Toslink to S/PDIF

[Igla]

Hi !

I have a new LCD TV and I want to connect it to my amp. To my misfortune the TV has only digital audio output (Toslink) and my amp has only RCA inputs.
I also have CS8412/TDA1543 NOS DAC.
As I understand I would need something between the TV and the DAC to transform optical digital signal to S/PDIF.
I have search the forum and web but couldn't find the right answer or I just didn't undrstand.
I am practicaly new to this stuff so the simplest as possible answer would be most appreciated.
Is there anyone to have a simple schematic to my needs?
Regards;
Igla

 

[jitter]

If you don't want to forfeit the warranty on your new TV by opening it up and DIYing a coaxial out, you can buy an optical to coaxial converter (see attachment). This is no DIY, but it is the simplest solution.

I found it at www.conrad.nl and used the same article number to search at www.conrad.si. This is an example, there are probably other (online) stores that sell opto-coax converters.

 

[Igla]

Thanks a lot jitter.
This is one of the options; however, I was thinking to build it by myself. I don't think I must open and DIY my new TV to do this. Since I already have a DAC and I have interest to this stuff I thought it would be a new experience to build my own Toslink to S/PDIF converter.
Still; if the thing is too complicated I might go easier way and just buy it.

 

[Iain McNeill]

Google the datasheet for the CS8412 and you'll see it's pretty easy to add a TORX receiver. I think they even give a circuit to use. The Crystal S/PDIF receivers are easy to DIY as all configuration is done with bitswitches.

 

[jitter]

Thanks a lot jitter.
This is one of the options; however, I was thinking to build it by myself. I don't think I must open and DIY my new TV to do this. Since I already have a DAC and I have interest to this stuff I thought it would be a new experience to build my own Toslink to S/PDIF converter.
Still; if the thing is too complicated I might go easier way and just buy it.

OK, the next simplest thing is to build the opto-coax converter yourself. Like the Conrad-device it would be a separate device, so you still don't have to open up anything.

If you take a look at the attachment, you'll see the schematics of a common opto>coax converting circuit that works well. As you see, you only need a handful of components:

1x TORX177 optical receiver
1x 74HCT04 inverter
2x 100nF capacitor
1x 150nF capacitor
1x 47uH inductor
1x 374R/1% resistor
1x 93R1/1% resistor

The circuit needs a stabilized 5Vdc power supply. If you don't have it, building one around a 7805 voltage regulator is easy. Any 9V or 12V (300 mA or higher) adapter would be able to supply the 7805 with the needed voltage.

 

[Igla]

Thanks a lot jitter;
this it what I was looking for.
Thanks again.

 

[dtses]

hello,

could anyone please clarify for me is it possible to use RX179 receiver instead of TORX177 in the circuit above?

thanks in advance!

 

[Iain McNeill]

You mean TORX179?
Isn't that a 3V part vs 5V part?
I think you have to sign up for Toshiba datasheets but just check on Digikey or your local online resource.

 

[dtses]

well I found a spare part and it's written RX179PL on it, perhaps it's some kind of old series or some abbreviation from TORX179. Datasheets show the same operating voltage conditions, though there are slight differences in optical characteristics, hence I asked.

TORX177 pdf
TORX179 pdf

I would like to use this optical->coax converter to connect LG TV to my Wolfson diy DAC (the scheme is in att). One thing confuses me a lot - where should I connect ground of the converter, should it be 'IA+' of 26C32 on the Wolfson scheme where Coax input is or the whole conversion would be a wrong approach?! I mean that it's possible to connect TOSLINK directly to DIR9001. I have found few links, but didn't get completely how should it be done:

SPDIF decoder (receivers VCC pin could be connected directly to +5v via L1 or somewhere else too?! pls see att)
audio DAC with 9001 and TOSLINK

I would very appreciate if anyone could help me with the simplest way connecting toslink to DIR9001

 

[johnm]

Would the circuit shown in post 5 be OK for use with 24/96 transmission via optical, and converted to SPDIF for 24/96 output?

Cheers.

 

[Iain McNeill]

A 5V TORX part into a 3V DIR part raises red flags. How is voltage limited to the DIR9001?

Yes, that's how they mark them. 177 and 179 are interchangeable. 177 is better part in my estimation. Though it doesn't have the chassis mount screw so more stress on PCB solder joints. Both are fine for optical links.

 

[dtses]

hi Iain McNeill,

thanks! seems I got the point. Voltage is limited to 3.6v on DIR9001 according to the manual, so 5V torx part as you've said will not suit then...

What could be the solution in this case? Making separate optical->coax converter and then connecting to coaxial input of my DAC?

 

[dtses]

I've mixed up already, here torx179 is connected directly to dir9001 and seems that was working fine

 

[johnm]

Would the circuit shown in post 5 be OK for use with 24/96 transmission via optical, and converted to SPDIF for 24/96 output?

Many thanks.

 

[Torchwood421]

Hi dtses, The circuit works fine because there is 3.3 volts supplied by a regulator. The DIR9001 is on 3.3 Volts, the DAC chip and Torx are on +5 Volts. The input signal compliance isn't an issue. I hope that answers you question.

 

[gabanyayaya]

OK, the next simplest thing is to build the opto-coax converter yourself. Like the Conrad-device it would be a separate device, so you still don't have to open up anything.

If you take a look at the attachment, you'll see the schematics of a common opto>coax converting circuit that works well. As you see, you only need a handful of components:

1x TORX177 optical receiver
1x 74HCT04 inverter
2x 100nF capacitor
1x 150nF capacitor
1x 47uH inductor
1x 374R/1% resistor
1x 93R1/1% resistor

The circuit needs a stabilized 5Vdc power supply. If you don't have it, building one around a 7805 voltage regulator is easy. Any 9V or 12V (300 mA or higher) adapter would be able to supply the 7805 with the needed voltage.

Is there any coloration of sound quality when listening a direct spdif signal vs an optical converted to spdif signal using converter circuit like the above ???

 

[jnewbold]

I don't need the USB input for a DAC. Can I simply leave off all the parts associated with PCM2706 etc? Seems pointless to populate the board with stuff I don't need.

Joe.

 

[PJN]

If you still want to build it yourself, try the kit that Twisted Pear offers. I've used two of their toslink to spdif kits in past DAC projects and they are reliable, and Brian and Russ are very helpful if you run into problems.

PJN

 

[dtses]

Hi dtses, The circuit works fine because there is 3.3 volts supplied by a regulator. The DIR9001 is on 3.3 Volts, the DAC chip and Torx are on +5 Volts. The input signal compliance isn't an issue. I hope that answers you question.

hi Torchwood421,

all in all, could I use in my diy wolfson dac torx179's connection scheme like in microdac-3 (scheme is above), I mean direct torx's signal to RXIN of 9001?

will the circuit in 5th post work with COAX input of my dac?

 

[audiodesign]

I have used today the circuit published by Jitter to convert the Toslink output of my Samsung Serie 6000 to drive a Harman Kardon SB15 Sound Bar.

I suggest the SB15 or the SB16 (with toslink input) to create a great result with few money and without an amplifier.

The +5V has been created using one USB port of my TV.

I use an Asus S1 barebone connected in HDMI to store and play MKP 1080p.