The Ampex ATR-102 Professional Tape Recorder.

For more than three decades, the Ampex® ATR-102 two-channel tape recorder has imparted the final cohesive sound to countless recordings with its distinctive low-end punch and ability to provide unique saturation and color. Even circa 2011, where a huge number of recordings are tracked and mixed completely within the digital realm with no analog processing whatsoever, many an audio engineer still want to pass an album’s final mixdown through the ATR-102 to give it that final mastering “glue.”

Read on for a look inside the legacy of the ATR-102 tape machine and more on the sound qualities that make it so desirable for producers and mastering engineers alike. You can also get more information on Universal Audio’s ATR-102 Mastering Tape Recorder Plug-In for UAD-2 here.

ABC used the Ampex Model 200 for the first ever
tape-delayed radio broadcast of the Bing Crosby Show. 

Ampex and Innovation

Established in 1944 by Russian-American electrical engineer Alexander M. Poniatoff, the Ampex Electric and Manufacturing Company derived its iconic moniker from the initials of Poniatoff’s name, plus the “e” and “x” of “excellence.” Operating to this very day in Northern California, the unmissable AMPEX sign can still be seen while driving highway 101 on the San Francisco Bay Peninsula.

The company first gained widespread visibility in 1947 with the release of the Ampex Model 200 tape recorder, which Bing Crosby famously used to broadcast the United States’ first tape-delayed radio show the year after. In 1956, CBS aired the first videotape-delayed broadcast, using Ampex’s Mark IV. A year later, the company won an Emmy® for video recording innovations. Ampex’s technologies continued to play key roles in journaling a diverse array of major events, including Elvis Presley’s first single, the live assassination of Lee Harvey Oswald, and the first videotape images of the Earth from the Moon. These, among many other seminal moments, were all recorded on Ampex inventions.

Unlike many companies known for music technology, Ampex’s business covered a much larger range of markets, perhaps one of the most unusual being national defense. In 1950, the company produced a Model 500 instrumentation recorder for use by the United States Navy. Ampex tape recorders were also used to help monitor and analyze guided missile flights. As a rocket would launch and carry out its flight path, coded data would be broadcast via radio to ground stations positioned along its trajectory. Ampex tape recorders documented these signals which contained data relating to the missile’s speed, fuel consumption, skin temperature, and other factors. By splicing the tapes from different ground stations together, technicians were able to reconstruct and document details from the projectile’s journey.

With thousands of patents to its name, the company has also won numerous awards since that first Emmy in 1957. Ampex received its 12th Emmy nod in 2005 for innovations in slow-motion color recording and playback. In 2008, the company was given a Technical GRAMMY® award, recognizing its contributions to the world of recording technology.

Its ease of use, reliability, and cohesive sound made the
Ampex ATR-102 a staple in the modern recording studio.

Enter the ATR-102

In 1976, the ATR-102 Professional Tape Recorder was introduced at the Audio Engineering Society convention, and emerged as the most ubiquitous model in the ATR-100 line. Other models included the ATR-116 and ATR-124 tape recorders –16- and 24-track models that were more expensive and difficult to maintain. Today, these two multi-track ATRs are coveted collectors items.

The ATR-102 itself was discontinued in 1982, but it quickly became a widespread favorite amongst recording and broadcasting professionals. To date, it continues to be held in high esteem by many recording and mastering engineers as the top choice tape machine for final mixdown.

It's All About the Sound

The secret behind the ATR-102’s original success was its transparent sound and rock-solid reliability. “The 102 has a very flat frequency response, tight tolerance, and sounds fantastic,” says mastering engineer Matthew Gray. “This makes it ideal for accurate transfers. It’s also a very robust, reliable machine with the fastest winding speed I’ve seen on any tape machine.”

The sonic accuracy that the ATR-102 provides as compared to other tape machines made it a staple in many 20th century recording studios. However, compared to the colorless sound of digital audio, the legendary Ampex machine is now used more for its unique analog tape warmth characteristics. Like many, Gray now uses the ATR-102 for “lay-back mastering, in order to smooth out some harsh digital recordings without losing too much detail.”

The characteristically unmistakable sound of the ATR-102 has a low noise floor, wide and deep soundstage, fat low end, and an excited high end that extends beautifully without getting shrill or harsh. Various genres can benefit from this tape “warmth,” including rock, blues, folk, indie, metal, and even hip hop recordings. Not all recordings benefit, however ­–– mixes that are already full in the low frequencies, or are heavily compressed, will have the low end exaggerated to the point of muddiness.

