AD-2850 is the dedicated phono equalizer unit. Analog records can be reproduced with high quality by installing AD-2850 in a rear-panel slot. The AD-2850 features separate input circuitry for MC and MM cartridges to ensure optimum matching and realize outstanding S/N ratio. 2 sets of analog-player input jacks, the AD1 and AD2 are equipped, and their selections are switchable with the INPUT selector of pre-amplifiers.
- Differential amplifier circuit with ultra low noise bipolar-transistors for MC cartridges.
- Differential amplifier circuit with ultra low noise junction-FET for MM cartridges.
- Differential RIAA equalizer circuit is designed to provide super accurate RIAA equalization characteristics.
- MC Load settings are selectable from among 4 values “10Ω/30Ω/100Ω/300Ω”. The input impedance for both MM settings is 47kΩ.
- Storing separate MC Load and/or AD GAIN settings for each installed AD input (AD1 and/or AD2) is available, and it enables the smooth switching of 2 kinds of analog players or tone arms.
- The printed circuits are made from glass cloth fluorocarbon resin.
Guaranteed Specifications [Guaranteed specifications are measured according to EIA standard RS-490] (Specifications installed in C-2850)
MM/40dB, MC ：20～20,000Hz ±0.2dB
MM/30dB ：20～20,000Hz ±0.3dB
AD Maximum input voltage (1kHz, 0.005% THD)
MM/30dB INPUT ： 310mV
MM/40dB INPUT ： 96.5mV
MC/60dB INPUT ： 9.5mV
MC/70dB INPUT ： 3.2mV
Gain (Gain selector set to 18 dB position, 12/18/24 dB settings available)
AD[MM:30/40dB]INPUT → BALANCED/LINE OUTPUT ：48/58dB
AD[MM:30/40dB]INPUT → REC OUTPUT ：30/40dB
AD[MC:60/70dB]INPUT → BALANCED/LINE OUTPUT ：78/88dB
AD[MC:60/70dB]INPUT → REC OUTPUT ：60/70dB
Input sensitivity and impedance
|Input||Input Sensitivity||Input Impedance|
|For Rated Output||For 0.5V Output|
|AD-MM/30 dB INPUT||8.0 mV||2.0 mV||47 kilohms|
|AD-MM/40 dB INPUT||2.5 mV||0.63 mV||47 kilohms|
|AD-MC/60 dB INPUT||0.25 mV||0.063 mV||10/30/100/300 ohms, switchable|
|AD-MC/70 dB INPUT||0.08 mV||0.02 mV||10/30/100/300 ohms, switchable|
|BALANCED/LINE||252 mV||63 mV||40/20 kilohms, switchable|
|Input||Input shorted (A weighting)||EIA S/N|
|S/N ratio at rated output|
|AD-MM/30 dB INPUT||94 dB||86 dB|
|AD-MM/40 dB INPUT||85 dB||86 dB|
|AD-MC/60 dB INPUT||80 dB||86 dB|
|AD-MC/70 dB INPUT||73 dB||87 dB|
|BALANCED/LINE||111 dB||110 dB|
AD-2850 circuit diagram (one channel)
A major feature of the AD-2850 is the use of a balanced configuration or the internal circuitry. Separate input stages optimized for MC and MM cartridges respectively bring out the best performance from every cartridge. When using the MM input, high output impedance matching is achieved by means of a low noise FET configuration. By contrast, the MC input needs to handle very low-level signals with low input impedance. This is realized by the use of a differential input circuit with low-noise bi-polar transistors together with a low-impedance NFB loop, resulting in playback with minimal noise. Also, the built-in differential RIAA equalizer circuit with using high-precise components for both feedback side and ground side is designed to provide super accurate RIAA equalization characteristics. The MC input impedance can be switched to 10, 30, 100, or 300 ohms, while the MM input impedance is fixed to 47 k ohms. In addition, the gain can be set to 60 or 70 dB for MC and to 30 or 40 dB for MM. All of these functions are controlled with switches on the front panel of pre-amplifiers. Operation convenience therefore is exactly the same as when using a pre-amplifier with built-in phono equalizer.
Printed circuit boards used in the AD-2850