|Home | Audio Magazine | Stereo Review magazine | Good Sound | Troubleshooting|
Last February, I attended the Detroit High Fidelity Show, and at one of the inevitable pre-Show cocktail parties I met Michael Noakes, the new director for Revox operations in the United Slates. We had a very pleasant chat, and quite naturally the emphasis was on tape recorders. I remarked that in 1976 the Revox tape machines had been on the market for 25 years, and this anniversary should not pass unnoticed. I said that some sort of special article might be appropriate to the occasion. Mr. Noakes suggested that if I was interested in how Revox tape recorders were manufactured, he would arrange a visit to the Revox plants in Switzerland and Germany.
To use that well-worn caché, I accepted with alacrity!
Thus early in July we were at Zurich airport, where we were greeted by Revox public relations man, Joe Dorner. Joe is a good-natured Viennese who with typical courtesy presented my wife Ruth with a lovely bouquet of roses. Joe was our very knowledgeable host and guide throughout our visit to Revox. After a memorable dinner at the Baur au Lac, it was time to plan our itinerary, since we would be visiting a number of factories in Germany, as well as in Switzerland.
At this point, some notes on the background of the Revox company would be pertinent. Revox is actually a companion company of Studer-Revox, founded in 1948 by Willi Studer.
The first products of the company were special high-voltage oscilloscopes designed by Mr. Studer. What happened in 1949 I find particularly fascinating...for Willi Studer got into the manufacture of tape recorders virtually by happenstance. Of all things, an importer brought some
American-made consumer-type tape recorders into Switzerland. Because of the voltage and line frequency differences between the two countries, the units could not be used. Somehow the importer contacted Mr. Studer, who checked over the machines and made new drive-pucks and capstan shafts so they would function properly. These tape machines inspired Mr. Studer to design an improved and better version of them, and when the importer placed an order for 500 of the Studer "Dynavox" machines, Mr. Studer was truly launched in the manufacture of tape recorders. To say that they had problems in producing these Dynavox machines is an understatement. They had to make their own recording heads ...cobble up most of the test equipment since such items were not "off the-shelf" equipment at that time.
Most amusing is that wow and flutter performance was checked by utilizing the "stability" of the telephone dial tone! The Dynavox production continued through 1950. In 1951 it was decided that all consumer tape recorders would henceforth be marketed under the name Revox. Studer decided to go into the manufacture of professional tape recorders, and later that year the Studer 27 was introduced. 1954 saw the debut of the Revox A36 recorder with a three-motor transport featuring direct tape drive. In 1955, the professional line of recorders was expanded with the Studer A37 and B37. In 1956, the Revox B36 became the first consumer recorder with three-head "off the tape" monitoring. By 1958, the Studer staff numbered 120 and a new factory was built in Regensdorf, a suburb of Zurich. 1960 marked the production of the first stereo Revox, the D36. The professional Studer C37 recorder was introduced and among its features was a real-time tape timer. (In 1965, when I was with RCA, I made the first several hundred classical music masters for 8-track cartridges on the C37, and the timer was invaluable in the sequencing operation.)
Black Forest Assembly
Through 1964, Studer-Revox business continued to expand, necessitating the opening of production facilities in Loffingen, Germany, the first of four similar installations throughout the Black Forest area in the intervening years up to 1974. The StuderRevox facilities in Regensdorf are expanded, and it becomes the company headquarters. In 1967, the last of 80 thousand Revox 36 series recorders comes off the line and Revox A77 stereo recorder was introduced. The modular construction of this machine and its new servo-controlled a.c. capstan tape drive motor are the beginning of a new era.
In 1968, Revox produced an FM tuner and amplifier, and designed special language laboratory equipment based on the A77. The Studer professional line expands to include mixing consoles. 1970 is a banner year for Studer with the production of the Studer A80 recorders, which are available up to 16 and 24 tracks. Through 1973 Studer-Revox keeps up the introduction of new recorders and associated equipment. Near the end of the year, the Revox A700, an advanced recorder with crystal-controlled capstan servo, is introduced. Studer later makes a professional version of this recorder, the A67. Now in 1976, in their 28th year, Studer-Revox enjoys a worldwide reputation for the manufacture of high precision tape recorders.
The day after our arrival at Zurich, Joe Doner picked us up early in the morning, as we had a long drive through the Black Forest to the Studer-Revox plants. We were to take a circular route, stopping at one plant on the outgoing leg, and two more plants on the return leg. The Black Forest is beautiful country, quite isolated from the hordes of tourists, and in some areas we didn't see another car in a half-hour of driving. Our first stop was at the little village of Ewattingen, where a smallish Revox plant is devoted entirely to the production of three models of loudspeakers. Yes, Revox makes speakers, even though none of them are presently exported to the U.S. All three speakers are the air suspension types...the smallest is a two-way system, said to handle 40 watts program material...the others are three-way systems, of 60 and 80 watts rating. Although small, the factory is well equipped with a good sized anechoic chamber, and B&K graphic level recorders, etc. The baskets, cones and surrounds, spiders, and magnet structures are from vendors which are assembled in the plant, along with the voice coil and crossover networks which are wound on the premises. In their demonstration room, I kept everyone happy by choosing their top speaker over competing units in a blind A/B test.
