Objective-Fi Optical Networking & SFPs

[kennyb123]

8 hours ago, plissken said:

 

From my POV:

 

1. It doesn't make a SQ difference

2. It adds unnecessary cost

3. It adds unnecessary complexity

4. Everyone knows what an RJ45 Ethernet cable is

5. WiFi offers just as much isolation while providing more than enough throughput on 5G / 80VHT

 

Per Chris' post:  "I'd like to use real science and a real scientific approach in this one. This means, we may have a belief one way or the other, but we should go into this with an open mind and follow the available objective evidence."  Can you provide any objective evidence?

[kennyb123]

On 6/15/2020 at 8:38 AM, The Computer Audiophile said:

Hi Guys, this is an objective topic to look at the assertions made by some that SFPs make a sonic difference in audio systems. I'd like to use real science and a real scientific approach in this one. This means, we may have a belief one way or the other, but we should go into this with an open mind and follow the available objective evidence. 

 

Great topic! Thanks for posting this.

 

@ray-dude has put forth the hypothesis that SFPs that draw lower power will sound better.  Thus far the subjective evidence seems to back this.  I'd love to understand why.

[kennyb123]

7 minutes ago, plissken said:

 

Sure. Would you take a ADC capture of a recording where I swap out cables during playback?

 

No, because none of your claims referenced audio.  For example you claimed that "WiFi offers just as much isolation while providing more than enough throughput on 5G / 80VHT".  I'd love to see proof.

 

Correction, your first claim did reference sound quality.  Your test would be acceptable only if you proved that your methodology was capable of detecting known differences that impact sound quality.  In other words, add noise to ethernet until the output changes to see if your test can identify this.

 

 

[kennyb123]

Just now, plissken said:

 

This is the objective-fi sub-forum.

 

Yes it is.  Hoping someone is able to provide some objective insight.

[kennyb123]

Just now, plissken said:

@kennyb123 What objective data would you accept?

 

 

[kennyb123]

9 minutes ago, plissken said:

 

Ok. so if I spin up my ADC, connect my DAC to it's MIC inputs, and capture 1Khz with both SFP+ and make available for download would you evaluate those?

 

If current circumstances didn't prohibit it: If I came out to you on you're setup with my playback computer with my dual SFP+ Solar Flare card and did this with you blind, would you evaluate that way?

 

We've gone round and round on conducting a proper test.  I'm sorry - but I have to ask you this:   what was your educational background?  You don't seem to be able to understand how to properly conduct experiments.  Nor do you seem to understand the need for experiments to be done properly.

 

Here's a picture for you.  See the "procedure working" step?  See the how the results that don't align only lead to constructing a new hypothesis.  You ignore these things.  

 

[kennyb123]

10 minutes ago, plissken said:

 

Ok, let's put up a hypothetical:

 

You've just met a person that says they, from a standing position, jump up and clear a 10' high bar.

 

Do you design an elaborate test or do you bring out a tape measure?

 

That you see this as analogous to the differences we are hearing is not at all surprising to me.  Your tests are constructed to take measurements without the necessary precision and you can't even see this.

 

This in an objective sub-forum.  Your approach would earn you an F and lots of derision at any engineering school.

[kennyb123]

5 minutes ago, ray-dude said:

 

FWIW, at the engineering schools I went to the reaction would have been "No way!  Let me hear that...  Huh...  Wow...  What the hell is going on?  Cool, let's try to figure this out!"  This is the exciting stuff!  I hope that is the spirit of this thread.

 

 

Same here.  I miss seeing that kind of curiosity.  

[kennyb123]

5 minutes ago, plissken said:

 

I've zero issue with that. I would even be willing, when this covid madness is over, set this up single blind and see you demonstrate this ability.

 

 

 

 

[kennyb123]

3 hours ago, Superdad said:

One thing I will point out--which I think you might find interesting--is something sort of obvious but overlooked:

All Ethernet RJ45 copper connections go though both a set of transformer cores (typically 2~8 tiny wound round cores, though for EtherREGEN we use 12-core-per-port magnetics) and PHY transceiver circuitry (mostly these days built into the Ethernet switch chip, but for some switches a discrete PHY chip, per port or grouped, is used--ala the old Cisco Catalyst 2960s, likely one of the things that made them special).

And the signals for SFP cages are always wired directly to the switch chip via the processor's SGMII interface (or even QSGMII or XGMII for much higher speeds--though those are not via SFP cages). Aside from that direct interface perhaps not activating as much circuitry/generating ground-current noise/clock-threshold jitter inside the chip, SGMII is also an LVDS interface, and that carries some advantages.  

