Theta Data Basic CD transport Measurements
Sidebar 3: Measurements
The Data Basic's S/PDIF jitter measured from the RCA jack was very low, measuring 30 picoseconds with an input signal of all zeros, 36ps with a full-scale 1kHz sinewave, and 123ps when outputting a 90dB, 1kHz sinewave (footnote 1). Fig.1 shows the jitter spectrum with these three test signals. With music (fig.2), the Data Basic's jitter was 71ps (a very quiet passagethe first 30 seconds from Sheffield's recording of The Firebird Suite) and 42ps (with full-scale music).
Fig.1 Theta Data Basic, jitter in coaxial S/PDIF data signal, 20Hz50kHz, when transmitting digital silence (bottom solid trace), a 1kHz sinewave at 90dB (top, dashed trace), and a 1kHz sinewave at 0dBFS (middle, light dotted trace) (vertical scale, 1ps2ns, 100µV = 1ps).
Fig.2 Theta Data Basic, jitter in coaxial S/PDIF data signal, 20Hz50kHz, when transmitting Sheffield Lab Firebird (solid) and Steve Morse (dashed) (vertical scale, 1ps2ns, 100µV = 1ps).
Overall, the Data Basic's jitter performance was excellent, and nearly identical tobut slightly higher thanthat of the PS Audio Lambda. Incidentally, the Data Basic's AES/EBU output had slightly higher jitter, measuring 44ps with a full-scale 1kHz sinewave, 165ps with a 90dB, 1kHz sinewave, and 32ps with digital silence.
The Data Basic's tracking ability, as revealed by the dropout tracks on the Pierre Verany Test CD, was better than average. The transport played track 36 (barely), but faltered on track 37.Robert Harley
Footnote 1: See last November's Stereophile for the full transport jitter testing methodology and results of these tests on other transports.