even faster broadband

Discussion in 'NZ Computing' started by Peter, Aug 14, 2010.

  1. Peter

    Murray Symon Guest

    Stephen Worthington wrote:

    > On Tue, 17 Aug 2010 12:38:30 +0000 (UTC), Sweetpea
    > <> wrote:
    >
    >>On Wed, 18 Aug 2010 00:28:59 +1200, Stephen Worthington wrote:
    >>
    >>> The VDSL2 splitters are better as the filtering has a very sharp cutoff
    >>> to allow more bandwidth for the DSL signals.

    >>
    >>How does that sharp filter affect the quality of sound on the telephone
    >>line?

    >
    > Not at all. The cutoff is still in the same place.



    "Sound quality" and "telephone line" in the same sentence??
    I thought that was just a sly joke at the expense of audiophiles.
    I remember the old days of debating CD player brickwall filters.
    I think some people must still react to the phrase "sharp cutoff"
    by getting upset about degraded sound reproduction.
     
    Murray Symon, Aug 18, 2010
    #21
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  2. Peter

    Sweetpea Guest

    On Wed, 18 Aug 2010 20:01:14 +1200, Stephen Worthington wrote:

    > On Tue, 17 Aug 2010 12:38:30 +0000 (UTC), Sweetpea
    > <> wrote:
    >
    >>On Wed, 18 Aug 2010 00:28:59 +1200, Stephen Worthington wrote:
    >>
    >>> The VDSL2 splitters are better as the filtering has a very sharp
    >>> cutoff to allow more bandwidth for the DSL signals.

    >>
    >>How does that sharp filter affect the quality of sound on the telephone
    >>line?

    >
    > Not at all. The cutoff is still in the same place.


    No phase distortion at higher audio frequencies?


    --
    "Filtering the Internet is like trying to boil the ocean"
     
    Sweetpea, Aug 18, 2010
    #22
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  3. Peter

    Sweetpea Guest

    On Wed, 18 Aug 2010 20:17:34 +1200, Murray Symon wrote:

    > Stephen Worthington wrote:
    >
    >> On Tue, 17 Aug 2010 12:38:30 +0000 (UTC), Sweetpea
    >> <> wrote:
    >>
    >>>On Wed, 18 Aug 2010 00:28:59 +1200, Stephen Worthington wrote:
    >>>
    >>>> The VDSL2 splitters are better as the filtering has a very sharp
    >>>> cutoff to allow more bandwidth for the DSL signals.
    >>>
    >>>How does that sharp filter affect the quality of sound on the telephone
    >>>line?

    >>
    >> Not at all. The cutoff is still in the same place.

    >
    >
    > "Sound quality" and "telephone line" in the same sentence?? I thought
    > that was just a sly joke at the expense of audiophiles. I remember the
    > old days of debating CD player brickwall filters. I think some people
    > must still react to the phrase "sharp cutoff" by getting upset about
    > degraded sound reproduction.


    Steep filters, unless they're very well designed, generally have issues
    with phase shift at higher frequencies.

    While telephone lines do have a limited audio bandwidth (and this is
    perfectly fine when you consider their primary purpose - communication of
    speech) one would expect that the analogue/digital/analogue signal being
    pushed through a telephone line wouldn't have any distortion deliberately
    introduced by the telephony equipment other than to limit the bandwidth.


    --
    "Filtering the Internet is like trying to boil the ocean"
     
    Sweetpea, Aug 18, 2010
    #23
  4. In message <i4g4ut$2u81$>, Murray Symon wrote:

    > "Sound quality" and "telephone line" in the same sentence??


    Aye, telephone engineers do take their 3.5kHz frequency response seriously.
    Got to make sure your customers can understand each other, you know.

    I myself suffered from a sound-quality problem on the line, which the
    Telecom folks were kind enough to fix over the weekend.

    > I remember the old days of debating CD player brickwall filters.


    You can do a brickwall filter in the digital domain, not in the analog one.
     
    Lawrence D'Oliveiro, Aug 18, 2010
    #24
  5. Peter

    victor Guest

    On 18/08/2010 8:10 p.m., Lawrence D'Oliveiro wrote:
    > In message<>, Stephen Worthington
    > wrote:
    >
    >> On Tue, 17 Aug 2010 12:38:30 +0000 (UTC), Sweetpea
    >> <> wrote:
    >>
    >>> On Wed, 18 Aug 2010 00:28:59 +1200, Stephen Worthington wrote:
    >>>
    >>>> The VDSL2 splitters are better as the filtering has a very sharp cutoff
    >>>> to allow more bandwidth for the DSL signals.
    >>>
    >>> How does that sharp filter affect the quality of sound on the telephone
    >>> line?

