Audioclinic (May 1978)

Bedroom System

Q. I have added a bedroom system to my home stereo system. My main system has a spare set of tape outputs and I would like to connect the systems from the tape output of the main system to the AUX inputs of the bedroom system. Can you recommend a method? I believe that a low impedance transformer is required but I'm not quite sure as to the specifications.

Also, can I run a stereo front channel pair of speakers in the same cable (four conduit under one shield) without crosstalk or loss of separation, or is there a cable with two pairs of conductors, each independently shielded?

-Stephen M. Shirley, Sierra Madre, Calif.

A. You can run a shielded cable from the main system to the bedroom system with few complications.

However, we must first be certain that the tape outputs provide signal regardless of the setting of the Normal/Monitor switch. Assuming that this is the case and the impedance is relatively low, about 2 or 3 kilohms, no transformers will be required.

However, if the tape output circuits are high impedance, 10 kilohms and up, it would be best to use a stepdown transformer so the impedance can be reduced to about 2 kilohms or less. In the event that a transformer is used there will be a loss of signal voltage, and you must be sure that there is enough voltage to drive your bedroom system.

However, there are two alternatives to this use of step-down transformers.

You could devise an emitter follower mounted at the main system through which you would feed the bedroom system, or you could use low capacitance cable to offset the high frequency losses which would otherwise be the case.

Because crosstalk is not a problem, you could use multi-conductor cable with no difficulty.

Phono Cartridge Deterioration

Q. I would like to know it phono cartridges can wear out in time?

-Adam Steiner, Livingston, N.J.

A. Moving-coil cartridges are delicate and can develop a number of problems. Even so, when properly constructed, you can expect years of trouble-free performance from such cartridges. Moving-magnet or variable reluctance cartridges are quite rugged because the coils are not moved by the stylus and so need not be lightweight.

Rochelle-salt or ceramic cartridges can fail over a period of time because of a gradual accumulation of moisture which ultimately dissolves the crystal element. Strain gauge cartridges, though rather early to be certain, appear to be very reliable.

Styli of any kind can either wear out or be damaged by misuse.

In general, with the exception of the seldom used rochelle salt, today's cartridges will provide, virtually, a lifetime of service. However, when most cartridges do fail, it is catastrophic rather than a slow deterioration.

Gauge of Speaker Wire

Q. The owner's manual for my speakers recommends 20-gauge wire for runs not exceeding 20 feet, 18-gauge wire for runs up to 30 feet, and 16 gauge for runs up to 50 feet. My speakers are positioned 20 and 50 feet from the receiver, and my dealer told me that 18-gauge wire would be completely satisfactory for both speakers.

Am I using the correct gauge wire, or would you recommend using 18-gauge wire for the shorter run and 16-gauge wire for the longer run? Will my performance be compromised?

-Robert Armen, Bay Village, O.

A. It is never wrong to use wire gauge larger than the minimum required. I would use 16-gauge wire for both speakers; if I was installing the system for you I might even use 14 gauge wire. The 14-gauge wire is more difficult to handle than the lighter gauges, but I have obtained better bass quality by using it. The performance will not be compromised by the difference in wire length as long as the wire gauge is great enough.

(Source: Audio magazine, May1978; Joseph Giovanelli)

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