Audio Database


Lo-D HA-8700
159,000yen(around the 1979 time)

The Integrated Amplifier which polished up further the know-how acquired by HMA-9500, applied to the pre-main, and was developed.

The power MOS FET which is the newly developed new power amplification element is adopted.
By Power MOS FET, switching speed 0.05microsec, the frequency characteristic of 1MHz (-2dB) of an amplification factor is attained, and the high-performance of single or more figures is realized compared with the conventional bipolar transistor. This realized power gain of 85dB in 100kHz of nakedness properties, the negative feedback stabilized [ 100kHz or ] enough started, and moreover, since switching speed is quick, the push-pull operation excellent also in B class circuitry has been realized.

In order to demonstrate the performance of this power stage, the three-step power circuitry with few phase changes is adopted. Moreover, in order to raise a low-pass property further, the electrical-power power-source part using the right-and-left independent source which began DC amplifier stream composition and was excellent in dynamic characteristics, and a quality mass capacitor is carried.

The gain of the main amplifier was raised to 45dB from 29dB, and the main direct switchpoint which connects a main amplifier to an equalizer-amplifier output directly is adopted.
Moreover, it is also possible to lower the gain of a main amplifier to the gain at the time of main directoff by a muting switch.

The whole page DC amplifier stream composition which removed the capacitor from the inside of the entry point of each amplification stage of head amplifier, an equalizer amplifier, a preamplifier, and a main amplifier and a negative feedback (NFB) loop is adopted.
The phase response and the response characteristic were raised sharply by this, and the improvement in a low-pass property and the modification of the transparency of a mid-high range are realized.

An equalizer-amplifier part serves as a cascade differential current mirror interrupt-control-logic circuitry, the 2nd step becomes a current mirror type differential circuit, the final stage has three-step hardwired-connection composition of an SEPP circuit, and 300mV of allowable inputs are secured.
Moreover, a head amplifier part adopts low-noise junction FET as the first rank, the 2nd step is made into a constant current driving circuit, and the final stage is considered as the three-step hardwired-connection stream composition of the SEPP circuit.

The power-source part has prevented the cross interferencee of amplifier, as a result of adopting a stabilizing supply as the tone amplifier of a small signal system, and head amplifier, while carrying the right-and-left independent-source transformer and the mass capacitor.

The loudspeaker output-terminals A and B did not let a signal pass to a loudspeaker change-over switch, but the direct output-terminal directly connected to a loudspeaker termination is adopted.

A 70-microsecond platform with twice [ over the past ] as many thickness as this is adopted as a power-source part and a main-amplifier part, and low-impedance-ization is attained from the power-source line to the output line.

Rating of a mode
Form Integrated Amplifier
<Main-amplifier part>
Effective output 90W+90W (8 ohms, both channel drive, 5Hz - 40kHz)
THD 0.008% (at 5Hz - 40kHz, the time of an Output power 8ohms)
0.02% (at 5Hz - 100kHz, the time of 45W output 8ohms)
0.002% (at 1kHz, the time of an Output power 8ohms)
Cross modulation distortion (60Hz:7kHz=4:1) 0.008% (at the time of an Output power 8ohms)
0.003% (at the time of 45W output 8ohms)
Frequency characteristic DC-100kHz+0 -1 dB (DC)
Input sensitivity/impedance Main in: 1V/47kohm
SN ratio (IHF, A network) 115dB
Dumping factor 80 (1kHz, 8ohms)
Load impedance 4ohm-16ohm
<Preamplifier part>
Input sensitivity/impedance Phono1, 2 man month: 2.5mV/100 ohm, 22kohm, 47kohm, 100kohm/
100pF, 200pF, 300pF, 400pF
Phono1, 2 MC: 250 microvolts/100 ohms
Tuner, Aux, Tape play1, 2:150mV/47kohm
An Output voltage/impedance Tape rec out1, 2:150mV/600 ohms
Pre out: 1V/600 ohm
Phono maximum permissible input
(1kHz, 0.005%)
THD (20Hz - 20kHz) Phono1, 2 man month, MC: 0.005% or less (AT Rec out, 1V)
Tuner, Aux, Tape play1, 2:0.005% or less (AT Pre out, 1V)
Frequency characteristic Phono1, 2:20Hz-20kHz±0.2dB (RIAA deflection)
Tuner, Aux, Tape play1, and 2:10Hz-100kHz+0 -2 dB
SN ratio (IHF, A network) Phono1, 2 man month: 90dB
Phono1, 2 MC: 73dB
Tuner, Aux, Tape play1, 2:100dB
Tone control Bass: ±8dB (100Hz, a turnover frequency: 50Hz)
Treble: ±8dB (10kHz, a turnover frequency: 20kHz)
A low filter 15Hz, 6dB / oct
Muting -16dB
Supply voltage AC100V, 50Hz/60Hz
Power consumption
(Electrical Appliance and Material Control Law)
AC outlet Power-switch interlock: Two lines
Power-switch un-interlocking.: One line
Dimensions Width 435x height 164.5x depth of 420mm
Weight 20kg