How to mod Nak OMS-5 for digital output

[gto127]

I was reading older forums and I recall a member saying that the Nak OMS-5 has the best transport of any player. I couldn't find any threads of exactly how to do a digital mod with this with this model. Do any you guys have a schematic on how to build a digital coax out and where to connect this on the nak?I have a OMS 5 service manual(paper) and a OMS5 that has the factory modifications to read off spec discs in excellent working condition. Any ideas would be appreciated.

[rfbrw]

It does not lend itself easily to adding a digital output. It has no biphase-mark output that can used with the addition of a connector and a few passive components and the data format is unsuitable for current SPDIF transmitters.

[gto127]

Bummer I was really hoping to get new life out of this. Thanks for the reply.

[anatech]

Hi gto127,
You may be quoting me on this.

I'm thinking the easiest way to do this would be to run the RF pattern into another, more modern CD player board. One "stupid" enough to simply process the data without worrying about controlling the transport. You would have to echo the "tray in" and "play" commands so the TOC could be read in.

This would be a great project to only use the DSP and related circuitry on a mod PCB. Then it could be added to any CD player without a digital out.

I lack the skill and time to figure this out by myself.

-Chris

[gto127]

Thanks anand-Does anyone know of a inexpensive cd player that would meet this description and how to do this?

[rfbrw]

Originally posted by anatech

I'm thinking the easiest way to do this would be to run the RF pattern into another, more modern CD player board. One "stupid" enough to simply process the data without worrying about controlling the transport. You would have to echo the "tray in" and "play" commands so the TOC could be read in.
-Chris

You would probably need an entire donor board. Perhaps one from a MK 2.

[gto127]

RFBRW-what is MK? I'm a relative newbie to this forum. Also do you think a nak cdplayer 4 board would work? I have one that needs a laser and I have a schematic for the unit.

[anatech]

Hi rfbrw,
Actually, one only needs a cheap CD mech (likely to play without being told). You only require the demod and digital out signals to function. I'm not sure that quality will have any bearing on the result.

I am in favour of a DSP board approach. Just use an available DSP chip with the RF amp built in and a mute input. Feed your RF signal into the RF input on the DSP chip after correcting the level and provide a toslink and RCA type output. This shouldn't be a large board. You could then adapt this to any CD player, or even use it as a sub section for a home brew model. The tough part about building a CD would be to tune the servo gains and filters.

I'm wondering if one or more of our members experienced in this area would take the project on?

-Chris

[rfbrw]

Originally posted by gto127
RFBRW-what is MK? I'm a relative newbie to this forum. Also do you think a nak cdplayer 4 board would work? I have one that needs a laser and I have a schematic for the unit.

An OMS 5E II. Couldn't tell re the Nak 4. No idea whats in it.

[anatech]

Hi rfbrw, gto127,
You don't want to use one of these. They expect all the signals to be there. Drawer, everything (ie. they are too smart for this). That and one of these is too nice to chop up for this project.

gto127,

what is MK?

It's like a major revision change in a model number. In this case an OMS-5 MKII only bears a resemblance to the original OMS-5 in the case appearance. Everything else is totally different, including the laser and transport. With other makes, a MKII may only be the addition of a remote or minor cosmetic change.

-Chris