I couldn't figure out how to link in images properly (new here and forum noobish), so I attached some of the results from dslstats.
I had a look into the possible power issue with the technicolor tg582n, and found this
http://npr.me.uk/telnet.html#cpu, and tried turning off the power saving features as suggested but the router became unstable for me so it didn't improve it but I don't think there's any power issues for me anyway. I'm not sure which set of tests reflect when I tried that (it was late) and it became unstable, but I'll post one set from when I think the line lost sync (test1). I just included basics for this, put in some more in test2 as I took snapshots of important changes this time.
The average errors:
Average error rates over a 24 hour period
24 hours starting 16 Feb 2014 14:20:23
Per second Per minute Per hour Per day
CRC Up 0 0 0 0
Down 0 0.01 0.44 10.5
FEC Up 0 0 0 0
Down 0.02 1.19 71.6 1718
HEC Up 0 0 0 0
Down 0 0 0 0
ES Up 0 0 0 0
Down 0 0 0 0
Basically a lot of errors but when the SNR went down, the amount of errors went up.
In the second test I put in the xte-2005 and the shielded adsl cable with two ferrites on it. I don't have the latency problem like before, I'm sure it will come back at some point but the averages are lower (test2):
24 hours starting 17 Feb 2014 14:20:42
Per second Per minute Per hour Per day
CRC Up 0 0 0 0
Down 0 0.01 0.41 9.79
FEC Up 0 0 0 0
Down 0 0.26 15.3 367
HEC Up 0 0 0 0
Down 0 0 0 0
ES Up 0 0 0 0
Down 0 0 0.20 4.90
This is over a longer time period than the last test, but I still think the errors are less.
Posting a fair few hours later but these are the stats now from the web interface:
Uptime: 0 days, 18:09:38
DSL Type: ITU-T G.992.5
Bandwidth (Up/Down) [kbps/kbps]: 973 / 12,189
Data Transferred (Sent/Received) [MB/GB]: 234.03 / 2.66
Output Power (Up/Down) [dBm]: 12.3 / 19.8
Line Attenuation (Up/Down) [dB]: 13.3 / 23.5
SN Margin (Up/Down) [dB]: 14.9 / 15.0
System Vendor ID (Local/Remote): TMMB / ----
Chipset Vendor ID (Local/Remote): BDCM / BDCM
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): -
Error Seconds (Local/Remote): 3 / 0
FEC Errors (Up/Down): 0 / 677
CRC Errors (Up/Down): 0 / 5
HEC Errors (Up/Down): 0 / 9
I've had a listen on the quiet line test again, but with another handset and it's quieter with this handset but still with a low hum. So, maybe the line isn't that capable or could it still be noise/interference?