    >>
    >> Not at all. The cutoff is still in the same place.

    >
    > Hard to believe. Analog filters with sharp cutoffs tend to have phase-shift
    > issues.


    How would you hear that ?
     
    victor, Aug 18, 2010
    #25
  6. Peter

    victor Guest

    On 18/08/2010 8:01 p.m., Stephen Worthington wrote:
    > On Tue, 17 Aug 2010 12:38:30 +0000 (UTC), Sweetpea
    > <> wrote:
    >
    >> On Wed, 18 Aug 2010 00:28:59 +1200, Stephen Worthington wrote:
    >>
    >>> The VDSL2 splitters are better as the filtering has a very sharp cutoff
    >>> to allow more bandwidth for the DSL signals.

    >>
    >> How does that sharp filter affect the quality of sound on the telephone
    >> line?

    >
    > Not at all. The cutoff is still in the same place.


    There is quite a gap between the upper frequency of the phone channel at
    3.5kHz and the lower band of ADSL at 25kHz.

    Here is some Telecom info

    http://www.telepermit.co.nz/PTC285iss4_06-2010.pdf
    http://www.telepermit.co.nz/PTC280.pdf

    As they point out, in addition to isolating your phone audio from DSL
    noises and isolating your router from the phone system interference, a
    central splitter might stop your home phone wiring radiating RF
    interference to your radio etc.

    Here's a splitter on Tardme
    http://www.trademe.co.nz/Browse/Listing.aspx?id=310661585
     
    victor, Aug 18, 2010
    #26
  7. Peter

    victor Guest

    On 16/08/2010 8:50 p.m., peterwn wrote:
    > On Aug 15, 11:18 am, victor<> wrote:
    >> the report is
    >> complete bullshit and the company should be embarrassed.
    >> It contains a master splitter for adsl/vdsl and has no more benefit to
    >> your broadband speed than installing a master splitter at the
    >> demarcation point.

    >
    > Anyone knows where you can buy these master splitters. Neither Dickies
    > or Jaycar have them. I have used one of the ordinary plugin splitters
    > as a master splitter but am feeling uncomfortable with it (I install a
    > 'slave' jack near demarc, plug a splitter into it, terminate the rest
    > of the wiring into a BT plug and plug it into the splitter).


    Dynamix or one of their resellers

    http://www.dynamix.co.nz/index.html?do=viewproduct&code=XDSL-MASTER&ID=3291922
     
    victor, Aug 18, 2010
    #27
  8. Peter

    Dave Doe Guest

    In article <c2505102-0ce8-4a32-9a8f-
    >, says...
    >
    > On Aug 15, 11:18 am, victor <> wrote:
    > > the report is
    > > complete bullshit and the company should be embarrassed.
    > > It contains a master splitter for adsl/vdsl and has no more benefit to
    > > your broadband speed than installing a master splitter at the
    > > demarcation point.

    >
    > Anyone knows where you can buy these master splitters. Neither Dickies
    > or Jaycar have them. I have used one of the ordinary plugin splitters
    > as a master splitter but am feeling uncomfortable with it (I install a
    > 'slave' jack near demarc, plug a splitter into it, terminate the rest
    > of the wiring into a BT plug and plug it into the splitter).


    Tastech have just got them...

    http://www.tastech.co.nz/product_info.php?products_id=330212

    --
    Duncan.
     
    Dave Doe, Aug 19, 2010
    #28
  9. In message <i4hhpm$ns8$-september.org>, victor wrote:

    > On 18/08/2010 8:10 p.m., Lawrence D'Oliveiro wrote:
    >
    >> Analog filters with sharp cutoffs tend to have phase-shift issues.

    >
    > How would you hear that ?


    Transients.
     
    Lawrence D'Oliveiro, Aug 19, 2010
    #29
  10. Peter

    Murray Symon Guest

    Lawrence D'Oliveiro wrote:

    > In message <i4g4ut$2u81$>, Murray Symon wrote:
    >
    >> "Sound quality" and "telephone line" in the same sentence??

