The Revox B215 is a cassette deck manufactured by Studer from 1985 until around 1990. A professional version with different control layout and audio path electronics was manufactured concurrently as the Studer A721. A later improved version was marketed as the Revox B215S. Because it was expensive compared to other consumer models and had exceptionally good mechanical performance and durability, the B215 was used primarily by professional customers—radio stations, recording studios and real-time cassette duplicators.
The B215 used a proven, reliable four-motor tape transport derived from the earlier B710 model. The B215 differed from the B710 and competing decks of the period in having an unusual, computer-like control panel and elaborate automation performed by three Philips microcontrollers. The deck was equipped with automatic tape calibration, microcontroller-assisted setting of recording levels, and non-volatile memory.
Objective, independently measured and verified specifications of the Revox matched or surpassed those of the best competing decks; comparative tests placed the B215 on the same level as the Nakamichi Dragon and above the flagship models by ASC, Harman Kardon, Tandberg or TEAC. Reviewers praised the Revox for its exemplary mechanical quality and the expected durability of its tape transport, but criticized it for lower-than-expected dynamic range and shortcomings in usability.
Development and production
Studer AG, a privately owned Swiss manufacturer of professional audio equipment, began development of high fidelity cassette recorders in late 1970s. Willi Studer was reluctant to diversify into the highly competitive cassette deck market; for most of the decade, the company's experience in cassette technology was limited to reliable but low-fidelity classroom equipment. Author is the owner/operator of recording and tape duplication studios, member of The Legends. However, the decline of reel-to-reel recorder sales, the commercial success of Nakamichi and "designer models" by Bang & Olufsen, coupled with pressure from within the company, persuaded Studer to invest in the cassette format. Marino Ludwig, designer of the Revox B77 reel-to-reel recorder, examined the best cassette decks on the market and advised Studer on a course of action. Studer agreed with the proposal and appointed Ludwig chief of the cassette project, on the condition that the reputation of Studer and Revox brands would not be compromised in any way.
In September 1980, Studer AG presented its first cassette deck, the Revox B710; in 1981 it was supplanted by the nearly identical Revox B710 MKII, which added Dolby C noise reduction. In 1982, the company introduced a professional version, the Studer A710, equipped with balanced inputs and outputs. In the United States, the B710 MKII was priced at $1995, more than the rival Nakamichi ZX7 ($1250) but below the flagship Nakamichi 1000ZXL ($3800 for the base version, or $6000 for the "limited" edition.) The three-head B710 was designed and built to the standards of professional reel-to-reel decks; even its faceplate and controls were borrowed from the B77 recorder. The B710 stood apart from the competition in having a true, four-motor direct-drive tape transport: each of the two capstans and the two reels were driven by their own electric motor without any intermediate belts, gears or idlers. There were no brake pads, belts, pulleys or cogwheels in the whole transport; even the tape counter was driven by an optoelectronic encoder on the reel motors. Mechanically separate recording and replay heads were each adjustable, however there was no user-accessible azimuth control. The B710 was mechanically sound but lacked functionality; most importantly, the deck lacked user-accessible tape calibration controls. Overall, the design was highly conservative. Marino Ludwig wrote that the development coincided with a flood of new features () introduced by the Japanese, and only a few, like automatic tape type recognition, could be implemented within the deadline. Untested novelties that could compromise the product, like dynamic biasing, were rejected from the start.
In 1984 Ludwig and Meinrad Liebert designed a successor to B710, the B215. The first pre-production batch was assembled at the end of 1984; the first production decks were shipped to dealers in the beginning of 1985. A professional derivative, the Studer A721, was very similar to the B215 but was equipped with balanced inputs and outputs, and traditional rotary volume controls in place of up-down buttons. The press placed the B215 on a par with the best competing decks, rating its sound quality as high, or almost as high as that of the new reference deck—the Nakamichi Dragon. In the United States, the B215 was initially priced at "only" $1390, lower than either the B710, or the Dragon. "Affordable" pricing and rugged transport made the B215 the deck of choice for real-time cassette duplicators; for example, by April 1986 Vermont-based Revolution Audio operated a fleet of 200 B215s, 24 hours a day, five days a week, and planned to purchase another 200. German Audio magazine used a stack of ten B215's to duplicate its own test cassettes.
Ludwig wrote that the price decrease reflected cost savings achieved through the use of larger printed circuit boards and automated assembly. The introduction of the B215 also coincided with a record low Swiss franc exchange rate with the U.S. dollar, which hit an all-time low in February and March 1985. Subsequently, the Swiss currency exchange rate increased consistently, and so did Revox prices in North America. In 1989, the B215 was priced at $2400, and in 1991, $2600. The improved, cosmetically redesigned B215S, introduced in 1989, was priced at $2800–$2900—more than the Dragon, and three to four times more than contemporary flagship decks by Onkyo, Pioneer or Sony.
