Complete newbie - audio options

I've heard this with a variety of DTTV and NICAM receivers, and it is
fully in keeping with what I'd expect anyway, knowing that DTTV uses
perceptual bit-rate reduction of a type that NICAM doesn't, so my
conclusion unless something indicates otherwise is that it is a system
effect, rather than an equipment effect.

Rod.

Prolly transcoding somewhere along the chain. Bit like vision nowadays
more and more is the quality on analogue PAL looking like DTV, seems
we're being "softened up".......
--
Tony Sayer

I
On 15 Jun, 17:42, Jim Lesurf wrote:

IIRC The original SPDIF standard defined *both* the logical protocol
and the physical means. i.e. a specific code system, using the
presence or absence of voltage toggling during each bit period,
conveyed via a coaxial line of defined impedance, etc. So far as I can
recall from Philips documents at the time, they weren't thinking about
other forms of physical means.


Sorry to sound thick, but is SPDIF synonymous with "coax"? Thanks,
regards, Robert.

You take your choice... ;-

A) In common use by many makers of domestic equpment, and in consumer
mags, yes.

B) But in more precise engineering terms, no.

So the chances are that if any makers or mags talk about an SPDIF input or
output they will mean a coax system that carries the information using the
methods originally specified by Sony and Philips. They will then call an
optical system something like 'optical' or 'TOSlink'.

The problem is that the initial SPDIF definition covered both the physical
form (75 Ohm coaxial cable and the range of voltage levels to be used)
*and* the protocol (the way the voltage was to be modulated to carry the
information). Then others decided to use optical fibre links and modulate
the light with a similar protocol. The result being physically incompatable
systems which used an equivalent information protocol.

So to an information engineer concered with interpreting the data as it
arrives, the common domestic coax and optical systems are *both* 'SPDIF'.
But in a shop if you ask if a unit accepts SPDIF they will almost certainly
assume you mean if it can take a coax digital input for stereo. Indeed, I
suspect many salespersons have no idea of any of the above and just regard
coax as SPDIF. If you asked if it was SPDIF or AES/EBU you'd probably get a
blank stare or some technobabble they made up on the spot. :-)

For this thread I chose (A) for my initial comment as it seems appropriate
to the context, and would avoid a mass of detail. :-)

In some ways I guess this is a bit like 'PAL' and 'NTSC' for DVDs which has
come to essentially mean a frame rate and number of lines, not the actual
analogue colour subcarrier modulation systems. Terms like these pick up
common meanings which an engineer or academic may quibble about for good
reasons.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html

In article , Roderick Stewart
wrote:
On Fri, 15 Jun 2007 02:46:24 -0700, Dot Net Developer
wrote:


Freeview box seems to output inferior analogue audio. Consequently,
want to try digital audio.

You'll probably find that's a result of limitations of the Freeview
system itself, rather than the decoding circuitry in any particular
equipment. I've listened to several receivers and haven't noticed any
significant differences between them.

Nor have I in terms of sound as yet. However I am wary of this as the
pictures can be obviously different from one DTTV RX to another.


The bit rate reduction used for the sound on DTTV is nothing like as
severe as on DAB, but it's noticeably not quite as good as NICAM, which
has practically none.

I can't say that I have ever found that NICAM on TV sounded better than a
decent Freeview RX feeding a digital signal to a good DAC. However I
suspect this may be because every TV I've tried had clearly audible
problems with its sound circuitry, so may be fouling up the results as soon
as they emerge from NICAM into analogue form. Typical problems being hums
and buzzes, white noise, and nasty distortion on peaks. All classic signs
of cheap and nasty analogue circuitry.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html

In article , tony sayer

wrote:
IIRC Later on other started to employ fibre systems to convey the same
basic form of protocol, but conveyed by modulation of the light. This
intended to make conversion between electronic and optical forms easy.

My understanding is that it is normal in domestic audio to use 'SPDIF'
to refer to the electrical coaxial system, and a specific name like
'TOSlink' or 'optical fibre' to indicate the use of one of the
fibre-based systems.

So, for example, the handbook for the Meridian 563 DAC says it has
three inputs for "SPDIF or AES/EBU" standard signals, and this refers
to the co-ax inputs. But it also says it has an "Optical EIAJ" input
for "TOSLINK" input with no mention of SPDIF.


AES/EBU is much the same basically as SPDIF but with extra info and
supplied balanced, some 5 volts peak to peak.

Yes. Looking again at the Meridian handbook before making the above
comments I was interested to see that it accepts both coax (unbalanced)
AES/EBU as well as having a balanced AES/EBU input.

SPDIF is very similar in level, impedance, etc to video and we have on
occasion used video senders to make sound links over some distances with
eternal aerials, but theres no error correction as such!........

FWIW Given the short distances I've sometimes used 50 Ohm cable when I
didn't have 75 Ohm to hand[1], and make up my own switch-boxes for the coax
SPDIF with no signs of any problems. For me this is an advantage of the
coax over fibre. :-) However it may be that Meridian DACs I prefer are
well designed and can cope easily with slightly degraded signals.

[1] TBH I wonder if most of the '75 Ohm' cables people use are actually 75
Ohm at such low frequencies anyway. 8-]

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html

In article , tony sayer

wrote:
I've heard this with a variety of DTTV and NICAM receivers, and it is
fully in keeping with what I'd expect anyway, knowing that DTTV uses
perceptual bit-rate reduction of a type that NICAM doesn't, so my
conclusion unless something indicates otherwise is that it is a system
effect, rather than an equipment effect.

Rod.

Prolly transcoding somewhere along the chain. Bit like vision nowadays
more and more is the quality on analogue PAL looking like DTV, seems
we're being "softened up".......