Our next stop should have been Loffingen, but we went on to Bonndorf, and then back to Loffingen. I'll explain. The construction philosophy on all Studer and Revox tape recorders is the modular concept. Various electronic modules, along with motors and mechanical sub-assemblies are made in the various plants in Germany and Switzerland. All of these elements are pre-tested, then shipped to the plants which assemble a specific tape recorder, such as a Revox A77 or a Studer A80, etc. There are, of course, basic starting points for many of these components, which is why we went on to Bonndorf. In a 56,000 sq. ft. plant, capstan and spooling motors, and printed circuit boards are manufactured from scratch. All Studer-Revox recorders use motors using the outside rotor principle. These rotors are fairly heavy chunks of metal.
In the initial operation, metal discs about four in. in diameter and a half inch thick are placed in a special hydraulic deep-drawing press. This monster machine then gives a mighty 100-ton press, and the disc is then formed into a rotor. Then hydraulically controlled automatic lathes rough turn the rotors, which are subsequently finely finished on yet another lathe. The stators of the motors are assembled with the plates and the complex electrical windings. Then the windings are impregnated with epoxy resin in an automatic dripping machine, and the resin is cured by electrically heating the windings. Finally, the stator is precision ground. In another section of the plant capstan shafts undergo precision honing. A proprietary electronic test apparatus measures the run-out accuracy of the capstan shafts. Maximum permissible eccentricity for a Revox A77 is one micrometer and the Studer A80 is half of that! When the capstan and spooling motors are fully assembled and statically and dynamically balanced, they are placed in a special rack and "run in" for many hours being checked for torque, bearing noise, hum, etc.
In still another area in the Bonndorf plant, printed circuit boards are fabricated, starting with the drawing, making the photo negatives, silk screen printing. Then into huge automatic galvanizing and etching tanks. Then the large multiple-print panels are automatically positioned with an accuracy of one-half thousandth of an inch, and then drilled and punched and into individual PC boards. Finally, the electronic components are added to the board and then dip-soldered.
After quenching our thirst with some of the local "Furstenburgerbrau", it was on to Lotfingen. This sizable plant is where specific electronic modules, motors and sub-assemblies flow, to wind up on the production lines assembling Revox A77 tape recorders and its several variants, and the Revox A700 recorder. I should mention that all Studer-Revox recorders use a die-cast chassis, which is supplied from a vendor foundry, then finished at which time all holes are precision drilled in one operation by numerically-controlled drill presses. Incidentally, all through the Studer-Revox plants, you will find these numerically controlled drills, lathes, grinders, punch presses, etc. These units are given a punched-tape programmed from blueprints with the aid of a computer. With an integral computer converting coded signals into control impulses, these machines will perform their various work functions with unflagging precision.
In one small room at the Regensdorf plant are three special machines, with tool-changer units that can accept 15 different tools, position them along three axes, and change tools within three seconds. The aggregate investment here is over a million dollars. In the Loffingen plant it is quite a sight to see dozens of Revox A77 recorders in the process of assembly. The girls on line test check every module in the machines with special test equipment developed by Studer for this purpose...there is no spot checking. A written log of all performance specifications is kept on file for each recorder. After all modules test OK, the entire recorder is given an alignment and final check.
It should be noted that it is a policy of Studer-Revox to make as many of their own parts as possible. In addition to those items I have already mentioned, they don't make transistors, resistors, resistors, capacitors, etc. A few small plastic parts are made by outside vendors, but almost everything else is under Studer-Revox control...and that is the way they want it! Another vitally important function of the Loffingen plant is the manufacture of the erase, record and playback heads for Revox recorders. Here again, they start from scratch...making the laminations for the C-shaped core sections, using proprietary machines for winding the cores, another special machine to precision work the head shell halves. Each assembled half section of the head shell must be lapped to a surface roughness of less than one-tenth micrometer. When the two half shells are assembled to make a complete head, a super thin "foil" of non-magnetic material is placed between the pole pieces to ensure exact gap dimensions.
Regensdorf Rendezvous Our heads swimming from all we had seen, we left the Black Forest and returned to Regensdorf. Next morning we went to the main Studer-Revox plant in Regensdorf. This is the headquarters of the entire organization, and contains administrative offices, sales offices, etc. in addition to the manufacturing facilities.
Many ultra-precise machining operations take place here, and while modules and parts are made for Revox, this is where the loving care is lavished on the big professional Studer recorders ranging from quarter-inch two-channel units to the two inch jobs handling 16 and 24 channels. The incredibly difficult-to-make multitrack heads are made in this plant, even to the vacuum deposition of silicon monoxide on the pole pieces to ensure precise gap dimension. Here is where you see some poor technician, doing the absolutely arduous job of final electronic checkout and alignment of 24 channels! Better him than me. A highlight of this visit to Regensdorf was a meeting with Willi Studer himself, and his son-in-law, Michel Rey, who is director of the Revox operation. Speaking through an interpreter, we discussed various aspects of magnetic recording. Mr. Studer very graciously took me through the research and development section and complex of laboratories. I saw some future developments there that would boggle your mind, but I had been asked to maintain secrecy for the present...so no can tell! I really enjoyed my visit to Studer-Revox. It was a fascinating and illuminating experience. I met a lot of nice people and their dedication to high standards of quality was most refreshing.
(Source: Audio magazine; Bert Whyte)
= = = =
Prev. | Next