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Toslink switch and TosLink/Coaxial SPDIF converter - Review and measurements

Rja4000

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I measure-checked 2 digital Toslink devices :
Toslink switch + Bi-directional TosLink/Coaxial SPDIF converter

_R9A0878_dxo_corrected.jpg


I needed to extend my digital inputs capacity for home living room and another location.
So I purchased
- a 3 inputs - 1 output small TosLink switch - with remote. (30€ - Audiophonics)
- a bi-directional Coaxial/TosLink SPDIF converter (26€ - Amazon.fr)

Both are pure digital SPDIF devices.
No DAC or ADC here.

As you may see on the picture, those are VERY small devices.
Even the remote is tiny, compared to the XLR connector that holds it straight.



_R9A0880_dxo_Corrected.jpg


The TosLink switch has 3 inputs and 1 output.
Input may be selected through the remote or the front switch.

The Coaxial/TosLink SPDIF converter has a coaxial SPDIF (RCA connector) and a Toslink on both sides: Inputs on one side, outputs on the other side.
A switch allows to select which of the 2 inputs you play from.
Both outputs are then receiving the signal (More on that later)

Both devices are powered with 5V and come with corrsponding USB connector.
The convertor came with a 5V adaptor, but with a US plug, so not really usable for me.



I wanted to validate those devices for transparency.

So I've set-up some measurements using a RME UCX II (digital source) and the RME ADI-2/4 Pro SE.
As Amir is doing, I measured performance on the analog side, after the DAC receives the digital signal through the device I wanted to test.
If they are transparent, we should see no difference in measurements.



1. Testing with the RME ADI-2/4 Pro SE as a DAC

First, I've performed measurement with my ussual tool, the RME ADI-2/4 Pro SE as a DAC
I measured the analog loopback (DAC + ADC) of the RME ADI-2/4 Pro SE when fed with a digital signal coming through those devices.

Warning: This will be boring !
So you may want to jump to the next paragraph directly ;)


SINAD

Because I wanted to check the functionality, all SINAD tests here were perfomed at 192kHz.

First, through the TOSLink switch
NB: I tested the 3 inputs, and there is no difference

SINAD - UCX II - TosLink - Switch - TosLink - ADI-2-4_crop..png



Then through the Coaxial>TosLink SPDIF converter

SINAD - UCX II -RCA - Converter - TOSLink - ADI-2-4_crop..png


Then the same converter but in the other direction: TosLink > Coaxial SPDIF Converter

SINAD - UCX II - TosLink - Converter - RCA - ADI-2-4_crop..png



And, in case you were wondering, the RME ADI-2/4 with SPDIF input (analog loopback)

SINAD - UCX II - TosLink - ADI-2-4_crop..png




Jitter

To save some time, I cascaded the 2 devices:

> SPDIF Coax > Coaxial/TosLink SPDIF converter > TosLink > TosLink Switch > TosLink > RME ADI-2/4

JTest UCX II - RCA - RCA-TosLink Converter - TosLink - Toslink Switch - TosLink - ADI-2-4_crop..png


then
> TosLink > TosLink Switch > TosLink > Coaxial/TosLink SPDIF converter > Coaxial SPDIF > RME ADI-2/4

JTest UCX II - TosLink - Toslink Switch - TosLink - RCA-TosLink Converter - RCA - ADI-2-4_crop..png



Multitone

Multitone tests were performed at 192kHz.

Same here
> Coaxial SPDIF > Coaxial/TosLink SPDIF converter > TosLink > TosLink Switch > TosLink > RME ADI-2/4

MT32 UCXII - RCA - RCA-TosLink converter - TosLink Switch - Toslink - RME ADI-2-4_crop..png


Then
> TosLink > TosLink Switch > TosLink > Caoxial/TosLink SPDIF converter > Coaxial SPDIF > RME ADI-2/4

MT32 UCXII - Toslink - TosLink Switch - Toslink - RCA-TosLink converter - RCA - RME ADI-2-4_cr...png


Just perfect.

I told you this would be boring :D





2. Testing with the Topping E30 II Lite as a DAC

I've been challenged on the fact that the RME is almost a "perfect" tool.
So there is a risk the test is not relevant, since the RME would fix any issue with the incoming digital signal.

That looked like a valid concern.

So I took a DAC I had at hand that I knew had some issue with Jitter on SPDIF input:
The Topping E30 II Lite I reviewed here.

So... here we go again.



This time I started with
Jitter measurement


Direct input in the DAC


RME ADI-2/4 Pro SE optical output > TosLink > Topping E30 II Lite > Analog output (L) > RME ADI-2/4 Pro SE

As you may see in the Topping E30 II Lite review, Jitter performance on SPDIF has some issue.
Not catastrophic;, but not stellar either.


