Coaxial output page


For this modification you have to things to your DAT recorder that surely void your warranty, and can possibly ruin it. Use at your own risk!

The complete schema is drawn above (click on it for a real size image). I builded and tested it in this form. Some parts are optional or do not apply (it is an adaption of the SCMS-killer circuit).

Part A is the buffer. This part is not essential, but leaving it out means you use the output of the CXD2605 directly. (Expensive to having this part replaced by Sony!). The 74HC240 part can be replaced by a circuit using a 74HC04 (or any HC-MOS buffer/inverter) (see the image below).

Part B is the only essential part of the circuit. It adapts the signal to regular S/P-DIF levels. I used 390 and 100 ohm resistors, but the official values are 374 and 90.9 ohm.

Part C is optional, but gives some extra protection. Like providing galvanic isolation. Some implementations omit it. I used a Amidon T-37-0 core, but Digi-Key sells the official part for this: 257-1025-ND (Schott Corp. no. 67129600) for $9.

Below is an impression of how the wire should be wound around the core. There are two wires: one coming from the left, seven times through the core and back to the left. The other wire comes from the right, also seven times through the core and back to the right. I used isolated 0.35mm (0.0137") wire.

The 790BOARD.GIF shows a scan of the board drawing of the DTC-790 as it appears in the service manual. Note it is viewed from the solder-side, while in the deck, you see it from the component side. The logic-level S/P-DIF signal is found at resistor R330. The signal is taken from the side closest to the front side of the DTC-790.

The wires JW029 and JW020 supply the power to the buffer.

The output signal can best be isolated from the chassis (unless you omit the transformer). Best is to get a RCA chassis part with an isolated ground.


The circuit can also be modified to drive a TCD-D7 directly via the 7-pin connector. Just omit the parts B and C. I did not test this. Making the TCD-D7 output S/P-DIF compatible is also possible. Just connect the 7-pin output to the input of part A (not tested either).

No, I don't know if it will work in machine XXX. You can try sending me the service manual, but I don't guarantee you'll get anything back. Or that my advice would be useful to you.

This modification will probably not make the FCC happy. I hope you realise it is your problem?

You could try sending me an entire DAT deck for modification, but if I like it, I might keep it. Don't tell me I didn't warn you :-).

On my dtc790 copybit modification page is a description of a board for a SCMS-killer circuit and this coax output circuit.