CPU Cores

My own dual-core PC was built in December 2006. For the previous seven years my rule of thumb had been that a PC musician who wanted to be able to run the latest audio software would, on average, need a major computer upgrade every two years. However, in the column mentioned above I also observed that I felt I'd be unlikely to need to upgrade by late 2008. So has that prediction come true?

Well, yes, it has. I certainly, at one stage, considered swapping my E6600 2.4GHz dual-core CPU for a Q6600 2.4GHz quad-core, but although I've reviewed a few sample libraries and VST Instruments that demand higher than normal processing power (mostly due to convolution features), I've still yet to run out of processing power in my own projects with the dual-core. So I'm perfectly happy with my current PC for the time being.

Scott Child of ADK Pro Audio (www.adkproaudio.com) has been carrying out some very interesting tests. His results suggest that if you routinely load lots of sample data into system RAM, a processor such as Intel's E8400, with two cores running at 3.0GHz and an FSB of 1333MHz, will manage to run considerably more voices before suffering audio glitching than a four-core Q6600 running at 2.4GHz with a lower FSB of 1066MHz. (Scott's tests use NI's Kontakt software, running an orchestral mock-up that fills a couple of gigabytes of RAM with sample data.)

For once, available processing power isn't the bottleneck, but rather memory bandwidth: the CPU meter might display plenty of power in reserve, but the sheer volume of data being shifted between the RAM and CPU becomes the limiting factor. Scott's results also suggest that switching from DDR2 to the newer, faster (and more expensive) DDR3 RAM may be of benefit in this particular scenario.

So when you're considering a new PC or an upgrade to an existing one, think about how you're going to be pushing the system. Musicians requiring large numbers of simultaneous audio tracks shouldn't run into limitations as long as they use a 7200rpm hard drive, as most such drives can easily manage many dozens of tracks without breaking a sweat, and they should also get away with a modest processor, unless they want to treat those tracks with lots of software plug-ins. Those wanting to run many heavy-duty VST Instruments through plug-in effects should get the fastest quad-core processor they can afford, or even an octo-core system (although many sequencer applications are still poorly optimised for eight cores, so you may not max them all out before audio glitching occurs). Finally, those who routinely need to load in several gigabytes of sample data should opt for the fastest FSB speed they can manage, and (unless they also want to run those samples through load of plug-ins) should investigate DDR3 RAM even if this means choosing a processor with a slightly slower clock speed to stay within their budget.

Traditionally, the cure is either using balanced audio cables (if both interface output and mixer/amp input are balanced), pseudo-balanced cables (between an unbalanced output and a balanced input), or a line-level DI box between the two offending items (if only unbalanced connections are available). However, a fourth possibility is a suitable replacement laptop PSU. While removing the earth connection from one with a three-wire (earthed) mains cable could be life-threatening if a fault developed, replacing the entire PSU with one that already has a two-wire cable will certainly cure many laptop ground-loop problems, without removing a vital mains earth connection. Double-insulated (aka Class 2) electrical appliances have been designed not to require a safety connection to electrical earth — and, indeed, must not have such a connection. They can be recognised by their 'square within a square' logo.

Entering 'Universal laptop power supply' into an Internet search engine should quickly unearth some models available in your part of the world. 'Universal' means that it will work with any mains voltage (typically from 100 to 240 Volts AC) and with most laptops from different manufacturers, by providing a switchable output voltage (typically varying from 15 to 24 Volts), plus a range of 'power tips' to fit the various laptop PSU sockets. You'll also need to make sure it can supply enough wattage for your laptop. Look on your existing PSU for this figure, and if it doesn't have one, multiply the PSU's output voltage by the rated output current (mine, for instance, states 19 Volts at 3.16 Amps, giving 19 x 3.16 = 60 Watts).

Finally, and most importantly, check that the PSU is double-insulated and therefore requires no mains earth connection. If the retailer doesn't mention this, look for the double square logo, or the typically oval cross-section of a two-wire mains cable (aka 'figure of eight'). Another giveaway is that many of the mains leads supplied with such PSUs have plastic rather than metal earth pins, or a two-pin 'shaver' plug. If the mains cable plugs into the PSU, rather than being captive, it is also likely to have a two-pin connector.

Suitable models can be found in the UK at Maplin (I found a 120W model for £45 at www.maplin.co.uk/Module.aspx?ModuleNo=219259, for example). A much cheaper 120W Taurus SCAC1260 model (www.computex.biz/aamax), widely advertised on eBay for around £25 in the UK, has already solved a few musicians' problems!