First, for reference, with none of the devices we want to test in the loop.

Here, I kept the measurement of the highest secundary peak, to allow some comparison.
NB: This figure doesn't mean much by itself - don't compare it to a SINAD value !

JTest E30 II Lite TosLink direct__crop..png



Through the Coaxial/TosLink SPDIF converter

> Coaxial SPDIF > Coaxial/TosLink SPDIF converter > TosLink > Topping E30 II Lite > Analog output (L) > RME ADI-2/4


JTest E30 II Lite TosLink through converter (RCA input)_crop..png


Here, we see a difference ! And this is not good.
The second peak (and all other peaks) raised by almost 12dB.

Is that a concern ? I don't know.


Let's try the other direction
(More important, since that's the one I, personnaly, plan to use ;))


> TosLink > Coaxial/TosLink SPDIF converter > Coaxial SPDIF > Topping E30 II Lite > Analog output (L) > RME ADI-2/4

JTest E30 II Lite TosLink through converter (TOSLink input)_crop..png


In that direction, we have less degradation of the result.
At least that's good.
It's still an average result, but it didn't become much worse than what the DAC can do.


Through the TosLink switch

> TosLink > TosLink Switch > TosLink > Topping E30 II Lite > Analog output (L) > RME ADI-2/4

JTest E30 II Lite TosLink through switch__crop..png


Same here.
Not worse than what the DAC can do.


SINAD measurement

Let's check the impact of this on SINAD, if any.
(As above, SINAD measurements here are at 192kHz)

Direct input in the DAC

RME ADI-2/4 Pro SE optical output > TosLink > Topping E30 II Lite > Analog output (L) > RME ADI-2/4 Pro SE

SINAD 191kHz BH7 E30 II Lite TosLink_crop..png

Our reference here.


Through the Coaxial/TosLink SPDIF converter

> Coaxial SPDIF > Coaxial/TosLink SPDIF converter > TosLink > Topping E30 II Lite > Analog output (L) > RME ADI-2/4

SINAD 192kHz BH7 E30 II Lite TosLink through converter (RCA input)_crop..png


Not much impact.

Let's try the other direction

> TosLink > Coaxial/TosLink SPDIF converter > Coaxial SPDIF > Topping E30 II Lite > Analog output (L) > RME ADI-2/4

SINAD 192kHz BH7 E30 II Lite TosLink through converter (TOSLink input)_crop..png


A bit more distortion, maybe. Still excellent.

Through the TosLink switch

SINAD 192kHz BH7 E30 II Lite TosLink Through TosLink Switch_crop..png


We see again a slight decrease in performance.
That remains very good, though.

Interestingly, the performance here degrades in the opposite direction than the Jitter above.
Why ? No clue.


Multitone measurement

Direct input in the DAC


RME ADI-2/4 Pro SE optical output > TosLink > Topping E30 II Lite > Analog output (L) > RME ADI-2/4 Pro SE

MT32 E30 II Lite TosLink_crop..png


That's our reference.


Through the Coaxial/TosLink SPDIF converter

> Coaxial SPDIF > Coaxial/TosLink SPDIF converter > TosLink > Topping E30 II Lite > Analog output (L) > RME ADI-2/4

MT32 E30 II Lite TosLink through converter (RCA input)_crop..png


Same thing: a bit more noise, but result remains excellent


The other direction

> TosLink > Coaxial/TosLink SPDIF converter > Coaxial SPDIF > Topping E30 II Lite > Analog output (L) > RME ADI-2/4

MT32 E30 II Lite TosLink through converter (TOSLink input)_crop..png


Nothing to complain about


Through the TosLink switch

> TosLink > TosLink Switch > TosLink > Topping E30 II Lite > Analog output (L) > RME ADI-2/4

MT32 E30 II Lite TosLink Through TosLink Switch_crop..png


A bit degraded still, but anyway still very very good.


We have seen some degradation with using a less performant device.
The Jitter test - which was meant to be very sensible to Jitter and other digital domain issues - shows some degradations, for the SPDIF converter (especially in the direction from Coaxial to TosLink).
Nevertheless, that doesn't really show in any of our classical analog measurements, which all score very good.
So it's probably benign.



3. Functionality

ADAT capabilities

Following a question of @Blumlein 88 , I'm happy to say that the small switch also works with 8 channels ADAT @48kHz

I've done a quick setup as follows:
PC generator > to 8 Dante channels (Dante controller) > to 8 ADAT output channels (RME 12Mic-D routing) > TosLink > TosLink switch > TosLink > UCX II

And we see the 8 channels in TotalMix

1694165433133.png



Port replicator capability of the SPDIF converter
The convertor always has both its outputs active.
When feeding the Coaxial/TosLink SPDIF converter with a TosLink input at 192kHz, the Coaxial output works perfectly, but the TosLink output's clock sometimes gets out of sync.
I didn't experience this issue at 44.1kHz, 48kHz and 96kHz though.
So it's acting perfectly as a converter, but it may give some issue to duplicate the output at high sampling frequency.


