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Q. I love the sound of my ADC ZLM cartridge, which I use with a Dual 727 turntable, a Soundcraftsmen PE-22 17 preamp, and a Phase Linear 400 Series Two power amp. Occasionally, however, there is severe distortion on loud high-frequency passages. Changing the stylus does not help, but switching to a Pickering XV 15-400E eliminates the problem. Can it he that the ZLM is too "hot" for my preamp? What can I do to get rid of the distortion without giving up the ZLM? -W. Sawrey, Chula Vista, Calif. A. Although the ZLM's output is a trace higher than average and the Soundcraftsmen's phono overload level is slightly on the low side, we doubt that this is the source of your problem. The fact that it disappears when you change cartridges and that it manifests itself only at high frequencies suggests that what you're hearing is plain old mistracking. First, make sure that your stylus and records are scrupulously clean, for dirt is a prime suspect in the situation you describe. Then make sure that your ZLM is correctly mounted and aligned in the Dual's headshell and that the antiskating is correctly set. Set the tracking force to the very top of the range ADC recommends, and double check it with an external VTF gauge. If the difficulty persists, you will probably have to change cartridges. Q. My speakers are rated to handle 100 watts of power, and the click stops on the volume control of my Technics receiver, rated at 150 watts per channel, are numbered from one to ten. Where should I set the volume control to keep my speakers from getting too much power and blowing up? -Leo Caruso, Tampa, Fla. A. There is no strict relationship between the setting of the volume control and the instantaneous power output of the receiver, which varies as the music itself becomes louder or softer. As for blowing up your speakers, there is little reason for you to worry. Under artificial conditions, it is possible to destroy almost any speaker with almost any amp or receiver, but in normal usage this is an uncommon occurrence, even with very powerful units. At extremely loud playing levels, your speakers will probably tell you that they are being overdriven by making distinctly nonmusical sounds well before they self destruct. To play it safe, you might want to write the manufacturer for instructions on how to fuse your speakers. This usually involves placing a low-value (1 amp or sol fast-blow fuse in the "hot" line to each speaker. Q. I recently moved from Northampton, Mass., where the FM reception on my Sherwood 7900 receiver was fine, to Norwich, Conn., where I have trouble receiving some of the stations I want to hear. In particular, I would like to get clear reception of WFCR in Amherst, Mass., and of WGBH in Boston, both about 80 miles away, as well as of two stations very close to each other on the dial: WPBH, 90.5 in Middlefield, Conn., about 50 miles away, and WRIU, 90.3 in Kingston, R.I., much nearer my home. Would buying a newer receiver help? -Walter B. Simon, Norwich, Conn. A. Perhaps. You would want a model with excellent sensitivity to bring in the weak distant stations and, most importantly, unusually high adjacent-channel selectivity to help separate those two kissing cousins. But we suspect that, given the circumstances you describe, you still would need a good high-gain directional antenna with a rotor, so why not try that first? It might give new life to an old friend and save you a few dollars in the bargain. Q. I am now using a pair of ESS AMT-10h loudspeakers. However, I like the warmer sound of some Quadraflex speakers I have heard. Could I use an equalizer to make my present speakers sound like the Quadriflexes I prefer? -Franklin Covey, Folsom, Calif. Q. An equalizer can he used to alter the frequency response of signals going to a loudspeaker, in effect modifying the frequency response of the speaker. Unfortunately, frequency response is not a simple thing: It varies as one moves from side to side or up and down relative to the speaker. The pattern of this variation (a speaker's polar response or directivity) depends on many things, including cabinet size and shape, the number of drivers and their placement on the cabinet baffle, the sizes and shapes of the drivers, and the crossover frequencies and slopes. Speakers differ considerably in all these respects and therefore in their directivity, as well-something an equalizer can do nothing to change. Added to that limitation is the fact that only the more elaborate graphic equalizers are split into bands narrower than one octave, which means that they cannot be used to eliminate (or mimic) response peaks or dips that are not fairly broad and smooth. Equalizers often can make two speakers sound similar, but seldom identical. In most cases, the simpler, more satisfactory, and perhaps less expensive alternative is to trade in your old speakers for a pair whose sound more nearly matches your tastes. When using my Nakamichi 480 cassette deck to tape records (played with an Ortofon Concord 30 cartridge fitted to the tonearm of a Yamaha YP-D4 turntable), I get infrasonic surges, aggravated by record warps, that read as high as -5 dB on my recording-level meters. The resulting recordings sound like they have a severe case of wow and flutter. Recording from the preamp-out jacks of my Mitsubishi DA-R20 receiver with its low filter engaged seems to solve the problem but makes monitoring inconvenient, because adjusting the volume control affects the recording level. What causes this problem, and how can I get rid of it? -Scott A. Ornat, Plymouth, Minn. A. Your system's arm/cartridge resonance is occurring at a frequency down in the range where warps are concentrated. You can attack this problem at its source by using a cartridge with lower compliance to raise the resonance frequency into the "safe" range between 8 and 12 Hz. Tonearm damping also can help, if you like to tinker and don't mind modifying the Yamaha. Much simpler is the indirect cure: inserting a sharp high-pass filter (such as Ace Audio's Model 4000) into the line between your receiver's tape outputs and the inputs to your tape deck. This will allow you to use the receiver's tape monitor loop for its intended function. --- We regret that, due to the volume of reader mail we get, we cannot give individual answers to all questions. ------------- (High Fidelity, USA print magazine) |
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