by BERT WHYTE
Remember way back in the early '50's when all the hi-fi shows were involved with binaural and stereo sound, which for the most part was of the ping-pong variety? One of the favorite stunts was to "run a railroad train through the room," between the two speakers. I was with Magnecord in those days, and we were great "train runners." You know what it took to make a stereo recording of a train in those days? You loaded up the trunk of your car with equipment and headed for the railroad tracks. Then we set up generators and converters, the old staggered head PT6 transport plus the stereo electronics, mike stands, cables, mikes. If you were going to be fancy and use U47 Telefunken's, you had to set up their power supplies and then run power lines to them.
Recently in a fit of nostalgia, I made a new stereo train recording. It was at night. There was a foot of snow on the ground. The temperature was 9 degrees. I made the recording on a battery operated stereo tape machine that measured 8 by 10 by 3 inches and weighed 8 pounds. I operated at 15 ips ... nothing chintzy about me! I had the recorder around my neck and my hand held an Electro-Voice RE15 cardioid mike which was connected to the left input of the recorder. My long-suffering wife held another RE15 thirty feet to my right facing the tracks. We hear the train whistling in the distance. I start the recorder and activate the stereo automatic gain control. The train roars down the track, whistle tooting, passes us (giving us a real nice Doppler effect) and the clinkety-clank of wheels on rails fades into the distance. We rewind the tape and listen to the recording via the monophonic monitor speaker. Crazy, man! It's on the tape all right! We rush home to play the tape on our big stereo system. 300 watts RMS per channel. That should do it! We crank up the gain control. The tape is now feeding through the gate of our big 15-ips machine and there is the first whistle and suddenly this monster train is roaring across the living room and the cat is running for it's life!
How good was the recording? Just superb. Terrifying in it's realism. Ultra wide range, top and bottom. Far better than the recordings we made in the old days. Now the cynics and skeptics among you are wondering how we could get such a good recording from a little old battery operated portable recorder.
Well, friends, this little recorder costs $1300 and it is worth every nickel. It is called the Stellavox SP 7 and is one of the most incredible pieces of precision audio equipment I have ever had the pleasure of evaluating. It is made in Switzerland and in feel and appearance reminds one of Leica and Linhof cameras. Incorporated in this tiny recorder are more advanced ideas and facilities than exist in even the most sophisticated full-size professional equipment. Hard to believe? The recorder operates on 12 penlight batteries. The alkaline type will permit 6 to 8 hours of recording. It can also use rechargeable nickel cadmium batteries and external a.c. power which will recharge the nicad batteries. The motor is a servo-control type which drives the capstan directly. A photo-electric sensor delivers a signal related to the speed of a special motor rotor. This signal is treated and amplified to control a servo amplifier, which supplies current to the motor. A tiny motor meter on the front panel of the recorder indicates correct motor speed. The pinch wheel is solenoid operated so the recorder can be remotely controlled. All the electronics for the recorder are epoxy-encapsulated plug-in modules. The recorder operates at 3 3/4 ips, 7 1/5 ips, 15 ips, and 30 ips. Speed change is completely electrical. With a special accessory, tape speed can be varied from 1 to 30 ips.
What is called the Stellavox Head Device is a precision die-cast head block which contains not only the heads but has incorporated in it the provisions for equalization and bias. The head blocks are interchangeable for different formats and speeds. All are biased for Scotch 203 tape.
Thus you can have mono full-track heads, or stereo half-track or practically any combination. The recorder furnishes synchronizing signals to drive movie cameras. The mono full-track assembly has erase, record, and playback heads, and a fourth neo-pilot sync head. The neo-pilot head cannot be fitted to the stereo head assembly because of crosstalk, so alternatively a third track is fitted in the center between the two stereo tracks and furnishes a synchrotone for camera sync. The third synchro track can also be used to activate a slide projector with a special accessory.
