Mark Levinson Reference Preamplifier N32 - Manual (Page 9)

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width and open loop gain to provide uncompromised performance
even at the 60db of gain required by a moving coil preamplifier. The
instrumentation amplifier stage offers high common mode rejection, a
noise-cancellation feature usually limited to transformer-based designs,
while avoiding the serious limitations of those same designs.
high accuracy
RIAA equalization
A balanced pair of active RIAA equalization circuits follows the gain
stages. The filter is built with 0.1%, plate style (non-inductive), thin
film resistors and 1%, stacked film, polypropylene capacitors. This
yields less than 0.1db deviation from the ideal RIAA curve. The user
may switch an additional 20Hz high pass filter into the circuit. This fil-
ter effectively removes the subsonic noise common to many turntable
configurations. The filter conforms to the RIAA/IEC phono equaliza-
tion curve.
DC servo stabilized Any potential for DC output from the phono preamp is nulled out by
an active DC servo. The servo is implemented with low noise, high per-
formance op-amps and film capacitors.
component selection As with the rest of the components in the Nº32, the selection process
involved many hours of controlled listening tests above and beyond the
usual measurements and lab work. Some examples of the selections in-
clude:
• Signal path resistors are 0.1% tolerance, non-inductive (plate-
style), thin-film parts.
• Signal path capacitors are also non-inductive (stacked construc-
tion), either polypropylene or polyester in parallel polypropylene
film caps.
• The preamp circuit board is four layer, Arlon™ N25 (an ultra
high speed, low loss material) construction.
• Even non-signal path parts are film resistors and caps for best
long-term stability.
• Low level signal interconnect is a flat conductor, Teflon™ insu-
lated balanced cable, soldered at both ends.
• Low level signal relays are a rhodium contact, hermetically-
sealed reed type, optimized for ultra-low signal levels.
• The entire module is fully enclosed in a conetic mu-metal shield
box for ultimate low frequency noise isolation.