but mastering-style processors can cause CPU or latency-compensation problems when applied to an already heavily loaded mix project, and I can do without glitches or crashes while mixing. Besides, anything that encourages people to apply mastering processing to their mix project is a bit hazardous in my view, because I’ve seen a lot of people come unstuck that way, effectively trying to master a quick fix to complex mix problems.



However, the main reason I like to bounce out the mix is purely psychological. You see, when I reference using a bounce-down in a separate project, I can’t change the mix while I’m listening, so it encourages me to take decisions much more rigorously before acting on them. In other words, I’m reminded to cross-check each decision across several different references and several different listening systems before actually tweaking any mix settings. It’s enormously tempting when referencing within your mix project to hear, say, that the hi-hat’s too loud in comparison with one of your references over your main monitors and then to immediately charge off and change it, without checking whether that hi-hat’s also too loud compared with another of your references, or on a different listening system. Referencing within the mix project is therefore all too often a recipe for tail-chasing, in my experience, and I prefer to remove that temptation from my workflow.



The other psychological advantage of the ‘separate reference project’ approach for me is that it makes me more confident of when the mix is finished. At each referencing iteration, I’ll build up a properly cross-checked list of tweaks I want to do, and then check the effectiveness of those tweaks at the next iteration. Once everything’s crossed off the list, I can feel pretty confident of signing off the mix. If you reference in a less structured ‘hunt and peck’ kind of way, I find it’s a lot trickier to know when you’re actually done.



The last thing to say is that while referencing I prefer to step back mentally from the technical details of a mix and listen more like a typical punter, which is far easier to do when I’m listening to a bounce-out. Because I can’t change anything, my whole mindset changes. Thanks to pure paranoia, I actually do most of my bounce-outs in real time, and I’m constantly amazed at how often I’ll spot some glaring oversight even during the bounce-down itself that I haven’t noticed for the last five hours of mixing, simply because of the change in mental perspective that occurs once I think “now I’m bouncing down the mix”. Also I’m more likely to transport the bounce-down to the car, the office PC (with my trusty old Goodmans multimedia grotboxes!), the iPod or wherever.



Sure, you could work around all of these issues when using a referencing plug-in on the mix project, but you’ll need a whole lot more self-discipline than I have, frankly! And besides, I think the little breaks you’re forced to have while bouncing things out and switching projects are good for perspective in their own right, but that might be the Luddite in me speaking — ah, the high jinks we used to get up to while the tape was rewinding...  

Published in SOS September 2015