NICAM sound

[catdog]

I am looking at building a NICAM decoder for the Philips/Sony SA tivos to use in New Zealand, similar to the "Mark 1 stereo decoder" used in Australia. The tivo will need to have a PAL tuner fitted along with this additional circuit - see TunerModALPSHowTo for details of the fitting a tuner and how the "Mark 1" stereo mod is used in Aussie.

Also see NzStereoSupport for details on why we cant get NICAM sound on the Philips/Sony tivos.

The cost of the required components is estimated to be about NZ$35-40, and will use the STV8216D

Since the minimum order quantity for this part is 25 units (and I don't own that many tivos!), is anyone else interested in performing this modification before I commit? All suggestions welcome!

[Islander]

Why not use a second MSP chip instead as per http://forums.oztivo.net/showpost.ph...8&postcount=10 ?

[catdog]

Effectively that is what I am doing, but the default reset settings of the ST part should decode the NICAM without having to program the chip each time the tivo boots. I agree that a second Micronas chip would work too, but I see it as more work as it requires software to configure it over I2C?

[DOlsen]

Sounds good. I've previously resisted putting in a pal tuner as I don't want to go without stereo sound. I'm currently using an external nicam video with the ir blaster control, which works well except for the occasional missed change of channel, and the delay, but an internal pal tuner which captures stereo would be much better.

[Skolink]

I'll do the PCB for you if you like, unless you can do that yourself? Depending on the size of the board, they will be about US$4 each.
I'll have a board and so will a friend of mine. Other people I know with TiVos probably don't care.

[catdog]

I have managed to source the ICs from a contact in Taiwan who had 5 in stock rather than using NZ distributors, allowing me to make sure a prototype works as expected before buying in lots of 25. I'll update here when I have received and tested it.

Skolink: Thanks for the offer but I can make a plain single sided PCB which will be fine for the prototype.

[slangnz]

Hiya.

I'll be in for one if you can supply chip and circuit board. Any idea on where to get PAL tuners from? Are you able to supply chip, circuit board and Tuner?

[Skolink]

Darren is the man for tuners: http://www.kingey1971.com/tivo/index.htm

[catdog]

Sorry for the delay on updates - schematic now attached!

I ran into an issue that the default settings for the STV8216 were all fine - except the outputs are muted on startup! The tivo I2C bus *should* have been capable of turning the mute off, but for some unknown reason it refuses to communicate with devices at normally unused addresses. I now have a PIC micro which turns the mute off instead, which is a simple workaround for the problem.

The prototype has been running for a month or two now without any issues and sounds much better/clearer than the mono sound from the tuner.

The circuit is shown in the photo to give an idea of what is required to build your own, it's a bit rough, but remember that it is a prototype (and it works)!

[DOlsen]

Glad to hear that the nicam problem has been solved.

Do you have the pcb design available to create a pcb with?
Pity about the tivo not letting you communicate with the decoder chip, nice workaround though.

Do you have the decoder chips available to purchase yet, or are the ones you've got so far taken?