The preamps keep on coming...
Over the past few months I've auditioned two more all-analog multichannel preamps, a fact that some might find remarkable. Just this past week I chatted with Jonathan Scull, who wondered about the market for a high-end, all-analog multichannel preamp. I don't know if such a market exists, and I, too, wonder about their future. But I do have a closet full of them, and during this period of transition from two to many channels, they're essential. Some of us still have traditional analog sources and we are also forced, for the most part, to use the analog…
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For those of us who have succumbed to the enticements of surround-sound for music, Audio Research's SDP1 is both vindication and cause for rejoicing: vindication because surround-sound's acceptance by such an ultraconservative, uncompromising company as ARC will give it a respectability in the high-end community that it never enjoyed before, and cause for rejoicing because someone has finally done music surround right.
High-end audio has a long history of minimalism—the view that, when it comes to active circuitry, less is definitely better than more. Tone controls disappeared from the…
Here's how it works: It takes our ear/brain system about 5 to 10 milliseconds to determine the direction from which a sound reaches us. If two sounds arrive from different directions during this lock-on period, we'll hear them come from different directions; we would hear the very poor separation between the front and surround channels. After that there's a 25ms lockout period (called the "fusion zone") during which no other directional cues can be processed. If a front-coming sound is followed during the lockout period by a second sound coming from somewhere else, the second sound is masked…
The center channel was of negligible value, though. When it was loud enough to stabilize center images for off-center listening positions, there was a marked loss of soundstage width and spaciousness (remember that 3dB adjacent-channel separation). I found myself leaving it off all the time, even for movies. Otherwise, the SDP1 did everything it was supposed to do—and did it without any audible degradation of the front-channel signals.
What does surround-sound do for music? I've described it before, but I'll reiterate: What it does, basically, is put the ambient space of the recording…
Sidebar 1: Specification
Description: L-R ambience extractor. Inputs: one pair, balanced or unbalanced. Input impedance: 1.5Megohms unbalanced, 3M ohms balanced. Gain: 12dB maximum (6dB balanced into unbalanced out, 10dB unbalanced into balanced out). Frequency response: 2Hz-400kHz +0, -3dB. Distortion: <0.01% at 2V out. Noise: <30µV RMS, IHF-weighted, center channel. Maximum output: 18V balanced. Controls: two surround level, one center level, surround delay (25, 28, 32, 38, and 45 milliseconds), Mute, Power. Outputs: one pair surround, one pair pass-through L and R, one center,…
Sidebar: Measurements
The Audio Research's input impedance was very high at around 1M ohms. It will feature very low insertion loss for the unprocessed Left and Right signals. The source impedance of all the SDP1's derived, unbalanced outputs was low, at around 28 ohms.
The SDP1 has controls to optimize the levels of the Surround and Center channels with respect to the main Left and Right signals. The tracking of the three separate level controls for the derived channels was only fair, with a typical error of around 0.2dB. The steps varied between 2 and 3dB at the very top and…
Kevin Hayes: Valve Amplification Company arose out of my dissatisfaction with the stereo gear I could buy. I've been an audiophile since before I knew what the word meant, going back to the mid-'70s. I had an epiphany when I first heard a piece of old tubed gear, a Fisher X101, that simply blew away a highly touted receiver that I happened to own. It was a 25W integrated amplifier, using 7591s on the output, and except for sustained organ-pedal notes, it was far better than what I had at that time.
My father trained as a BS/EE in 1951, and that put a lot of old electronic texts and old…
Hayes: That's primarily a concession to price—I like having the option of variable feedback. However, I feel that the value we've dialed-in on the '80 is optimal; there's only a narrow range on either side of the value we've specified that would sound as good as the one we set.
We make a derivative of the PA80/80, called the PA35/35 ($2950), which changes the output tubes to EL34 pentodes and takes both the suppressor grid and the screen grid directly to the anode, forming a real triode structure—which is different from the way almost everyone (including us, in our earlier designs) does…
Electrostatic speakers are my passion. Why else have I put up with their high prices, unreliability, low power handling, tendency to arc, high-frequency beaming, limited bass response, and widely fluctuating impedances?
Take the Quad ESL-57 (footnote 1). Configured as a gnarly, stubby panel, it was often mistaken for an oversized space heater. Left on, it sucked up dust and grime as its panels filtered the air. Far worse, it arced—those flickering blue lights in the panel signaled diaphragm perforation and eventual destruction.
But the sound! When I sat in their tiny sweet spot,…
The bass module is a sealed dual-woofer design. The forward-facing 10" ScanSpeak aluminum-cone woofer carries the bass audio signal. An independently enclosed, 10" ScanSpeak fiber-cone cone faces to the rear and is driven by a circuit that processes level, phase, and frequency range to create a partial cancellation of the front woofer's output in the lower frequencies (footnote 2). This ForceForward technology specifically reduces the common 50Hz null and 100Hz peak found in many rooms. For those requiring more forward bass, the Prodigy has a rear-panel switch for increasing the below-50Hz…