Q. Which mixer should I choose for drum recordings?

By Various

I'm looking for something to record my latest project with. I currently own an Apple iMac running OS X Tiger, and the main program I use for recording is Apple's own Soundtrack. I'm thinking of upgrading at some point to Logic Pro 8, but for the moment I'm with Soundtrack. I have eight Audio Technica mics for the drum kit and I'm really looking to record through a mixer into Soundtrack (Logic in the future). However, I still want to be in control of individual mic levels after I've recorded within Soundtrack or Logic, even having those individual mics on different tracks.

I'm wondering if you could help me in choosing some kind of mixer with eight XLR inputs that will let me control individual tracks within the drum mix afterwards?

 
Mackie's 1642 VLZ3 mixer, with eight good-quality mic preamps, looks like a good bet if multitrack drum recording is part of your studio workload.George Barnett

SOS Reviews Editor Matt Houghton replies: Dilemmas like this are rather difficult to advise upon without knowing anything about your budget, but I'll try...

Let's start with the cheapest and simplest option. If you plan to do all the mixing and processing 'in the box', you don't really need a mixer at all: you just need an audio interface and sufficient mic preamps. Something like the recently announced Focusrite Saffire Pro 40 would give you all of this in a single unit, and although I've not used it myself I hear good reports, and it looks to be very decent value. Alternatively, you could choose an interface with eight line inputs and use external mic preamps — or, of course, a mixer. There are so many interfaces you could use with this, at so many different prices, that I can't really list them here, but most recent 24-bit interfaces should be up to the job.

If you want to use an analogue mixer to feed the line inputs of your interface, I'd suggest something like the Mackie 1642 VLZ3, taking a feed from its direct out sockets. It will probably have more functions than you need, but I doubt you'll find eight preamps of this quality in anything cheaper — the VLZ3 series preamps are neutral sounding and offer plenty of headroom. Mixers, of course, can be useful if you want to add some processing while recording — meaning that if you like to tweak EQ and compress to get the right sound before recording, so that you only need to do smaller tweaks in the computer, a mixer would still be a good option. Personally, unless you're used to working in that way, I'd opt to do that in the computer, but mixers can also double up as monitor control systems, without running the risk of latency in your computer, which is useful if you're doing a lot of recording. Alternatively, choosing a mixer with Firewire or USB2 connectivity would mean there's no need for a separate audio interface. Something like the Alesis Multimix Firewire 16 would do the job, offering you all the preamps and I/O that you need to record your eight tracks simultaneously. Whichever option you choose, you just need to select the appropriate audio interface driver in your DAW and assign the physical input channels of your interface to separate software input channels in your DAW. In this way you can record several tracks simultaneously, so that you can do whatever you want with them in your DAW software.

Speaking of your DAW, I must admit that I'm not that familiar with Soundtrack Pro. I believe it offers sufficient input tracks and I know that you can do plenty of processing in there, but I suspect it will lack some of the useful features commonly found in music-oriented DAWs such as Logic, Cubase and Pro Tools. You could certainly do worse than purchasing Logic, as it comes with a great bundle of plug-ins as standard and the current price is very competitive. If that's too pricey, there's always Logic Express, from which you can upgrade to Logic Pro when you can afford it.

Published December 2008

Kronos -- Split Functionality

Q. Why does my USB mixer make a whining sound?

By Various

I have a Core 2 Duo PC, Yamaha MW10 USB mixer, Alesis RA150 power amp and JBL speakers. I use high-quality cable from amp to speakers, a TRS-wired jack lead between the mixer output and amp, and a good-quality USB cable between my mixer and computer.

My problem is a slight, audibly noticeable (and recordable!), annoying high-pitched 'whine' from both speakers when Reaper is booted up and set ready for recording. To date I have isolated or switched off all other equipment and had only the computer, amp, mixer and LCD monitor powered from one surge-protected domestic plug board going to its own mains power socket in my small bedroom studio, but the noise persists. Apart from this noise, all the audio works fine via the loaded MW10 drivers. Other stuff in my studio includes some outboard hardware powered by wall-wart PSUs, but I've had these switched off and disconnected and the whine still persists. I'm stumped.

 
Reason's Hardware Interface is the key to using up to four external hardware controllers to control the devices in the Reason rack. Devices are chosen for each MIDI input bus using pop-up menus accessed by the arrow button under each channel 'LCD'.

Malcolm Furneaux

SOS contributor Martin Walker replies: I suspect that you have run into a common problem faced by many musicians who use USB and Firewire peripherals. The whining noises you hear are due to a ground loop, and you may also notice them changing when you move your mouse, access your hard drive or update your graphic display.

