Tape Guide (Jan. 1982)

Slip Sliding Away

Q. After having the record head of my open-reel tape deck replaced, I tried to make recordings with good tape, but could not due to an excessive amount of wow and flutter. I returned the deck to the service center and was told it needed a new pinch roller. After having the pinch roller replaced, the problem remained. The odd thing is that I can record on cheap tape without any problem with wow and flutter. Is there a lubricant of some kind on the better tape that allows it to slip as it passes the capstan and pinch roller?

-James Fellwock; Santee, Calif.

A. Yes, a good tape often contains a fair amount of lubricant (silicone or such), as it should in order to permit passage of the tape past the heads, guides, etc. with a minimum of friction. But, as you suggest, the lubricant may be permitting slippage of the tape with respect to the capstan and pinch roller.

Possibly the audio shop put in a defective pinch roller (with glazed rubber), or it may have improperly adjusted the tension exerted by the roller against the tape and capstan. I think that you are entitled to a free return trip to that shop.

Before doing so, carefully clean the capstan and pinch roller, as well as the heads, guides, and other parts contacted by the tape. Ordinarily, unless your manual recommends another substance, isopropyl alcohol will do a satisfactory job, and it's important to check this. If you still have slippage, take the deck back to the shop. Another alternative would be the use of back-coated tape, which aims to eliminate slippage.

Leftist Leanings

Q. I have noticed that my cassette deck records a stronger signal in the left channel. To balance the left and right channels while recording, I have to cut back the left-channel input. I am using the deck with a new receiver, whose left output meter always shows a stronger signal than the right output meter.

Balancing of the channels helps to solve the amplifier problem. Does this affect the problem with my tape deck?

-Gary Guarneri; Danville, Calif.

A. Tape deck imbalance between the left and right channels may arise from (1) imbalance in the record amplifiers; (2) imbalance in the circuit that feeds the record level meters; (3) imbalance in the bias circuit (at the same time, reduced bias in the right channel will produce over-bright sound there); (4) imbalance in the playback amplifiers; (5) a defective record head; (6) a defective playback head, or (7) imbalance in the preamp or receiver that feeds the tape deck.

From your description, it appears the fault lies in your receiver, which is feeding a stronger signal to the left channel than to the right. Even though you say that you balance your receiver, such balancing apparently occurs at a point after the signal is fed to the tape deck.

Ups and Downs

Q. Some of the new cars have vertically mounted radios instead of the standard horizontal mount. This poses a problem when installing an aftermarket cassette unit because the standard horizontal in-dash unit is said to be manufactured to only play at a maximum 30° oft horizontal without causing unusual wear of the unit. What can the owner of one o1 these new cars do?

-Phil Miltenberger, Wabash, IN, USA.

A. Some tape decks are designed so that they can be operated in virtually any position, while others are limited in this respect. If the unit you want to use has a tuner section with a vertical scale, then you'll be okay. The only other answer I can give you is to consult the manufacturer of the deck you intend to use as to the effect of vertical mounting.

Off the Track

Q. I recently purchased a cassette deck with Dolby calibration and no external bias adjustment. My problem is that when listening to A-B playback between source and tape, there is noticeable lack of highs with Dolby NR on. Without Dolby NR, the source and the tape are almost indistinguishable. The Dolby calibration controls don't help they appear to be just a gimmick. I wonder if I could alleviate my problem by making an internal adjustment of bias.

-Andy Ulloa, Red Bluff, Calif.

A. I recommend against any adjustment of bias inasmuch as you are getting good performance with the present bias and with Dolby NR off.

Your problem seems to lie in the Dolby calibration, or rather mis-calibration, which can result in what is called mis tracking; the effect is to either accentuate or depress the treble frequencies.

The degree of mistracking that occurs can vary with the output level of the tape, and hence the proper Dolby calibration can vary from one type or brand of tape to another.

Your best course is to take your deck and a cassette of your preferred brand to an authorized service shop for proper Dolby calibration. Have the shop record with the deck while you are present so that there is agreement as to the specific problem.

Dolby calibration controls are not a gimmick. It is possible that one of these controls, or the Dolby circuitry, may be defective. If your deck is still under warranty, the service should be free. After the deck is serviced and you come to pick it up, ask for a bench check, which will demonstrate to you in the shop that the deck is working correctly.

Playing Percentages

Q. While I was recording an album with my cassette deck, I left the machine for a minute. When I returned, the meters were bouncing far into the red, +5 dB. I thought my recording was ruined, but when I played it back it sounded good. Why didn't I hear a lot of distortion? How much distortion is audible in tape machines? By the way, my deck is supposed to have less than 1.5% distortion at 0 dB. At the time of the recording I was using a high-quality ferrichrome tape.

-Carl Smith, Mt. Home A.F.B., Idaho

A. I assume that the meters of your deck are a peak-reading type. If distortion is 1.5% (harmonic) at 0 dB, it is probably about 3% at +5 dB. Harmonic distortion reaching about 3% on peaks is generally considered acceptable in tape recording. This may vary somewhat with the nature of the music and with the acuity of the individual. The briefer the peaks, the less likely that distortion will be unacceptable.

Further, tapes vary somewhat, roughly on the order of 3 to 5 dB, as to the amount of signal they can accept before distortion becomes noticeable. It may be that the tape you used can accept substantially more signal than the average tape without going into distortion.

On single steady tones, few persons can detect distortion below approximately 0.5%, although some exceptional individuals, it is claimed, can detect distortion as low as 0.1 %. But on mixed tones program material it appears that distortion can rise as high as 5%, and perhaps even as high as 10%, yet escape notice by most listeners.

First and Format

Q. I'm in a quandary. I want to tape my record collection and FM broadcasts.

For this purpose, would it be to my advantage to buy a cassette or an open reel deck?

- Joseph Banks, Jamaica, N.Y.

A. For live recordings, an open-reel deck operating at 7 1/2 ips should give you distinctly better recordings than a cassette deck operating at 1 7/8 ips. If the open-reel deck is operated at 3 3/4 ips, its margin of superiority may be marginal.

But if your principal purpose is to copy phono discs and FM programs, you may be hard pressed to detect the difference between the performance of an open-reel deck and a cassette deck of good quality.

Another factor is cost. Generally, the better open-reel decks tend to cost from $700 upward. On the other hand, there are very good cassette decks available for under $400. With improvements in cassette decks and cassette tapes, the cassette format gets better and better.

Off-Speed Pitches

Q. I have a problem with one of my three open-reel decks. When I record a tape on it and play the tape on the other decks, the pitch drops. When I record on the other decks and play it on the problem deck, the pitch rises. I lubricated this deck, but without success. I ordered a new idler wheel, but after it was installed the deck still ran fast.

-Alfred Hernandez, Santa Juanita, Bayamon, P.R.

A. First, there is a slight possibility that the other two decks are at fault, that is, they may be running slow.

Assuming that the deck you question is at fault, the trouble could be in the diameter of either the idler wheel or the capstan. The fact that a new idler wheel did not cure the problem does not eliminate this component as the culprit.

Some manufacturers have several slightly differing sizes of idler wheels, and they use the one which brings a given deck closest to nominal speed. I don't know whether this is the case with your deck, but I know the practice exists.

It seems that your best course is to have the deck checked out by an authorized service shop which is capable of checking tape speed as you watch.

(adapted from Audio magazine, Jan. 1982; HERMAN BURSTEIN)

= = = =