The variety of available tape speeds on the ATR-102 gives engineers the flexibility to experiment with varying ranges of fidelity, from near-pristine audio quality to a more classic, colored, analog-tape sound. At a tape speed of 30 IPS (inches per second), more tape is being used, thus more audio signal is being captured than at, for example, 15 IPS. The higher speed makes for a higher signal-to-noise ratio and a more transparent sound. At slower speeds, such as 15, 7.5, or 3.75 IPS, the warm analog character begins to emerge. The ability to switch easily between differing degrees of these characteristics is a large part of the ATR-102’s success.

The transport controls of the ATR-102.

The Stable Mechanics of the ATR-102

The ATR-102’s sound may have made it the king of the mixdown decks, but the stability of its design is what kept it there. Ampex’s designers went to great lengths to ensure that the transport of the ATR-102 was smooth at varying tape speeds to create a consistent sound and predictable response.

“Ampex did a very good job of keeping electronic noise out of it,” says mastering engineer and longtime ATR-102 user Michael Romanowski. “You don’t get motor noise seeping into the heads and added to playback or recording. Other machines sometimes suffer from that. Also, because of its overall clarity, you’re able to hear a real difference when you use different tape speeds.”

How did they do this? For starters, the designers of the ATR-102 did not use the standard pinch rollers to guide the tape. These often-rubberized wheels typically pressed the moving tape against the recorders magnetic erase, write, and read heads. Since the ATR-102 was specifically created to maintain constant tension on the tape, regardless of the size of the tape reel being used or the position of the tape in the reel, pinch rollers went out the window.

In addition, the ATR-102 was built with an unusually large capstan drive wheel, roughly 2 ⅜” in diameter, with one revolution being equal to 7 ½” of tape. Ampex designed the size of the capstan to specifically fit intervals of time, with a speed of 30" of tape per second equaling four capstan revolutions per second.

In addition to its timing precision, another benefit of a larger capstan is the machine’s resistance to “run-out” — and the resulting tape flutter — which occurs when a rotating shaft gets bent and doesn’t revolve consistently. “The [capstan] shaft simply can’t be made or supported in its bearing perfectly,” said one Ampex engineer. “That run-out translates directly to flutter . . . The larger you make the capstan radius, maintaining the same number for the run-out, say one one-thousandth of an inch, the more you proportionately reduce your flutter.”

The bi-directional servo motors that power the ATR-102’s transport are rated at a beefy ¼ horsepower. This is significantly more juice than is needed just to move tape, but the added power aids the machine’s stability. Furthermore, given the servo motors’ ability to sense and react to changes in tension, the ATR-102 does an admirable job of keeping tape tension constant throughout a recording, mastering, or playback session.

With easily accessible components and
calibration settings, the ATR-102 is easy to customize.

Customizability is Key

The robust backbone and simplicity of design makes the ATR-102 open to easy customization by engineers. Adjusting the machine for different tape widths is relatively straightforward — just change the head stack and two guides, one on the left and one on the right. On other tape machines, adjusting for different tape widths can be a more arduous task, with more rollers, guides, and trickier head stacks to navigate.

Inside the ATR-102, the I/O module and alignment electronics are easily accessible, adding to ease of replacement and customization. Various updates and “hot rods” are common.

“Our machine was sourced from the University of Wisconsin, from where it was shipped directly to ATR Services for a complete internal rebuild with the highest grade components,” explains mastering engineer Matthew Gray. “This rebuild also included an exchange of the stock electronics for Aria Class A Reference Series electronics and flux magnetics mastering grade half-inch heads which gives it maximum transparency and detail.”

Regardless of whether you're a reggae aficionado, classical buff, or hard rock devotee, chances are you've heard the unmistakeable analog richness of the ATR-102 on countless recordings over the last three decades. Thanks to its unique combination of sonic integrity, mechanical robustness, adjustability, and overall excellence in design and construction, the tape recorder has locked in a revered place in audio history – and helped define the identity of contemporary recorded sound in the process.

Special thanks to engineers Matthew Gray (www.matthewgraymastering.com) andMichael Romanowski (www.michaelromanowski.com), and UA Product Manager Will Shanks for their help with this article.

For more on the Ampex legacy, visit the Ampex website.

For more information on the Ampex ATR-102 and analog tape, check out Matthew Gray’s blog or UA’s Studio Basics article.