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Krell KSA-50S power amplifier Measurements

Sidebar 3: Measurements

I primarily measured the Krell KSA-50S in its balanced mode. Unusually but gratifyingly, Krell provided a full set of Audio Precision measurements for the review sample. (I wish more manufacturers did this!) The '50S's two bias LEDs came on at 8 ohm output power levels of 765mW (red) and 25.2W (blue). Though the KSA-50S's heatsinks were hot following the 1/3-power, one-hour preconditioning test, I could still keep my hand on them.

The KSA-50S's input impedance measured 49k ohms unbalanced, the same for each leg of the balanced input; its output impedance…

Krell KSA-50S power amplifier Follow-up from September 1995

Sidebar 4: Follow-up from September 1995 (Vol.18 No.9)

In my review of the $3300 Krell KSA-50S stereo power amplifier last month (Vol.18 No.8, p.165), an obvious point of sonic comparison would have been the $3495 Conrad-Johnson Premier Eleven A that Wes Phillips wrote about in the same issue (p.195). Time constraints, however, prevented that from being possible, hence the appearance of this Follow-Up.

For details of the system used, see my review of the AR 303 loudspeaker. The main loudspeaker used in the comparison was the B&W Silver Signature, although I also used the AR…

Magnepan Magneplanar MGIIIA loudspeaker

I must confess to a certain sentimental affection for Magnepan products. An early version of the Tympani did more to rekindle my interest in audio than any other speaker I can think of. In a world which seemed doomed to finding out just how small and dull it could make acoustic suspension boxes, the Magnepans reminded me that speakers could produce a large open soundstage, real dynamics, and musical life.

Both box speakers and electrostatics have gotten far better since that time, but Magnepan has continued to steadily improve its planar speakers. It also has introduced some superb ribbon…

Magnepan Magneplanar MGIIIA loudspeaker Page 2

There were very slight problems apparent in the transition from ribbon tweeter to planar midrange. They were far less apparent than with all but a handful of cone speakers, and compensated for by very wide dispersion, and a midrange sound which was open and live without making the listener feel the usher had just dragged him into the front row. The overall timbre was excellent, with no change from the midrange up to the limits of my hearing (and that of assorted family females).

Getting the best transition from midrange to bass, and overall bass energy levels, required careful amplifier…

Magnepan Magneplanar MGIIIA loudspeaker Martin Colloms January 1987

Martin Colloms wrote about the MGIIIa in January 1987 (Vol.10 No.1):

Panel speakers are back in fashion. After years of determined effort on the part of a few established manufacturers, the number of these designs has seen a marked increase, and many new exotic models have appeared. Stereophile has recently reviewed two leading examples of the genre, the $2780/pair Apogee Duetta and the $2490/pair Martin-Logan CLS, (both reviewed in Vol.9 No.7). To judge by the tone of letters arriving at the magazine's offices, those reviews generated heated controversy. John Atkinson asked me,…

Magnepan Magneplanar MGIIIA loudspeaker Measurements

Sidebar 1: Measurements

Fig.1 is a "snapshot" of the forward axial response, showing some lift up to 16kHz. The mid-treble is linear and well integrated, while the bass is more or less level to 40Hz, in good proportion with the rest.

Fig.1 Magnepan MGIIIa, response on listening axis.

The response in the listening room (fig.2) was remarkable at first sight, although the upper treble was just too good to be true. In addition, the moderate prominence at 60-80Hz could ideally have been avoided. This curve confirms both the inherent neutrality of the IIIa, and its new…

Magnepan Magneplanar MGIIIA loudspeaker Specifications

Sidebar 2: Specifications

Description: Three-way planar-magnetic bass and midrange system, with ribbon tweeter. Bass driver: 620 square-inch planar magnetic. Midrange: 170 square-inch planar magnetic. Tweeter: ¼" W by 57" L by 0.0001" thick ribbon. Crossover: 18dB/octave low-pass Butterworth at 300Hz, 6dB/octave high-pass at 800Hz, and at 3kHz between midrange and treble. Frequency response: 37Hz-40kHz ±4dB. Power recommendation: 50W minimum, 200W maximum. Impedance: 4 ohms in the bass, 3 ohms in the treble, pure resistive. Sensitivity: 83-85 dB/W/m.
Dimensions: 23" W by 72" H by 2" D…

Surrounded By Space

During the late 1950s, when high fidelity exploded into a multimillion-dollar industry, product advertisements bragged about bringing the orchestra into your living room. Apparently, no one realized what an absurd concept it was, but there are still many people today who believe that's what audio is all about. It isn't. There is no way a real orchestra could fit into the average living room, and if it could, we would not want to be around when it played. Sound levels of 115dB are just too loud for most sane people, and that's what a full orchestral fortissimo can produce in a small room.

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Surrounded By Space Page 2

So-called Dolby Surround was first used in A Star Is Born (1976), and has been featured in practically every subsequent Hollywood blockbuster. When stereo came to home videotape, and consumers learned that all those fabulous surround-sound effects were encoded into their videotapes of those same films, they started demanding decoders to separate the surround from the stereo. Today, there are more than 60 different models of Dolby-Surround decoders on the market, and they're selling like rack systems in Racine. But few Dolby Surround users realize that it can be used for other program sources…

Sony TA-P9000ES multichannel analog preamplifier

Sony describes the $700 TA-P9000ES as "a pure audio multichannel preamplifier equipped with two inputs for 5.1 analog multichannel audio sources, enabling selection, volume control, and amplification." A relay with twin gold-plated crossbars switches the two six-channel sources. Then follows a class-A solid-state push-pull amplifier in discrete configuration. Separate transistors, resistors, and capacitors populate the printed circuit boards. An oxygen-free copper shield surrounds each channel to prevent crosstalk between the channels. In addition, there is a relay-controlled gain stage…