Living Room System

Friday, August 29, 2014

John Siau on DSD

This is a great read for DSD non-believers like me, and I think I've linked it before also.

John Siau does not say that DSD is a bad distribution medium.  Like people I've read at Hydrogen Audio, Dr. Siau believes DSD to be roughly equivalent to PCM.  But it creates many issues for mixing and mastering, as well as end user DSP for DSD purists.  Siau says conversion of DSD into PCM is fine, it's the conversion of PCM into DSD that raises issues.


Thursday, August 28, 2014

New Sonos in 2nd bedroom sounding great

Gallo speaker mounted in right upper corner of bedroom 
In the past week I've fixed two fundamental problems with Sonos in the 2nd bedroom.  First, I made it possible to get the ethernet connection from the Kitchen (which has a Dlink fast managed switch that now directly connects to all Sonos boxes in my house) instead of the Computer Room (where the old internet router creates a bottleneck for the whole network), by changing the HDMI over Cat6 video extender to a better model which only requires one Cat6 cable, leaving one of the Cat6a STP lines from Kitchen to 2nd bedroom available.  Then, I figured out how to fix the persistent ground loop without ground lifting the Parasound Zamp V.3 amplifier--by attaching the Sonos box with a short length of unshielded ethernet cable.  (Currently using an ethernet coupler at the end of the existing 10' Cat6a STP which attaches a 5 ft Cat5e UTP, the best short UTP I could find on hand; I have purchased online a 10' Cat6a UTP which will ultimately replace the 10' STP.)

On Tuesday I went even further and figured out how to get mono out of the Sonos box with two Harrison Labs attenuators and a Y adapter.  I also neatened up the cabling somewhat (though you might not see that from the picture) and tucked the bare metal shielded ethernet coupler (possibly having some inductive leakage, though I couldn't feel any) in between the gear so it would not be touched by dog or cat under the desk.

Zamp, Sonos, and outlet strip installed below small desk

It makes a huge difference to get the full L+R output rather than just Right Channel even though there is still only one speaker.  I've started working on mounting the Left speaker but it may not be fully hooked up for awhile because I'm planning to use "invisible" paintable flat cable.



I was enjoying listening to KPAC over the Sonos in this room, in true mono L+R, while simultaneously playing line inputs through all other Sonos boxes in the house.  Using the line-input feature in Sonos is the hardest test of Sonos networking, and in my experience, the most valuable usage of Sonos.  In one test, I was even playing the input from the master bedroom on the 2nd living room box, even though that box isn't hooked up to anything.  With all 5 boxes in line-input play on other boxes, I might have heard some glitching while I was brushing my teeth (so I couldn't be sure it wasn't the station having trouble at 5am).  When I rolled back to the 4 boxes I actually play from, there hasn't been any glitching in 3 days.  So the new network design using a fast switch in the Kitchen is now a proven success.

(When first setting up the 5 line-input test, the living room box hung and needed rebooting.  That box has needed a lot of rebooting over the last few years and possibly should be replaced for better health of the entire system.  Since the last reboot, however, everything has been running fine and glitch free for days using 4 boxes for playback of line inputs on other boxes--except that the living room box has only been used to play it's own line input.)

Tuesday, August 26, 2014

ZSYS

Dirac vs REW vs DSPeaker

This is quite a long blog about Dirac at WBF and it was all worth reading.

DSPeaker like REW appears to be minimum phase and IIR based.  Dirac is mixed phase and so can correct some additional time delay problems.

I just can't use full range correction with electrostatic speakers because they are very complex in the high frequencies.  Tiny changes in position make huge differences in response.


Sonos Hum caused by STP cables

I'd started to think it was inevitable that there would be hum in the 2nd bedroom Sonos unless I ground lifted the amplifier.  The previous version of the Parasound Zamp V.3 did have a ground lift switch, but mine does not.  It seemed possible that it had been shipped with a 2 wire power cord, but I have been unable to get that confirmed.  I tossed the original power cord into my spare box without checking until later, and when checking later the cord that most likely came with Zamp has only two connectors on the plug (but three slots in the IEC female portion that connects to chassis).

Ground lifting the amplifier might not meet electrical code UNLESS the amplifier was supplied with the ground lifted cord.  And even then, a paranoid electrician might say you are better off having the actual ground connected, which the 3 connector IEC on the chassis permits.  Some equipment is deliberately designed with 2 wire IEC connectors which can't be grounded no matter what kind of cord you attach.  But not in this case, grounding is clearly an option, and an option which would be better used if possible, any good electrician would say.  It protects both against breakdown of the insulation in the amplifier transformer, and current which might be carried inadvertently by the network cables (say, if they had an insulation failure in the attic).

An extra line of defense in my case is that the circuit to which the amplifier is attached has an upstream GFCI outlet which provides GFCI to this outlet.  I tested it with a GFCI tester to be sure.

However, despite all my precautions, my friend who is interested in staying in the Queen's room is never convinced I'm a safety freak (compared with most audiophiles, anyway, who often ground lift and neutral reverse with enthusiasm).  She's constantly convinced I'm creating some kind of electrical safety hazard, even though the truth is I'm constantly thinking about safety issues that hardly anyone else thinks about.  "Everybody does it" would not be an acceptable alibi if she discovers something arguably substandard about the wiring.  This would prove, finally, that I'm a reckless fool to be watched constantly.  So I do really want to do things "the right way" especially in this room.

