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Silverline Audio Technology Prelude loudspeaker Measurements

Sidebar 3: Measurements

All my measurements were performed on samples of the "Revised" version of the Prelude. The terminal posts were loose on both samples and one of the samples (serial no.2041A) appeared to be miswired: the drive-units were silent when driven individually, the speaker giving out sound only when both sets of terminals were connected to the amplifier. Although its farfield response and sensitivity then matched that of the second sample (serial no.2041B), I put it back in the box and performed all the measurements on the second speaker. (I left the grille off.)

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Rogue Audio Atlas power amplifier

When I unpacked the Rogue Audio Atlas, I didn't know how much it cost. After examining its chassis of high-grade steel, its silver-anodized aluminum faceplate, its sleek and slightly rounded edges, and, above all, its two chunk-o'brick transformers—for such a little thing (a foot-and-a-half square by half-a-foot high), it's heavy—I guessed around five grand. Then I called Rogue Audio and learned that it retails for $1395.

I was startled. It seemed crazy cheap. At 55 lbs and 55Wpc, that's about $25 per watt and per pound—bargain-basement for a tube amp. Then (I'm not proud of…

Rogue Audio Atlas power amplifier Page 2

There's a wonderful, unjustly obscure 1981 Chico Freeman album, The Outside Within (LP, India Navigation 1042). The first track on side 2, "The Search," begins with a very slow, bluesy duet between Freeman's bass clarinet and Cecil McBee's bowed bass, the two playing in perfect unison. A good test of midbass clarity is whether the two players sound clearly distinct up and down the scale, tonally, spatially, and harmonically—ie, whether you can pinpoint where each is standing on the soundstage and which player is bowing, which blowing. The Atlas passed the test, but not with aces; I had to…

Rogue Audio Atlas power amplifier Specifications

Sidebar 1: Specifications

Description: Two-channel, tubed power amplifier. Tube complement: four KT77 (or EL34), two 12AU7, two 12AX7. Maximum output power: 55Wpc into 8 ohms (17.4dBW). THD: <0.1% typical, <1% at rated power. Input sensitivity: 1.0V RMS.
Dimensions: 18" (460mm) W by 5.5" (140mm) H by 17" (435mm) D. Weight: 50 lbs (22.7kg) net, 55 lbs (25kg) shipping.
Serial Number Of Unit Reviewed: ATL-0604.
Price: $1395. Optional cover, $100. Approximate number of dealers: 55. Warranty: 3 years (6 months for tubes).
Manufacturer: Rogue Audio Inc., 3 Marian Lane,…

Rogue Audio Atlas power amplifier Associated Equipment

Sidebar 2: Associated Equipment

Analog Source: VPI HW-19 Mk.4 turntable, VPI JMW Memorial tonearm, Clearaudio Victory H cartridge.
Digital Sources: Krell SACD Standard SACD/CD player, Simaudio Moon CD 5.3 CD player.
Preamplification: Audible Illusions Modulus 3a used as full preamp and as phono stage only, Krell KAV-280p line stage.
Power Amplifier: Krell FPB-400cx.
Loudspeakers: Verity Audio Parsifal Ovation.
Cables: Nirvana.
Accessories: Bybee Technologies Signature power purifier, Monster Cable AVS-2000 voltage regulator, Black Diamond Racing Mk.4 Cones, Mapleshade…

Rogue Audio Atlas power amplifier Measurements

Sidebar 3: Measurements

Before performing any measurements on the Rogue Audio Atlas, I checked the bias of its four KT77 output tubes. All were running at around 40mA bias current, close to the 35mA recommended by the manufacturer. I tested the Atlas with its output transformer hooked up for 8 ohm operation, as usually supplied by Rogue, and also as wired for 4 ohm operation, as ultimately used by Fred Kaplan in his auditioning. To my surprise, the voltage gain into 8 ohms was the same from both output-transformer windings—26.5dB—despite the 8 ohm tap's greater intrinsic gain. This is…

Joseph Audio RM7XL Special Edition loudspeaker

Jeff Joseph always causes a stir at Stereophile's annual Home Entertainment Shows. No matter which speakers he exhibits, he invariably gets wonderful sound in his room. He's fooled more than one Stereophile writer who thought he was listening to Joseph's flagship Pearls when, behind a curtain, it was actually two of his in-wall models that were playing. And his competitors seem to envy his hi-fi show sound more each year.

My experience with Joseph Audio speakers had been limited to show demonstrations, as their prices have always far exceeded my self-imposed ceiling for "…

Joseph Audio RM7XL Special Edition loudspeaker Specifications

Sidebar 1: Specifications

Description: Two-way, reflex-loaded, stand-mounted loudspeaker. Drive-units: 1" Sonatex soft-dome tweeter, 7" metal-cone woofer. Frequency response: 42Hz–20kHz, ±2dB. Sensitivity: 86dB/2.83V/m, 4 pi (anechoic). Impedance: 8 ohms nominal, 7 ohms minimum.
Dimensions: 15" (381mm) H by 9" (228.6mm) W by 12" (304.8mm) D. Shipping weight: 55 lbs (25 kg)/pair.
Finishes: wood veneer.
Serial Number Of Units Reviewed: 70821 L/R.
Price: $2299/pair. Approximate number of dealers: 32.
Manufacturer: Joseph Audio, Inc., P.O. Box 1529, Melville, NY 11747. Tel: (…

Joseph Audio RM7XL Special Edition loudspeaker Associated Equipment

Sidebar 2: Associated Equipment

Analog Sources: VPI TNT IV turntable, Immedia RPM tonearm, Koetsu Urushi cartridge; Rega Planar 3 turntable, Syrinx PU-3 tonearm, Clearaudio Virtuoso Wood & Aurum Beta S cartridges.
Digital Sources: Lector CDP-7T, California Audio Labs Icon Mk.II Power Boss, Creek Destiny, Creek CD53 Mk.II CD players; Pioneer DV-333 DVD player.
Preamplification: Vendetta Research SCP-2D phono stage, Audio Valve Eklipse line stage.
Power Amplifier: Audio Research VT100 Mk.II.
Integrated Amplifiers: Creek Destiny & 5350SE.
Loudspeakers: Amphion Helium2…

Joseph Audio RM7XL Special Edition loudspeaker Measurements

Sidebar 3: Measurements

My estimate of the Joseph Audio RM7XL Special Edition's voltage sensitivity on its tweeter axis was within experimental error of the specification, at 85.5dB(B)/2.83V/m—slightly below the average of 87dB for the 630 or so speakers I have measured over the past 17 years. Its impedance remains above 8 ohms at almost all frequencies, dropping to a minimum value of 7.15 ohms at 200Hz (fig.1). This, in combination with the generally low electrical phase angle, will make the RM7XL a very easy load for an amplifier to drive.

Fig.1 Joseph Audio RM7XL…