A ground loop occurs when there's more than one ground path between two pieces of gear, and nowadays is comparatively common when connecting an earthed computer via an audio interface to an earthed mixing desk or power amp. As I described in SOS July 2005 (www.soundonsound.com/sos/jul05/articles/qa0705_1.htm), there are three common ways to break such loops safely (depending on whether or not the gear you're using provides balanced inputs and outputs), and they are: using balanced audio cables; using pseudo-balanced audio cables; or using a ground-loop eliminating box containing an isolating transformer, such as the ART Cleanbox II, reviewed in SOS August 2005 and typically costing under £35 in the UK or around $50 in the US.

 
They may not be touch-sensitive, but the motorised faders on the Behringer BCF2000 are a bonus at this price point.

In your case, the Yamaha MW10 mixer and the Alesis RA15 power amp both provide balanced I/O on TRS-wired jacks, so if you've already got a pair of balanced, TRS-wired cables between the two for left and right channels there's no possibility of a ground loop here. You've already been systematic by unplugging all the gear except the computer, monitor, mixer, and amp, to rule out other ground-loop possibilities.
So where's the problem? Well, since your PC and USB mixer are each earthed via their respective mains plugs, the ground loop is, on this occasion, completed via the USB cable that connects the two. Try unplugging the amp and USB cable, and then listening to the headphone output on the Yamaha MW10. If the whine only reappears when you plug the USB cable back in (or even touch the metal of its plug to the chassis of the other gear), you've confirmed the culprit.

I'm sure that many manufacturers of mains-powered USB and Firewire audio peripherals incorporate safeguards that circumvent such computer ground-loop problems. Nevertheless, I know of many owners of USB or Firewire mixers, audio interfaces, MIDI interfaces, and even the occasional music synth/keyboard controller with USB MIDI output for connection to a computer, that have been plagued by them.

Synth users can often cure such problems by abandoning the USB output in favour of the alternative opto-isolated MIDI connection, while laptop owners can safely bypass their computer's mains earth by running on batteries or replacing an earthed mains PSU with a Universal double-insulated model (see the PC Notes column in this very issue for more details). However, desktop and tower PCs require a mains earth, and you can't remove this for safety reasons. US readers might like to try Ebtech's Hum X adaptor (www.ebtechaudio.com/humxdes.html), but I haven't yet found a European equivalent.

I have heard of a few musicians modifying the USB or Firewire cable by cutting through its outer plastic sheath near the plug at one end and carefully severing its outer screen connection, but although this may cure the audio interference, it often prevents reliable data transmission. Specialist USB isolators are available that are, in effect, DI boxes for USB connections (one example is the USB-GT from Meilhaus Electronic (www.meilhaus.com), but they generally don't come cheap.

If you experience this problem, you may simply have to minimise its effects. Plugging all your mains appliances into the same mains distribution board, to create a 'star' system with everything powered from the same mains wall socket, can often reduce the interference, as can trying different lengths of USB/Firewire cable (generally, shorter ones will be better). If I track down any more definitive solutions, I'll publicise them in PC Notes.

Published December 2008

Korg PS60 -- Split Functionality

Q. Can digital audio cables cause ground loops?

By Various

In SOS December 2008, you explained how USB and Firewire cables could complete ground loops and result in audio problems. Is the same true of digital audio cables?

Philip Bramley

 
M-Audio's Audiophile 192 is an example of a soundcard with well‑designed S/PDIF sockets. Their metalwork is insulated from the PCI backplate, and the small black component immediately above them on the circuit board is the pulse transformer for the output, which prevents ground loops.

SOS columnist Martin Walker replies: In theory, most digital connection formats incorporate safeguards to prevent ground loops. Unfortunately, in practice such problems do occasionally occur, either due to incorrectly wired cables or to shortcuts taken by the manufacturer of the gear in question. The tiny ground‑loop signals are rarely sufficient to result in corruption of the digital data itself, since that either gets through or it doesn't. However, if a digital audio connection completes a ground loop, it may indeed result in characteristic hums, digital whistles and whines appearing in your analogue audio signals. Here's a quick run‑down of possible problems you might experience, plus some ways to avoid them. Let's look at the easiest options first.

ADAT and S/PDIF optical both use fibre‑optic cables, giving true galvanic isolation, just like a transformer, so they can never result in ground loops. MIDI inputs also incorporate opto‑isolators, so plugging in a MIDI cable should never result in a ground loop. A few MIDI In ports (mostly on budget PC joystick/MIDI adaptors) may omit this circuitry, to save a few pennies, but the most common cause of MIDI ground loops is using an incorrectly wired cable. Avoid five‑pin DIN hi‑fi cables and use proper MIDI cables, which use only pins four and five for data transfer, and connect the cable screen to pin two only at each end of the cable, but not to the metal shell of the plugs themselves. If a multimeter shows zero resistance between the metal shell of the plugs at each end of a MIDI cable, discard it.

AES/EBU normally uses balanced connections with transformer isolation (signal 'pulse' transformers are used, which are the tiny black boxes you can often see on soundcards near their digital I/O sockets). It's very rare to run into AES/EBU ground‑loop problems, since these sockets generally appear on professional gear where no corners are cut.

