Thread by @d_olex

I have a new weird obsession: DAT recorders! So, here's a really long thread about this outstanding piece of obsolete tech ⬇️⬇️⬇️

DAT was introduced by Sony in 1987 as recording and playback medium for digital audio. It adopted 16-bit PCM format with 44.1, 48 or 32 kHz of sampling rate. It's like an audio CD but stored on the magnetic tape. DAT cassette is about half size of the compact cassette

Commercially available DAT cassettes was able store up to 180 minutes of stereo signal recorded with 48 kHz sample rate. Also, exactly the same cassettes was used for DDS-1 streamers to store 2 GB uncompressed or 4 GB compressed data on standard cartridge

To fit such amount of data on relatively small medium DAT machines used helical scan recording method, same as VHS, Betamax and other standards of video cassette recorders that time but with much smaller size of the head drum and whole mechanical transport

The PCM itself begins its history from early 70-s. Before the DAT introduction there was standalone PCM processors to encode digital audio signal and record it into the video channel of analog VCR. Sony PCM-1630 and PCM-F1 from the beginning of 80-s are quite notable examples

It's also worth to mention Technics SV-P100 − absolutely insane machine released in 1981 that combines PCM processor and VHS recorder as single device for digital audio application

So, by its nature DAT allowed to distribute bit-perfect copies of audio CDs using cheap re-writeable media (in 1987, a year before CD-R Orange Book standard release 🤯🤯🤯), a pirate's dream! But why they didn't become popular for home audio? Well, Thanks to the fucking RIAA

So, by its pressure Sony introduced Serial Copy Management System (SCMS) for DAT machines. It utilizes PCM sub-code area to store two bits: "Cp" (copy protected) and "L" (signal is an original medium) which prohibits to record second generation copies of the DAT tapes

Here you can see pretty much comprehensive table from "IEC 60958-3: Digital audio interface, Part 3: Consumer applications" standard that describes effects of this bits in case of various media formats used as recording source

Of course, enthusiasts developed their own hardware to connect it in the middle of S/PDIF link for copy protection circumvent. For example, SCMS Copybit Killer Kit from Elektor, it uses cheap 27C512 EPROM and 74 series shift registers to implement signal processing state machine

Another reason why most of you didn't have DAT recorder at home in 90-s was the price. For example, first ever DAT recorder on the market, Sony DTC-1000ES, was available in Japan for 200.000 JPY, while you can buy a decent compact cassette recorder just for 50.000 JPY or less

Also, Sony made professional version of DTC-1000ES − PCM-2500 recorder. It has an additional block with more advanced A/D part along with PCM transcoding features. Small switches at the bottom right corner allows to control SCMS copy protection bits

By the way, well designed and reliable mechanical transport of DTC-1000ES/PCM-2500 with four direct drive motors (for the head drum, capstan and tape reels) also was used for the quite popular Sony TCD-D10 Pro portable DAT recorder, its price in 1992 was 100.000 JPY

However, DAT machines successfully found their place for professional use in the recording industry as part of the production chain: this medium was used for the master recording for more than decade. An example of sticker insert from DAT cassette alludes to its non-home purpose

So, speaking about obsession, recently I bought Sony DTC-1000ES and Sony TCD-D8 DAT recorders on Yahoo Japan auction. TCD-D8 (on the pic) is fully working and I had no reason to disassemble it yet, but DTC-1000ES was bought as "not tested, can't open the tray". Let's look inside!

Tray opening issue was caused by thickened grease on the gears of the tape loading mechanism, a typical problem of vintage audio components. Here you can see DTC-1000ES structural diagram from the service manual and its view with top cover and tape loading mechanism removed

On the right board you can spot two Sony CX20018 A/D converters for left and right channels and Philips TDA1541, a notable stereo D/A chip of Hi-Fi golden era that also can be found in many CD players from 80-s

Except thickened grease this machine also had more weird issues: sometimes it won't rotate the tape reels or starts rewind instead of play. It turns out that it was because improper zero position of the rotary encoder used as feedback sensor to control the mechanical transport

This encoder is very sensitive and its zero position can be disturbed by vibration and hits during the transportation, after its alignment my DTC-1000ES works like a charm. Overall, it's very reliable and well built machine that is a pleasure to maintain

In the future I'm planning to buy more non-working DAT recorders and try to bring them back to life: obsession is obsessive 😊