I have not had a hum problem with any other of my Sonos connections.  I suspect Sonos uses ethernet transformers for the network connections.  But it occurred to me that a ground loop could be caused by the shielding in my Cat6a STP network wiring.

So I tried isolating the ground by using an ethernet coupler to attach a second piece of unshielded network cable.  Sure enough, that fixed the hum!

(Other "fixes" like using short and stout RCA line cords didn't help.)

Now I had been persuaded that shielded network needs to be shielded everywhere.  And I think that's generally desirable.  But this is only one line that goes straight back to the main fast switch in the kitchen.  I believe it won't cause any harm to the rest of the network to have the very end of this line unshielded and ungrounded.  The ethernet line is way shorter than the maximum run of 330 meters, more like 40 meters.

In fact, I've seen this specifically advised for home networks.  Only shield ethernet cables at one end, some people say.  Others, a whole slew of professionals, recommend avoiding shielded cables altogether, and especially in the home, saying that it's incredibly complicated and difficult to terminate the shielding correctly.  But my thinking now is that the solution is easy.  When ground loops occur, lift the cable shields at one end.

The problem here must be that the Sonos modules wouldn't be correctly designed for use with shielded cables because they have no ground connection themselves.  It's funny, however, that this has never caused a problem before, especially for the last year (that's how long it's been) since I installed an all new home network with all Cat6a STP cables.  When an ethernet shield enters the Sonos chassis it becomes, for all purposes, the effective ground.

I've decided to make the permanent solution a new 10 ft length of unshielded Cat6a cable, from the wall panel to the Sonos box in the queen's room.  Using a coupler is ugly (and the current coupler is especially ugly because it's a Cat6a Shielded coupler, and I think all exposed metal is connected to the shield, making it no good for wet noses.

I don't think the 10 foot length of unshielded cable on one dedicated line will adversely affect my overall network at all.  And the Queen's room is a relatively low RFI/EMI area anyway.  The main purpose of the shielding was to protect the long runs of cable in the attic.

I did also order a 1 foot length of unshielded cable and could use that with a nice unshielded coupler.  That way I could limit the amount of unshielded cable to 1 foot.

Monday, August 25, 2014

EQ thoughts

I'm now leaning toward getting the OpenDRC-DI hardware for room correction, and using Room EQ Wizard to design the filters.  I like the fact that OpenDRC-DI has AES/EBU digital connectors, which can plug right into my existing system, and make the best digital connections over short range.  I like the fact that R.E.W. is an open software product, and I can see what it is doing, and possibly what I would like to change.  The downside of this solution is that I believe it does not allow for multipoint correction.  In contrast, DSPeaker dual core does have a multipoint correction feature, though it is not clear how well it works (and the manual doesn't talk about it much).  And it has only Toslink digital connections, which don't work well with much of my stuff (such as the DCX2496, which has no Toslink input, and my Tact 2.0 RCS, for which the Toslink output seems to be no longer working).

OpenDRC is actually more powerful than some other MiniDSP products.  It has enough power to run both IIR and FIR filters.  REW apparently creates IIR filters, much like old fashioned analog filters.  FIR filters allow for the correction of phase and amplitude separately, which makes it possible to do lots of interesting things, such as remove the time delay variation produced by a speaker crossover, or design a speaker crossover with no group delay.

Sophisticated commercial correction products (Acourate and probably Dirac) use FIR to correct system phase response, but that goes along with doing a full range correction.  I strongly dislike full range correction and want bass EQ only.

http://www.minidsp.com/forum/minidsp-for-newbies/7204-can-i-use-rew-with-opendrc-di-for-roomcorrection-answered


Friday, August 22, 2014

Belden 1695a is Teflon FEP (not the holy grail, Teflon PTFE)

Teflon is an audiophile holy grail.  It has superior dielectric properties to all other plastic dielectrics.

So based on that, I was about to buy a Belden 1695a cable for the final stretch of my SPDIF line from kitchen servers to living room stereo.  Instead of 1694a, which is basically the same, but uses PE foam instead of "teflon."  Even though it's a digital line, the dielectric properties could be important.

But reading the fine print, I see that the Teflon used in 1695a is Teflon FEP.  This is not the Teflon that audiophiles seek out (if they know what they are doing, anyway).  Teflon FEP has dielectric nonlinearities 6 times greater than Teflon PTFE.  Comparing the linearity of FEP with Foamed Polyethylene, I'm not sure which is actually better, but I suspect it might well be the Foamed Polyethylene.  I know that's what my friend Tim thinks.

So I'm getting the cheaper 1694a.

I feel similarly about the FEP used in Valhalla cables.  I don't think much of it.

I wonder about the Teflon used in Cardas cables.

Meanwhile, I've decided to get 1695a to connect the Oppo to the SPDIF panel in the kitchen, because the 1695a is said to be slightly more flexible.  I used 1505F for the line from Mac to SPDIF panel because I thought that needed some more flexibility also.  Now I think I might have used 1695a for that one as well, regarding the solid core 1695a to be the better cable compared with 1505F.