MQA alternative - open source
 

On Sat, 10 Sep 2016 12:27:27 +0100, "Dave Plowman (News)"
wrote:

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.

The AM receiver I was using at the time was a two foot square frame
aerial, a variable capacitor and a diode - that was plugged in to a
Phillips tape recorder. It had plenty of bandwidth...

d

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MQA alternative - open source
 

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!

Even if the '5 microseconds' as true, even 44.1/16 achieves a temporal
resolution of less than 1 *nanosecond*.

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.

Indeed. But when will we actually see that stated in an audiophile
(or even mainstream hifi) magazine?

MQA alternative - open source
 

In article ,
Don Pearce wrote:
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.

The AM receiver I was using at the time was a two foot square frame
aerial, a variable capacitor and a diode - that was plugged in to a
Phillips tape recorder. It had plenty of bandwidth...

True. But the problem with crystal sets was getting rid of unwanted
trassmissions. Unless you are pretty close to a single frequency
transmitter.

--
*The problem with the gene pool is that there is no lifeguard *

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

MQA alternative - open source
 

On Sat, 10 Sep 2016 13:07:28 +0100, "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
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.

The AM receiver I was using at the time was a two foot square frame
aerial, a variable capacitor and a diode - that was plugged in to a
Phillips tape recorder. It had plenty of bandwidth...

True. But the problem with crystal sets was getting rid of unwanted
trassmissions. Unless you are pretty close to a single frequency
transmitter.

That was no problem back in the sixties. Living in London, and only
really using it during the day, there were no interfering signals. I
could really only find two stations. It was a different story after
dark, of course, but I had a little tranny for that (Radio Luxembourg,
naturally).

d

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In article , Johan Helsingius
wrote:
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!

Even if the '5 microseconds' as true, even 44.1/16 achieves a temporal
resolution of less than 1 *nanosecond*.

Yes. One of the problems here is that the proponents tend to get a bit
vague and sweeping about what they mean by terms like 'resolution' etc in
this context.


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.

Indeed. But when will we actually see that stated in an audiophile (or
even mainstream hifi) magazine?

Maybe I'll say it sometime. At present I'm (slowly) going though this area
in detail, running down references, etc. I'll then write a detailed webpage
saying what I found, and then probably write about it for HFN.

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 , Dave Plowman (News)
wrote:

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?

Agreed. However the MQA argument slips into a vaguely defined (so far as I
can see thus far) argument that we need 'temporal resolution' without
necessarily accurately reproducing the actual HF precisely.

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 , Don Pearce
wrote:

That was no problem back in the sixties. Living in London, and only
really using it during the day, there were no interfering signals. I
could really only find two stations. It was a different story after
dark, of course, but I had a little tranny for that (Radio Luxembourg,
naturally).

One interesting aspect of having been trawling 1930s and 1940s publications
is that there was a time when AM could deliver far higher quality than it
can nowdays. The spectrum was much less crowded, and TX filtering could be
more lax.

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 ,
Don Pearce wrote:
True. But the problem with crystal sets was getting rid of unwanted
trassmissions. Unless you are pretty close to a single frequency
transmitter.

That was no problem back in the sixties. Living in London, and only
really using it during the day, there were no interfering signals. I
could really only find two stations. It was a different story after
dark, of course, but I had a little tranny for that (Radio Luxembourg,
naturally).

Interesting. At school in Aberdeen schools broadcasts were recorded on a
Ferrograph using a Truvox radio jack. And being Aberdeen, quite a long way
from other than BBC transmitters. Ie the AM one at RedMoss. And you could
just hear something else burbling away. Sounded like another BBC prog.

--
*When cheese gets its picture taken, what does it say? *

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

MQA alternative - open source
 

On Sat, 10 Sep 2016 13:48:04 +0100, Jim Lesurf
wrote:

In article , Don Pearce
wrote:

That was no problem back in the sixties. Living in London, and only
really using it during the day, there were no interfering signals. I
could really only find two stations. It was a different story after
dark, of course, but I had a little tranny for that (Radio Luxembourg,
naturally).

One interesting aspect of having been trawling 1930s and 1940s publications
is that there was a time when AM could deliver far higher quality than it
can nowdays. The spectrum was much less crowded, and TX filtering could be
more lax.

Jim

It certainly could. And I remember the first trials of stereo AM too.

d

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MQA alternative - open source
 

In article ,
Jim Lesurf wrote:
In article , Don Pearce
wrote:

That was no problem back in the sixties. Living in London, and only
really using it during the day, there were no interfering signals. I
could really only find two stations. It was a different story after
dark, of course, but I had a little tranny for that (Radio Luxembourg,
naturally).

One interesting aspect of having been trawling 1930s and 1940s
publications is that there was a time when AM could deliver far higher
quality than it can nowdays. The spectrum was much less crowded, and TX
filtering could be more lax.

I've got a twin track recording somewhere (or maybe not) made in the late
'60s of a simulcast with R1 AM from BP and R2 FM from Wrotham, both from
Quad valve tuners. On a Revox A77. Not a lot of difference - although AM
was slightly noisier. But not obviously lacking in top as you'd expect.

--
*For every action, there is an equal and opposite criticism *

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