Re: "Listeners don't want DAB"


"DAB sounds worse than FM" <dab.is@xxxxxxxxxx> wrote in message
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"jamie powell" <jamie_p84@xxxxxxxxxx> wrote in message
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"DAB sounds worse than FM" <dab.is@xxxxxxxxxx> wrote in message
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You've acknowledged in your quack equation that L-R gets subtracted
from
the right channel, and the correct minus symbol is there as it should
be. But that last + should be a minus too.


No. It doesn't matter whether you add or subtract n2.

End of story.

It does in the context of the issue we were debating,


Actually, that reminds me, because THE MOST HILLARIOUS part of the thread
was the realisation that you thought that an FM tuner would reconstruct
the mono signal as follows:

http://groups.google.com/group/alt.radio.digital/msg/719a50b7afea2b0f?hl=en

"Stereo FM tuner set to FM mono mode:
Left = (L+R+n1)/2
Right = (L+R+n1)/2
Sum of Left and Right = L+R+n1"

OMG!!!!!!!!! The L+R signal is sitting at the output of the FM demodulator
ready and waiting to be sent to the Left and Right channels. But no, Jamie
the Software Engineer has got a better idea. He thinks that it's a good
idea to add the Left and Right channels together to get, er, an identical
signal, apart from the fact that its amplitude is double what it was -
even though the signal would be amplified by both the tuner and the
system's amplifier anyway, therefore making Jamie's addition utterly
redundant. That spoke volumes about your maths skills as well. That is,
er, you should stick to software, son.

Considering we were actually debating ***what happens when the FM tuner is
set to mono mode*** VS ***what happens when the FM tuner is set to stereo
mode and its L and R outputs are subsequently summed into mono***, I think
it was quite reasonable to actually talk about what happens during these two
scenarios!! Cretin!

That's why I also included this equation for the latter scenario:

"Stereo FM tuner set to FM stereo mode:
Left = ((L+R+n1) + (L-R+n2)) /2
Right = ((L+R+n1) - (L-R+n2)) /2
Sum of Left and Right = ( ((L+R+n1) + (L-R+n2)) /2 ) + ((L+R+n1) - (L-R+n2))
/2 ) = L+R+n1 "




I think you've finally cracked and gone insane. Perhaps it was Peter
Watson's thorougly correct post on the "Roberts Gemini 49" thread (which
totally backed up what I've been saying to you all along, and totally
wripped apart all the usual bullshit you've been posting over there) that
finally burst your massive bubble of delusion and pushed you over the edge.






which was the issue
of whether n2 gets cancelled out when the L and R outputs of an FM stereo
tuner (set to stereo mode) are summed into mono.
"n2" is the label you assigned to the noise present on the demodulated
L-R
AM subcarrier which forms part of a Zenith FM stereo transmission.
Because
n2 gets added to the left channel, and subtracted from the right channel,
it ends up being 180degrees out of phase between the two channels.


Here you go again. That's the same incorrect nonsense that I've just
pointed out above. The FM multiplex signals are L+R+n1 and L-R+n2. Er, the
L+R+n1 IS THE MONO SIGNAL, so n2 doens't come into it at all.

You just haven't got the faintest clue how any of this works, have you?
You've completely misunderstood the incredibly simple principles which I and
others have taken the time to spell out to you (with Sesame Street
simplicity no less). It's all just gone completely over your head.




For this reason, when the two channels are summed into mono


They aren't summed into mono. The only time the stereo FM channels are
summed to produce a mono signal is in the special case that Richard
mentioned where his amplifier had a button on it, which when pressed
suppressed the hiss.

I bet your idiotic brain thinks it surpressed the hiss due to some form of
low-pass filtering, or witchcraft, or something.

It surpressed the hiss because n2 cancelled itself out. This also happens
when a radio with a MONO speaker has a stereo-capable FM tuner which is set
to stereo mode, such as the one you "reviewed" in some 3rd rate hifi
publication, and misinformed your audience (of one person I bet) about the
amount of hiss they'd hear, due to your general lack of basic understanding.


(such as
happens in a mono radio,


Wrong. An FM portable radio will output the L+R+n1 signal sitting there
ready and waiting to be used at the output of the FM demodulator.

Unless it's a stereo-capable FM tuner set to stereo mode, and the summed
outputs of which then feed the mono speaker.



when said radio includes only an internal mono
speaker, yet features an FM stereo tuner for use with stereo headphones),
n2 completely cancels itself out.
n2 - n2 = 0.


But my equations were SPECIFICALLY about the reconstruction of the stereo
FM channels:

"The Left and Right stereo channels are reconstructed as follows:

Left = 0.5 * [(L + R + n1) + (L - R + n2)] = L + (n1 + n2)/2

Right =0.5 * [(L + R + n1) - (L - R + n2)] = R + (n1 + n2)/2"


There's an error in that "equation" - the final plus should be a minus.


btw, you're a sad case. But I think you knew that already, deep down inside.



.

Relevant Pages

  • Re: "Listeners dont want DAB"
    ... "Stereo FM tuner set to FM mono mode: ... that it's a good idea to add the Left and Right channels together ... were adding two identical signals together, ...
    (alt.radio.digital)
  • Re: Morphy Richards DRM27024
    ... The left and right channels are NOT added together in the FM ... a single mono speaker, then the hiss from decoded FM stereo would ... stereo signals THEN add them back together only to get a signal that's ... all the FM stereo hiss disappears and switching the actual tuner to ...
    (alt.radio.digital)
  • Re: Roberts Gemini 49
    ... mono, versus what happens when the FM tuner is *set to mono mode* ... You're assuming the hissing from the L & R channels will be exact ... The signals that are used to reconstruct the Left and Right stereo ... But these signals have noise added by the RF front-end, ...
    (alt.radio.digital)
  • Re: Roberts Gemini 49
    ... produces the separate channels, so it sounds like there's a fault with the ... You could easily downmix the stereo signal to mono within the digital domain ... of its stereo output via headphone socket (in fact I think all current DAB ...
    (alt.radio.digital)
  • Re: DAB Radio & digital audio out
    ... so no problem with signal strength - it has to be the ... a while ago I grabbed these three snatches straight from the tuner - ... I switched from mono to stereo and back again a couple of times. ...
    (uk.rec.audio)