Equalization will be correct for a given speed only if the corresponding head block is plugged in. For example 7 1/2-ips speed with 7 1/2 stereo head block in place. All heads in the blocks are pre-aligned and no adjustment is necessary when interchanging head blocks. All head blocks permit off-the-tape monitoring, which can be checked either by mono speaker or headphones.
---------Stelavox tape recorder
On the top plate of the recorder is a two-position switch which controls mike input. One position is for conventional low-impedance dynamic types, the other for transistorized condenser mikes of the type that can be powered through the audio connection lines. This means you can do remote or location recordings with the SP7 with such mikes as the Sennheiser MKH405 powered right from the recorder.
On the front panel of the recorder are the monitoring facilities, consisting of two calibrated VU meters, which read on playback as well as record. Two calibrated volume controls handle the stereo channels for recording. A switch on the right side of the panel controls tape motion and there is a special position labeled "automatic." This starts the tape and activates a stereo automatic gain control, which can be very handy if you are in a situation where you may not have time to set your gain manually. I used this facility when I recorded the train. The left panel of the recorder accepts stereo mike inputs, line in and out, headphone input, camera sync-signal output, and external power supply.
This remarkable unit normally uses 5 inch reels which have screw-down reel holders. There is a smoked Plexiglas top cover which latches securely to the top plate. In this fashion the recorder can be subjected to high "G" forces while in operating condition ( reporter running after Racquel Welch for example) without any tape-speed variation or stalling. With the top cover removed and the addition of extension arms, reels up to the professional 10.5 inches can be accommodated! It seems inconceivable that this small-motored unit would have sufficient torque to handle these large reels ( and I haven't seen them at all ), yet it is so claimed. We had extension arms on the old Magnecords, but they never worked too well, having high wow and flutter. I could go on and on about this Stellavox, like gold-plated battery contacts, and so on, but I think you can believe by now what a fantastically versatile unit the Swiss have built.
What about it's performance? I have made flawless recordings from discs and "off the air." In a few days I am going to record a jazz group in a night club. My good friend Marc Aubort, of Elite Records, one of the top recording engineers in New York owns this particular Stellavox. In his studio I have heard a recording of soprano and chamber orchestra that Marc made with the Stellavox in Boston Symphony Hall. The quality was quite literally astonishing! Utterly clean, without the slightest hint of wow or flutter. No one, including Marc, is suggesting that this tiny recorder can replace all the big professional recorders. But it can do things few other units are capable of duplicating. With this kind of quality so easily portable, all sorts of fascinating ideas come to mind for location and outdoor recording. This Stellavox is so "far out," that at the 30-ips speed and some special plug-in modules, recordings can be made up in the ultrasonic region, and it has been used to record the sound of dolphins and certain insects! The Stellavox SP7 is imported by the Sennheiser Electronic Corp. of New York.
Noise Reduction
In this month's tape column, you will find me lamenting about the excruciating hiss which is such a drawback to the otherwise attractive idea of cassettes. Hiss is of course a problem with open-reel tapes and 8-track cartridges as well. By the time you read this, the Advent Corp. of Mass. will have demonstrated the first Dolby consumer-type noise reduction unit, built by Advent under a license agreement with Dolby Laboratories. This unit is basically similar to the Dolby system built into 2 models of KLH tape recorders. It employs what Dolby terms "B Type" noise reduction, which is a single-band system, as opposed to the 4-band system of the professional A310 unit. The band used covers the hiss frequencies and the device gives 8 dB of reduction at 2 kHz, rising to 10 dB at 5 kHz. With the Advent unit you have the facility of using the Dolby System with any kind of tape-recording format. Reportedly, you can record and playback with the unit. Presumably a playback only unit will be forthcoming and this assumes the existence of "Dolbyized" pre-recorded tapes. There is little doubt that some company will take the plunge in this direction, and when they do, others will surely follow suit.
(Audio magazine, Apr. 1970; Bert Whyte)
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