In article , Paul

wrote:
It still makes for an interesting discussion, however, as many
appeared to have forgotten just how 'vinyl' actually works.
----------------------------------------------------

The problem is nobody here will discuss it! I do not believe they are
(all) stupid so I can only assume that they are in denial else why
would they attempt to defend the indefensible? However, I must admit
that there was no defence offered to the Physics issue. I wonder why!

I can't speak for others, but if you are referring to your statements
regarding RIAA correction and 'physics' I didn't comment in detail as it
seemed unnecessary. However I can make the following comments if they will
help you... :-)

The basic 'physics' that led to the RIAA equalisation (and various other
equalisation curves for analog discs that became obsolete once RIAA became
established) was:

1) That by definition, the signal level from a disc is proportional to the
transverse *velocity* of the stylus.

2) That (1) then means that surface roughness produces a background noise
level which rises with frequency.

3) That the accellerations (and hence forces) required also rise with
frequency for a given stylus velocity.

4) That the amplitude of modulation increases when we *reduce* the signal
frequency for a given stylus velocity.

The RIAA curve pre-whitens the recorded signal so as to get the typical
signal spectrum to be a closer match to the mechanical noise spectrum. This
is common engineering practice when the noise in the channel does not have
a uniform power spectral density. Reason being that it tends to optimise
the available dynamic range.

The curve also has the effect of reducing the required velocities and hence
amplitudes at low frequencies. This avoids the problem of the groove
transverse modulation becoming too large and either leading to mistracking,
or having a record which can only play for a short period. It also helps to
keep down the geometric distortions at LF.

The drawback is that the result is also to enhance any LF noise from
'rumble', and lowers the peak HF levels which can be used before
mistracking.

Personally I would not have said any of the above means the system is
'broken'. Just that as with any real engineered system, it has
imperfections and limitations that stem from its design. Any analog system
has equivalent limitations. But digital systems also have limitations.
Simply the price of any real system being able to exist in our universe.
:-)

Slainte,

Jim

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