Cutting Up: Stereophile's Liszt Piano Sonata LP
Although we did record backup analog tapes at the 1993 Sonata sessions, the edited four-track master existed only in digital form, as 18 gigabytes of 20-bit data on the Sonic Solutions digital audio workstation hard drives. The sound quality of these 20-bit data was actually analoglike in that it was free from high-frequency glare and other digital artifacts. It also offered a view into the acoustic of the Albuquerque church that the 16-bit noise-shaped CD, as good as we felt it to sound, only hinted at (see Larry Archibald's sidebar comments).
The CD had been mastered from a CD-R, which in turn had been created from a two-channel mixdown from the four individual 20-bit microphone tracks, noise-shaped to 16-bit resolution with the Meridian 518 processor. For the LP, an identical two-channel master tape but with 20-bit resolution would be played back on a Nagra-D digital tape recorder with the data decoded to analog by a Mark Levinson No.30.5 D/A processor. (The Levinson has a 20-bit signal path and true 20-bit resolution.) The analog signal would feed the Neumann cutting lathe at AcousTech Mastering, the facility shared by RTI and Acoustic Sounds.
However, as we were reminded by veteran cutting engineer Stan Ricker, the lathe's computer needs enough advance warning of changes in the signal's envelope to optimize the track pitch to accommodate the music's dynamic range. When an LP master is cut from an analog tape, a special preview playback head provides this advance warning, but this is not possible with a digital tape. The answer was simple. As only two of the Nagra's four tracks are used for the stereo master data, I duplicated the data on the other two tracks, but advanced in time by about two seconds. These second two tracks could be used to feed the lathe's preview computer with the exact preview time adjusted with a Lexicon Model 300 digital delay unit. (This unit output the analog preview signal but was not in the signal path for the cutting.)
To capture the sound of Bob Silverman's 9' Steinway D, Robert Harley and I had used a central Schoeps "Sphere" stereo microphone, with outrigger B&K omni mikes (see sidebar). Because there's a significant difference signal between the channels, a result of the "bloom" added to the sound by the spaced-omni mikes, I asked Stan Ricker if cutting this LP would present any problems. He laughed, and reminded me that he had cut some of the early Delos albums in the late '70s, which he had recorded with spaced omnis. "The engineer's art is to cut what's on the tape," he told me, "not to compromise it to make the cutting or the playback easier."
It was with some trepidation, therefore, that I lowered my Linn Arkiv phono cartridge into the lead-in groove of the test pressing. Although the groove's vertical velocity is large, the Arkiv could track it set to 1.9gm downforce. I breathed a sigh of relief. Wes Phillips's Transfiguration also had no problem staying in contact with the groove walls—I'll leave it to him to give a blow-by-blow account of the cutting and to analog maven Michael Fremer to decide whether we were successful.—John Atkinson