What I tend to notice more nowdays is the variability of the picture
quality, sometimes on programmes where I'd expect good images to matter. An
example being last night's "Gardner's World". The picture quality varied
wildly from one section of the programme to another, and was often poor
even to my bad eyesight.

Living as I do in Scotland, I do wonder if such periods of poorer video on
DTTV correlate with when there is a BBC Scotland opt-out. The BBC Scotland
news at 6:30 is distinctly fuzzy compared with the UK News at 6:00.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html

In article , Jim Lesurf [email protected]
and.demon.co.uk writes
In article , Roderick Stewart
wrote:
On Fri, 15 Jun 2007 02:46:24 -0700, Dot Net Developer
wrote:


Freeview box seems to output inferior analogue audio. Consequently,
want to try digital audio.

You'll probably find that's a result of limitations of the Freeview
system itself, rather than the decoding circuitry in any particular
equipment. I've listened to several receivers and haven't noticed any
significant differences between them.

Nor have I in terms of sound as yet. However I am wary of this as the
pictures can be obviously different from one DTTV RX to another.


The bit rate reduction used for the sound on DTTV is nothing like as
severe as on DAB, but it's noticeably not quite as good as NICAM, which
has practically none.

I can't say that I have ever found that NICAM on TV sounded better than a
decent Freeview RX feeding a digital signal to a good DAC. However I
suspect this may be because every TV I've tried had clearly audible
problems with its sound circuitry, so may be fouling up the results as soon
as they emerge from NICAM into analogue form. Typical problems being hums
and buzzes, white noise, and nasty distortion on peaks. All classic signs
of cheap and nasty analogue circuitry.

I'm beginning to think that the local TX there must be getting decrepit
as we just do not have these problems here from Sandy Heath!.

Prolly their not bothering with it pending the DTV switchover
disaster....

Slainte,

Jim


--
Tony Sayer

On Sat, 16 Jun 2007 14:34:07 +0100, Jim Lesurf
wrote:

What I tend to notice more nowdays is the variability of the picture
quality, sometimes on programmes where I'd expect good images to matter. An
example being last night's "Gardner's World". The picture quality varied
wildly from one section of the programme to another, and was often poor
even to my bad eyesight.

The decline in standards goes right through the whole programme chain,
beginning with operators who don't seem to know how to focus a camera
on a foreground talking head instead of the trees or buildings in the
background. This must be on Page 1 of the Ladybird Book of
Photography, but few of them seem to have read it. If they've got
people of the same calibre working elsewhere in the system it would
explain quite a lot.

Rod.

"Roderick Stewart" wrote in message
...
On Sat, 16 Jun 2007 14:34:07 +0100, Jim Lesurf
wrote:

What I tend to notice more nowdays is the variability of the picture
quality, sometimes on programmes where I'd expect good images to matter.
An
example being last night's "Gardner's World". The picture quality varied
wildly from one section of the programme to another, and was often poor
even to my bad eyesight.

The decline in standards goes right through the whole programme chain,
beginning with operators who don't seem to know how to focus a camera
on a foreground talking head instead of the trees or buildings in the
background. This must be on Page 1 of the Ladybird Book of
Photography, but few of them seem to have read it. If they've got
people of the same calibre working elsewhere in the system it would
explain quite a lot.

I thought that sort of thing was confined to the one person and home video
camera type of satellite TV station like Roma Uno where it was the norm.
It sounds as though the rot has spread up to the major broadcasters too.

Roger R

On Sat, 16 Jun 2007 21:41:22 +0100, Roderick Stewart
wrote:

The decline in standards goes right through the whole programme chain,
beginning with operators who don't seem to know how to focus a camera
on a foreground talking head instead of the trees or buildings in the
background

It's called auto focus!


regards

Stuart

www.mckears.com
www.cyclewriter.org

In article , tony sayer

wrote:
In article , Jim Lesurf [email protected]
and.demon.co.uk writes
In article , Roderick
Stewart wrote:
On Fri, 15 Jun 2007 02:46:24 -0700, Dot Net Developer
wrote:


Freeview box seems to output inferior analogue audio. Consequently,
want to try digital audio.

You'll probably find that's a result of limitations of the Freeview
system itself, rather than the decoding circuitry in any particular
equipment. I've listened to several receivers and haven't noticed any
significant differences between them.

Nor have I in terms of sound as yet. However I am wary of this as the
pictures can be obviously different from one DTTV RX to another.


The bit rate reduction used for the sound on DTTV is nothing like as
severe as on DAB, but it's noticeably not quite as good as NICAM,
which has practically none.

I can't say that I have ever found that NICAM on TV sounded better than
a decent Freeview RX feeding a digital signal to a good DAC. However I
suspect this may be because every TV I've tried had clearly audible
problems with its sound circuitry, so may be fouling up the results as
soon as they emerge from NICAM into analogue form. Typical problems
being hums and buzzes, white noise, and nasty distortion on peaks. All
classic signs of cheap and nasty analogue circuitry.

I'm beginning to think that the local TX there must be getting decrepit
as we just do not have these problems here from Sandy Heath!.

My first comment was re how different DTTV RXs show different results from
the same transmission.

My second was how the analogue circuits in all the TVs I've used (in
various locations around the UK) showed obvious imperfections that seemed
to have nowt do do with NICAM.

FWIW The same problems show up when I feed audio *into* the TV and take it
out again. (Hence why I bypass that and run the audio by a route that
avoids the TV when playing discs or using the DTTV RX.)

It should be clear that neither of these points have much to do with the
local TX having problems. What they do show is that the RX/TV can degrade
the results. So my point was that NICAM and PAL may be capable of superb
results, but I (and I suspect many others) have never seen/heard them due
to the problems that analogue TV tends to have in practice.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html