The most problematic digital connections tend to be S/PDIF coaxial (phono) ones, which, although unbalanced, should, in theory, have transformer‑coupled outputs just like AES/EBU ones, so that when you connect them to an S/PDIF input no ground loop is created. Unfortunately, this is an area where corners get cut on budget audio interfaces, and if your S/PDIF phono sockets are bolted direct to the metalwork, no transformer has been used.

It's not wise to attempt removing the screen connection at one end of an S/PDIF cable, since this can cause signal degradation and data errors. If you suspect a coaxial S/PDIF connection is causing your problem, switch to Toslink optical, if both pieces of gear offer this option. M‑Audio's CO2 (around $60) is also a handy gadget to have, as it converts between coaxial and optical S/PDIF, and also features transformer‑isolated phono sockets so you can use it in‑line to cure ground loops.

Finally, it pays to be extremely systematic when tracking down digital ground loops, as I found recently. My studio developed annoyingly intermittent digital noises that disappeared as soon as I disconnected an S/PDIF lead between my audio interface and D/A converter. However, this connection wasn't, in fact, to blame. I had two half‑rack‑width devices bolted into a rackmount tray, and had scrupulously made sure neither of them touched the metalwork of the tray or each other. Unfortunately, the bolt heads used to secure them to the tray had eventually worked their way through the paintwork on the top panel of the rackmount device beneath, which then completed the circle of this particular ground loop. On this occasion, some nylon bolts cured the problem!

Published February 2009

Korg Kross -- Split Functionality

Q. Which mixer should I choose for drum recordings?

By Various

I'm looking for something to record my latest project with. I currently own an Apple iMac running OS X Tiger, and the main program I use for recording is Apple's own Soundtrack. I'm thinking of upgrading at some point to Logic Pro 8, but for the moment I'm with Soundtrack. I have eight Audio Technica mics for the drum kit and I'm really looking to record through a mixer into Soundtrack (Logic in the future). However, I still want to be in control of individual mic levels after I've recorded within Soundtrack or Logic, even having those individual mics on different tracks.

I'm wondering if you could help me in choosing some kind of mixer with eight XLR inputs that will let me control individual tracks within the drum mix afterwards?

 
Mackie's 1642 VLZ3 mixer, with eight good-quality mic preamps, looks like a good bet if multitrack drum recording is part of your studio workload.

George Barnett

SOS Reviews Editor Matt Houghton replies: Dilemmas like this are rather difficult to advise upon without knowing anything about your budget, but I'll try...

Let's start with the cheapest and simplest option. If you plan to do all the mixing and processing 'in the box', you don't really need a mixer at all: you just need an audio interface and sufficient mic preamps. Something like the recently announced Focusrite Saffire Pro 40 would give you all of this in a single unit, and although I've not used it myself I hear good reports, and it looks to be very decent value. Alternatively, you could choose an interface with eight line inputs and use external mic preamps — or, of course, a mixer. There are so many interfaces you could use with this, at so many different prices, that I can't really list them here, but most recent 24-bit interfaces should be up to the job.

If you want to use an analogue mixer to feed the line inputs of your interface, I'd suggest something like the Mackie 1642 VLZ3, taking a feed from its direct out sockets. It will probably have more functions than you need, but I doubt you'll find eight preamps of this quality in anything cheaper — the VLZ3 series preamps are neutral sounding and offer plenty of headroom. Mixers, of course, can be useful if you want to add some processing while recording — meaning that if you like to tweak EQ and compress to get the right sound before recording, so that you only need to do smaller tweaks in the computer, a mixer would still be a good option. Personally, unless you're used to working in that way, I'd opt to do that in the computer, but mixers can also double up as monitor control systems, without running the risk of latency in your computer, which is useful if you're doing a lot of recording. Alternatively, choosing a mixer with Firewire or USB2 connectivity would mean there's no need for a separate audio interface. Something like the Alesis Multimix Firewire 16 would do the job, offering you all the preamps and I/O that you need to record your eight tracks simultaneously. Whichever option you choose, you just need to select the appropriate audio interface driver in your DAW and assign the physical input channels of your interface to separate software input channels in your DAW. In this way you can record several tracks simultaneously, so that you can do whatever you want with them in your DAW software.

Speaking of your DAW, I must admit that I'm not that familiar with Soundtrack Pro. I believe it offers sufficient input tracks and I know that you can do plenty of processing in there, but I suspect it will lack some of the useful features commonly found in music-oriented DAWs such as Logic, Cubase and Pro Tools. You could certainly do worse than purchasing Logic, as it comes with a great bundle of plug-ins as standard and the current price is very competitive. If that's too pricey, there's always Logic Express, from which you can upgrade to Logic Pro when you can afford it.


Published December 2008