This paper: UNDERSTANDING SIGMA–DELTA MODULATION: The Solved and Unsolved Issues provides a nice summary: limit cycles idle tones harmonic distortion noise modulation deadzones instability These problems apply in varying degrees whether the modulator is single- or multi-bit. Other stuff I...

Yesterday I visited HiFi Headphones at their office in Lancing on the south coast near Brighton, for a very useful demo. They were all very friendly and I had the full use of the dem room for around 6 hours, which was very generous. I took along my Sennheiser HD650s both to keep me amused on...

I abuse Sennheiser HD650s. I run them off the motherboard line-out jack on my PC. I have tweaked the Windows Media Player equaliser so that I can hear the treble. Occasionally I plug them into my Lumia 520 (stuffing yards of cable into a pocket) for music during a long train journey.   When I...