Coaxial SPDIF experiment

[onlyoneme]

to get an eye-pattern. An ordinary RCA analog cable used, terminated with 50 ohm and a PicoScope 4444 oscilloscope working with 20 MHz BW.

48 kHz:



96 kHz:


192 kHz:


Any thoughts?

 

[Mr Ee]

You need a new spyrograph?
tbh, I've no idea what you're trying to show us!

 

[onlyoneme]

OMG

Eye pattern - Wikipedia

en.wikipedia.org

 

[OldNick]

Spdif coax spec is 75 ohm if I remember it right. 1.2 m minumum length. Not sure how that might affect your results..

 

[onlyoneme]

Spdif coax spec is 75 ohm if I remember it right. 1.2 m minumum length. Not sure how that might affect your results..

I know, but I was getting much worse visualization when terminating with 75 ohm. Maybe the cable I've used is closer to 50 ohm. No idea what's the impedance usually for analog RCA cables.

 

[onlyoneme]

A short explanation - I'm trying to figure out how a cable can influence the carrier jitter and noise for different sample rates.

 

[C3pored]

If only it was as simple as that! it would put reviewers out of business overnight.

look at audio science review website for ways of using scopes to see Jitter (and basically how insignificant jitter is in the world of modern Dacs)

 

[canard]

a 20mhz is not enough for this kind of observations
;-)
(
the rise times of the scope are too long for a relevant observation...
;-)..
but an example of a really clean 44/16 signal at the output of a drive..
but again on a too limited scope like 50mhz .. the rise time marred by 7ns plus a little the probe ...to do well, you need 350-400mhz mini and adapted probe..i have but..not wiim pro i cant help...

 

[Mr Ee]

If I'm reading it right, you're showing that the digital signal degradation increases with the increase in frequency?
Isn't that to be expected?

 

[onlyoneme]

a 20mhz is not enough for this kind of observations
;-)
(
the rise times of the scope are too long for a relevant observation...
;-)..
but an example of a really clean 44/16 signal at the output of a drive..
but again on a too limited scope like 50mhz .. the rise time marred by 7ns plus a little the probe ...to do well, you need 350-400mhz mini and adapted probe..i have but..not wiim pro i cant help...

Why? SPDIF frequency for 192 kHz is less than 13 MHz.
Different cable, still 50 ohm, different triggering.

48 kHz:


96 kHz:


192 kHz:

 

[canard]

it's just that you don't have enough margin..
the rising edges are tainted by the slow rise times of the 20mhz
(350/20...17.5ns...350/50..7ns etc)
It makes reading a bit clumsy...
etc
;-)

 

[onlyoneme]

Are we talking about the bandwidth or about the sampling rate?

 

[onlyoneme]

Do you have an example of the spdif eye pattern with much higher BW?

 

[canard]

no, I have nothing on hand.(but these are square signals..explain the difficulty for a scope without a large margin in bw...)
automatic edge calculations give how many ns?...(x-17.5ns?)
(from memory the example I show was a + 3.5 4ns+7 type of flipflop output...)
but it's not a standard 0.5v spdif output?

 

[canard]

ps
I would like to know if wiim has put a transformer in spdif output
but we still don't have a photo.
but if there is one side external dac .. not a problem

 

[Wiimer]

ps
I would like to know if wiim has put a transformer in spdif output
but we still don't have a photo.
but if there is one side ac .. not a problem

I found a photo of the inside of the Pro here.

Стример-плеер WiiM Pro/Wiim Mini/Wiim Pro Plus— а 12 000 рублей не могут спасти гиганта цифрового стриминга? Теперь с Roon.

Лев, фото внутри покажете?..

www.dastereo.ru

 

[canard]

I found a photo of the inside of the Pro here.

Стример-плеер WiiM Pro/Wiim Mini/Wiim Pro Plus— а 12 000 рублей не могут спасти гиганта цифрового стриминга? Теперь с Roon.

Лев, фото внутри покажете?..

www.dastereo.ru

cheer..
the first images that I come across!
(my skills, and not helped by the cms, are limited but seem to me not to be isolated....)
;-)

 

[onlyoneme]

I found a photo of the inside of the Pro here.

Стример-плеер WiiM Pro/Wiim Mini/Wiim Pro Plus— а 12 000 рублей не могут спасти гиганта цифрового стриминга? Теперь с Roon.

Лев, фото внутри покажете?..

www.dastereo.ru

Finally, thx

 

[onlyoneme]

no, I have nothing on hand.(but these are square signals..explain the difficulty for a scope without a large margin in bw...)
automatic edge calculations give how many ns?...(x-17.5ns?)
(from memory the example I show was a + 3.5 4ns+7 type of flipflop output...)
but it's not a standard 0.5v spdif output?

It's a standard spdif output but impedance mismatch - 50 ohm termination plus a cable - probably affects a voltage.
I know I won't get a square wave representation, I don't expect this. But I think the noise and jitter can be still observed on the pattern.

 

[merifon]

Any thoughts?

hi frequencies loss and increasing impedance mismatches?
Did you try other cables on 75 Ohm?