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Grace Design m902 Reference D/A headphone amplifier Sam Tellig, October 2008

Sam Tellig wrote about the m902 in October 2008 (Vol.31 No.10):

John Atkinson and Wes Phillips reviewed the Grace Design m902 Reference in April 2006, and since then it's remained essentially unchanged.

As standard, for $1695, the Grace m902 offers four digital inputs—RCA/S/PDIF, TosLink optical, USB, and AES3—plus two pair of analog inputs (unbalanced RCA, balanced XLR). The analog output is a pair of unbalanced RCAs—or, for $1850, you can have a pair of ¼" TRS balanced outputs instead. An additional $125 puts into your hands a beautifully machined remote control—an option that's…

DVD-A <I>vs</I> SACD

"This is offensive!" muttered usually mild-mannered Malcolm Hawksford, who was sitting next to me. "I'm leaving." The good professor was right. One thousand or so attendees at the 103rd Audio Engineering Society Convention, held at the end of September in New York, were being subjected to truly terrible sound. The irony was that the sound was that of 2- and 5-channel recordings made with 24-bit resolution and a 96kHz sampling rate, being played over a colored PA system to demonstrate the future of audio, in the form of DVD-Audio.

Of course, it wouldn't be right to draw any inferences…

Acoustic Sciences Corporation Studio Traps

Over time I've successfully used a variety of tuning devices to refine the acoustics in Kathleen's and my listening room. But I've always suspected that Acoustic Science's Tube Traps might be a good way to finish it off. I've occasionally asked visitors to stand in one spot or another behind the speakers as I listened for tergiversation (ie, "to change one's tune"; Hoo-hah!). I found several locations where a nice, dense audiophile body made an improvement to the sound.

Since installing the JMlab Utopia speakers (a bass-reflex design), I've been aware of a low-level boom in the mid- and…

Acoustic Sciences Corporation Studio Traps Specifications

Sidebar: Specifications

Description: Tripod-mounted room-tuning devices adjustable for height and rotation. Absorption: 6dB/octave rolloff, 3dB down at 110Hz. Reflection: active over 41/2 octaves, treble diffusion 400Hz-7kHz, 12dB/octave crossover, 3dB down at 400Hz.
Dimensions: 9" diameter by 48" H. Weight: 28 lbs.
Finishes: Available in 5 stock colors and 55 custom colors in an architecture-grade, fire-resistant fabric.
Price: $315 each. Approximate number of dealers: 140.
Manufacturer: Acoustic Sciences Corporation, P.O. Box 1189, Eugene, OR 97440. Tel: (541) 343-9727. Fax…

Rogue Audio Magnum Ninety-Nine preamplifier

Rogue Audio's Magnum Ninety-Nine tubed preamplifier is derived from the original Rogue Sixty-Six that I reviewed in October 2000. The Sixty-Six was designed to offer consumers a taste of high-end performance in a vacuum-tube line stage. By constrast, the Magnum Ninety-Nine's pedigree is pure audiophile, with a more sophisticated mu-follower circuit topology aimed at the purest expression of performance.

"We eliminated the balance circuit for that reason," O'Brien explained. "It loaded down the input a little bit, but we still included mute and mono switches, and a headphone…

Rogue Audio Magnum Ninety-Nine preamplifier Page 2

Using the low-output Grado Statement Master with the Rega Planar 25 turntable had eliminated all the interactions and hum I'd previously experienced in mating the unshielded, high-output, moving-iron Grado Statement Reference with the unshielded motor of the Rega 3. A Ringmat 330 and a Signal Guard II Isolation Stand on a PolyCrystal equipment rack had substantially isolated the turntable from extraneous vibrations, but I'd never managed to find a phono stage that gave me the clearly articulated, realistic, high-gain structure I've grown accustomed to from digital gear. The Stealth not only…

Rogue Audio Magnum Ninety-Nine preamplifier Page 3

But where the Rogue truly excelled was in its control of bass and the palpable three-dimensionality of its images. On the Keith Jarrett Trio's Always Let Me Go: Live in Tokyo (CD, ECM 1800/1801), the Magnum did a much more efficient job of fleshing out the attack and harmonic content of Gary Peacock's lightly amplified upright bass, even as it illuminated a vividly perceptible image of the instrument on the visual plane.

To double-check, I listened to pianist Bill Cunliffe's Live at Bernie's (LP, Groove Note GRV1009-1DD), a superb direct-to-disc, 45rpm trio recording engineered by…

Rogue Audio Magnum Ninety-Nine preamplifier Specifications

Sidebar 1: Specifications

Description: Tubed, remote-controlled line preamplifier with separate power supply, 5 inputs, 2 line outputs and 1 headphone output. Tube complement: four 6SN7 (two 12AU7, two 12AX7 in optional phono stage). Frequency response: 1Hz-100kHz, ±1dB. THD: <0.1% (no level specified). Voltage gain: 23dB (line stage), 65dB (optional MM phono), 7d5dB (optional MC phono). Output: 1.5V RMS. Output impedance: 350 ohms.
Dimensions: 17" W by 5.5" H by 14" D. Weight: 25 lbs. Power supply: 4" W by 3" H by 9" D. Weight: 4 lbs.
Serial number of unit reviewed: R99-0546.…

Rogue Audio Magnum Ninety-Nine preamplifier Associated Equipment

Sidebar 2: Associated Equipment

Analog sources: Rega Planar 25 turntable, Rega RB600 tonearm, Grado Statement Master cartridge, Marantz PMD430 portable cassette recorder.
Digital sources: California Audio Labs Delta transport, Alpha 24-bit/96kHz DAC, CL-20 DVD/CD player; Sony SCD-777ES SACD/CD player.
Preamplifiers: Musical Fidelity Nu-Vista, VTL TL-5.5, Rogue Audio Stealth phono.
Power amplifiers: Musical Fidelity Nu-Vista 300, Mesa Baron, VTL MB-450, Rogue Magnum M-120 monoblock.
Loudspeakers: Joseph Audio RM33si Signature & RM7si Signature, Meadowlark Hot Rod…

Rogue Audio Magnum Ninety-Nine preamplifier Measurements

Sidebar 3: Measurements

The five positions of the Rogue Magnum Ninety-Nine's front-panel gain switch correspond to maximum voltage gains of 18.7dB, 13.8dB, 8.6dB, 3.2dB, and -4.4dB. This will be very useful in optimizing the preamp's amplification and noise floor to best match the overall gain structure of its user's system. The Magnum Ninety-Nine inverted signal polarity, and its input impedance measured a usefully high 36k ohms at 1kHz, this dropping slightly at the edges of the audioband.

The Ninety-Nine's output impedance was a fairly low 466 ohms over most of the frequency…