    >
    > Aye, telephone engineers do take their 3.5kHz frequency response
    > seriously. Got to make sure your customers can understand each other, you
    > know.
    >
    > I myself suffered from a sound-quality problem on the line, which the
    > Telecom folks were kind enough to fix over the weekend.
    >
    >> I remember the old days of debating CD player brickwall filters.

    >
    > You can do a brickwall filter in the digital domain, not in the analog
    > one.


    You can implement them either way, both of which can be tricky and
    result in unwanted artifacts. Digital keeps component costs down.
     
    Murray Symon, Aug 19, 2010
    #30
  11. Peter

    Murray Symon Guest

    Lawrence D'Oliveiro wrote:

    > In message <i4hhpm$ns8$-september.org>, victor wrote:
    >
    >> On 18/08/2010 8:10 p.m., Lawrence D'Oliveiro wrote:
    >>
    >>> Analog filters with sharp cutoffs tend to have phase-shift issues.

    >>
    >> How would you hear that ?

    >
    > Transients.


    Do homeless people have telephones?
     
    Murray Symon, Aug 19, 2010
    #31
  12. In message <i4ilu6$t50$>, Murray Symon wrote:

    > Lawrence D'Oliveiro wrote:
    >
    >> You can do a brickwall filter in the digital domain, not in the analog
    >> one.

    >
    > You can implement them either way, both of which can be tricky and
    > result in unwanted artifacts. Digital keeps component costs down.


    Time to pull out my old copy of “The Art Of Digital Audio, 2nd Ed†by John
    Watkinson. Section 3.19, “Oversamplingâ€, page 147:

    Figure 3.44 shows the main advantages of oversampling. In (a) it will
    be seen that the use of a sampling rate considerably above the Nyquist
    rate allows the anti-aliasing and reconstruction filters to be realized
    with a much more gentle cut-off slope. There is then less likelihood of
    phase linearity and ripple problems in the audio passband.

    Those “anti-aliasing and reconstruction filters†are analog filters. Making
    them loose means the digital filters need to be correspondingly tighter,
    which can be done easily and cheaply and is not “tricky†at all. Continuing
    from page 151 onwards:

    If the oversampling factor is /n/, the analog input must be bandwidth
    limited to /n/.Fs/2 by the analog anti-aliasing filter. This unit need
    only have flat frequency response and phase linearity within the audio
    band. ...
    Next, the anti-aliasing function is completed in the digital domain
    by a low-pass filter which cuts off at Fs/2. Using an appropriate
    architecture this filter can be absolutely phase linear and implemented
    to arbitrary accuracy. Such filters were discussed in Chapter 2. ...
    The analog filter serves only to prevent aliasing into the audio band
    at the oversampling rate; the audio spectrum is determined with greater
    precision by the digital filter.
     
    Lawrence D'Oliveiro, Aug 19, 2010
    #32
  13. Peter

    victor Guest

    On 19/08/2010 3:29 p.m., Lawrence D'Oliveiro wrote:
    > In message<i4hhpm$ns8$-september.org>, victor wrote:
    >
    >> On 18/08/2010 8:10 p.m., Lawrence D'Oliveiro wrote:
    >>
    >>> Analog filters with sharp cutoffs tend to have phase-shift issues.

    >>
    >> How would you hear that ?

    >
    > Transients.


    What happens to them and what does it sound like ?
     
    victor, Aug 19, 2010
    #33
  14. Peter

    Sweetpea Guest

    On Thu, 19 Aug 2010 20:11:16 +1200, victor wrote:

    > On 19/08/2010 3:29 p.m., Lawrence D'Oliveiro wrote:
    >> In message<i4hhpm$ns8$-september.org>, victor wrote:
    >>
    >>> On 18/08/2010 8:10 p.m., Lawrence D'Oliveiro wrote:
    >>>
    >>>> Analog filters with sharp cutoffs tend to have phase-shift issues.
    >>>
    >>> How would you hear that ?

    >>
    >> Transients.

    >
    > What happens to them and what does it sound like ?


    What happens is higher frequencies sound muffled because the transients
    are behind where they should be and are masked.

    A signal sounds clear, clean, and airy in comparison with a the same
    signal that has had phase distortion introduced.


