[Mr.T]

"Dick Pierce" wrote in message
...
On Jun 25, 6:30 am, "Mr.T" MrT@home wrote:
No it doesn't - the RIAA curve is a factnor of the LP.
Nothing to do with the type of cartridge.

Not so, a ceramic, or crystal cartridge, (and some of
the new el-cheapo USB turntables use cheap ceramic
cartridges once more) do NOT require the same
EQ as for magnetic types.

Actually, if you understand why the magnetic phono preamp
response is what it is, than it is. There are actually two
components dealing with two separate properties. One
is the "RIAA" playback equalization, which consists of a
zero at 318 uS (about 500 Hz) and a pole at 75 uS (about
2120 Hz). This was developed and adopted in the '50s
as a means of dealing with dynamic range and noise
issues on LPs. This equalization MUST be handled by
ALL types of cartridges, magnetic, ceramic, electret,
strain gauge, whatever. In that sense, Geoff is absolutely
100% correct.

There's a second response issue. Record (ignoring the
RIAA EQ discussed above), are cut so that what exists
on the groove is a facsimile of the time-dependent
amplitude of the original waveform.

Ceramic, electret and similar cartridges have an
output voltage proportional to the instantaneous
displacement of the stylus. Magnetic cartridges,
on the other hand, have an output voltage
proportional to the instantaneous velocity of the
stylus. In other words, the output voltage is the
first derivative of position with respect to time,
which means its the first derivative of the original
waveform's amplitude WRT time.

The second component of a magnetic phono preamp's
response is a broadband -6 dB slope. This is, in fact,
a integration function: the output voltage is the integration
over time of the input voltage.

So, you take a waveform, you differentiate it with
respect to time, then you integrate that result
over time, and you end up with the original waveform
back again.

In a broad sense you could call it "equalization,"
but it's not in the sense that it's not correcting or
compensating for anything: it's an inherent
requirement of the medium, unlike the RIAA
shelving EQ which exists to try to shoehorn
a wider dynamic range into a limited range
medium.

--------------------------------------------

All perfectly true, but ignores the fact that cheap compatibility was always
a consideration, and the standard RIAA playback curve provided by the EQ
components of a pre-amp designed for magnetic cartridges is not only
unnecessary, but unsuitable for ceramic cartridges. The only reason for
ceramic cartridges is low cost, and reducing the cost of the playback amp
was also a major benefit.

MrT.