Audio Database
AD-275
Commentary

A phono equalizer unit developed exclusively for the control amplifier C-275.
By adding this unit, C-275 can play back analog records.

A current feedback amplifier circuit is used for the circuit configuration.
By operating a circuit with good bare characteristics with a small amount of NFB and slight phase compensation, natural response and sound field feeling can be obtained.
All of these circuits are composed of discrete parts for sound quality.

It has a dedicated input circuit that takes into consideration the characteristics of each MM/MC type cartridge.
Since the output voltage and output impedance of the cartridge are high at the MM input, it is composed of FET elements that can maintain high input impedance over the entire frequency band. Since the MC input receives minute signals with low impedance, it is composed of an input circuit with low-noise elements.
The MC input can adjust the impedance by three stages and the gain by two stages.

The AD 275 uses a gold-plated glass-epoxy print substrate and consists of two left and right boards with independent constant-voltage power supply circuits.
Each board is contained in a sturdy aluminum housing to limit external influences.

As it is only for C-275, it cannot be used with other devices.

Model Rating
(when connected to C-275)
Type Phono equalizer unit exclusively for C-275
Frequency characteristic AD Input : 20 Hz to 20 kHz ± 0.2 dB
Total harmonic distortion factor 0.005%
Input Sensitivity / Impedance
Input sensitivity
Input terminal Rated output 0.5 v Output Impedance
AD MM: 4.0mV 1.0mV 47k Ω
AD MC(60dB): 0.25mV 0.063mV 10 Ω / 30 Ω / 100 Ω
AD MC(66dB): 0.125mV 0.0315mV 10 Ω / 30 Ω / 100 Ω
S/N / input conversion noise
Input short IEC-A correction
Input terminal S/N at rated input Input reduced noise EIA S/N
AD MM: 92dB -134dBV 85dB
AD MC(60dB): 79dB -151dBV 85dB
AD MC(66dB): 75dB -153dBV 84dB
Rated output voltage 2.0mV
AD Maximum Input Voltage (0.005% Distortion Factor) MM:250mV
MC(60dB):8.0mV
MC(66dB):4.0mV
Gain AD MM Input → Balanced/Unbalanced Output : 48 dB
AD MM Input → Rec Output : 30 dB
AD MC (60/66dB) Input → Balanced/Unbalanced Output : 78/84dB
AD MC (60/66dB) Input → Rec Output : 60/66dB