4. Conclusion

This review I thought would be quick and easy, and at the end, it took me almost the whole day...
But we learned a few interesting things.

After testing with the RME only, I wrote "Those devices are adding or substracting nothing to the signal they receive".

After further look and check with the more Jitter-sensitive (and way cheaper) Topping E30 II Lite, this is not absolutely true.
There are measurable performance degradations.

I still think we may trust those devices to do exactly what you want them to do.


So I would rate them as
Good for the job
(with this specific config)


Also, it's important to note that, even if those devices are not perfect, they absolutely don't prevent a well engineered device to perform perfectly through them.

So that's not -not only- those devices' "fault" if the Topping is giving some lower results with them.

Good engineering is not only about good raw figures.
It also gives you more freedom.
 
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Blumlein 88

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These could be useful to me. How about the names and maybe links to them?

Also could you confirm if either works with ADAT? That would be really handy.
 
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Rja4000

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RandomEar

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Very useful info! And impressive to get to 120 dB SINAD using RCA for less than 20$. That's as good as the best DACs around - I'm surprised.

Small oddity: The text describing the signal chain for the last two images is identical. Is that correct?
 

morillon

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Hi

I measure-checked 2 digital Toslink devices :
Toslink switch + Bi-directional TosLink/RCA converter

View attachment 310509

I needed to extend my digital inputs capacity for home living room and another location.
So I purchased
- a 3 inputs - 1 output small TosLink switch - with remote. (30€ - Audiophonics)
- a bi-directional TosLink/RCA converter (26€ - Amazon.fr)

As you may see on the picture, those are VERY small devices.
Even the remote is tiny, compared to the XLR connector that holds it straight.



View attachment 310511

The TosLink switch has 3 inputs and 1 output.
Input may be selected through the remote or the front switch.

The RCA/TosLink converter has a RCA and a Toslink on both sides: Inputs on one side, outputs on the other side.
A switch allows to select which of the 2 inputs you play from.
Both outputs are then receiving the signal (More on that later)

Both devices are powered with 5V and come with corrsponding USB connector.
The convertor came with a 5V adaptor, but with a US plug, so not really usable for me.



I wanted to validate those devices for transparency.

So I've set-up some measurements using a RME UCX II (digital source) and the RME ADI-2/4 Pro SE.
As Amir is doing, I measure performance on the analog side, when the RME ADI-2/4 receives the signal through the device I wanted to test.
If they are transparent, we should see no difference in measurements.


Warning: This will be boring !
So you may want to jump to the conlusion directly ;)


SINAD

Because I wanted to check the functionality,
all SINAD tests here were perfomed at 192kHz.

First, through the TOSLink switch
NB: I tested the 3 inputs, and there is no difference

View attachment 310514


Then through the RCA>TosLink converter

View attachment 310515


Then the same converter but in the other direction: TosLink > RCA Converter

View attachment 310517


And, in case you were wondering, the RME ADI-2/4 with SPDIF input (analog loopback)

View attachment 310518



Jitter

To save some time, I cascaded the 2 devices:

> RCA > RCA/TosLink converter > TosLink > TosLink Switch > TosLink > RME ADI-2/4

View attachment 310521

then
> TosLink > TosLink Switch > TosLink > RCA/TosLink converter > RCA > RME ADI-2/4

View attachment 310522


Multitone

Multitone tests were performed at 192kHz.

Same here
> RCA > RCA/TosLink converter > TosLink > TosLink Switch > TosLink > RME ADI-2/4

View attachment 310524

Then
> RCA > RCA/TosLink converter > TosLink > TosLink Switch > TosLink > RME ADI-2/4

View attachment 310523

I told you this would be boring :D




Conclusion

The conclusion is quite obvious.

Those devices are adding or substracting nothing to the signal they receive.
So you may blindly trust them to do exactly what you want them to do.



Just one comment though:
When feeding the RCA/TosLink converter with a TosLink input at 192kHz, the RCA output works perfectly, but the TosLink output's clock sometimes gets out of sync.
I didn't experience this issue at 44.1kHz, 48kHz and 96kHz though.
So it's acting perfectly as a converter, but it may give some issue to duplicate the output at high sampling frequency.
I'm sorry..
but experiments using the rme's digital inputs (except perhaps in extreme cases) are of no interest...
their powerful "steadyclock fs "input processing levels absolutely everything... so it is normal that you observe...nothing...
You need practically unprocessed inputs to be able to make interesting observations.
I have a lot of respect for your efforts...but there they were in vain
;-)
(This is a situation that sometimes comes across on ASR, typically also in observation in the digital domain...and which must be clearly explained to avoid misunderstandings, or irrelevant measurements-observations..I had even one day gently asked “gentleman rme” if it would be possible to disengage him for this type of observation..
but it was not well understood I think)
 
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OP
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Rja4000

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Also could you confirm if either works with ADAT? That would be really handy.

