Objective-Fi Optical Networking & SFPs

[bernardl]

I have added a stretch of optical fiber in my system between my home router and my Melco S100 switch. The s100 does have a SPF port its connected to. The RJ45 -> optical conversion is done by a cheap non audio grade device with a stock power supply connected to a different power line from the critical audio component in the system.

 

My Mac mini (source) and my Devialet (dac) are both connected to the S100, meaning downstream of the optical segment.

 

I do unfortunately not have the means to measure any objective value it may have brought. I did frankly not notice a significant difference in sound although I was hoping to hear one.

 

Cheers,

Bernard

[cat6man]

i don't want to derail the topic, but this seems to be related (at least to me)

 

what if we back up a bit.  forgetting for the moment sfp variations and if/how they are real, what about basic galvanic isolation?  do we agree that it is real and a good thing?  if so, how can it be measured?  has anyone done so?

[plissken]

12 minutes ago, cat6man said:

i don't want to derail the topic, but this seems to be related (at least to me)

 

what if we back up a bit.  forgetting for the moment sfp variations and if/how they are real, what about basic galvanic isolation?  do we agree that it is real and a good thing?  if so, how can it be measured?  has anyone done so?

 

Optical by it's nature is galvonically isolated by the fiber run. The thing some people want to put their head in the sand over, especially at 10G, is that the engineering standards for it even to work require incredibly low jitter. Then you have to consider that fully realized 10G is 1250MB / Second. That is 48MB every 1/60th of a second. That is, on average, a 16/44.1 PCM track in 1/30th of a second transferred to a system that would say have 256MB of buffer. 

 

The PRAT, airieness, extended highs, better slam? It's all out of buffer while that connection just sits there IDLE. 

[cat6man]

1 hour ago, plissken said:

 

Optical by it's nature is galvonically isolated by the fiber run. The thing some people want to put their head in the sand over, especially at 10G, is that the engineering standards for it even to work require incredibly low jitter. Then you have to consider that fully realized 10G is 1250MB / Second. That is 48MB every 1/60th of a second. That is, on average, a 16/44.1 PCM track in 1/30th of a second transferred to a system that would say have 256MB of buffer. 

 

The PRAT, airieness, extended highs, better slam? It's all out of buffer while that connection just sits there IDLE. 

 

yes, i know.  i'm asking if the isolation of fiber can be measured relative to copper ethernet which is not isolated.

can the isolation aspect specifically be measured?  i'm not talking about sound or PRAT or air or buffers, but simply "can the isolation of fiber" be measured somehow?  objectively, how is that done?

[cjf]

4 minutes ago, cat6man said:

 

yes, i know.  i'm asking if the isolation of fiber can be measured relative to copper ethernet which is not isolated.

can the isolation aspect specifically be measured?  i'm not talking about sound or PRAT or air or buffers, but simply "can the isolation of fiber" be measured somehow?  objectively, how is that done?

I wouldn't think there would be a need to measure the isolation of fiber as it is absolute by default. In other words, the medium used to transmit the 1's & 0's from point A to B is not conductive and the light traveling thru that medium is also not conductive so isolation would be absolute and total

[cat6man]

26 minutes ago, cjf said:

I wouldn't think there would be a need to measure the isolation of fiber as it is absolute by default. In other words, the medium used to transmit the 1's & 0's from point A to B is not conductive and the light traveling thru that medium is also not conductive so isolation would be absolute and total

 

guys, you really don't get my question (and i'm really not trying to be cryptic or difficult here)

 

i understand fiber is isolated.  replace the fiber with copper (not isolated).  what would i measure that would not be there with fiber? (i.e. the objective benefit of isolation if it exists)

 

measurement A (with copper, no isolation)

measurement B (with fiber, provides isolation)

 

A-B=benefit of isolation/fiber (assuming fiber isolation provides an objective measurable benefit)

 

so what would the 'measurement' procedure be?

[plissken]

21 minutes ago, cat6man said:

 

guys, you really don't get my question (and i'm really not trying to be cryptic or difficult here)

 

i understand fiber is isolated.  replace the fiber with copper (not isolated).  what would i measure that would not be there with fiber? (i.e. the objective benefit of isolation if it exists)

 

measurement A (with copper, no isolation)

measurement B (with fiber, provides isolation)

 

A-B=benefit of isolation/fiber (assuming fiber isolation provides an objective measurable benefit)

 

so what would the 'measurement' procedure be?

 

Far as I'm concerned would be single or multi-tone test from DAC output into a very good ADC. 

[cjf]

20 minutes ago, cat6man said:

so what would the 'measurement' procedure be?

Maybe the simplest  test would be to grab your favorite AM/FM clock radio or similar and tune into an AM band without a radio station, turn up the vol a bit and run the antenna near the cat based eth cable first and listen to the hash, noise...etc then do the same to the fiber cable.

