SGI: Hardware

Octane / Radical Audio

I bought new headphones today and found something quite annoying. At gains of +10dB and above the on-board RAD generates audible high freq. tone related to the sampling rate (~1/4 the sampling frequency) on the amplified output (headphones/speakers). A quick check revealed that the same tone is present on the analog output, 'though at considerably reduced level. Strange enough it's the first time I'm noticing it.
Has anybody experienced something like this before? If so, is there a solution?
It smells like a hw problem or a nasty driver/mixer "feature" (int overflow/aliasing/...).