[X4U] phono to CD

[David Ledger]

>From: Crandon David <tabdave at comcast.net>
>
>Hmmm....you're going to have to refresh my memory here. What I remember
>is that a ceramic cartridge has much higher output voltage than the
>usual MM (moving magnet) cartridges, so a preamp isn't necessary, but
>the RIAA Eq curve is a function of the pressing of the record, and is
>independent of the type of cartridge, whether it's MM, Ceramic or MC
>(moving coil).

Magnetic cartridges produce output where the instantaneous voltage is 
proportional to the instantaneous lateral velocity.  This means that 
low notes produce much smaller output than high notes.  RIAA Eq was 
introduced so that there don't have to be larger stylus swings for 
the low note components which would increase the groove spiral pitch 
and shorten the playing time.

Ceramic (and crystal) cartridges produce output proportional to the 
displacement of the stylus and so is pretty well frequency 
independent.  It turns out that the output from a ceramic cartridge 
is fairly close to what is required.  If you apply RIAA to it, the 
sound will be wrong.  You could say that the workings of a ceramic 
cartridge gives it a roughly RIAA response naturally.

Ceramic cartridges are piezo-electric and do give much higher outputs 
than magnetic.  Magnetic devices rely on movement; piezo ones on 
force.  With magnetic, the small wiggles in the groove give a small 
output; with ceramic, the force due to the wiggles depends on the 
stiffness of the coupling between the stylus tip and the 
piezo-electric elements.  Magnetic stylus couplings are floppy, 
ceramic ones are stiff.  This stiffness also means that ceramic 
cartridges cause more record wear and don't follow the groove as 
cleanly.

David


-- 
David Ledger - Freelance Unix Sysadmin in the UK.
Chair of HPUX SysAdmin SIG of hpUG technical user group (www.hpug.org.uk)
dledger at ivdcs.co.uk
www.ivdcs.co.uk