Having measured a number of idiosyncratic tube amplifiers in the last few issues, I was pleased to get a straightforward solid-state design on the test bench. With its volume control set to its maximum, the Arcam DiVA A85's voltage gain into 8 ohms was a sensible 32.5dB. (So many integrated amplifiers offer far too much gain for any practical combination of source and loudspeaker.) At this volume-control setting, the A85 clips with a 600mV input level, which is well within the reach of any modern source component I can think of. Its input impedance at 1kHz was a…
search
The innocuous nature of low-order harmonics present in an amplifier's output depends on there not being high levels of intermodulation distortion. This was true of the Arcam; fig.6 shows that, even close to the clipping point with the punishing 1:1 mix of 19kHz and 20kHz tones, the 1kHz difference product remained below -80dB (0.01%). However, the higher-order products at 18kHz and 21kHz did rise in level as the load impedance dropped, which suggests that those admittedly rare speakers that drop to 2 ohms and below at high frequencies are perhaps best avoided.
Fig.6 Arcam DiVA…
Because I'm suspicious of just twiddling knobs to make the sound "nice," I didn't rely solely on my ears when I used the Z-Systems rdp-1 that I review elsewhere in this issue for speaker and room contouring. Instead, I used the ETF speaker/room-analysis software from Acoustisoft to help me manipulate the equalizer properly. This program can measure the first-arrival, on-axis speaker response, as well as the room response with its early and late reflections and its resonances.
Without the visual and objective feedback that ETF provides, each adjustment would have required extended…
Back in 1992, Robert Harley's Stereophile review of the McCormack DNA-1 and Parasound HCA-2200 amplifiers (April 1992, Vol.15 No.4) and the accompanying technical measurements piqued my interest. So, with great curiosity, I arranged to borrow a DNA-1 to audition, along with competitive amps from Aragon, Bryston, and PS Audio. They were all a leap ahead of my Adcom GFA-555, but it took an act of great courage to accept that, despite its less-than-stellar measured performance, the DNA-1 was my favorite. The bottom line was that the DNA-1 excelled at driving my Apogee Duettas to make lively and…
The DNA-225 is a bear. Not since the pricier Simaudio W-5 had I used a single-chassis amp of such seemingly unlimited power. I used the DNA-225 with the Revel Studios, and the combination was capable of clean sound at unconscionable, painful, downright unneighborly levels way beyond what I could tolerate with the original DNA-1. Large dynamic shifts could be enormous, as was apparent with Mahler's Symphony 6 (Glen Cortese/Manhattan School of Music Orchestra, Titanic Ti-257). If I listened to the piquant details in quiet sections at reasonable levels, the louder portions demanded—and achieved…
Sidebar 1: Specifications
Description: Solid-state stereo power amplifier with one pair of line-level, RCA inputs and four multiway binding posts. Continuous power: 225Wpc into 8 ohms (23.5dBW), 400Wpc into 4 ohms (23dBW), both channels driven, 20Hz-20kHz, 1% THD. Input sensitivity: 1.25V. Input impedance: 100k ohms. Harmonic distortion: 0.5% (1kHz, 8 ohms). Frequency response: 0.5Hz-200kHz, -3dB. S/N Ratio: 100dB. Voltage gain: 30dB. Signal polarity: noninverting. Power requirements: 1.1A/130W at idle, 5A/600W at clipping (8 ohms).
Dimensions: 19" W by 6 7/16" H by 16" D. Shipping…
Sidebar 2: Associated Equipment
Digital sources: Meridian 508-24 CD player, Meridian 800 DVD/CD transport, Mark Levinson No.360 D/A converter.
Preamplifier: Sonic Frontiers Line 3.
Power amplifiers: McCormack DNA-1 and DNA-1 Rev.A+, Sonic Frontiers Power 3.
Loudspeakers: Revel Ultima Studio, OLS Kharma Ceramique 2.0.
Cables: S/PDIF digital: Apogee Wyde-Eye, Illuminations D-60. Interconnects: Cardas Golden Cross, Straight Wire Maestro II (DAC-preamp); Cardas Cross, JPS Balanced Super-Conductor 2 (preamp-power amp). Speaker: AudioQuest Granite, Straight Wire Maestro II.—Kalman…
Sidebar 3: Measurements
After a one-hour preconditioning period at one-third power, which maximally works an amplifier with a class-B output stage, the McCormack's heatsinks were too hot to keep my hand on. After another 30 minutes of continuous high-power testing, the DNA-225's thermal trip circuit turned off the power until the amplifier had cooled down.
The DNA-225's input impedance was high at 91k ohms, dropping slightly to 73k ohms at 20kHz. The voltage gain into 8 ohms was higher than usual, at 30.5dB. Both of these factors will make the McCormack a good choice for use with…
The big McCormack more than meets its specification under continuous drive conditions with both channels driven (fig.7). Defining clipping as 1% THD+N, the maximum power raised was 262W into 8 ohms (24.2dBW), 430W into 4 ohms (23.3dBW), and 795W into 2 ohms (23dBW, only one channel driven). The shape of the traces in this graph reveals that noise dominates the measured figure until quite high levels.
Fig.7 McCormack DNA-225, distortion (%) vs continuous output power into (from bottom to top at 2kHz): 8 ohms, 4 ohms, and 2 ohms (both channels driven).
With a low-duty-…
Brilliant designs, spectacular initial success, rave reviews, explosive growth that stretches resources way beyond limits, too much attention to technology and too little to manufacturing and business practices, long hours, quality problems, conflicts between partners, and finally...
It's a familiar story with a predictable ending. About four or five years ago, VTL was following this script to a "T." But their ending has a twist. Not only have they survived, they've muscled their way into the small group of companies defining the state of the art. Their spectacular showings at hi-fi…