Digital Optical (Toslink) conversion to Digital Electrical (SPDIF)

[Brandson]

Hi everyone,
I am considering buying a TOSLINK to digital SPDIF adapter / converter.
Couldn't find information online regarding the conversion between digital optical to digital electrical.
Does anyone know about the performance of the conversion and if signal degradation is to be expected?

Thanks a lot in advance.
Best, Diogo

 

[Brandson]

Something like this:

Toslink/Coaxial to Toslink/Coaxial Optical SPDIF Converter Adapter - Audiophonics

This little converter is very practical, allowing you to transform a Toslink optical SPDIF audio signal into a coaxial one, and vice versa. It supports Dolby, DTS, AAC and PCM technologies as well as streams up to 192kHz sampling rate.

www.audiophonics.fr

 

[LTig]

I own two converters, one from Toslink to Coax, and one from Coax to Toslink. Both were 10€ each including wall power supply and worked flawless (I don't remember whether I used them above 44/16 though). Hence I think the one you mention should be fine. Which means no signal degradation.

 

[Brandson]

I own two converters, one from Toslink to Coax, and one from Coax to Toslink. Both were 10€ each including wall power supply and worked flawless (I don't remember whether I used them above 44/16 though). Hence I think the one you mention should be fine. Which means no signal degradation.

Thanks a lot for the prompt answer!

 

[mansr]

Something like this:

Toslink/Coaxial to Toslink/Coaxial Optical SPDIF Converter Adapter - Audiophonics

This little converter is very practical, allowing you to transform a Toslink optical SPDIF audio signal into a coaxial one, and vice versa. It supports Dolby, DTS, AAC and PCM technologies as well as streams up to 192kHz sampling rate.

www.audiophonics.fr

I have one that looks exactly like that. It works as advertised. Since it's just a dumb converter, it doesn't care about things like sample format or Dolby encoding.

 

[Brandson]

I have one that looks exactly like that. It works as advertised. Since it's just a dumb converter, it doesn't care about things like sample format or Dolby encoding.

On Amazon they “claim” the sample rates etc. i just wanted to get some factual data on conversion reliability and signal degradation but couldn’t find any info

 

[mansr]

Since I couldn't remember if I'd ever used it with 192 kHz, I decided to give it a try. It doesn't work. It's fine at 96 kHz, though, and that's as high as most Toslink inputs go anyway.

 

[DVDdoug]

They are both S/PDIF so it's a "physical conversion" but the digital data is the same.

 

[mansr]

Just for laughs, I hooked it up to the scope, measuring the coax input (top, yellow) and output (bottom, blue). (Yes, it's a pointless configuration.)

Here's what it looks like at 48 kHz:

At 96 kHz (different time scale on scope):

And finally at 192 kHz:

In that last capture, the shortest pulse has been mangled badly enough that the DAC I tested it with no longer recognises the signal. It's fine when fed the source signal directly.

 

[Brandson]

Thank you everyone, especially @mansr for having taken the time to check. Amazing forum

 

[LTig]

Since I couldn't remember if I'd ever used it with 192 kHz, I decided to give it a try. It doesn't work. It's fine at 96 kHz, though, and that's as high as most Toslink inputs go anyway.

I think for Toslink 192/24 to work both sides of the Toslink chain must support it, including the cable (not too long). Not all Toslink transmitters and receivers are able to support 192/24. I had problems with some combinations of transmitter, receiver and cable even with 44/16. 5m cable worked always, 10m sometimes not.

 

[mansr]

I think for Toslink 192/24 to work both sides of the Toslink chain must support it, including the cable (not too long). Not all Toslink transmitters and receivers are able to support 192/24. I had problems with some combinations of transmitter, receiver and cable even with 44/16. 5m cable worked always, 10m sometimes not.

Right, but this thing fails at 192 kHz even with coax in and out, no optical involved at all.

 

[LTig]

Pity.

 

[MRC01]

Sorry to resurrect this necro-thread, but I could use a converter that actually works.
I have this one: https://www.amazon.com/gp/product/B07D7TDXF6
It works for a few minutes, randomly from 1 to 10 minutes, then inevitably the signal just stops. I suspect it's losing data or time sync. This at undemanding rates of 44.1 and 48 kHz.
Can anyone recommend a specific model that actually works?

 

[LTig]

The ones I have are cheap and sold by many different brands, like goobay for example.

 

[venquessa]

The odd thing about SPDIF (and Toslink) is they aren't really digital. (not intending on kicking that hornets nest so directly), but I mean the protocol involves quiet a lot of multiplexing of different digital streams. The audiophiles would understand there are corner cases in that multiplexing where data has to be transformed to work and not "untransformed" either at the other end. For most people it's fine. Whats a bit here or there between friends.

It's been a while since I checked, but I believe Toshiba just used Philip's protocol and octo-coupled it.

The 2 Opti-I2S-ADC-SPDIF bridge boards I have (one for Rx, one for Tx) both do straight passthrough from SPDIF to OPT (or vice versa). They only require you switch if the ADC or the I2S is the input/output.

As a long shot you could just try plugging something into the SPDIF port while the TosLink is also plugged in and running. They might just couple fine electrically.

 

[Bernard23]

Slightly OT, but given the choice what is preferable, using a coax or optical between streamer and dac, or does it not really matter?

 

[staticV3]

Slightly OT, but given the choice what is preferable, using a coax or optical between streamer and dac, or does it not really matter?

Using optical can in some cases interrupt ground loops, reducing noise.

DACs can also have different jitter depending on what input is used, but this depends on the specific model and even then, is usually below audible levels.

 

[Bernard23]

I found a thread just now on this very topic. Apart from electrical isolation, no practical difference between the two.

 

[venquessa]

The term "ground loop" gets over used. It originates in the days of large, high voltage valve equipment when the grounds where often offset by some stupid DC voltage and other bizarre things. Spend time with the valve aficionados and you'll see some things. It will also ruin your day setting up a large high power rig for a gig etc. With high AC currents you get real magnetic fields building up in loops of wire and loops between devices, it can start to resonate, usually the 50Hz mains hum or the 100Hz stage drone that ends up sounding like feedback.

What people in consumer audio are usually taking about is just common mode noise and power rail noise. Digital gear is noisy. All those sudden transitions require current to overcome the capacitance of the circuit. 24 million times a second or 1 billion times a second, or maybe it's just clicks and buzzes. If it gets audible on your gear it's a real pain in the backside to locate it and remove it. The usual culprits are digital hardware devices, the higher the performance and the lower the price the noisier they will be. PCs are bad, laptops are hideous usually.

When you get one device with a noisy ground connected to others, they all have noisy grounds. If the noise on the grounds is exactly the same and your ground paths are all low impedence ... you are extremely lucky. If however you end up with slightly different noise on one devices ground compared with the others, you get common mode noise between them, which may, or may not get onto your audio. "Mixed signal" design is a whole thing in itself on keeping the two noises domains apart.

Optical provides total electrical isolation, but if you then power the two devices from the same power supply it defeats a large part of the purpose.