When I asked if the Amp C1 used any feedback at all, he said there's a problem with using the term local feedback—but he assured me that a type of feedback was used in the Amp C1, otherwise it would produce "crazy gains."
Candeias then talked about the difference between a standard attenuator and what he's done in the Amp C1: "…
Description: Two-channel integrated amplifier. Line inputs: 2 balanced (XLR), 3 single-ended (RCA). Output power: 175Wpc into 8 ohms (22.4dBW), 330Wpc into 4 ohms (22.1dBW). Frequency range: 20Hz–20kHz. Bandwidth at 1W: 2Hz–180kHz –3dB. Total harmonic distortion+noise at 1W, 1kHz: 0.01%. Signal/noise at DIGM57 (relative to Pmax): 110dB. Input impedance: 50k ohms (RCA), 100k ohms (XLR).
Dimensions: 17.1" (435mm) W by 5.9" (138mm) H by 15.9" (405mm) D. Weight: 88 lbs (40kg).
Serial Number of Unit Reviewed: AC11010009309.
Price: $7990. Approximate…
Analog Sources: Continuum Audio Labs Caliburn turntable with Cobra tonearm & Castellon stand; Graham Phantom II, Kuzma 4Point tonearms; Ortofon A90, Lyra Atlas, Miyajima Labs Premium BE mono cartridges.
Preamplification: Ypsilon VPS-100 phono preamplifier, darTZeel NHB-18ns preamplifier.
Digital Sources: Simaudio Moon Evolution 650D DAC/CD player, BPT-modified Alesis Masterlink hard-disk recorder, Meridian Sooloos Digital Media System, Pure Music software.
Power Amplifiers: darTZeel NHB-458 monoblocks.
Loudspeakers: Wilson Audio…
To perform the measurements on the B.M.C. Amplifier C1, I used Stereophile's loan sample of the top-of-the-line Audio Precision SYS2722 system (see www.ap.com and the January 2008 "As We See It"). Before testing the B.M.C., I ran both channels at 1/3 the rated power into 8 ohms for 60 minutes, which thermally is the worst case for an amplifier with a class-A/B output stage. At the end of that time the C1's chassis was too hot to touch, at 145°F (62.9°C), but the amplifier was otherwise operating correctly.
The volume control operated in 66 accurate 1dB…
It was the spring of 1982. John Crabbe, then editor of the British magazine Hi-Fi News & Record Review, and I had driven up to Quad's factory in Huntingdon, England. The ESL-63 electrostatic loudspeaker had been launched the previous summer, and we were to interview its designer, Peter J. Walker, for an article that would appear in the July 1982 issue of HFN/RR. Peter set up a pair of ESL-63s on wooden kitchen chairs, fed one of them a 300Hz…
Super Sonics
Setting up the Quad Reference ESL-2805s in my room was straightforward, with…
Description: Full-range, floorstanding, electrostatic loudspeaker. Membrane: ultra-low-mass (0.5gm), tensioned, split into 4 elements. Frequency response: 37Hz–21kHz, –6dB. Sensitivity: 86dB/2.83V/m. Nominal impedance: 8 ohms (4–15 ohms variation). Rated input level: 10V; program peak for undistorted output, 40V; permitted peak input, 55V. Distortion at 100dB at 1m: 1.0%, 50–100Hz; 0.5%, 100Hz–1kHz; 0.15%, >1kHz. Operating supply voltages: 110–120V AC; 220–240V AC.
Dimensions: 41" (1040mm) H (plus feet) by 27.4" (695mm) W by 15.2" (385mm) D. Weight: 76.6…
Digital Sources: Ayre Acoustics C-5xeMP & DX-5 universal players; Apple G4 Mac mini running OS10.5.8, iTunes 10, Pure Music 1.83; Shuttle PC with Lynx AES16 soundcard & dual-core AMD Athlon processor running Windows 7, Foobar 2000, Adobe Audition 3.0; dCS Debussy, Logitech Transporter, Mark Levinson No.30.6 D/A converters; Empirical Audio Off-Ramp4 USB-S/PDIF converter.
Preamplifiers: Classé CP-800, Ayre Acoustics K-5xeMP.
Power Amplifiers: Classé CT-M600, Lamm M1.2 Reference, MBL Reference 9007 (all monoblocks).
Loudspeakers: BBC LS3/…