California Audio Labs Tempest CD player Page 2

The DACs produce a current output which has to be converted to a more conventional voltage form. Normally, solid-state op-amp circuitry performs this task, but in the Tempest, the current-to-voltage conversion is performed by triodes running in class-A! Conventional Philips-based players follow this stage with a gentle Bessel-type low-pass filter to reject the ultrasonic spuriae around 88.2kHz and 176.4kHz, and a switchable feedback-type HF shelf filter to perform de-emphasis where necessary; this circuitry is almost ubiquitously based on solid-state op-amps. The Tempest, again, uses class-A triodes exclusively, with "zero negative feedback"—presumably CAL mean by this that there is no overall loop feedback, just local cathode degeneration—and what CAL term "active distortion correction," for which they have applied for a patent. No details, by request.

Both final low-pass filtering and de-emphasis shelving are performed with passive networks, which have the benefit of being overload-proof: some designers, such as PS's Paul McGowan, feel that conventional active filters can be driven into slew limiting by the ultrasonic spuriae. Again here, the use by Philips of an elegant digital filter for primary reconstruction of the signal means that a benign passive filter is practicable.

Lifting the lid reveals a couple of op-amps; these, however, are used for "housekeeping" of the tube operating points and are not in the signal path. The automatic switching of the de-emphasis network is also claimed not to be in the signal path.

The Tempest is not supplied with a remote control, but owners can use the Magnavox 2041's control. Elsewhere in this issue, JGH describes his dissatisfaction with the ergonomics of the Philips transport used in the PS Audio CD1. Well, I suppose it all depends on what you want from a CD player. Certainly something like the Sony CDP-55 allows you to program tracks in any order, with astonishingly quick access. Other machines allow you to place "markers" and repeat bleeding chunks of music ad nauseam. But so what? I think music deserves a little more respect (footnote 1). Having lived with various Linn Sondeks for nearly nine years, I am used to functional simplicity. The transport in the Tempest gives me all I need: location by track or index; display of track time; enough programming facilities to make life convenient; and not enough to get in the way of enjoying the music.

And music is what it is all about; how does the Tempest fare?

Scene: A tempestuous noise of thunder...
The problem with assessing CD players is that, to a large extent, you are stuck with the unknown sonic quality of the software. If you get a bad sound with a CD player, how do you know that what you have is not a mediocre player, but something ruthlessly transparent and revealing of all the sonic nasties recording engineers have kindly included in the mix? If the sound is warm and natural, the player may be showing how good a job responsible engineers, mindful of the delicacy of live sound, have done; on the other hand, it may, as JGH has proposed, be less faithful to what is encoded in the pits, er, bumps. Either the CD is too dry and the player adds euphonic warmth; or the CD is faithful to the digital master tape and the player is accurate.

Unless the reviewer has access to the master tape, he is in a double-bind; what can he do?

Well—long drawn-out breath—he can trust to his feeling that if the sound is consistently good, with many discs, of all musical kinds, from a number of companies, statistical truth will ensure that his conclusion that the player must be good is probably correct.

Or he can indulge in a little conjecture.

For example, a couple of years back, I recorded a young Polish pianist, Anna-Maria Stanczyk, playing Chopin, with both a Revox A77 and a Sony PCM-F1. The microphone was the Calrec Soundfield, used as a crossed pair of synthesized figure-eights, and although the hall had a sympathetic acoustic, it took quite some time to establish the optimum balance between the direct sound of the Steinway and the reverberant background. Comparing the off-tape sound with the direct feed at the time revealed that, hiss and modulation noise aside, the analog tape closely approached that balance. The F1 tape was more transparent, and more true to the bass weight of the piano sound, but interfered a little with that balance I had worked to achieve.

Both those tapes are still in the UK, but one track, the Waltz in C-sharp minor, Op.64 No.2, mastered from the digital tape, appears on the Hi-Fi News Test CD. With every player I have tried, that delicate balance between direct and reverberant sound has been further affected in the direction of dryness, only the Meridian Pro-MCD and the Sony '520 getting close to the digital tape.

Until now.

The sound of the CAL Tempest playing that track gets closer than any CD player I have heard in remaining true to what I had originally intended!

Footnote 1: But what about musicians who need to study/learn new pieces of music? Such programming can be invaluable.—Richard Lehnert
California Audio Labs
SONICblue Inc.
Santa Clara, CA
(877) 563-9388