I am thinking of buying a McIntosh amp with 100 watts per channel, and either a JBL Model 200 or 300, Altec Model 19, or Klipschorn speakers. I know all these speakers are supposed to handle this kind of power, but will they? A friend of mine blew an Ohm F with a 75-watt receiver. I would appreciate your opinion.
-Garth S. Nelson, Sussex, Canada.
The speakers you are considering are safe (as are most speakers) with 20 dBW (100 watts) as long as the amp is not driven into clipping. We cannot imagine that an Ohm F was destroyed by a clean signal from a 75-watt receiver, as that speaker has been known to remain unimpressed while driven from amps rated at 23 dBW (200 watts) or more. Either the receiver was driven into heavy clipping, or it failed under excessive drive and put DC through the voice coil.
Record stores check styli microscopically free of charge, but I have found this service to be very careless and poor. I had a stylus checked in a store that declared it to be worn out and unusable, and several minutes later another store nearby said the same stylus was in perfect condition.
Because of that, I want to buy a microscope for my own use and would like your suggestions. How strong should the magnification be (25X, 100X, 1,000X)? What features are significant and necessary in a good stylus microscope, and which are insignificant except in raising the price? Which brands can you recommend that are good and not very ex pensive (for example, one can buy very good binoculars for $50, while slightly better ones cost around $400)?
- Omelan Kulyckyj, New York, N.Y.
The personnel who check styli in record and audio stores often lack expertise and may be plagued with poor equipment. On the basis of the sophisticated hardware we have seen manufacturers use to check stylus wear (and the dismal results we have gotten using cheapies) we would suspect that a usable microscope for this purpose is an expensive item. But the microscope won't do you any good unless you know what to look for, and more to the point-when a stylus shows faults that are obvious to the untrained eye it may already be damaging records. It seems to us that you can save yourself grief, trouble, and money by simply replacing a stylus routinely after 500 to 600 hours of use and forgetting the microscope.
Akai and Hitachi now have tape recording and playback heads within a single housing that eliminates height and azimuth adjustment problems. Is this type of construction an ad Vantage over that of such decks as the Tandberg TCD-330 and the Nakamichi 1000 II, which feature adjustable azimuth?
-Richard Reid, Grand Rapids, Mich.
The two-head-in-one arrangement, by placing the playback gap very close to that for recording, minimizes the amount of tape twisting (and hence misalignment) that can take place between the two. But the physical space limitations put constraints on the de sign and construction of the head. Nakamichi and Tandberg are saying, in effect, that they would rather go for the best possible heads and solve the alignment problems inherent in separate heads via an adjustment system: Hitachi and Akai prefer to minimize the alignment problem and avoid potentially annoying (and costly) adjustment systems by accepting some compromises in the heads. Incidentally it is conceivable that Hitachi's new Hall effect heads may make possible the best of both worlds, though any judgment on that will have to wait until products are available.
I'm a bit obsessive when it comes to conserving electricity and would appreciate information on power consumption in stereo amplifiers. Do the figures listed by some manufacturers represent consumption only at full volume-which I'm not likely to re quire? Does consumption increase as I turn up the volume? If so, would an amp use relatively little power at low volume? If the amp is switched on but no input provided, what percentage of its peak consumption does it draw? Does a more powerful amp use a lot more electricity or will things balance out somewhat because it can be used at a lower volume setting than a less powerful amp? I don't mind a higher initial investment but would dislike a higher monthly electric bill.
-Michael D. Scherer, Teaticket, Mass.
We covered this subject in some detail in our July 1974 issue ("High Fidelity and the Energy Crisis" by Edward J. Foster), though amplifier design has altered the figures somewhat since then. First. we doubt that your audio equipment is using any significant fraction of your total electricity demand (certainly, if we assume solid-state equipment: tubes draw a lot of current just to heat their filaments). The wattage drawn by a power amp (regardless of its output ratings) depends on how much output power it actually is called upon to deliver. Idling power increases with output rating but usually not proportionally. A typical amp rated at 20 dBW (100 watts) per channel and designed for Class-B operation might draw about 80 watts at idle and perhaps 250 watts at around 13 dBW (20 watts) average-the point at which instantaneous musical peaks may be expected to go into clipping. At full output the power drain should be about 300 watts and at one-third power (where efficiency is close to its lowest) 320 watts. For comparison, a typical Class-A amp with the same rating might draw 800 watts at idle. 400 at full power.
So figuring how much electricity your amp actually will eat up is not easy. It is further complicated by the fact that (as you suggest) a single power-consumption figure, where the manufacturer shows it at all, represents consumption at rated output: your actual demands will be lower. Some manufacturers do show idling consumption as well, and for background-music levels this figure will be close to what you actually use. With a medium-power amp of conventional design, this level may require less (say, 25 watts or so) than is drawn by a hefty-motored open-reel deck (which might easily be in the 100-watt range). So don't overlook your other components when making your calculations, and remember that most will draw their full rated power consumption (which may be shown on the serial-number plate or in the owner's manual) all the time they are turned on.
Recently I had the chance to purchase a Dual CS-704 turntable for an exceptionally good price. Your test report [March 1977] said the following: "The excellent damping provided by the anti-resonance filter results in less recorded rumble and low-frequency chaff being transferred through the stylus and pickup to the preamp. This translates into a small but perceptible increase in the over-all clarity of sound." If that is actually the case, shouldn't the arm come in for censure rather than approbation? That is, if the filter really is able to re move some recorded rumble and other low-frequency noise, then conceivably it also filters out musical material in the same frequency range, or some nonmusical material that is still part of the musical performance (say, the pedal action in some of Anthony Newman's harpsichord recordings). Perhaps I am guilty of what HIGH FIDELITY has else where called "perfectionism run rampant"; after all, who isn't in favor of the greatest possible clarity of sound, and who wants to listen to recorded rumble and other noise?
-Paul Seydor, Los Angeles, Calif.
The tonearm of the Dual CS-704 does not, in fact. remove anything; it simply doesn't accentuate as much noise in the low-frequency resonance range (below musical frequencies) as many other tone arms do, be cause it keeps the resonance very well damped.
A friend gave me a pair of Delta Scientific transmission meters. I would like to use these meters to show the output in watts of my Pioneer 737 receiver. Since my friend is not sure how to do this and I cannot find the company's address, I am hoping you can tell me what procedure to use and if it is safe to do.
-Adam Kaplan, Plainview, N.Y.
We are not familiar with Delta Scientific, and without certain knowledge and data about the meters we cannot tell you how to use them. Why don't you ask your friend where he got them and get the company's address from the store? You might also look into the Realistic APM-100 audio power meter as an alternative.
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(High Fidelity, Nov. 1977)
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