I'm happy to say that the switch works with 8 channels ADAT @48kHz

I've done a quick setup as follows:
PC generator > to 8 Dante channels (Dante controller) > to 8 ADAT output channels (RME 12Mic-D routing) > TosLink > TosLink switch > TosLink > UCX II

And we see the 8 channels in TotalMix

1694165433133.png
 
OP
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Rja4000

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Very useful info! And impressive to get to 120 dB SINAD using RCA for less than 20$. That's as good as the best DACs around - I'm surprised.
This is not a DAC. Just a digital converter. The DAC is the RME ADI-2/4 Pro SE or the Topping E30 II Lite, at the end of the chain.

Small oddity: The text describing the signal chain for the last two images is identical. Is that correct?
Corrected. Thanks.
 
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Blumlein 88

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I'm happy to say that the switch works with 8 channels ADAT @48kHz

I've done a quick setup as follows:
PC generator > to 8 Dante channels (Dante controller) > to 8 ADAT output channels (RME 12Mic-D routing) > TosLink > TosLink switch > TosLink > UCX II

And we see the 8 channels in TotalMix

View attachment 310531
This is pretty terrific. Thanks.
 
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Rja4000

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experiments using the rme's digital inputs (except perhaps in extreme cases) are of no interest...
their powerful "steadyclock fs "input processing levels absolutely everything... so it is normal that you observe...nothing...
You may have a point here.
I'm checking... with what I have at hand.
 

morillon

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You may have a point here.
I'm checking... with what I have at hand.
it's even sure.... ;-)
if it's to observe the efficiency of the powerful steadyclock, and even more obvious if the observations in the digital domain... it's good... everynum source is good..miraculus ;-)

but if to observe the jitter etc behavior of digital sources etc.. it will work not so...
(]to observe the impact of these switches etc. it will be better to observe them in the digital domain...
these are observations that can be very biased by the receiver's input processing bias... the more "bad", the more interesting it will be...)

;-))
 
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RandomEar

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This is not a DAC. Just a digital converter. The DAC is the RME ADI-2/4 Pro SE, at the end of the chanin.


Corrected. Thanks.
Ahhh, now I see: It's Toslink to S/PDIF over coax. OK, in that case, I would expect it to perform like it did. Every outcome other than "bit perfect" would be bad.

I would recommend to not call the connector "RCA", though. While the coaxial S/PDIF connector is mechanically compatible (identical?) to a regular RCA plug, the term RCA is commonly used to refer to the analog variant. It's not technically wrong to call that coax plug "RCA", but it's gonna lead to misunderstandings - like in my case ;)
 
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Rja4000

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As you may read with the additional measurements I added, there is an impact with a (very) cheap (but still very good) DAC.
Not very big or significant, but there is one.
 

morillon

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As you may read with the additional measurements I added, there is an impact with a (very) cheap (but still very good) DAC.
Not very big or significant, but there is one.
the most effective way to observe digital is to do it in digital...
I'll try to clarify by example:
I have several digital acquisition cards and no need to use a DAC ouput etc
some from the professional world like the rme are heavily processed in input and offer, like the rme, practically constant results whatever the quality of the incoming signal...
but I also have a general public card that is very poorly processed in digital input..
it allows observations, comparisons jitter mesurment that are truly differentiated according to the quality of the sources..

conclusion for this type of observations of digital sources only the modest one is useful and allows us to sort things out and avoid major misunderstandings.... .
;-)
 
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MRC01

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Thanks for the useful review. I use similar devices and never measured them as they are digital-only so I didn't expect them to make any difference. The jitter differences you measured will vary depending on how well the receiving device is designed.

I ran across this one too.
Or this one that has two outputs that work at the same time. Maybe good for feeding subs and main speakers or some such.
The first toslink/coax adapter that I tried a couple of years ago worked just well enough to realize that it didn't work. It would work fine for a few minutes then start to fail. So don't use this one:

Then I replaced it with this one, which works reliably up to 192-24:

They look the same but in functionality they are not!

The ViewHD device mentioned above is another I tried for a while. It caused some intermittent issues so I replaced it with this one, which works reliably:
 

morillon

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I didn't test for that, so I can't comment.
I'll start using them in my system, so we'll
you clearly show that these observations are very determined by the processing at the input of the acquisition...
constant with rme..
more variable with the topping...just that my point...
(we are in complete agreement in rme directly via steadclock...on topping its ana output to ana rme?)
small example



stop for me...
 
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