I'm emailing you in the hope that you can help me with some problems I am having in my home studio. Each time I record audio I get a continuous buzz and high-frequency noise recorded along with any music. It is clearly audible during intros, quieter passages and outros. However, when my screensaver comes on, this noise drops considerably. I have an Inta Audio AMD 64 system with a 19-inch TFT monitor, an Emu 1820M interface, and I'm running Cakewalk Sonar 3 Producer Edition.
The other problem which I cannot trace is that my speakers quite frequently crackle and cut out, especially if I happen to play a harder or slightly louder note or sound. My suspicions are that the problem might lie in the main output area of my ageing Studiomaster Mixer. The monitors I have are passive Tannoy Reveals driven by a Samson Servo 170 amp.
SOS Contributor Martin Walker replies: Your buzz troubles sound suspiciously like a ground loop problem, especially since the noises change with computer monitor activity. It's always difficult to diagnose the culprit from a distance, but I wrote a step-by-step guide to tracking down such problems back in SOS July 2005 (www.soundonsound.com/sos/ jul05/articles/pcnotes.htm). Essentially, you have to temporarily unplug all the cables between your power amp and mixer, and whatever gear is plugged into the mixer. If the buzzing and high-frequency noises go away, this probably confirms a ground loop problem.
First, reconnect the cables between your mixer and amp/speakers and listen for the noises. If they have returned, you need to switch to using balanced or pseudo-balanced cables between the two. Next, connect the output of your Emu 1820M to your mixer and listen again. Again, if the noise returns, you either need balanced or pseudo-balanced cables between the two, although many mixers provide balanced inputs, in which case balanced cables are the better option. A search on www.soundonsound.com will provide you with details of cable wiring.
Continue to reconnect all your other gear, and you should end up with a hum-, buzz- and whistle-free system. If at any stage you can't get rid of a noise, try using a DI (Direct Injection) box between the two items to break the ground loop.
As to the crackling, it could well be your mixer. In my experience, the push-button switches used for routing are prime culprits, so try operating all such switches on your mixer that affect the main output, including any that affect the control room output, such as monitoring options. Often a few repeated push-on, push-off actions will clean the contacts sufficiently to cure the problem, temporarily at least. Other possible causes of intermittent audio are dirty pots or faders — again, moving them back and forth may clear the problem, although a quick spray of a suitable fader lubricant is a slightly more long-term solution.