Theta Digital Generation VIII D/A converter
Although Audio Alchemy was probably responsible for popularizing the standalone DAC, back in the early 1990s, Theta pioneered the use of proprietary software running on DSP engines rather than on off-the-shelf digital chips with their DSPre from 1988. We continue to see rapid decreases in the cost of processing power; increasingly sophisticated processing can be incorporated into consumer products at prices that, only a year or two before, seemed impossibly low. Not only has this freed Theta to modify their algorithms at will as advances are made, it also permitted them to upgrade their existing products. Still, it has been about 10 years since the introduction of Theta's DS Pro Generation V; only now is Theta Digital releasing its successor, the $10,000 Generation VIII.
Theta showed a prototype of the Gen.VIII two years ago, and have skipped Generations VI and VII altogether—by which, clearly, they mean that the Gen.VIII is more than a mere incremental advance over the Gen.V. Actually, they'd be remiss if the Gen.VIII turned out to be just another revision, and could not accommodate multibit inputs from 32kHz to 96kHz as well as DSD input at 2.8224MHz for SACD (footnote 1). Moreover, multichannel operation has also been provided for, with the stacking of three Gen.VIIIs controlled from a single Theta Casablanca or Casa Nova processor.
As attractive as that is to me, Theta sent me only one unit, which meant that I could review the Gen.VIII only as a two-channel DAC, albeit one with promise for the future. It almost goes without saying that the Gen.VIII oversamples all inputs to as much as 384kHz, depending on original input, and that it buffers and/or reclocks the signals. Full details are offered at the Theta website.
The New Generation
Unpacking the Theta Generation VIII, I was immediately impressed with its weight: At 29 lbs, it outweighs many power amps! Its appearance is distinctively Theta, with a swooping, satiny aluminum panel on the left front that serves as a surprisingly convenient handle in concert with the more obvious pillar on the extreme right. On the right, more than half of the front panel is occupied by the controls and a bright, distinct, vacuum-fluorescent digital display. Beneath the VFD display are the five selector buttons and the Setup button. These buttons are normally used to select the source. In Setup mode, the five buttons switch among the various setup options. To their left and beneath the Theta logo are the remote-control receiver and the Standby button/LED.
To the right of the VFD are four buttons, arranged as segments of a circle, which provide Up, Down, Left, and Right operations for volume/balance and for the setup menus. Finally, there are Mute and Display buttons. All front-panel controls are duplicated on the remote, which is large enough that the buttons are logically grouped and, after a little experience, easily operated without the user having to look at them. The Gen.VIII is fully balanced in both digital and analog domains, and the remote includes a handy phase-switch button.
The central portion of the rear panel is a power input/control section that separates the analog from the digital connections. Immediately to the right of the power panel are digital control inputs and outputs, which allow the Gen.VIII to be smoothly integrated into more complex systems. The rest of the right side is occupied by a bank of digital inputs: three S/PDIF (two RCA, one BNC), one AES/EBU, one TosLink, and, optionally, one AT&T. Above these is a removable panel, similar in size to the panel space occupied by the inputs, to accept future options. Right now, the only available option is a Sample Rate Lock Board to accommodate low-precision digital sources, but I suspect that an SACD/DVD-A input options can't be far off. The left side of the panel bears analog inputs and outputs, both RCA and XLR.
There are no digital outputs, which is significant: Although I've been speaking of the Gen.VIII as a D/A converter (even Theta refers to it as such), it is also a serious two-input (three, if you consider the built-in DAC) analog line preamplifier. In the past, Theta distinguished their DACs without volume controls (DS Pro) from those with (DS Pre), but I see no such designations in their literature or on the website. I do note that my Gen.VIII's shipping carton indicated that the unit had a volume control, which implies that one can obtain a Gen.VIII without.
The Gen.VIII's analog circuits are fully balanced, differential, discrete, and class-A. All signals—the digital after conversion, the analog directly—are handled by the output stages and controlled by banks of switched resistors in the analog domain, for volume and balance. Only two analog inputs? In this century, that's just enough for my phono preamp and FM tuner. Everything else comes in as ones and zeros.
I won't subject you to the intricacies of reprogramming the Gen.VIII except to say that, with the aid of the explicit menu display, it wasn't difficult. You can set which inputs are directly accessible from the five buttons, which processing (reclocking or Theta's Jitter Jail) each of the digital inputs is subjected to, startup volume level, which external power triggers the Gen.VIII will respond to, and the protocols for the RS-232 control interface. You can also select whether or not the Gen.VIII responds to external volume control instructions for multichannel use, and invoke the Gen.VIII's built-in white-noise generator for burn-in.
The noise generator is an intriguing option. Theta recommends breaking-in the Gen.VIII for a week, using music and/or the internal burn-in signal. However, Theta also states that, after assembly and before testing, each Gen.VIII is put on a burn-in torture rack for 100 hours at the factory. Because the noise generator is right there in the machine, I used it for a week or two, usually when I was out of the house. However, I couldn't discern any change during the course of this uncontrolled experiment. One could also feed the burn-in signal to other components.
Plug it in!
Because I'd been shown the prototype of Theta's Generation VIII at the 2002 Consumer Electronics Show and been regaled with its blandishments by Neil Sinclair, I was not exactly panting for its arrival as 2003 began winding down. However, when the Gen.VIII was inserted into my system, I was stunned. The Gen.VIII seemed so much more dynamic than anything else that I immediately thought the ghosts of Fletcher and Munson must be abroad and haunting.
However, even when I'd carefully matched output levels with an audio-frequency voltmeter, and had substituted the Gen.VIII for other DACs or players, the Theta still made a distinctive difference—much as a 2-3dB difference in volume would fool the unsuspecting in a showroom. Digital inputs came from a variety of sources (see Sidebar, "Associated Equipment";), but the Gen.VIII played no favorites among them or among its various digital connectors—as it should not, assuming the DAC is doing its job in buffering and reclocking the input data. The Gen.VIII's Jitter Jail option of buffering digital inputs played an important role in this, which can be easily tested by switching the option in and out while listening. There's a small hiccup as you make the switch, but the superiority of Jitter Jail buffering over mere reclocking should be apparent to any careful listener.
Footnote 1: Current-production Gen.VIIIs have no SACD hardware connector. However, Sony has begun to offer its SACD players with a FireWire-based digital output (see John Atkinson's review of the Sony SCD-XA9000ES in the December 2003 issue), so this will surely come soon.—Kalman Rubinson