Lo-D HMA-9500

Commentary

First stereo power amplifier using power MOS FET.

Power MOS FET is adopted as the amplifying element of the power stage.
Compared with conventional small-signal MOS FETs, this power MOS FET has high amplification factor (mutual inductance) and good linearity. Moreover, it has superior high-frequency characteristics by more than one order of magnitude compared with bipolar transistors. In addition, the switching speed is fast based on the operating principle. It is more resistant to electrical breakdown than power transistors and can simplify the protection circuit of the amplifier. Since the input characteristics are enhancement characteristics, the bias circuit is simpler than that of a FET with depletion characteristics. When used as an audio amplifier in a complimentary service circuit, it can be used as a push-pull amplifier with less distortion compared to an amplifier using a power transistor.

The circuit configuration consists of a differential amplifier in the first stage and a differential amplifier in the second stage with a current mirror circuit as a load.
The power MOS FET has large transconductance, good linearity and frequency characteristics, large power gain, and good uniformity of complimentary service characteristics of N channel and P channel, resulting in a simple three stage circuit configuration including the power amplifier stage.

A DC amplifier configuration with no condenser inside the NFB loop and no input condenser is used to eliminate components that degrade sound quality and enable more accurate waveform transmission.

Crosstalk is eliminated by installing power transformers independently on the left and right sides of the power supply section, and configuring the rectifying and smoothing circuit of the power amplifier stage and stabilizing power supply for small signals independently on the left and right sides.
In addition, in order to reduce interference between the left and right channels, it is designed with symmetrical separated input / output.

Uses gold-plated input pin jack.

Model Rating

Type	Stereo power amplifier
Circuit system	Pure complimentary service OCL circuit for 2-stage differential-amplifier pre-direct-coupled power MOS FET
Effective output (both channel drive)	100W + 100W (8 Ω, 5 Hz to 100 kHz) 120W + 120W (8 Ω, 5 Hz to 20 kHz)
Total harmonic distortion factor (8 Ω)	0.01% (5 Hz to 100 kHz, Rated Output) 0.005% (5 Hz to 20 kHz at Rated Output) 0.002% (1 kHz, Rated Output) 0.002% at 1 kHz, 50W output
Intermodulation distortion factor (60 hz : 7 khz = 4 : 1)	0.003% (8 Ω at Rated Output) 0.003% (at 8 Ω, 50W output)
Frequency characteristic	DC: DC ~ 100 kHz + 0 -0.5 dB DC ~ 300 khz + 0 -1dB Low cut: 3 Hz ~ 300 kHz + 0 -1dB
Input Sensitivity / Impedance	1V/50k Ω
Channel separation (Input Short)	85 dB (5 Hz to 100 kHz) 95 dB (5 Hz to 20 kHz)
S/N (input short)	110dB
Damping factor	70 (5 Hz ~ 20 kHz)
Optimum load impedance	4 Ω ~ 16 Ω
Power supply voltage	100 VAC, 50Hz/60Hz
Rated power consumption	350W (Electrical Appliance and Material Control Law)
External dimensions	Width 435x Height 192x Depth 410 mm
Weight	28kg