Teac DX-2A
A small accessory box that Teac sold to unlock the full dynamic range of its flagship open-reel decks. A used X-10R with no DX-2A is only half a machine.
Overview
The DX-2A is not a tape deck. It is the optional dbx noise-reduction unit Teac built for its X-series open-reel machines. Teac's own manual for the X-10R and X-7R says the DX-2A brings "breath-taking dynamic range and signal-to-noise ratio" to the X-10R, and the company was not being modest. The manual calls the dbx system the breakthrough that could let a recording enthusiast capture the full 100 dB dynamic range of live music on tape for the first time. That is a marketing claim and should be read as one. It is still the reason the DX-2A exists and the reason collectors still hunt for one.
Teac integrated the DX-2A cleanly. The X-10R's rear panel carries a dedicated DBX UNIT CONTROL SIGNAL socket. The manual is explicit that if the dbx unit is not in use, special shorting links must be in place as shown in the illustration. So the deck runs either way, but the socket and the links show the X-10R was built with the DX-2A in mind from the start, not retrofitted later. According to the manual, connection is simplified by the specially provided sockets on the rear panel, and full instructions for connecting the DX-2A come with the unit.
In Teac's literature the DX-2A is also an X-10R-only proposition. The manual's specification table lists the DBX Terminal as a feature of the X-10R, with no equivalent entry for the X-7R. The X-7R's column shows the same track system, head system, tape speeds, wow and flutter, frequency response, signal-to-noise ratio, harmonic distortion, stereo channel separation, fast wind time, inputs, and outputs as the X-10R, but the DBX terminal line is blank on the X-7R side. So if you own an X-7R and hope a DX-2A will plug in, the manual suggests otherwise. The DX-2A is an X-10R accessory.
Modern Recording (March 1980, p.74) reviewed the X-10R at a price of $1300, supplied with an empty reel, reel adapters, patch cords, splicing tape, and sensing tape. That $1300 figure is the deck, not the DX-2A — the DX-2A was a separate purchase, and the review's list of supplied accessories does not include it. The same review, by L.F., noted the X-10R's dual-capstan closed-loop transport, electrical braking that proved positive and reliable, two-way cue monitoring, and punch-in recording, and then asked the question that still hangs over the machine: what was its intended market? Features like those suggest a semi-pro unit, the reviewer wrote, and yet the DX-2A's dbx capability points in a different direction — toward the home recordist chasing the dynamic range of a live performance.
The DX-2A is a box that makes a consumer deck behave like something more serious, and Teac sold it as an add-on. The X-10R's manual spends real space on why it matters. It says the dbx system brings greater dynamic range and also a better signal-to-noise ratio. The deck's overall signal-to-noise ratio is rated at 63 dB (3% THD level, weighted) without dbx. The DX-2A is what takes that respectable number toward a quiet recording.
Key Features
The DX-2A's job is dbx noise reduction, and the manual is careful about the trademark. The dbx noise reduction system was made under license from dbx, Incorporated, and the word dbx and the dt symbol are trademarks of dbx, Incorporated. Teac did not invent the system. It licensed it, and the DX-2A is the licensed implementation built to mate with the X-10R's rear-panel socket.
The DBX UNIT CONTROL SIGNAL socket is the handshake between deck and outboard unit. The manual's warning about shorting links is the detail that trips up new owners. Run the X-10R without a DX-2A and the links must be in place, or the deck will not behave. Run it with a DX-2A and the links come out, the unit connects via the specially provided sockets, and the deck's full dynamic range opens up.
Beyond that, the DX-2A is a black box with a specific purpose and a specific host. In the chunks available to this archive, the manual does not describe its controls, dimensions or weight. It gives no price for the unit itself, only the X-10R's $1300 figure from Modern Recording (March 1980, p.74). The manual does make clear that the DX-2A is not a generic dbx box you can hang off any deck. It is the X-10R's dbx unit, wired for the X-10R's socket, and the X-7R's spec sheet leaves its DBX terminal line empty.
Why It Matters
The X-10R's numbers are already strong on their own. The manual rates overall frequency response at 30-28,000 Hz, with ±3 dB from 40 to 20,000 Hz at -10 VU at 7-1/2 ips, and 30-20,000 Hz with ±3 dB from 40 to 16,000 Hz at -20 VU at 3-3/4 ips. Wow and flutter is 0.03% at 7-1/2 ips and 0.04% at 3-3/4 ips, NAB weighted. The transport uses a dual-capstan closed-loop system, which the manual notes was a technique whose expertise and precision had hitherto confined it only to the costliest decks. The capstans ride on Magnefloat bearings, which use opposed magnetic poles to eliminate vertical play with no mechanical contact at all. The X-10R also has electrical braking. It sends reverse polarity to the supply reel motor on the way out of fast wind, and only engages the lighter mechanical brakes once a magnetoresistive motion sensor confirms the tape is slow enough. The practical payoff is that you can hand-turn the reels for threading and cueing with one hand.
All of that is the deck. The DX-2A sits on top of it. The X-10R's overall signal-to-noise ratio is 63 dB at 3% THD, weighted, and the DX-2A is the box that pushes past that ceiling. The manual's claim of capturing the full 100 dB dynamic range of live music on tape is the pitch. Whether a given owner ever needs that much range is a separate question.
Collectibility
The DX-2A is hard to find because it was sold as an option, not bundled. The review of the X-10R in Modern Recording (March 1980, p.74) lists the deck's supplied accessories without mentioning it. A lot of X-10Rs were bought without one, and a lot of DX-2As were separated from their decks over the decades. When buying a used X-10R, check that the DX-2A comes with it. If it does not, check that the shorting links are present.
The shorting links are the practical trap. An X-10R missing its links and its DX-2A will not run correctly. A DX-2A without its connecting instructions is a box with a socket on the back and no obvious way in. According to the manual, the unit was supplied with full instructions, and they matter more than they would for a self-contained piece of gear.
An X-10R on its own is a fine open-reel deck with a 63 dB signal-to-noise ratio and a dual-capstan transport that the manual says was once reserved for the costliest machines. An X-10R with its DX-2A is the machine Teac was actually selling, the one the manual describes as capable of capturing the full dynamic range of live music on tape. The difference between the two is one small box.
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