 

You would have to be measuring the cables themselves and not the termination points as that is were the elc connection starts for both cable types.

[cat6man]

36 minutes ago, plissken said:

 

Far as I'm concerned would be single or multi-tone test from DAC output into a very good ADC. 

 

has anyone done this to prove or disprove that fiber isolation helps?

[cat6man]

34 minutes ago, cjf said:

Maybe the simplest  test would be to grab your favorite AM/FM clock radio or similar and tune into an AM band without a radio station, turn up the vol a bit and run the antenna near the cat based eth cable first and listen to the hash, noise...etc then do the same to the fiber cable.

 

You would have to be measuring the cables themselves and not the termination points as that is were the elc connection starts for both cable types.

 

simple but useless to evaluating if we might be getting an audible and measurable difference.

[cjf]

11 hours ago, cat6man said:

simple but useless to evaluating if we might be getting an audible and measurable difference.

I see. So the person asking everyone else how to conduct a test and measure results because "they" dont believe there are isolation benefits to using fiber is now all of a sudden qualified to judge if a proposed test has any value. Interesting.

[cat6man]

5 hours ago, cjf said:

I see. So the person asking everyone else how to conduct a test and measure results because "they" dont believe there are isolation benefits to using fiber is now all of a sudden qualified to judge if a proposed test has any value. Interesting.

 

nope, you still have it wrong.

 

i, in fact, do believe it but the test you propose is too artificial and contrived to prove that it has a benefit on a reasonably well designed and configured audio system.  i have no doubt that it is not good running a copper wire past my microwave or a power saw, and that a fiber connection would have more isolation or immunity. 

 

@plissken had a reasonable suggestion for a test but unfortunately i do not have test equipment available.

has anyone done a test as suggested by @plissken?

[kennyb123]

20 hours ago, cat6man said:

 

has anyone done this to prove or disprove that fiber isolation helps?

I think it’s important to point out that all fiber only isolates up to the receiver.  The FMC is a powered device that could leak noise back into the system.  I mention this because the measurement method needs to account not just for the fiber run but also the transmitting and receiving electronics.  That points us right back to what Chris first asked. 
 

I do think that ground plane noise at the transmitter may introduce receiver jitter.  The Startech FMC used upstream had a noise signature not evident in the opticalModule.  Measuring all this would likely require some higher-precision equipment.  And that finally leads me to an answer:  “that fiber helps” is too broad of a term to begin with, at least as far as considering it objectively.  The hypothesis must be “testable”.  It must be able to be proven true or proven false.  If “it depends” then the hypothesis needs to be narrowed.  

[plissken]

1 hour ago, kennyb123 said:

I think it’s important to point out that all fiber only isolates up to the receiver.  The FMC is a powered device that could leak noise back into the system.

 

At this point your only option is to win the lottery and hire a permanent live band. 

[Audiophile Neuroscience]

14 minutes ago, plissken said:

 

At this point your only option is to win the lottery and hire a permanent live band. 

 

I think before squandering money on a permanent live band, to be objective about it, you would need to run them through a very good ADC then DAC output into a very good ADC. Tested blind of course!🤷‍♂️

[plissken]

Just now, Audiophile Neuroscience said:

 

I think before squandering money on a permanent live band, to be objective about it, you would need to run them through a very good ADC then DAC output into a very good ADC. Tested blind of course!🤷‍♂️

 

If I saw that many gremlins in a hobby I would pick a new hobby. This is getting absurd. 

[kennyb123]

28 minutes ago, plissken said:

 

At this point your only option is to win the lottery and hire a permanent live band. 

I was happy to see an objective sub-forum created as it used to be that so-called objectivists kept intruding on subjective conversations.  It shouldn’t now be that the so-called objectivists who remained do the same thing to the objective conversations.  
 

Do you have any objective proof that my assertion is false?

[plissken]

1 hour ago, kennyb123 said:

I was happy to see an objective sub-forum created as it used to be that so-called objectivists kept intruding on subjective conversations.  It shouldn’t now be that the so-called objectivists who remained do the same thing to the objective conversations.  
 

Do you have any objective proof that my assertion is false?

 

You can use the search function. Years ago I did ADC captures and posted a D/L link when it was still Computer Audiophile.  I was randomly swapping an Ethernet cable in/out during playback.

 

No one could tell when the change was made.

[jabbr]

On 6/18/2020 at 7:33 PM, ray-dude said:

With the Planet Tech SFPs, I preferred copper NIC on the Extreme (fiber to the opticalModule+PlanetTech to copper to the Extreme).  With the Finisars, I'm back to preferring the optical NIC, esp. now that I have my audio network isolated from my home network, but it isn't a clear preference.  

 

FWIW, subjectively, reduced network traffic to the my music server NIC does have an impact.  This is contributing to my hypothesis of laser switching-induced electrical noise being the mechanism in play.

