Turntable Conversion
On occasion I play 78 rpm records on my turntable, usually for the purpose of taping and preserving them.
Unfortunately very few of the present high quality manual turntables have provisions for playing 78 rpm discs.
Shortly after purchasing my Philips turntable I discovered a simple modification which allowed me to play 78s with ease. By moving the drive belt from the inner (Photo 1) to the outer step of the motor pulley (Photo 2), then depressing the 33 button, the platter will rotate at 78 rpm. Minor corrections in the speed can be made with the unit's adjustment screw. I have successfully used this arrangement for the past two years.
-R.F. Kilcoyne, Mequon, Wis.
You were fortunate to have a "step" on the motor pulley that was usable in making your conversion. Unless the motor pulley has just the right diameter on some normally unused portion, this procedure would not have worked. Some motor pulleys may be readily removed. Where this is possible you have the means to machine additional pulleys which can be used for 78 and 16 2/3 rpm.
Speaker Power
Q. Would a speaker system need a low minimum power requirement and a high maximum power-handling capability to reproduce wide dynamic range material?
-James W. Jones, Richmond, Va.
A. The maximum power handling capability of any loudspeaker is that power beyond which the speaker would be either overloaded or physically damaged in some way. The minimum power requirement is simply that power which is required to fill an average listening room with sound that most listeners consider to be sufficiently loud. The difference between the minimum and maximum power output, therefore, represents a power reserve for that loudspeaker, which can also account for momentary transient peaks. Assuming that the minimum power produced by your loudspeaker system is satisfactory in your listening room, then the speaker under discussion should be capable of reproducing a wide dynamic range.
Twin Antennas
Q. In my remote area there are only two sources of FM signals and I want to avoid using antenna rotators. Can two antennas be mounted on one tower provided that two separate lead-ins are used? Will a switch be needed between the lead-ins or can they both be connected to the input of my equipment?
-Hardy Morgan, Hico, Tex.
A. Because there are two separate sources of programming, you can use two directional antennas as you described. You must, however, keep them separated by a distance of at least six feet so they will not interact, and use two separate lead-in cables. It is possible to connect both lead cables to the input of your equipment. However, this gives rise to some multipath problems, as well as producing some signal loss. Therefore, it is best to arrange some kind of switching between the two lead-in cables.
If the lead-in cable is in the form of coaxial cable, there are special coaxial switches available for this application.
If you are using a twin-lead, then a simple knife switch, DPDT, will work nicely.
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(Source: Audio magazine, Dec. 1978; Joseph Giovanelli)
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