Boston Audio Society
If you are like most audiophiles you have probably wondered about the cumulative results of the Marantz and McIntosh Amplifier Test Clinics which are often hosted by local hi-fi retail dealers. And if you are like myself you have probably wondered what the clinics really tell us.
The Marantz and McIntosh amplifier clinics are free to the consumer, and everyone is invited to bring in their unit to be tested. Both amplifier test-clinics are geared primarily to give you the harmonic distortion produced by your unit from 20-20,000 Hz. at the manufacturer's rated full RMS power. Usually there is a long line of units to be tested, and most clinics have at least two technicians, one to plot the graph while the other performs the tests. Receivers, integrated amplifiers, and preamplifiers are tested at the clinics but generally only the amplifier section of a unit is measured. High quality test equipment is used by both clinics to insure accurate results.
I decided to collect the results of the test-clinics from some of the dealers in the Boston area that had hosted a clinic. The test results I collected cover four separate clinics of which three were sponsored by McIntosh. The results include the years from 1969-72, and include over 237 amplifiers and receivers representing a total of thirty-four manufacturers. (I did not include preamplifiers in the results because all the units tested performed excellently in the categories I established.)
To organize the data I arbitrarily had to limit myself to ranking only those manufacturers that had at least four or more units tested. I divided the results of the HD into three categories: Category I - included units tested with less than one percent HD from 20-20,000 Hz. at the manufacturer’s rated full RMS power. Category II - included those units with less than two percent, and Category III - included those units with greater than two percent HD.
Numbers were assigned to the categories in order to establish a ranking of the units. Six points, the highest possible, was given to the units that fell in Category I, four points to Category II and two points for Category III, the lowest possible score.
What do the results tell us? The results are a good indication of how a manufacturer will rate his amplifier's power output. As can be seen from the list, it is easy to identify those manufacturers that tend to rate their units conservatively, like McIntosh, or which manufacturers tend to overstate their units. The results indicate that there is a drastic need to adopt a uniform standard of rating amplifiers at least in their power handling ability. The results may be some indication of reliability but to a smaller degree. Most of the units brought to the clinics by their owners were at least two years old. The results do tell us that the top five manufacturers were still holding their original specifications after several years. For example, one of the McIntosh units tested was fifteen-years old!
The results tell us also that an AR amplifier rated at fifty watt RMS/channel by its manufacturer is not the same as a Fisher rated by its manufacturer at the same RMS power. An AR fifty watt RMS/channel amplifier could conceivably turn into a Fisher seventy watt RMS/channel model by merely swapping advertising departments. It is interesting to note that Fisher which is among the lowest in rank is also the world's largest manufacturer of high quality stereo equipment according to Avery Fisher, founder of Fisher Radio.
The top five manufacturers, or those manufacturers which tend to rate their product most conservatively in order are: McIntosh, Marantz, Heath, AR, and Sony. The lowest seven or those manufacturers which tend to 'stretch' their power output in order are: Scott, Dynaco, Lafayette, Eico, Realistic, Fisher, and Bogen.
If you buy a McIntosh amplifier your chances are probably one hundred percent that it will meet its manufacturer's specifications. And if your unit falls among the top five your chances are at least seventy-five percent that it will test in Category I. If you are the owner of a Bogen the chances of it meeting its manufacturer's stated full RMS power output from 20-20,000 Hz at less than one percent HD are probably nil. And if your unit falls in Category III, or the lowest seven ranked, the chances of it falling in the under one percent HD department are about 1.3 percent. Of course these figures are only applicable to the 237 units tested covering only thirty-four manufacturers. Generalizations to other units not included in these four specific clinics may not be applicable.
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