Harry: I’ve had similar experience. An LPS on my server and optical isolation improved the sound in my system quite notably…and I did test it extensively.
@Graeme_Finlayson : I happen to think optical isolation has improved the resolution and soundstage on my headphone path which includes some very decent equipment, so we will disagree about that. But I do agree with you that optical isolation can be had at much cheaper price point than SmallGreenComputer and others sell it for. FinisarSFP’s can be obtained for a fraction of the price as sold by Sonore distributors…and FMC converters are cheap too. So for many, it would be a reasonable investment to set up optical isolation late in their path for ABX testing. This is what I did. After much testing, I put optical isolation in the path of other setups I have, and I am convinced after a lot of listening that it improves things.
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@Harry_Brandt I will concede, there may be instances where optical isolation improves matters. The only technical example I can think of would be where one is using ethernet cabling of Cat6A or above. In doing this, Ethernet’s inherent galvanic isolation is defeated, allowing a path for noise or ground loop hum to enter the analogue circuitry.
Optical isolation restores the compromised galvanic isolation to put one back where one should have started (Cat6 at most).
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Hi Graeme. How would one know if a system is impacted by noise or groundloops? Does this happen with all Cat6A or above, or is it rather the exeption? I use CAT7 and my system sounds great, but wondering based on your info if I should switch to Cat6. I do not make any claims, I have never done any comparisons, and just assumed like many others that Cat7 has the potential to eliminate noise due to better shedding. Kind regards
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You could try playing a “silent” test tone created in Audacity or a -120 dBFS test tone in REW and winding the volume up to see what you can hear vs winding the volume up with nothing playing. The first ensures that your DAC doesn’t mute with nothing playinng to it. With the second, your DAC may or may not mute, so it may sound different. You’re listening out for noise and mains frequency hum (50 or 60 Hz depending on your country’s mains frequency). If you have a ground loop, you’ll normally hear the mains hum very prominently.
Some Cat 6 and Cat6A patch cables are UTP (unshielded), some are FTP (foil shielded) or STP (braid shielded). I’ve simplified a little here, if you want the full breakdown, This guide expalins it. Cat6 UTP is all you need for music streaming. In fact, basic Cat5 can easily satisfy music streaming’s bandwidth needs. For really long cable runs Cat6 FTP may be marginally better in terms of shielding than UTP, but the foil shouldn’t be connected to ground at either end. I have some Cat6 F/UTP installed in a duct between the house and the office, but all of the faceplate modules and patch panels are Cat6 with no earth connection.
Shielded patch cables will have a metal part on the plug body to connect the shielding to ground at both ends of the cable. This is where ground loop issues and noise can occur. You’re connecting the grounds of two pieces of equipment together via the cable shielding which defeats ethernet’s galvanic isolation.
Cat7 and Cat8 are always shielded (S/FTP) and will allow ground continuity between connected equipment.
Cat7 is an oddball in that it doesn’t really exceed the capability of Cat6A and doesn’t have ANSI/TIA approval, only IEC/ISO.
Cat8 is designed for use in data centres and server rooms where high bandwidth (typically 40GbE) and minimal crosstalk is required.
I hope this helps.
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Thank you for the detailed response, Graeme, it does help. One more question. If one has multiple CAT7 cable’s in the chain, say from optical network box to Router, from router to switch, and from switch to DAC, Devialet Expert Pro in my case, Does one only need to replace the cable from switch to DAC to achieve desired galvanic isolation? Kind Regards.
CAT-7 data wires (TX/RX pairs) are galvanically isolated, but the cable screen will connect the safety/case grounds together, and this might cause audible hum (through the power rails) depending how the ground circuit is bonded, eg. if the negative rail is bonded to safety ground (which it often is, but its not a given).
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Simple message is not to use CAT7 and beyond if audio is concerned. CAT5e and 6 are perfectly fine. Stop right there. UTP (unshielded!)
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^ exactly, STP is designed for specific applications with specific challenges, not encountered domestically.
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Yes. After all, you’re only isolating the DAC, so that one cable is the key. You might consider replacing other cables that may go to sensitive electronics, but that’s another issue.
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Hi Graeme, so I specifically ordered a CAT 6 UTP and delivered to me is a CAT6E cable, not what I ordered. Is my understanding correct that CAT6E has a foil , which is connected to ground, with the same potential issues as 7, or 8? Best.
Cat-6e probably doesn’t have a foil shield… check the RJ-45 ends, if there’s a foil there’ll be metal shielded connectors - connecting equipment like this can cause ground-loops:
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Hmm, Cat6E isn’t actually a recognised standard, though some manufacturers label cable as Cat6E. It has a higher twist rate than Cat6 and a claimed higher bandwidth.
It is often shielded and grounded at the ends. You can easily tell if it is shielded as there will be metallic parts on the RJ45 plug:
An unshielded plug is all plastic:
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In my experience, fiber gives an increase in clarity, but also slightly thinner sound. I still prefer it though, and is using an opticalModule for fiber conversion (fiber from computer to opticalModule, then homemade ethernet adapter to streamer).
I have some HiFi friends who don’t like fiber though, since it does take the sound a step away from “analog” sound.
Btw, opticalModule gives a slight increase in SQ compared to the cheap TP-Link MFC I used before.
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Replace the speakers, for “thicker sound” speakers 
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@Magnus - What are you using as SFP? And switch?
I have a Cisco Meraki Go 8 Port Switch (GS110-8-HW-EU) and it is not sure if it will work with Finisar SFP
I don’t have a switch, but 1 extra fiber network card in computer (and 2 regular ethernet ports on motherboard). Don’t remember what SFP I used, but same as is delivered with opticalModule.
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Finisar SFP works with my Meraki MS220-8P
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