MQA alternative - open source
 

On 09/09/2016 15:41, Don Pearce wrote:
On Fri, 09 Sep 2016 13:32:50 +0100, "Dave Plowman (News)"
wrote:

In article ,
Vir Campestris wrote:
A quick rummage in my tracks seems to show brick wall at 16kHz.

Just for info, 16kHz was regarded by the BBC as the upper limit needed for
the highest quality radio transmissions.

On any true programme material, there was no useful information above this.

And of course they had to leave room for an analogue notch filter to
take out the 19kHz stereo pilot tone. But of course the distribution
standard to all the BBC FM transmitters is NICAM, which is sampled at
32kHz, so 16kHz is very much the upper limit of possibility.


There is audio above 16kHz, and something must happen to it. Even if it
can't be 'heard' in the conventional sense, can it be experienced in
some other way?

The reason for asking is a little more involved than the fact that I can
no longer hear a 15kHz signal :-)

--
Cheers, Rob

MQA alternative - open source
 

In article , RJH
wrote:

There is audio above 16kHz, and something must happen to it. Even if it
can't be 'heard' in the conventional sense, can it be experienced in
some other way?

There are arguments and some experiments which indicate the answer *may* be
'yes'. *However* this really depends on the details of the case. And a lot
of the experimental reports may be mis-interpreting or erronious for all
kinds of reasons. And may only apply to some people in some specific
situations - which may not be equivalent to what people do at home with a
hifi system.

It is, however, generally accepted that younger people can hear tones up to
around 20kHz or above. Varies from one person to another, and with time and
exposure.

So your question would need to be more specific for us to say more than
'perhaps'. :-)

FWIW One of the 'axioms' (as stated by the authors) of MQA is the idea that
we can 'resolve' timing of the order of 5 microseconds and that this is
then presumed to mean we have to include the components that cue this for
human hearing. Alas, beyond that the definitions of what they mean that
I've so far seen seem to drift into being vague or hand-waving.

I have my doubts. Some of which should be plain from the URLs given
earlier.But I'm currently looking in more detail at the 'evidence' for this
'axiom'. :-)

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

MQA alternative - open source
 

On Fri, 09 Sep 2016 16:38:52 +0100, Jim Lesurf
wrote:

In article , Don Pearce
wrote:

And of course they had to leave room for an analogue notch filter to
take out the 19kHz stereo pilot tone. But of course the distribution
standard to all the BBC FM transmitters is NICAM, which is sampled at
32kHz, so 16kHz is very much the upper limit of possibility.

Yes. Although I think I recall reading that in the early stereo days when
only Wrotham was occasionally used for stereo on Radio 3 they had to fit
filters for the first time to fix some problems. Before that they hadn't
explicltly added them. Probably relied on the feeds not to have much above
about 15kHz and the - then analogue transmission lines to TX - not actually
carrying it!

Jim

In the early days they used GPO lines, and they had a dreadful
roll-off above about 4kHz. They fed the light programme medium wave
transmitter. The Beeb allowed for that roll-off in their top end
filtering to maintain the 8kHz channel width. Anyway, at some point
the GPO replaced those lines, and the new ones were flat to a few 10s
of kHz. The BBC didn't change their compensation network for a while,
and for several months we had proper Hi Fi medium wave. It was AM (but
then so is FM with a Foster-Seely discriminator) but the signal was
loud enough that Top Gear on Sunday afternoon was great (That is the
John Peel version, Not Jeremy Clarkson).

d

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On Fri, 9 Sep 2016 17:21:39 +0100, RJH wrote:

On 09/09/2016 15:41, Don Pearce wrote:
On Fri, 09 Sep 2016 13:32:50 +0100, "Dave Plowman (News)"
wrote:

In article ,
Vir Campestris wrote:
A quick rummage in my tracks seems to show brick wall at 16kHz.

Just for info, 16kHz was regarded by the BBC as the upper limit needed for
the highest quality radio transmissions.

On any true programme material, there was no useful information above this.

And of course they had to leave room for an analogue notch filter to
take out the 19kHz stereo pilot tone. But of course the distribution
standard to all the BBC FM transmitters is NICAM, which is sampled at
32kHz, so 16kHz is very much the upper limit of possibility.


There is audio above 16kHz, and something must happen to it. Even if it
can't be 'heard' in the conventional sense, can it be experienced in
some other way?

The reason for asking is a little more involved than the fact that I can
no longer hear a 15kHz signal :-)

The problem with audio that is not heard is that it is probably not
controlled either. A great deal of it will make itself known by
aliasing back down into the audible band in unpleasant ways. Much
better to chop it out early in the signal chain so it can do no harm.

Anyway - what is your reason for asking? I'm intrigued now.

d

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There is audio above 16kHz, and something must happen to it.

There is signal content from many sources way beyond 16k, but
I am not sure you can call it "audio" if it isn't audible :)

Even if it
can't be 'heard' in the conventional sense, can it be experienced in
some other way?

Yes, definitely. A lot of the studies quoted by "hi-res" proponents
all show that yes, you can hear signals above 22 kHz - especially
when non-linearities in the audio chain cause reflected intermodulation
products much lower down in the frequency spectrum. Just not sure it
is a good thing...

