AUDIOCLINIC (Q and A) (Aug. 1975)

by Joseph Giovanelli

"Stuck" Stylus

Q. After balancing the tonearm, setting the tracking force for 2 grams (required by my cartridge), and setting the anti-skating force for that same 2 grams, and making sure that the cartridge is adjusted properly for overhang, I put on a record. All went well until the arm was about an inch and a quarter into the record, the stylus then gets "stuck." This happens on ALL of my records, new and old. I found that I could move the arm slightly inward, and once again, all goes well for a time. When the arm reaches four and a half inches in, it once again "sticks." I have tried mounting and remounting my cartridge. I've changed the tracking force to 1.5 grams, using both antiskating settings for conical and elliptical. My tonearm still "gets stuck." I know that this is not a problem related to worn or dirty records because it occurs with all of my records.

I hope the problem is that I am doing something wrong and not my turntable. Your advice will surely be of help.

-R. Padilla, New York, N.Y.

A. I suggest that you obtain a force gauge. Use it to check the accuracy of your tracking adjustments. Sometimes the calibrations for tracking force are incorrect, and this can only be determined by the use of an independent tracking force gauge. Like the tracking force adjustments, the antiskating force calibrations could be incorrect, so that you are using too much antiskating force. To obtain a reasonably good setting, consider obtaining a blank disc (one having no grooves at all) from a recording studio. Set the antiskating force so that the arm moves neither inward nor outward. Move it to various points on the surface of the disc. You may have to compromise on this adjustment. In some parts of the disc the arm will tend to pull inward slightly; in other parts, it may pull outward by an equal amount.

Your problem also could be the result of defective bearings. They may have so much friction that the arm is not free to be pulled along by the stylus. In that case, the turntable should be returned to your dealer for repair or replacement.

Paralleling Speakers

Q. My receiver puts out 70 watts at 8 ohms and 90 watts at 4 ohms. There is provision for two sets of speakers on this receiver. Does this mean that my resistance is 4 or 8 ohms? I am using four 8-ohm speakers.

- Mark Smith, East Hanover, N.J.

A. First you should understand that speakers are rated as to impedance, not resistance. It's easy to confuse these two related, but different things. The term impedance takes into account both resistance (which is the same regardless of frequency) and inductance (which changes with frequency).

The switch on the front panel of your amplifier selects Main, Remote, or both Main and Remote (together). It is not intended to select the impedance presented to the amplifier.

When both the Main and Remote speakers are operated at the same time, the speakers are wired in parallel. Thus, in your case, you would have two 8-ohms speakers in parallel on each channel, resulting in an impedance of 4 ohms. Do not add more speakers in parallel. To do so might well result in such low combined impedance (two ohms or less) that your amplifier would be damaged.

More Power From an Amplifier?

Q. I have a Lafayette 8-track recorder. I have found that I can run the FM portion of my receiver through the deck. With the tape switch on, I notice a tremendous increase in bass and I also notice a considerable increase in volume. What I think is happening is that the tape deck is used as an amplifier. Please give me an estimate of the increase in power that I can expect from this arrangement.

-Mark Smith; East Hanover, N.J.

A. Your tape machine, when used to alter the sound from your receiver, is acting as an amplifier, just as you have said. Probably there is a playback correction network in that amplifier, which accounts for the added bass.

Your receiver does not produce more power when the tape deck amplifier drives it. The power amplifier can deliver only so much power. A preamplifier can only boost the input voltage feeding the power amplifier.

When the voltage reaches the point at which the amplifier is delivering its rated power, no additional increase can take place. Increasing the signal input voltage further can only produce distortion and possible damage to the amplifier's output stage.

There are also preamplifiers which are incorrectly called "power boosters." These preamplifiers amplify the output of musical instruments such as electrical guitars. They do not add power. They boost the signal to the point where it can drive the power amplifier to obtain its maximum rated power.

Wiring a Cartridge for Mono

Q. In some phono cartridge installation instructions, the user is directed to join the left and right channel leads, either at the cartridge or at the preamplifier for monophonic service.

Might this practice not upset the cartridge loading characteristics or spoil the response in some other way?

-(Name Withheld), Los Angeles, Cal.

A. Wiring a cartridge for monophonic service in the manner described in the instruction manual will change the recommended optimum load. The actual, audible effect of such a change will ordinarily be of so little consequence that it is ignored. Frequency response and distortion are substantially unchanged. Distortion is probably a bit less because of the cancellation of the vertical component caused by the "pinch effect."

Turntable Cueing Revisited

In the December, 1974 issue of Audio you described one way to cue up turntables. I can suggest another, simpler method which I've used for several years to produce top-quality tapes, using only a reel-to-reel tape deck, two turntables, two Shure pre amps, and a Crown IC-150 preamplifier/control unit. Here's how it works:

1. Plug outputs from arm into Shure stereo preamps.

2. Plug output from preamplifiers into the two tape inputs on the preamplifier.

3. To play each table: turn the IC 150 function selector to Tape 1 or Tape 2.

4. To cue each table: push Tape Monitor 1 or Tape Monitor 2.

As you can appreciate, when the monitor is depressed, there is no effect on the Line outputs feeding any connected tape machines. However, the main outputs feeding the power amps now carry the cue information.

Further, any adjustment in cue volume has no effect on the line outputs. When the monitor function is released, the straight program material is still available.

The separation between the line and monitor functions in the IC-150 is around 75 dB, more than enough for this scheme to work well. This scheme will work with any preamplifier or integrated amplifier having two tape inputs and two tape monitors.

True, with this system, no segue is possible. In such a situation, I use another approach. At my studio, we have a Sony MX-16 mixer. It is set up so that, at the bottom of each slide pot fader, a micro-switch switches the output of the phono preamplifier from the mixer input to a pair of (added) stereo output jacks, which are then connected to a cue amp. Each slide-pot on this mixer has been equipped with its own micro-switch so that all signal sources can be cued.

Multi-source montages are easy to accomplish. This micro-switch idea could be used just as easily with any small, straight-line mixer, such as a Sony MX-12, Telefunken, etc.

By adding a switch to the pots on mixers equipped with rotary pots (Shure, etc.); these mixers can be used for cueing. In other words, when any pot is turned off, it is placed automatically into cue! Works well, too!

-Stephen H. Lampen, San Francisco, CA.

Note. I hope that you find this sort of material interesting and helpful.

Those readers who are kind enough to take the time to write up this sort of information are specialists in their fields, and, as such, are privy to knowledge not normally available to most of us.

So for myself and the rest of my readers, thanks to all of those who have written, and to those who will do so in the future.

I will be especially glad to hear from any one out there who has had success dealing with line transients. I refer to those instances where a refrigerator, fish tank, oil burner, etc., puts a pulse on the power line, which, in turn, finds its way into a music system and produces audible pops or other noise from the loudspeakers.

Some equipment is more sensitive to this than others. While this sort of interference can often be eliminated by placing a constant voltage transformer between the power line and the music system, this is an expensive cure.

(Audio magazine, Aug. 1975, JOSEPH GIOVANELLI)

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