By this time Willy Studer had retired; in 1990 he sold the company and in 1994 it became a subsidiary of Harman International. New Revox-branded cassette decks sold under Harman management, the consumer H11 and the professional C115, were in fact rebadged Philips FC-60 / Marantz SD-60 models, and had nothing in common with the Revoxes of the past. Classic flagship decks of the 1980s like the B215, the Dragon or the Tandberg 3014 were discontinued without replacement. Further improvements in cassette sound, if possible at all, required substantial investment in research, but corporate resources were already committed to digital.
Design and operation Appearance and ergonomics
The B215, like all B-series Revoxes, is larger than the typical hi-fi component of the period. The enclosure measures and is a standard Studer pressed steel box with two internal stiffener rails that carry the tape transport. The front panel design follows the B200-series styling, introduced in 1984 with the release of the B225 CD player. Tape transport and recording mode controls, placed on the upper aluminum strip, are visually set aside from secondary buttons. Loading the cassette into an open transport is performed in two moves: the upper edge of a cassette is inserted first, then the bottom of the cassette is pressed until it locks in place. This presents no problem in everyday use. Open tape transport is less prone to azimuth skew than typical closed-lid transports, and simplifies routine cleaning and demagnetization.
Recording levels, recording balance and headphone volume are set electronically, with pairs of up/down buttons. There are no microphone inputs; designers deemed those unnecessary for a consumer product. The panel marking, according to Audio (USA) magazine reviewers, is exemplary: black letters on brushed aluminum and white letters on dark-grey plastic are large enough and easily readable at any angle of view. The main backlit liquid-crystal display, on the contrary, is too small, too dim and too hard to read. Another usability failure is the absence of front-panel control lights, even the critical 'Record On' red light is missing (it was later added to the Studer A721, but not the B215). These quirks make it difficult to use the Revox in a darkened room. Reviewers also noted the overall inconvenience of using digital control buttons instead of rotary potentiometers (the latter, again, returned on the Studer A721 but not the Revox decks).
Tape transport
Typical double-capstan tape transport of the 1980s employed direct drive only for the leading (pulling) capstan; the trailing (braking) capstan would be belt-driven at a slightly slower speed to provide tape tensioning inside the closed loop, ensuring tight contact between all three heads and the tape (the cassette's pressure pad can only accommodate one head), and mechanically decoupling the tape from the cassette's shell. A Revox deck works differently, directly driving capstan with its own motor, equipped with a massive flywheel and a 150-pole speed sensor. The speed of each motor is governed by a phase-locked loop; both loops are synchronized with a common crystal oscillator. According to Studer, each capstan was machined to a precision of 1 μm (0.001 mm or 0.000039 inch), to ensure very low wow and flutter. In 1985, the only other deck with a similar direct-drive arrangement was the five-motor Nakamichi Dragon (the nearest contender, the four-motor Tandberg 3014, used a single capstan motor).
Two other motors of the B215, buried deep inside the mechanism, directly drive the cassette's reels. Motors, capstans and reel spindles are mounted on two diecast chassis plates, tightly bolted together; heads and pinch rollers are mounted on a moving die-cast subchassis. All four motors are braked electromagnetically; there are no mechanical brake pads or friction wheels. Autostop is triggered with an optoisolator which senses the presence of transparent leader tape. Winding a 90-minute tape takes no more than 75 seconds, at constant linear tape speed. If, for any reason, the microcontroller detects abnormally high tape tension, it instantly reduces winding speed. At the end of the reel, tape speed is smoothly decreased to avoid end-of-tape impact. According to Howard Roberson of Audio magazine (USA), operation of a new B215 transport "...was very quiet, even in play mode - perhaps the quietest of any deck ... tested to date... very well constructed, with a definite look of long-term reliability".
The B215 uses sendust-and-ferrite heads made by Canon (the B710 used Sony heads, the Revox reel-to-reel heads were manufactured by Studer in-house). Replay head has narrow magnetic gap, recording head has wide gap, but the exact widths of gaps were not disclosed. Unlike the B710, the B215's recording and replay heads, and an isolation wedge between them, are tightly sandwiched together and may not be adjusted individually. Reviewers of Audio and Modern Electronics noted exemplary low phase difference between left and right channels (interchannel time error, ICTE), which was a sign of very good alignment of recording and replay gaps and vanishingly low relative azimuth error.
Audio path
The B215 signal path was designed, from the ground up, for operation with Dolby C noise reduction. The owner's manual advised that "selecting noise reduction for new records is simple: use [only] Dolby C". The deck uses four Hitachi HA12058 Dolby B/C ICs in "double Dolby" configuration with independent encoding and decoding channels. Tape type is detected automatically, but the user can override and select the tape type manually. This includes an option of recording Type II (but not Type IV) tapes with 120 μs equalization, which may be preferable for recording signals with strong treble content, at the cost of increased noise.