 

 

It is hard to know with "Startech" and "Planet Tech" equipment. Since you are not cost constrained, is there are reason not to use major brand 10Gbe or faster NICs, switches which have known engineering and are known to have gone through the stressed eye-pattern testing? Intel (I have x520), Solarflare (I have 6322f and 7322f), Mellanox (I have ConnectX-4 and ConnectX-5) hmmm .... let's see I know the jitter budget for the cards goes in reverse order (the new Mellanox is crazy low) but I can't personally hear a difference among those three NICs. I mean sure Finisar (and get a new SFP28 module for the Mellanox) but I can't vouch for any objective performance numbers on the equipment you list, nor do I know who makes the ASICs, lasers etc. My current path up to the endpoint is Mellanox FWIW.

 

But you are correct, some of the older, off-brand/generic fiberoptic hardware may not have been adequately tested (newer standards are tighter and tighter) so you can't make blanket statements about old fiber being automagically better.

 

What I *can* say is that leakage currents through the fiber will be zero!

[kennyb123]

54 minutes ago, plissken said:

 

You can use the search function. Years ago I did ADC captures and posted a D/L link when it was still Computer Audiophile.  I was randomly swapping an Ethernet cable in/out during playback.

 

No one could tell when the change was made.

What does “randomly swapping an Ethernet cable” have to do with my claim that:  “The FMC is a powered device that could leak noise back into the system.  I mention this because the measurement method needs to account not just for the fiber run but also the transmitting and receiving electronics.  That points us right back to what Chris first asked.”

[plissken]

1 hour ago, kennyb123 said:

my claim that:  “The FMC is a powered device that could leak noise back into the system.

 

Then why even bother with a Media converter? Other than the 328 foot length limitation of copper Ethernet?  You're still last legging it over copper.

 

The point I made should be evident: While audio was playing I removed the cable. While your audio is playing try removing the FMC.

 

If someone wants to send me an FMC I'll record a few tracks.

[kennyb123]

2 hours ago, plissken said:

 

Then why even bother with a Media converter? Other than the 328 foot length limitation of copper Ethernet?  You're still last legging it over copper.

 

The point I made should be evident: While audio was playing I removed the cable. While your audio is playing try removing the FMC.

 

If someone wants to send me an FMC I'll record a few tracks.

I don’t know what’s worse, his replies - or that I keep responding and expecting a cogent reply.

Clearly it was the latter.  I’ll add you to my ignore list, @plissken, as it’ll benefit the others here.  

[cat6man]

On 6/20/2020 at 9:06 PM, plissken said:

 

Far as I'm concerned would be single or multi-tone test from DAC output into a very good ADC. 

 

i personally define objective proof in audio as requiring measurements that confirm a hypothesis.

i do not include blind or double blind testing as 'objective' (your mileage may vary)

so let's continue on my version of a possibly 'objective' answer.

any engineers or scientists here?

 

i'll assume the audio precision top end stuff is sufficiently accurate (correct me if that is not right).

 

now, can the audioprecision (or other) equipment collect a histogram of DAC output as well as instantaneous peak errors or just averages?  when it plots snr vs. frequency for a single or multi-tone test, can it save peak or just average noise?

 

if so, can anyone point me to published material where the average vs. instantaneous and peak distortions are shown?

[plissken]

10 hours ago, kennyb123 said:

I don’t know what’s worse, his replies - or that I keep responding and expecting a cogent reply.

Clearly it was the latter.  I’ll add you to my ignore list, @plissken, as it’ll benefit the others here.  

 

These are your words, no?

 

" “The FMC is a powered device that could leak noise back into the system. "

[pkane2001]

1 hour ago, cat6man said:

 

i personally define objective proof in audio as requiring measurements that confirm a hypothesis.

i do not include blind or double blind testing as 'objective' (your mileage may vary)

so let's continue on my version of a possibly 'objective' answer.

any engineers or scientists here?

 

i'll assume the audio precision top end stuff is sufficiently accurate (correct me if that is not right).

 

now, can the audioprecision (or other) equipment collect a histogram of DAC output as well as instantaneous peak errors or just averages?  when it plots snr vs. frequency for a single or multi-tone test, can it save peak or just average noise?

 

if so, can anyone point me to published material where the average vs. instantaneous and peak distortions are shown?

 

I have a feeling we've had this discussion before. First, you don't have to use FFTs to average the results. Use peak-hold or maximum value, instead. Any sudden temporary peaks will be present in the spectrum.

 

Second, you don't have to do the comparison in the frequency domain, you could do it all in the time domain. Exactly what DeltaWave software does: take two signals and subtract them so as to find the difference. No averages used and any instantaneous peak errors will become obvious. It computes all kinds of metrics from this, including jitter, group delay, linearity, etc., etc. or just zoom-in on the difference waveform. Look at the individual samples, if you want, or look at it in the frequency domain, on a phase plot, or a spectrogram. It'll even tell you how close to bit-perfect the capture is.