It is in very good condition with few scratches and stains. Operation is also Good condition. We do not have any equipment to measure sound quality. We do not know the exact value of the sound quality. This stereo power amplifier was developed based on the “Magni-Wide Power Range” design concept, which states that amplifier performance must be able to reproduce full power with low distortion over an ultra-wide bandwidth, not just within the audible bandwidth. To enable low distortion full power reproduction in the ultra-high frequency range, a group transistor RET (Ring Emitter Transistor) with excellent high frequency switching characteristics has been developed and employed. This transistor is a parallel synthesis of several hundred small power transistors with excellent high-frequency characteristics, and its breakdown strength is increased to achieve high power without compromising the high-speed switching characteristics of the small power transistors. Structurally, it is an epitaxial planar transistor, named ring emitter transistor because the emitters are arranged around the base electrode in the form of a doughnut-shaped ring. The RET has extremely superior switching characteristics compared to ordinary power transistors, with good signal response and low carrier accumulation. In order to secure sufficient power with minimal distortion even at ultra-low frequencies, a DC amplifier configuration is employed, which has no capacitor in the NFB circuit and eliminates transient distortion and phase distortion even at ultra-low frequencies. In addition, to ensure sufficient power, the M-25 is equipped with a large power supply unit with independent large transformers on the left and right sides and large capacitors (22,000µF x 4). The M-25 uses Class-A operation up to 3 watts, and Class-AB operation for higher outputs. This ensures both sound quality and high output power. The power utilization ratio is high, close to that of ordinary class-B amplifiers, so the peak components of the music signal are reproduced with a generous amount of power. To ensure low impedance inside the amplifier, a pure copper plate 12 mm wide and 1 mm thick is used on the ground side from the power supply capacitor to the speaker terminals. In addition, for the hot line from the rectifier to the speaker terminals, where large current flows, an extra thick No. 14 wire (2.03f Yori wire) is used, whose resistance value is 1/4 that of conventional thick wire, and the charging capacity of the power supply capacitor is increased to sufficiently cope with sudden current changes. In addition, the copper foil on each circuit board has been doubled to 70µ, and the collectors of the two power transistors are connected by a short bar of pure copper sheet 12mm wide and 1.2mm thick to reduce impedance. High separation is achieved by a mono construction that minimizes the separation between the left and right channels. Gold plating is applied not only to input/output terminals but also to terminals on the board. The power relay in the protection circuit uses a parent-child relay with two contacts, one for small currents and one for large currents, to prevent deterioration of the contacts. Specifications at the time of release. Type Stereo power amplifier. Circuit method First stage differential current mirror load 3-stage Darlington. Parallel push-pull pure complementary OCL circuit. (Class-AB operation, DC amplifier configuration). Effective output (both channels driven). 8O: 120W+120W (5Hz to 30kHz, Harmonic distortion ratio 0.01%). 120W+120W (5Hz to 80kHz, Harmonic distortion ratio 0.05%). 4O: 120W+120W (5Hz to 20kHz, Harmonic distortion ratio 0.02%). Harmonic distortion (5Hz to 30kHz, 8ohm) at effective output: 0.01. At 60W output: 0.01. 0.007% at 1W output. Modulation distortion ratio (50Hz:7kHz=4:1, 8ohm) 0.006% at actual output. 0.005% at 60W output. 0.005% at 1W output. Output bandwidth (IHF, both channels driven) 5Hz to 45kHz (distortion: 0.01%). 5Hz to 100kHz(distortion rate 0.05%). Frequency response 5Hz to 200kHz +0 -1dB(at 1W output). Input terminal Input:1V/50kO. Output terminal Speaker:4O to 16O. Damping factor 100 (20Hz to 20kHz, 8O). SN ratio (IHF, A-network, short-circuit) 120dB. Channel separation 1kHz:105dB. Power supply voltage 100V, 50Hz/60Hz. Power consumption 280W (Electrical Appliance and Material Control Law). Maximum power consumption 800W. Dimensions Width 420 x Height 153 x Depth 370mm. International Buyers – Please Note. Feedback is very important for everyone participating in community. Please kindly leave feedback once you get the package, we will leave same for you.
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