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Channel Islands Audio VHP•1 headphone amplifier Measurements

Sidebar 3: Measurements

I measured the Channel Islands VHP•1 using the VAC•1 AC power supply. The maximum voltage gain was 16.2dB or 5.9dB, depending on whether the front-panel gain button was pushed in or not. The VHP•1 preserved absolute polarity, and its input impedance was a fairly low 6.9k ohms across the audioband. Its output impedance was a low 11 ohms at all frequencies.

The frequency response was wide and flat, and just 0.2dB down at 200kHz (fig.1). The negligible infrasonic rolloff below 20Hz seen in this graph, which was taken into 150 ohms, disappeared when the…

Quad ESL-63 loudspeaker

Warning to Purists: Despite certain qualities about the ESL-63 speakers which you will probably like, Quad equipment is not designed primarily for audiophiles, but for serious-music (call that "classical") listeners who play records more for musical enjoyment than for the sound. Quad's loudspeakers do not reproduce very deep bass and will not play at aurally traumatizing volume levels, and Quad's preamplifier is compromised through the addition of tone controls and filters, all for the purpose of making old, mediocre, and/or worn recordings sound as listenable as possible.

The Acoustical…

Quad ESL-63 loudspeaker Page 2

Incidentally, Quad's instruction booklet for the 34 preamplifier makes a very good point about listening level, asserting that for a given recording there is only one correct volume setting. I agree generally, but with qualifications. The "correct" setting is where the perceived volume of the instruments "agrees" with their apparent distance from the listener, which makes perfect sense when the recording was done with "purist" microphone technique—two, or at most three, microphones for pickup of the entire group.

But many multimiked recordings produce an ambiguous perspective, where…

Quad ESL-63 loudspeaker Follow-Up November 1983

Follow-Up from November 1983 (Vol.6 No.5):

Our full report on the Quad ESL-63 electrostatic loudspeaker last month was inconclusive because (1) our first two samples of it broke down and started arcing, protection circuit or not, and (2) 1 had the feeling that there must be amplifiers which would them sound better than I had them sound to date.

Since then, we obtained two more of the speakers; here's what we found:

On most program material, the '63s would play cleanly at levels up to 98dB SPL, measured at 1 meter on-axis. Above that, one speaker's protection started…

Quad ESL-63 loudspeaker Anthony H. Cordesman

Anthony H. Cordesman wrote about the Quad ESL-63 in December 1984 (Vol.7 No.7):

Calling these Quad ESL-63s "Improved" may be a bit misleading. The only significant change in the latest Quad is a pad built into the dust cover to damp vibration in the diaphragm and control a 60Hz resonance. This change begins with serial number 13,041, and is not retrofittable.

However, there have been enough significant changes in the ESL-63 since its introduction for us to view current production as a different product, thus justifying the appellation "Improved." These changes have been: the…

Quad ESL-63 loudspeaker Sam Tellig

Sam Tellig wrote about the Quad ESL-63 in July 1985 (Vol.8 No.3):

"You sold your Quads!!!"

My son had just returned home from college.

I wondered myself whether I had done the right thing. Probably I'd done it as an audiophile version of the three-year itch more than anything else—always trying something new. (That's why I became a reviewer: to save myself from personal bankruptcy!)

Or did I have good reason to sell the Quads? I still don't know for certain, but my time without them has convinced me that, as superb as they are, the ESL-63s are still not perfect…

Quad ESL-63 loudspeaker Martin Colloms

Martin Colloms added some comments in January 1987 (Vol.10 No.1):

The Quad ESL-63 uses an 0.00137" diaphragm, with 0.001" plastic film for the dust-cover membranes. (The ESL-63's diaphragm weighs just 0.003gm, or 3 milligrams, not too far removed from the tip mass of a pickup cartridge!) The diaphragm diameter is subdivided no less than eight times, providing a controlled reduction of element size with frequency, and thus maintaining a good radiation angle.

Electrostatics generally have a finite sound-level limit, due to considerations of peak voltage and electrical flashover, or…

Quad ESL-63 loudspeaker Larry Greenhill

Larry Greenhill reviewed the Quad ESL-63 US Monitor in February 1989 (Vol.12 No.2):

Electrostatic loudspeakers (ESLs) have always held a fascination for audiophiles. The Jantszen, Beveridge, KLH, Acoustat, Stax ESL-F81s, and Servo-Static models in the late 1960s and '70s, as well as the MartinLogans and Sound Labs of today, all promise faster transient response, low distortion, and a higher order of "transparency." Why? The driver, instead of being a cone with a mass of several ounces, is an extremely thin sheet weighing mere grams, often made of Mylar, and suspended between two charged…

Quad ESL-63 loudspeaker Larry Greenhill part 2

This inability to play loud turned out to be related to an altitude effect, the speaker being unable to play any louder than 97dB at the 7000' Santa Fe elevation (still, the original '63s were no rock loudspeaker, even at sea level). Stands (Arcicis, sand-filled to reduce vibration and increase stability), subwoofers (perhaps Celestion System 6000 dual-mono subwoofers), and tube amps (Futtermans) were recommended associated components for the owner willing to go the full route.

Then came the next period in the life of the Quad ESL-63—modifications and improvements. Some were done by Quad…

Quad ESL-63 loudspeaker Larry Greenhill part 3

The US Monitor stayed very close to the sound of the my early '63s for most vinyl recordings and CDs. The new speakers played louder than my originals, and there was an enhanced openness, particularly in the upper midrange. In addition, the amplifiers continued playing as I cranked up the volume control (my older Quads would shut down just as the amplifier's protection circuits or fuses acted). By comparison, my older ESL-63s had a "dark" tonality. In many respects, the "intact" US Monitor (with its metal screens on) sounded like the older Quad with the screens off (footnote 1). As a result…