Julf

MQA alternative - open source
 

In article ,
Don Pearce wrote:
In the early days they used GPO lines, and they had a dreadful
roll-off above about 4kHz. They fed the light programme medium wave
transmitter. The Beeb allowed for that roll-off in their top end
filtering to maintain the 8kHz channel width. Anyway, at some point
the GPO replaced those lines, and the new ones were flat to a few 10s
of kHz. The BBC didn't change their compensation network for a while,
and for several months we had proper Hi Fi medium wave. It was AM (but
then so is FM with a Foster-Seely discriminator) but the signal was
loud enough that Top Gear on Sunday afternoon was great (That is the
John Peel version, Not Jeremy Clarkson).

I had a mate who worked in lines at the BEEB, and he reckoned the only
truly wideband AM transmission was the Brookman's Park 247 one, up until
they were all limited to 4.5 kHz or whatever. Something to do with both
that frequency being a unique BBC one, and the land line being
particularly good. Sadly, he's no longer around to get the full story from
him.

--
*The best cure for sea sickness, is to sit under a tree.

Dave Plowman London SW
To e-mail, change noise into sound.

MQA alternative - open source
 

On Sat, 10 Sep 2016 00:42:44 +0100, "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
In the early days they used GPO lines, and they had a dreadful
roll-off above about 4kHz. They fed the light programme medium wave
transmitter. The Beeb allowed for that roll-off in their top end
filtering to maintain the 8kHz channel width. Anyway, at some point
the GPO replaced those lines, and the new ones were flat to a few 10s
of kHz. The BBC didn't change their compensation network for a while,
and for several months we had proper Hi Fi medium wave. It was AM (but
then so is FM with a Foster-Seely discriminator) but the signal was
loud enough that Top Gear on Sunday afternoon was great (That is the
John Peel version, Not Jeremy Clarkson).

I had a mate who worked in lines at the BEEB, and he reckoned the only
truly wideband AM transmission was the Brookman's Park 247 one, up until
they were all limited to 4.5 kHz or whatever. Something to do with both
that frequency being a unique BBC one, and the land line being
particularly good. Sadly, he's no longer around to get the full story from
him.

That would have been during the period I remember. And Brookman's Park
sounds like the right transmitter too. Thanks

d

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In article , Johan Helsingius
wrote:

Yes, definitely. A lot of the studies quoted by "hi-res" proponents all
show that yes, you can hear signals above 22 kHz - especially when
non-linearities in the audio chain cause reflected intermodulation
products much lower down in the frequency spectrum. Just not sure it is
a good thing...

That sums up the area to me. Various experimental tests have been said to
'show' we can hear the presence/absence of related components well above
20kHz. But in general those experiments are open to various mechanisms that
cloud the reasons for this.

I've been reading the 'Kunchur' papers on this recently. These are amongst
those quoted for the MQA claims about '5 microsecond temporal resolution'.
Yet the results could be explained in various ways that don't require the
listener to actually be able to hear anything above just *7* kHz, let alone
22kHz!

e.g. the results may stem from something as simple as the listener becoming
'trained' by the tests into hearing signal level changes of the order of
0.2dB, say, when the signal level is switched abruptly. And - as Johan
points out - there are other possible reasons for the results.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

MQA alternative - open source
 

In article ,
Jim Lesurf wrote:
There are arguments and some experiments which indicate the answer *may*
be 'yes'. *However* this really depends on the details of the case. And
a lot of the experimental reports may be mis-interpreting or erronious
for all kinds of reasons. And may only apply to some people in some
specific situations - which may not be equivalent to what people do at
home with a hifi system.

It is, however, generally accepted that younger people can hear tones up
to around 20kHz or above. Varies from one person to another, and with
time and exposure.

Surely the argument is not what the upper limit of some may be, but if
there is any need to reproduce those frequencies in practice?

--
*PMS jokes aren't funny; period.*

Dave Plowman London SW
To e-mail, change noise into sound.

MQA alternative - open source
 

In article ,
Don Pearce wrote:
On Sat, 10 Sep 2016 00:42:44 +0100, "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
In the early days they used GPO lines, and they had a dreadful
roll-off above about 4kHz. They fed the light programme medium wave
transmitter. The Beeb allowed for that roll-off in their top end
filtering to maintain the 8kHz channel width. Anyway, at some point
the GPO replaced those lines, and the new ones were flat to a few 10s
of kHz. The BBC didn't change their compensation network for a while,
and for several months we had proper Hi Fi medium wave. It was AM (but
then so is FM with a Foster-Seely discriminator) but the signal was
loud enough that Top Gear on Sunday afternoon was great (That is the
John Peel version, Not Jeremy Clarkson).

I had a mate who worked in lines at the BEEB, and he reckoned the only
truly wideband AM transmission was the Brookman's Park 247 one, up until
they were all limited to 4.5 kHz or whatever. Something to do with both
that frequency being a unique BBC one, and the land line being
particularly good. Sadly, he's no longer around to get the full story from
him.

That would have been during the period I remember. And Brookman's Park
sounds like the right transmitter too. Thanks

He also said - and I've got no reason to not believe him - was the wide
bandwidth land line was in part due to the original TV sound one to AP. In
the early (pre WW2) days of TV, it was advertised as having better sound
quality than radio.

Of course the other thing is that the vast majority of AM receivers
restricted the bandwidth themselves. Although Quad and some others did
offer wideband designs.

--
*If you're not part of the solution, you're part of the precipitate *

Dave Plowman London SW
To e-mail, change noise into sound.