    --
    "Filtering the Internet is like trying to boil the ocean"
     
    Sweetpea, Aug 19, 2010
    #34
  15. Peter

    Richard Guest

    victor wrote:
    > On 18/08/2010 8:01 p.m., Stephen Worthington wrote:
    >> On Tue, 17 Aug 2010 12:38:30 +0000 (UTC), Sweetpea
    >> <> wrote:
    >>
    >>> On Wed, 18 Aug 2010 00:28:59 +1200, Stephen Worthington wrote:
    >>>
    >>>> The VDSL2 splitters are better as the filtering has a very sharp cutoff
    >>>> to allow more bandwidth for the DSL signals.
    >>>
    >>> How does that sharp filter affect the quality of sound on the telephone
    >>> line?

    >>
    >> Not at all. The cutoff is still in the same place.

    >
    > There is quite a gap between the upper frequency of the phone channel at
    > 3.5kHz and the lower band of ADSL at 25kHz.
    >
    > Here is some Telecom info
    >
    > http://www.telepermit.co.nz/PTC285iss4_06-2010.pdf
    > http://www.telepermit.co.nz/PTC280.pdf
    >
    > As they point out, in addition to isolating your phone audio from DSL
    > noises and isolating your router from the phone system interference, a
    > central splitter might stop your home phone wiring radiating RF
    > interference to your radio etc.
    >
    > Here's a splitter on Tardme
    > http://www.trademe.co.nz/Browse/Listing.aspx?id=310661585


    Also the wire in ones filter both sides of it, most plugin ones only do
    one leg, so make a massive imbalance and allow the unfilted wire to
    nicely couple AM radio back into the line, which isnt really an issue on
    1.2m of line cable, but when people start to hang extension cords etc
    off the filter it really can add up to many unusable freqs on the DSL line.
     
    Richard, Aug 19, 2010
    #35
  16. Peter

    victor Guest

    On 19/08/2010 8:59 p.m., Richard wrote:
    > victor wrote:
    >> On 18/08/2010 8:01 p.m., Stephen Worthington wrote:
    >>> On Tue, 17 Aug 2010 12:38:30 +0000 (UTC), Sweetpea
    >>> <> wrote:
    >>>
    >>>> On Wed, 18 Aug 2010 00:28:59 +1200, Stephen Worthington wrote:
    >>>>
    >>>>> The VDSL2 splitters are better as the filtering has a very sharp
    >>>>> cutoff
    >>>>> to allow more bandwidth for the DSL signals.
    >>>>
    >>>> How does that sharp filter affect the quality of sound on the telephone
    >>>> line?
    >>>
    >>> Not at all. The cutoff is still in the same place.

    >>
    >> There is quite a gap between the upper frequency of the phone channel
    >> at 3.5kHz and the lower band of ADSL at 25kHz.
    >>
    >> Here is some Telecom info
    >>
    >> http://www.telepermit.co.nz/PTC285iss4_06-2010.pdf
    >> http://www.telepermit.co.nz/PTC280.pdf
    >>
    >> As they point out, in addition to isolating your phone audio from DSL
    >> noises and isolating your router from the phone system interference, a
    >> central splitter might stop your home phone wiring radiating RF
    >> interference to your radio etc.
    >>
    >> Here's a splitter on Tardme
    >> http://www.trademe.co.nz/Browse/Listing.aspx?id=310661585

    >
    > Also the wire in ones filter both sides of it, most plugin ones only do
    > one leg, so make a massive imbalance and allow the unfilted wire to
    > nicely couple AM radio back into the line, which isnt really an issue on
    > 1.2m of line cable, but when people start to hang extension cords etc
    > off the filter it really can add up to many unusable freqs on the DSL line.


    True
    Here's a page showing the internals of various plugin filters
    http://www.adslnation.co.uk/support/filters.php
     
    victor, Aug 19, 2010
    #36
  17. On Wed, 18 Aug 2010 13:53:29 +1200, Lawrence D'Oliveiro
    <_zealand> wrote:

    >In message <>, Stephen Worthington
    >wrote:
    >
    >> Apparently Chorus will be putting in one of the SDP (Service Delivery
    >> Point) boxes at all sites they are called out to. I am not sure if
    >> that is happening yet, as they have only limited stocks of SDPs so
    >> far, but soon all you should need to do is develop a fault to get a
    >> VDSL2 splitter installed.

    >
    >I reported a fault, and had it fixed over the weekend. It was a fault with
    >the voice line—does that count?


    Ask Chorus, but yes, I think any fault where a tech comes out on site
    counts.
     
    Stephen Worthington, Aug 20, 2010
    #37
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