Equalizer is used to recover the original sound signal from the
RIAA modulated recorded signal. The conventional equalizers are
designed for the precision of only the gain curve, and not much
attention is paid to the phase shift happening while equalization.
The circuit of HEQA01 is successfully suppressing this phase shift
while pursuing the precise equalization. Accordingly, this is an
ideal partner for HCTR01 (super low impedance MC cartridge) which
is specifically designed to minimize the phase shift.
The equalizing circuit is NF+CR type, adjusting the lower
frequency range to RIAA curve by NF low boost circuit, and then
rolling off the high frequency range by CR circuit. It uses the
highest quality chips for its circuit to maximize its performance,
such as, AD797 based input buffer and OPA627 based NF low boost
and output buffer circuits.
Due to this phase sensitive design policy, the output from the
RIAA equalization has flat gain and phase curves over full range
of audio bandwidth, boosting less than ±1° phase deviation over
20Hz through 20kHz, and RIAA deviation of less than ±0.2dB. It
also has the built-in demagnetizer, which can be activated while
the playback, by simply pushing the Degauss Button on the panel, which shunts the circuit to release the core magnetization.