I have been using TP-Link 200 models on my network for a little while and they work fine but do seem pretty slow. I live in a house built in 1936 and it's a big rambling place and I do not know about the wiring in it. btw 200 refers to the max speed obtainable and may well be an optimistic number, be surprised if it weren't!
The speed of the 200s became a problem when I tried to stream 24/192 WAV files to my NAIM UnitiLite from a QNAP NAS. These are transcoded from FLAC btw, not that that should make any difference to network throughput. The NAS is connected to a Megabit switch and thence to the powerline adaptor, from the other end of the adaptor it makes no difference to performance if it goes to NAIM directly or via another switch (not megabit). I also have a powerline adaptor in my office upstairs at the back of the house and this works OK but is slowish but acceptable for most things.
So I decided to invest in the purchase of kit of 2TP-Link 500s and I set them up and bingo it worked just dandy. 24/192 files gave a 100% buffer, my vast outlay (<£20) on powerlines proved to be a good investment. I say vast because I have 1 Jewish grandmother and I Scottish grandfather. Och aye the noo, Oy Vay.
Now last night was Yoga night for the missus and so I sat down for a nice loud session through my speakers and all was well..... Until I played a 24/192 file and I kept getting buffer underruns --> buffer to 0% and music stops for a while. What!!???!!!
Why did it work on the morning I set it up but not in the evening? I was not running a download or anything like that. In fact apart from my iPad all computers were off.
Well I have an idea. After I setup the 500s I connected in a 200 unit just as a test, it seemed to connect OK. So I disconnect and relegated it to my memory for further tests and possible use on my office computers. Now I expected that when I connect a 200 to a network of 500s then the lowest common denominator comes into play and everything collapses to a 200 network. I think that must be the case.
Now the 500 powerline adaptor next to my NAIM is powered off every night but the one next to the NAS is not. So is it possible that an adaptor when it drops down to powerline 200 speed then it stays that way and won't go back to 500 until it is powered off and then on?
So I did the obvious thing and powered off the powerline 500 next to the NAS, so now both had been powered off. Run the test with a 24/192 file and bingo it works fine - 100% buffer all the time.
Anyone got any ideas? The final test will be to test it again this evening at about the same time as I had problems last night. It could be that the mains voltage is different in the evenings from that during the day. Just don't know if this is the case and whether or not it will affect Powerlines.
Posted on: 06 June 2014 by rjstaines
You're not alone BB. I have installed a TP Link 500 system with 3 receivers handling three Naim streamers (Uniti2, UnitiLite, & a Qute2) all fed from a Unitiserve and installed in a large house mansion with dubious electrics.
Sometimes it all plays fine, other times one (but just one) of the devices buffers - the Uniti2 and the Qute2 have done this.
Plan B is to move the Uniti2 from a Powerline connection to a wired LAN and to move the 'Serve and TP-Link gigabit router closer to the mains distribution boxes (all 3 of them !)... and after that to keep fingers crossed 
If YOU find anything that firms up or fixes the scenario, I'd love to hear about it ! Likewise if I do, I will post back here.. As this is a customer, not my own place (like I could afford a riverside mansion - not), my next outing is mid June to install plan B, so no feedback from me till then.
"Bon chance" as they sometimes say in Salisbury 
Posted on: 06 June 2014 by Big Bill
Blimey I only have the one device!
I have often wondered just how these Powerlines run things. LAN Ethernet wiring has had 2 incarnations: (I) Coax - which is a long piece of coax but broken in places to insert T-pieces to connect a device to an (II) UTP (Unshielded Twisted Pair) cable originating from a hub or switch. But what is the structure of Powerlines over mains? If one powerline device transmits then all of the others will receive it, but these may be connected to a hub or switch. So what happens then? Anyone know?
Posted on: 06 June 2014 by Big Bill
Actually the way to understand these devices is to think of each one as a hub (or switch) and the mains is the UTP connecting the hub (or switch). That's simple, why didn't I think of that before. NO, that doesn't work because all powerline adaptors are connected to all other powerline adaptors in the network. Oh um.
RJ I will do some more 'speed' tests BUT I can't see how you could drive 3 of these beasties on a Powerline network at the same time, unless of course you are running 16/44 FLAC files only. Or your mains is better than mine
Posted on: 06 June 2014 by Simon-in-Suffolk
Bill, indeed, RFI issues aside, this is one of the key drawbacks in my mind of these devices, as clearly with a hub (as opposed to a switch) only one device can use the network at a time. Probably ok for casual use until low latency and discovery protocols are working amongst steady throughputs like media transfer, where the network could start to get clogged.
Simon
Posted on: 06 June 2014 by Big Bill
Originally Posted by Simon-in-Suffolk:
Bill, indeed, RFI issues aside, this is one of the key drawbacks in my mind of these devices, as clearly with a hub (as opposed to a switch) only one device can use the network at a time. Probably ok for casual use until low latency and discovery protocols are working amongst steady throughputs like media transfer, where the network could start to get clogged.
