Description: Two-channel DSP-based room-correction system and digital preamplifier. Includes complete FFT measurement system, calibrated microphone, digital volume control with 0.1dB resolution, IR remote control, 2 RS-232 ports, 1 microphone input (XLR). Digital inputs: 3 S/PDIF, 1 AES/EBU, 1 TosLink. Digital outputs: S/PDIF, AES/EBU, TosLink. Optional: ADC and 4 analog inputs (3 RCA, 1 XLR). Optional: DAC and 2 analog outputs (RCA and XLR). Resolution: 16-24-bit. Sampling frequencies: 44kHz, 48kHz, 96kHz. No distortion or noise in digital domain. Power…
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Sidebar 2: Speakers, Rooms, & Flat Response
At first glance, it seems reasonable to regard the tonal balance of a real speaker in a real room as the sum of the performance characteristics of speaker and room. If there's something amiss in the sound, just find the offending frequencies, by ear or meter, and adjust the incoming signals with an equalizer.
Unfortunately, rarely will the result be the desired flat response. There will be a change, but, depending on how and from where you listen, there may or may not be an improvement. The reason is that the interaction of speakers…
Sidebar 3: Associated Equipment
Analog source: Heybrook TT2 turntable, SME III tonearm, Ortofon SME30H cartridge.
Digital sources: Meridian 800 DVD/CD transport, Mark Levinson No.360 DAC, Perpetual Technologies P-3A DAC, Philips SACD 1000 SACD player.
Preamplification: Sonic Frontiers Line-3 preamplifier, Audiolab 8000PPA phono stage.
Power amplifiers: Bel Canto EVo 200.2 monoblocks, McCormack DNA-1 with SMc Rev.A mod, Sonic Frontiers Power-3.
Loudspeakers: Revel Ultima Studio.
Cables: Interconnect: DAC-preamp: Cardas Golden Cross, Straight Wire Maestro II. Preamp-power:…
Sidebar 4: Measurements
As supplied for review, the TacT RCS 2.0 comprises three separate components: a D/A processor, an A/D converter, and a digital equalizer. I therefore examined the TacT's measured performance in each of those regions.
Looking first at the D/A converter section with the digital EQ set to Bypass, the RCS 2.0's maximum analog output level was 1.671V from the single-ended outputs, 3.356V from the balanced, with the volume control set to "93.9," the unity-gain setting. (The volume control goes up to an indicated "99.9"; ie, a maximum gain of 6dB, in accurate 0.…
Confirming the excellent resolution and dynamic range seen in fig.3, the RCS 2.0's DAC linearity error was less than 1dB down to below -110dBFS (fig.5), which is superb. As a result, the TacT's reproduction of an undithered 1kHz sinewave at -90.31dBFS was effectively perfect (fig.6), while increasing the bit depth to 24 bits gave a reasonable facsimile of a sinewave (fig.7), even at this very low level.
Fig.5 TacT RCS 2.0 D/A module, departure from linearity, 16-bit data (2dB/vertical div., right channel dashed).
Fig.6 TacT RCS 2.0 D/A module, waveform of…
However, other than this behavior and the presence of power-supply-related artifacts, the TacT's D/A section offers very high performance. This is particularly notable in that it adds only $599 to the unit's price.
The $699 A/D module operates at 44.1kHz, 48kHz, and 96kHz sample rates, these selectable by navigating the front-panel keypad. Its input impedance was a moderate 18.6k ohms via the balanced jacks, but a low 4.6k ohms via the single-ended RCA jacks. Some capacitor-coupled, tubed phono stages might sound too lean with this low a load. The A/D frequency response was flat (not…
Ah, Brazil...land of coffee, the samba, Pelé, Rio-by-the-sea-o, and tube amplifiers. All right, so perhaps the amplifier connection isn't quite as well-established. But one Brazilian amplifier designer, Eduardo de Lima, has published articles in Glass Audio magazine that are viewed by many as groundbreaking, and his evolving products have been seen at various specialist tube equipment shows. De Lima—president, founder, product designer, and principal owner of Audiopax Sistemas Eletroacusticos—is an electrical engineer who started out designing equipment for a telecommunications company, but…
Why is Timbre Lock important? This is where things get a bit complicated—and controversial. De Lima suggests that an amplifier of relatively high distortion, when combined with a given speaker, can actually produce less total system distortion than the same speaker driven by an amp of lower distortion. According to this view, a higher-distortion amp may sound superior to a lower-distortion one not just because low distortion in an amplifier is usually achieved through the use of greater negative feedback, tilting the distortion spectrum toward the more objectionable higher-order harmonics (…
I found the controls quite fiddly to operate, the LED display changing with the slightest turn of the knob. The bias levels indicated by the LEDs tended to drift after the nominal warmup period, so that while the bias levels may have been adjusted an hour after turn-on to read 11/3, a few hours later they could be at 11/2. Having tweaked the bias to read 11/3 near the end of a late-night listening session, it was not unusual for me to find the next day, after a half-hour warmup, that the bias levels were off by one or more LED indicators. I can't say that the sonic effect of the bias drift…
In the case of the Audiopax Model Eighty Eight, the answer to all these questions was a resounding "Yes." The music just seemed to be there, the amplifier (and the rest of the system) getting out of the way. The most striking aspect of the Model Eighty Eight's contribution to the system's sound was that it seemed to reduce much of the harshness and edgy quality that I'd assumed was simply a characteristic of certain recordings. Whether this was due to the claimed reduction of total system distortion or the effect of a kind of "harmonic enhancement," perhaps replacing what had been lost in…