RIAA distortion [was Re: Firewire under Linux, was: Re: [linux-audio-user] Setting...

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and then at Mon, 23 Aug 2004 07:24:25 -0400, it was written ...
 >> > > to.  (You cannot directly connect a record player to most soundcards
 >> > > because of RIAA distortion, you need a real phono input.)
 
Kids today ... RIAA distortion ... good grief! Standards based equalisation 
designed to extract the optimal performance from the technology at hand - a
very sharp diamond tipped point tracking a dust coated furrow in relatively
soft vinyl - is not what's normally considered distortion.

The levels generated by quality magnetic pickups are real low, ~= 5mV
into ~= 50K termination, which is way below the specified line input levels
for the average soundcard.  Plugging a phono cartridge directly into
line-in is asking for very poor signal to noise, virtually at the source.
For any expectation of quality, you need to put it through a low noise
preamp first, which is where the RIAA (de)equalisation is generally applied.

There's no problem with applying the eq later in the chain, eg, in Jamin,
but the problem of boosting the very low input level remains, suggesting
that a low noise preamp stage is needed for quality results.  Then there's
the issue of termination impedance/capacitance characteristics affecting the
correctness of the frequency response of the phono cartridge's generated
output ...  Naaaah, let's not go there.  

Cheers folks, luv yer work!
Cal.


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