High Definition Compatible Digital^® (HDCD^®), the proprietary process for improving the sound of 16-bit digital audio, has finally arrived. More than a dozen digital processors using the technology are on the market, and the professional encoder used to master HDCD discs is following closely behind.

Okay, we know that Humphrey Bogart didn't utter that immortal instruction in Casablanca, but we couldn't resist, given that this issue includes Jim Austin's adventures with Apple's HomePod, the first smart speaker with hi-fi pretensions, which is featured on our August issue's cover.

When it comes to amplifiers, ya gotcher tubes, yer solid-states, and yer hybrids. Although amplifier manufacturers would have you believe otherwise, the majority of designs within each category are variations on a few fairly-well-known themes. Everyone agrees that the power supply is extremely important. Most designers try to obtain the amplifier's desired frequency response and distortion characteristics with a minimum of negative feedback. It's also agreed—at least among designers of solid-state amps—that the ability to drive a variety of speakers, including those that present a low-impedance and/or reactive load, is an important priority.

For most people the terms hi-fi and stereo are synonymous, and yet it is clear that there is still a great deal of confusion over what the word "stereo" actually means. There isn't even a consensus of opinion amongst producers of records, designers of hi-fi equipment, audio critics and music lovers as to the purpose of stereo, and considering that the arguments show no sign of diminishing in intensity, it is instructive to realise that 1981 sees both the 100th anniversary of Clement Ader's first stereo experiments and the 50th anniversary of Alan Blumlein's classic patent on stereo.