Lo-D HA-7700
¥ 99,000 (around 1979)
Commentary
Premain amplifier equipped with power MOS FET applying the know-how obtained in HMA 9500 to premain.
The power MOS FET has achieved a switching speed of 0.05 μ sec and an amplification factor of 1 MHz (-2dB). Compared with conventional bipolar transistors, it has achieved a high performance of more than one order of magnitude. As a result, a power gain of 85 dB at 100 kHz is achieved. Even at 100 kHz, a stable negative feedback can be obtained. Moreover, since the switching speed is fast, excellent push-pull operation can be achieved even in class B circuit configuration.
In order to maximize the performance of the power stage, a simple 3-stage power circuit with little phase change is adopted.
In addition, the operation stability is improved by the all-stage DC amplifier configuration.
In the equalizer amplifier section, three stages of cascode differential ICL circuit, current mirror differential circuit and SEPP circuit are directly connected to each other to ensure an allowable input of 300 mV against an SN ratio of 85 dB and an input sensitivity of 2.5 mV.
The head amplifier also has a 3-stage direct connection structure to ensure excellent SN.
The power supply section is equipped with a left / right independent power transformer and a large-capacity capacitor to suppress transient crosstalk.
A Phono selector switch is mounted to adjust the amplifier input to the recommended load resistance of the cartridge.
The value of the resistance connected to the input of Phono1 and 2 can be changed by four levels at the MM position and by one level at the MC position.
Equipped with a subsonic filter.
Model Rating
| Type | Pre-main amplifier |
| Main Amplifier Section | |
| Effective power | 70W + 70W (8 Ω, double-channel drive, 5 hz to 30 khz) |
| Total harmonic distortion factor | 0.008% (5 Hz to 30 kHz, 8 Ω at Rated Output) 0.02% (8 Ω at 5 Hz to 100 kHz, 35W output) |
| Intermodulation distortion factor (60 hz : 7 khz = 4 : 1) | 0.008% (8 Ω at rated output) 0.003% (8 Ω at 35W output) |
| Frequency characteristic | DC ~ 100 kHz + 0 -1dB (DC) |
| Input Sensitivity / Impedance | Main in : 1V/47k Ω |
| Signal-to-noise ratio (IHF, A-network) | 115dB |
| Damping factor | 60 (1 kHz, 8 Ω) |
| Load impedance | 4 Ω ~ 16 Ω |
| Preamplifier Section | |
| Input Sensitivity / Impedance | Phono1, 2 mm : 2.5mV/100 Ω, 22k Ω, 47k Ω, 100k Ω Phono1, 2 mc : 250 μ V/100 Ω Tuner, Aux, Tape play1, 2 : 150mV/47k Ω |
| Output Level / Impedance | Tape rec out1, 2 : 150mV/600 Ω Pre out : 1V/600 Ω |
| Phono maximum allowable input (1 kHz, 0.01%) | MM:300mV MC:30mV |
| Total harmonic distortion rate (1 kHz) | Phono1, 2 mm : not more than 0.002% (AT Rec out, 1 v) Phono1, 2 mc : 0.01% or less (AT Rec out, 1 V) Tuner, Aux, Tape play1, 2 : 0.005% or less (AT Pre out, 1 v) |
| Frequency characteristic | Phono1, 2 : 20 Hz to 20 kHz ± 0.2 dB (RIAA deviation) Tuner, Aux, Tape play1, 2 : 10 Hz to 100 kHz + 0 to 2.5 dB |
| Signal-to-noise ratio (IHF, A-network) | Phono1, 2 mm : 86 dB Phono1, 2 mc : 68 dB Tuner, Aux, Tape play1, 2 : 100 dB |
| Tone control | Bass : ± 8 dB (100 Hz) Treble : ± 8 dB (10 kHz) |
| Low filter | 15 Hz, 6dB/oct. |
| Muting | -16dB |
| <Others> | |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption (Electrical Appliance and Material Control Law) | 175W |
| AC outlet | Power switch interlock : 2 systems Power switch not linked : 1 system |
| External dimensions | Width 435x Height 164.5x Depth 383 mm |
| Weight | 16kg |