Audioclinic (Q and A) (Jul. 1973)

by Joseph Giovanelli

Further Notes About the Recording Field

In the March, 1973 Issue of AUDIO MAGAZINE I wrote a piece dealing with careers in the recording field.

Among other items was a list of schools which offer courses to train people for employment in the recording field.

Since then I have received the names of four more schools doing this same work. I am taking this opportunity to print their names and addresses. As was true of the original list of schools, neither AUDIO MAGAZINE nor I are recommending any of these; we are printing this information with the hope that it will aid those seeking to enter this most exciting profession.

Should we hear from other schools, I will again print their addresses.

Fanshawe College P. O. Box 4005 Terminal C, London, Ontario, Canada

Valparaiso Technical Institute Valparaiso, Indiana, 46383

Humphreys College 6650 Inglewood Avenue, Stockton, California, 95207

Brown Institute 3123 E. Lake Street, Minneapolis, Minnesota 55406

Connecting Dolby Units and Equalizers

Q. Here is a problem which no one seems to be able to answer.

My components include a Quad-Sansui 6500 with preamplifier connections, two A.N. 180 Dolby units. Eventually I plan to buy an equalizer.

My question is: Can I connect the Dolby units into my preamplifier and my equalizers into my Dolby units and still obtain proper performance?

Shall I forget the whole thing and hook the Dolbys into the tape monitor? Should I then connect the equalizers into the preamplifier setup?

-William J. Ashworth, Independence, Missouri.

A. If you wish to play back Dolby processed tapes and use equalization, the equalizer must be placed between the output of the Dolby system and the input of the receiver. Whether you use the "tape monitor" or "preamplifier" section of the equipment is not important. You could even have the tape machine in the "tape monitor" section and the equalizer connected to the preamplifier section of the equipment.

This will all depend on what you plan to do with your system. In any case, the only consideration here is that the equalizer should not be placed between the output of the tape machine and the input to the Dolby playback circuitry.

If you want to record a Dolby encoded tape, but with equalization on the program source, the equalizer must be placed between the program source and the recording input of the Dolby system. The equalizer must never be placed between the tape machine and the Dolby, since it is neither related to the playback nor recording functions of the Dolby system. The Dolby "box" and its various connections to the tape machine must not be interrupted by any other piece of equipment.

If you plan to use your equalizer for introducing correction during recording or to introduce it during playback, you will need to make provisions for reconnecting it to accomplish these functions because there is no one place to which you can leave the equalizer connected permanently and still have all functions performed properly.

You may find it necessary to make up some kind of switching system to make all connections rapidly, or perhaps a patch panel will be required in order to provide you with the required flexibility.

RC or LC Filtering

Q. I have an old tube amplifier which has only a 100 ohm resistor to filter the B plus, along with the usual capacitors.

Would a 120 ohm, 8 Henry choke be better than the resistor?

-Name Withheld.

A. If your power amplifier is now reasonably free from 120 Hz hum, there is no reason for switching to an inductor. I do not think that the improvement, though measurable, could be detected aurally. If there is hum, perhaps the choke would be best. Chances are, however, that the hum you now have is a result of aging filter capacitors which are in need of replacement. Do this before adding the choke.

(Audio magazine, Jul. 1973)

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