Tape Guide (Dec. 1977)

CrO2 Pros and Cons

In the six years that chromium dioxide tape has been on the market, there has been a discussion of its pros and cons compared with ferric oxide tapes.

Physical as well as magnetic performance have been the subject of debate, particularly the question of abrasiveness.

Recently some new materials, again pro and con, have appeared on the subject. The interested reader can obtain them free of charge by writing to the companies indicated below. While the charge that chrome tape is more abrasive appears to have died down, discussion of other aspects of performance continues. The materials are:

1. Backgrounder on Headwear, a paper published by E.I. du Pont de Nemours & Co., Photo Products Department, Magnetic Products Division, Wilmington Delaware 19898.

Primarily this refutes the claim that chrome tape is more abrasive than ferric oxide tape.

2. The Advent Chrome Paper, published by Advent Corporation, 195 Albany St., Cambridge, Mass 02139.

This too defends chrome tape against the charge of abrasiveness, and goes on to other aspects of performance such as drop-outs, uniformity, signal to-noise ratio, price relative to performance, print-through, modulation noise, etc.

3. Nakamichi Technical Bulletin 5, published by Nakamichi Research Inc., 220 Westbury Ave., Carle Place, N.Y.

11514. This deals with past or present claimed failings of chrome tape with respect to abrasiveness, distortion, consistency of performance, head room, etc.

Poor Erasure

Q: I have a Lafayette RK520 stereo cassette deck which erases poorly. I have to run the tape through the erase five or six times before the erasure is complete. This problem did not occur when I first had the machine. What can I do to troubleshoot the problem?

-Tim Mamassia, Baltimore, Md.

A: The trouble might lie in either a defective erase head or in the absence of sufficient oscillator current to power the head. If your recordings are normal-about the same frequency response, recorded level, and distortion problems as before the erase problems arose-it seems unlikely that the oscillator circuit is defective because this circuit supplies the record head as well as the erase head. Check the components (resistors and/or capacitors) leading from the oscillator to the erase head and make sure that they are of proper value. Check the oscillator operating voltages specified in the ser vice manual. If all this checking fails to turn up any suspects, then turn your attention to the erase head and the best check here is by substitution of a new head.

High-Frequency Dropouts

Q: My problem is dropout during playback of the tape on either of two channels (not both at the same time) for about a half second or so, which is especially noticeable on the high frequency portion of recorded material. I am using a Teac 1500U tape deck, Dyna PAT-4 preamp, Dyna 120 power amplifier, an AR turntable, and a Shure V15 phono cartridge. I had the deck checked by Teac, and they claimed that it was the fault of the tape, that is, wearing of the oxide (I use BASF low-noise tape). The dropout occurs at the same point on the tape during successive replays, so I would tend to agree with them. Is it possible that either the preamp or the pickup could be causing the dropout?

-R. Sadowsky, Brooklyn, N.Y.

A: I doubt very much that the pre-amp or cartridge could be the source of your problem. However, there is a slight possibility that on a high signal level the preamp might block causing a brief absence of sound. You can easily check this if you bypass the preamp and feed the tape signal directly into your power amplifier. If the problem remains, this clearly exonerates your preamplifier.

It seems the difficulty probably does lie in the tape you are using or possibly in the electronics of your tape ma chine. It could be that a high signal level on the tape causes blocking in the deck's playback amplifier. Try playing your tape on another machine and if the dropout remains, then it must be the tape.

Tape Speed Synch

Q: Some tapes I recorded abroad at 3 3/4 ips on an Akai M-9, using a power supply of 220 V at 50 Hz, play back slightly fast on my Akai 250-13, using a power supply of 120 V at 60 Hz. Even when I switch the power supply to 50 Hz the playback is still fast. However, the recordings made on my 250-D play back normally, so this machine seems okay. How can I slow down the play back speed?

-Reuben Wilson Jr., Poplar, Mont.

A: Your 250-D tape machine may be fast so that tapes recorded at the correct speed on another machine come out fast on yours. The fact that recordings made on your 250-D machine play back satisfactorily is not proof that the machine speed is accurate. All that is happening is that the speed error in recording is matched by the same error in playback. On the other hand the M-9 tape machine may have been slow while the 250-D is accurate. To tell which machine is at fault, play a commercial prerecorded tape on the 250 D, and if it sounds right, then the 250-D is exonerated.

One thing you can do to make the machine at near the proper speed is to hook the voltage tap on the power sup ply to the next higher voltage above 120 V. If the machine is hooked to the 150 V position but connected to a 120 V supply, then it will tend to run slow.

Direct Dubbing

Q: When dubbing, is it better to go direct from one tape deck to another, or should one go through the inputs and outputs of a receiver?

-Leonard Weiner, Chicago, Ill.

A: The fewer electronic stages a signal goes through the better as this minimizes the chances of additional noise and distortion, along with altered frequency response. Hence it is better to dub directly from one tape deck to another.

Tape Set Q: Assuming that one has only played partly through a reel of tape and will not be able to complete the reel until a day or so later, is it better to re wind the tape or can it be left in the partly played position?- Leonard Weiner, Chicago, Ill.

A: Leaving your tape in a partly played position for a day or so is hardly apt to cause a problem.

Stereo Jack Recording

Q: Can recording be done through the stereophone jack of a receiver if one wants to introduce tone or other adjustments?

-Leonard Weiner, Chicago, Ill.

A: I think that, ordinarily, you could record from your receiver's stereo-phone jack into a tape deck. Depending on the output impedance of this jack, you might have to be careful about the length of cable to the tape deck in order to avoid treble loss. However, I doubt that you are likely to run into this problem.

Tape Dubbing

Q: If I wanted to make a tape of a musical selection which would yield better results, dubbing from a pre recorded tape or copying a phono disc?

- Leonard Weiner, Chicago, Ill.

A: Generally it is preferable to copy from a record rather than a tape since the disc usually has a superior signal-to-noise ratio. Each tape dubbing adds about three dB of noise, and a pre recorded tape has gone through several stages of dubbing. However, this is better than it used to be owing to the use of the Dolby noise reduction system in making prerecorded tapes.

Tape Pop

Q. When my TEAC tape deck is put into the record mode, an audible pop is recorded on the tape. Is there any way I can eliminate this?

-Richard Renfrow, Lakewood, Col.

A. A capacitor of about 0.1 µF mounted across the switch that puts your machine in the record mode may help. Results may be better if you put a 100-Ohm resistor in series with the capacitor, and place this series combination across the switch. It would be best to consult TEAC if this effort fails.

(Audio magazine, Dec. 1977; Herman Burstein)

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