Alesis ADAT XT-20
Twenty bits on tape, a six-pound die-cast chassis, and a list price of $2,599.
Overview
The number on the XT-20 is twenty. It writes twenty bits to tape, ADAT Type II, with no external converters or multiplexers in the signal path. Alesis pitched the jump from 16-bit to 20-bit as more than a 25 percent increase in resolution. The company's own literature claimed sixteen times the detail of 16-bit compact disc sound, with wider dynamic range and lower quantization noise. That is marketing arithmetic, but the format change was real. Type II is the format that writes 20 bits to tape, and the XT-20 was built around it while staying compatible with ADAT Type I at 16 bits. Mix (February 1998, p.120) covered the machine's debut at that year's NAMM show. Sound on Sound (April 1998, p.7) described it as raising the standard of sonic excellence the ADAT line had established since its 1991 introduction. It also noted the compatibility with the enormous installed base, over 100,000 ADATs worldwide by the magazine's count.
The converters are where the XT-20 separates itself from the cheaper LX20. The XT-20 carries 24-bit, 128-times-oversampling delta-sigma A/D converters and 20-bit, 128-times-oversampling delta-sigma D/A converters, running at 44.1 and 48 kHz. It takes 24-bit ADAT Optical input and writes 20-bit data to tape. The LX20 is the economy path into Type II. It uses the same 20-bit format but has fewer of the high-end control features. Know the difference before buying either one used, because the two machines look like siblings on a spec sheet and behave very differently in a session.
In the room, what the XT-20 gives you is control. The transport is software-controlled and intelligent, with the familiar ADAT track copy, tape offset and track delay functions intact. There is an onboard 10-point autolocation system and automated punch in/out. The LX20 makes do with five locate points. Balanced analog I/O runs through a 56-pin ELCO connector, with eight unbalanced RCA analog inputs and outputs alongside optical digital I/O. The optional BRC remote controller was listed at $1,499, more than half the price of the recorder itself. Alesis evidently expected these to be racked modules under centralized control, not standalone boxes on a desk.
The chassis is six pounds of die-cast aluminum. That is light for a multitrack, and it is deliberate. The XT-20 was designed to be stacked and racked in quantity, the way the earlier ADATs had been. Collectors and techs note that the light die-cast construction cuts both ways. It keeps the footprint manageable in a rack full of them, but it does not absorb vibration the way a heavier steel chassis might, and the tape transport inside wants a stable, level mounting.
Launch pricing put the XT-20 at a manufacturer's list of $2,599, with the street price settling around $1,847 in the pages of the trade press. The LX20 listed at $1,399 and sold for roughly $1,052. That gap, $1,200 list and $800 street, bought the autolocation, the punch automation, and the better converter set. Mix (February 1998, p.120) covered the XT-20's debut at the NAMM show that January and framed it as the new flagship of the ADAT line. A Mix marketplace notice from June of that same year (p.264) ran under the headline that 20-bit ADATs had arrived.
The XT-20's working life ran well past its launch window. Pro Audio Review (March 2001, p.27) reported using the high-sample-rate ADAT optical mode to send four channels of 96 kHz audio across eight tracks on an XT-20 with apparent success. That is a useful data point for anyone wondering whether the optical I/O is good for more than 48 kHz multichannel. By 2001 the XT-20 was still being used as a reference machine in a 96 kHz workflow, which is more than can be said for a lot of 1998 digital gear.
Maintenance is the part nobody advertises. Mix (December 2001, p.150) ran a tech piece on ADAT head assembly cleaning, with diagrams of the retaining clip and the spring assembly. These are tape machines, and the heads need cleaning on a schedule. The same magazine's EQ counterpart (July 2001, p.126) fielded a steady stream of reader questions about syncing an ADAT to the outside world, most often to Pro Tools, and about the BRC settings that trip people up. The "Ext Sync" mode has to be enabled, and the LED stays lit solid when active and clocked. Anyone buying an XT-20 today should expect to learn that sync menu, because the machine's value in a modern setup is as a converter and tape transport feeding a DAW, not as a standalone recorder.
The XT-20 is a narrower proposition than the launch copy suggested. It is a 20-bit, 8-track modular digital multitrack on tape, compatible with the Type I and Type II ADAT ecosystem, with a decent converter set, real autolocation, and a light die-cast chassis built for rack density. It is not a hard-disk recorder, it does not do 24-bit to tape, and its six-pound frame and tape transport mean it wants a stable home and periodic head cleaning. What it does have is a huge installed base, optical and ELCO connectivity that other gear was built to talk to, and a used-market price that makes a rack of eight tracks cheaper than most people's first interface. Budget for the BRC if you want the autolocation to earn its keep.
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