INSIDE SPECTRA 1964
Many times when mastering I’ve needed sporadic limiting to protect against the ‘overs’ caused by intersample peaking, as shown when using a true peak meter. These overs can cause distortion when codecs are applied for streaming or MP3s, but many of the digital limiters I’ve tried did not provide effective protection. I compared virtually every digital limiter on the market, and measured the true peak outputs, but wasn’t in love with the sound of any of them. Wouldn’t it be great to be able to pump up the volume of a master, with no intersample peaks, and remain completely in the analogue domain?
Researching ultra-fast analogue limiters, I learned that the Spectra Sonics 601 limiter is the fastest on the planet – even though it’s an original design from 1969. It’s a fixed-timing, fixed-threshold peak limiter circuit that operates fully within a 180 nanosecond range [0.00000018 seconds], transparently eliminating voltage transients and thereby providing more headroom for any device placed after it in the signal chain. Many of these transients are inaudible except for how they affect the operation of analogue and digital processing downstream.
Spectra Sonics is the same company that built the desks in many of my favourite studios, including Muscle Shoals, Ardent, Stax, Advision, Chateau d’Herouville and the Record Plant studios. Their 101 preamp was the soul of these desks, and many of my favourite-sounding albums were done on them. In fact, their preamp and limiter modules were used to make much of the music that has influenced me. Here’s a very abbreviated list: T. Rex’s Electric Warrior, Aerosmith’s Toys in the Attic and Get Your Wings, Led Zeppelin’s III, Elton John’s Honky Chateau and Don’t Shoot Me I’m Only the Piano, Big Star’s , most of the albums Tom Dowd recorded, all the Stax and Muscle Shoals output from the mid-sixties onwards, and more.
