|Harvard Electronics Futterman H-3 stereo power amplifier|
THE EQUIPMENT: Futterman H-3, a stereo basic amplifier. Dimensions: 17 by 10¼ by 7½ inches. Price, including cage (removed in our photo), $288. Manufacturer: Harvard Electronics Co., 693 Broadway, New York, N.Y. 10012.
COMMENT: The Futterman H-3 is a high quality basic amplifier of unusual design: it employs tubes but no output (or interstage) transformers. Intended for use with a control preamp (or, for that matter, any signal source providing about 1 to 2 volts signal and equipped with its own level control, such as a tuner or tape playback deck), the Futterman has no operating controls. Instead, the chassis contains numerous potentiometer adjustments for "trimming up" the circuit to get optimum performance. According to the instructions furnished with the unit, these adjustments are to be made after every thousand hours of use, or after any tube is changed. The apron of the chassis contains a pair of octal sockets (for each channel) through which the connections are made when performing these adjustments. In addition there are speaker terminals for each channel, phono-jack signal inputs, two fuse-holders, and one AC convenience outlet. An examination of the amplifier indicates that it is built of top-grade components and with an exceptionally high quality of workmanship; the underside of the chassis has that "hand-made-with-loving-care" look.
The Futterman amplifier is rated by its manufacturer at 50 watts per channel, when operated from a 120-volt source and feeding a 16-ohm load. Enough measurements were made at United States Testing Company, Inc., under these conditions to confirm the power output rating, but inasmuch as the existing standard for testing amplifiers calls for a 117-volt source, measurements of power and other characteristics were made from 117 volts, which is used for testing all equipment.
The question of line voltage, incidentally, has been raised by a few other high fidelity manufacturers who suggest that the 120-volt figure is closer to what is being supplied as line voltage in many locales. No change has been made, however, by the various professional and trade associations, and so the 117-volt standard prevails. From the standpoint of most equipment users, the difference of 3 volts in the AC line is of relatively little importance; the higher source voltage will produce somewhat higher amplifier power output, but will not appreciably change other important operating characteristics. The difference in line voltage used, of course, could account for differences in published specifications and test measurements of the same amplifier.
Another related factor is the load into which the amplifier works. The Futterman is rated for a 16-ohm load, into which it will deliver its specified power. With lower impedance levels, power output is lower, but over-all performance into an 8-ohm load (the most widely used speaker impedance) is still excellent. No measurements were made for a 4-ohm load inasmuch as the Futterman is not recommended for use with 4-ohm speakers. At loads higher than 16 ohms, the amplifier furnishes well above its rated power, and USTC measured better than 74 watts per channel at 0.5% distortion into a 30-ohm load. (Such a load is represented by a speaker like the KLH-9 full-range electrostatic, with which the H-3 amplifier has been teamed for reportedly superb sonic results.)