Simon
Well I always thought that a switch differed from a hub because it partitions the network into 'collision-domains', or is that what you meant. Do you know for sure that a powerline net behaves like a hub (ie one collision domain only).
Mind you for my little network it doesn't really matter. What worried me was that it worked at 24/192 at one time and not at another time and as I said above I have a theory but don't actually know.
Posted on: 06 June 2014 by Simon-in-Suffolk
Yep that is what meant, ie the hub uses the connected network as a single collision domain, that is only one device can use the network at a time, and a switch has a separate collision domain on each port, that is each switched port can operate at the same time. As a consequence hubs can only work at half duplex, and switches can work full duplex.
As far as the Powerline adapters running effectively half duplex.. I don't know how the low level mechanism works for sure as it is proprietary, but the bandwidth is converted into phase shift modulated spot frequencies across the RF spectrum and when I looked at some frequency spectrum traces there was no obvious send and receive spectrum visible.. Which of course would half the bandwidth thru put.. Probably not attractive for the average consumer doing simple point to point.
I suspect there is some sort of semaphoring system to stop actual collisions, unlike with half duplex Ethernet.
Powerline devices are susceptible to mains interference as I am sure you are aware, and that will reduce throughput as the interference will mask out some of the usable RF spectrum. It could be when your throughput dropped you had a noisy device on the mains?
Simon
Posted on: 06 June 2014 by Big Bill
Originally Posted by Simon-in-Suffolk:
Powerline devices are susceptible to mains interference as I am sure you are aware, and that will reduce throughput as the interference will mask out some of the usable RF spectrum. It could be when your throughput dropped you had a noisy device on the mains?
Simon
No, as far as I could tell I did not. In fact this was one of my first thought and I turned everything I could off. As I said earlier all PCs were off, apart from my iPad, I even turned the fridge and freezer off, unfortunately the freezer alarm was still sounding when my missus got back from Yoga. Of course I can't tell if there is some external device that starts up in the evening near by that caused it.
I am still a bit confident that when the 500s drop down to 200meg that they stay until powered off - I live in hope. Otherwise I will have to wire it up and that is not going to be easy in my house, perhaps I could move. Hey that ain't a bad idea. 
I am now at about the time I was playing last night so I am going to try again now.
Posted on: 06 June 2014 by Big Bill
Nah, it looks like you are right - it fails again. I reckon it's my neighbours coming home from work and then downloading from the 'Gentleman's Sites'. If anything we have less stuff on than we do during the day. The missus has got the TV on at the moment but it is not a smart set or anything like that with a connection to the internet.
Just checked my NAS and nothing is happening their, no virus check or downloads.
The really annoying thing is that it is so marginal, a 24/172 file plays OK, it is that marginal. Luckily I don't have many 24/192 files but I suppose I will turn transcoding off. Be interesting to see what difference it makes or I could put the few I have on Twonky and not use transcoding there.
Cheers Simon, Thanks.
Posted on: 08 June 2014 by Big Bill
Originally Posted by Simon-in-Suffolk:
Bill, its hard to comment other than it is probable some device is interfering with the PLA at certain times of the day and thereby reducing its throughput. And by their nature they are prone to this. Perhaps the ultimate solution might be to hardwire?
Simon
It is the pattern that is so befuddling though, I will check again today as well. When it happens it always takes about 1.5 minutes from the start of the track to give a gap and why does Saturday behave the same as midweek days? It is a puzzle.
btw I have checked with a very long Ethernet cable (always a useful thing to have around) and it was OK - I did that test in the evening, although not by planning I should add it just was that way, it was on Yoga night. I have run a cable test on all cables involved, mind you why they should be time dependent I don't know.
We live in area where there is no industrial or commercial areas within miles of us and it is not a very built up area. The only thing I can think that is different at night is the streetlights but I get the issue at about 20:30 before the streetlights come on. The voltage of the mains may be different later on but that should not have an effect, compared to some parts of the world the UK mains voltage is fairly stable.
Yeah I would love to hardwire because that would mean end-of-problem and I think I might have to byte the bullet. Ah well.
Posted on: 08 June 2014 by Big Bill
Originally Posted by DWO-Naim:
Bill,
All good stuff above. Not seen it mentioned in the thread but have you tried using (borrowing?) a different manufacturers devices ie not TP. Some perform a bit better than others - reports are available on the Net. Also some appear to be more intolerant of routing via "consumer boxes" than others. Whilst this does not answer the timing issue it may just be that at those times of poorer performance another manufacturers device may be capable of maintaining the stream. Note it is usually not recommended to mix manaufacturers on each end of the link.
Yeah I will have a butchers at these but I only currently have 4 albums at 24/192 and one of those was a free sample. So I will probably go for a workaround for now. Like decreasing the sample rate in Audacity, the track I down sampled to 174 sounded OK, my other option is to save to a USB stick.
But ultimately I will have to hard-wire. My mem sahib is making noises about re-decorating our living room (where t'NAIM lives), so I will have to be careful and not sound too enthusiastic but slowly and slyly go along with what she says.
The room gets decorated and I can get rid of those ugly boxes stuck in the mains sockets dear. Hey that works for me.
