"Dave Higton" <davehigton@dsl.pipex.com> wrote in message
news:2ee3287350.davehigton@dsl.pipex.com...
> In message <VA.00000751.00af3130@escapetime.removethisbit.myz en.co.uk>
> Roderick Stewart <rjfs@escapetime.removethisbit.myzen.co.uk>
> wrote:
>
>> In article <ba9c9e7150.davehigton@dsl.pipex.com>, Dave Higton wrote:
>> > I /do/ understand the technologies involved. FM is worse than DAB
>> > because all the decoders we use are non-linear, therefore FM
>> > broadcasts, once received, are subject to intermodulation and
>> > harmonic distortions. DAB isn't. It is very much like the vinyl
>> > versus CD and valves versus transistors arguments.
>>
>> My apologies for repeating myself, but this silly argument seems to
>> have been repeated a few times and needs nailing down.
>>
>> Saying that a comparison between FM and DAB is like a comparison
>> between vinyl and CD is nuts. DAB uses destructive digital bit-rate
>> reduction; CD doesn't. CD audio is sampled at more than twice the
>> highest frequency most people can hear, with enough bits to give a
>> dynamic range greater than any mechanical gramophone system and
>> certainly well beyond that of a typical living room, and then no
>> information is thrown away. None at all. It's better than FM, better
>> than gramophone records, better than tape cassetes, and it stays that
>> way all the way to the customer.
>>
>> The main criticisam of DAB is that information *is* thrown away in such
>> a manner that it can never be completely recovered, not even
>> theoretically, and this is done by the broadcasters themselves before
>> the signal even gets to the transmitter.
>
> Yes, it's thrown away. But it doesn't necessarily result in a
> reduction of quality, which is all down to perception.
>
> You appear to be avoiding my point that FM, being analogue and
> being demodulated by a system that is non-linear, inevitably
> introduces non-linear distortions: intermodulation and harmonic
> distortion, to the audio. The DAB system can be engineered so
> that the non-linearities are arbitrarily small, perhaps just a
> few parts per million.
>

The point is that analogue systems are generally very linear by design, even
if individual components aren't. The major distortion as such is that the
bandwidth may not be perfectly flat, but our ears are fairly tolerant to
such errors.

Don't forget that our ears aren't entirely linear!

DAB on the other hand has an alarmingly low bit rate. The consequence is
where the decoded signal doesn't follow the original.