Lastly, most good switches will dedicate a 3.3V regulator to provide power to whatever SFP transceiver is plugged into the cage (as we do with an LT3045 just one centimeter behind the EtherREGEN's SFP cage).

 

@Superdad any chance you can summarize this for me?  It sounds like you are saying that one interface has an advantage over the other, but I’m unfamiliar with some of these terms so I’m not able to interpret which is better and why that’s so.

[kennyb123]

1 hour ago, Superdad said:

 

Some of those might be an advantage favoring the use of optical, some of them might instead favor--or at least influence interaction (and sonic differences)--towards copper.

 

 

Ah maybe that's why I was having difficulty determining if you were saying one was better than the other.  Appreciate you sharing those insights. 

[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.  

[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?

[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.”

[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.  

[kennyb123]

5 hours ago, bluesman said:

 

The problem with most amateur DBT is how it’s done, not the principle behind it.

 

DBT proponents seem to see this as feature and not a bug.  Their desired outcome is guaranteed and made bulletproof (so they think) because properly-conducted DBT has been demonstrated to be a valid research tool.  Valid questions about how the test was conducted are ignored.  That's why I've said that those who press for amateur DBTs are actually the ones behaving like snake oil salesmen.  

[kennyb123]

27 minutes ago, bluesman said:

Maybe they just don't know enough about it to do it right (or that it's not a valid methodology for answering the question being asked). You're talking about a fairly sophisticated methodology that requires specialized knowledge.  When you encounter a specious application of it, you'd be of much more help identifying the flaws in it than simply dismissing it. 

 

Name calling reduces you to the level of those you're criticizing.  As they say at the airport, if you see something.......say something.  But you're only part of the solution if what you say is meaningful and constructive.  Otherwise, you're part of the problem.

False accusations reduce one to an even lower level.  Are you accusing me of not pointing out the flaws?  
 

I agree that name calling is bad but that’s different than employing a metaphor to illustrate the hypocrisy in holding certain positions.  The snake oil salesman pitching pseudo-scientific arguments in favor of a product that he knows isn’t going to produce positive results is very much akin to putting forth a blind test methodology one knows won’t produce positive results.

[kennyb123]

2 hours ago, ray-dude said:

I bring this up on this thread, because SFPs are falling into that same pattern for me.  This is a class of component where I'm finding I have to ignore my initial experience and preference, and gauge my mood after extended listening.  Do I want to listen to music longer?  Am I able to focus on work more or less when listening to music with a particular SFP pair?

 

Like my user experience example above, once I identify a long term preference, I then look for what short term identifyable characteristic is a "tell" for what that long term experience will be, then look for components that have more or less of that tell.  I'm starting to find that "tell", but I still have to lean into extended listening.

 

Very well said.  For me, spending more time listening to a SFPs has told me more.  Listening to music with varying levels of recording quality reveals what might be missed with a quick shootout.  Also the Pepsi and Coke example is very apt as something that might have sounded great after a shootout could very well drive you mad after extended listening.  

[kennyb123]

 

5 hours ago, jabbr said:

 

Why do you assume that in all or any implementations the laser actually turns on and off?

 

Whether it's on and off there is electrical activity that brings about whatever the laser is doing.  

 

5 hours ago, jabbr said:

 

https://www.optcore.net/transceiver-laser-types/ the more modern lasers are DML/DFB and EML https://community.fs.com/blog/silicon-photonics-and-lasers-in-100g-optical-transceivers.html

 

In any case if there is an irregularity on the power/ground planes, this would be evident in the eye pattern, no?

 

I'm really trying to understand what lasers are doing if not on and off.  Any chance you could explain what is actually occurring instead of providing links that don't clearly explain this either?

 

The article from FS that you provided mentions "injecting current".  The link mentions this too.  If current is being injected, why is it wrong to assume that this could result in a "pulsing load on the power lines"?

 

[kennyb123]

 

4 hours ago, jabbr said:

This has a list of SFP/SFP(+) and QSFP(+) modules with the type of laser in https://www.finisar.com/sites/default/files/resources/finisar_optical_transceiver_product_guide_3_2015_web.pdf

As you can see the SFP multimode modules tend to be VCSEL and the single mode modules tend to be DFB ... as of 2015 

 

Thanks!  
 

The text at the end is repeated in their data sheets. “Finisar’s transceivers feature a microprocessor and diagnostics interface that provides performance information on the data link. Users can remotely monitor—in real-time—received optical power, transmitted optical power, laser bias current, transceiver input voltage and transceiver temperature of any transceiver in the network.”

 

The only way I’ve found to see this is when I use one of their SFPs in one of UniFi switches.  Not sure why current is 0, but it could be that it requires UniFi products at both ends.