MITSUBISHI/DIATONE DA-55U
¥ 88,000 (released in 1968)
Commentary
The first amplifier announced by Diatone.
A quasi complimentary service SEPPP OTL parallel push-pull circuit is used.
The preamplifier section uses a 3-stage direct-coupled amplifier with a large amount of negative feedback to minimize degradation of various characteristics.
The equalizer amplifier section is also an NF type with a 3-stage direct-coupled amplifier, and the quality is controlled within 0.5 db of the deviation from the RIAA curve.
The tone control section employs a step-type tone control using a rotary switch. It has a characteristic and straightforward change curve depending on the method of switching elements.
An electronic switch type protection circuit using a silicon thyristor is adopted to protect the power transistor.
It is equipped with a muting circuit that cuts off the speakers for 3 to 7 seconds after power is turned on to prevent damage to the speakers due to clipping noise when power is turned on.
A 4-channel volume is used for volume adjustment, and the S/N ratio for small output is improved by adjusting both the input and output sides of the preamplifier section.
A highly reliable epoxy-based printed circuit board is used.
The preamplifier section and main amplifier section can be used independently.
In the DA-55U, terminals are provided on the horizontal surface and part of the upper lid of the cabinet is made into a slide mechanism to improve operability.
Uses the same Eurasian cheek oak finish as the diatone speaker.
Model Rating
Type | Stereo pre-main amplifier |
Output / Distortion | Continuous output : 100W + 100W (4 Ω) / 0.3% or less Music Power : 130W + 130W (4 Ω) / 0.5% or Less |
Output impedance | 4 ~ 16 Ω |
Input Sensitivity / Impedance | Phono1, 2 : 3mV/30k Ω Tape, Tuner : 100mV/250k Ω Aux : 100mV/250k Ω (Semi-fixed) |
Output level | Rec out:100mV Tape moni:100mV |
Tone control | Low frequency : ± 6 dB (100 Hz in 2 dB steps) High frequency : ± 6 dB (10 kHz, 2 dB step) |
Filter | Low Frequency : 50 Hz -12dB/oct-cut High Frequency : 9 kHz -12dB/oct-cut |
Frequency characteristic | Preamplifier section : 20 Hz to 50000 Hz ± 1 dB Main Amplifier : 15 Hz ~ 70000 Hz ± 1 dB |
S/N | Aux : 75 dB or more |
Damping factor | 30 ~ 40 (8 Ω) |
Transistor used | Silicon transistor x44 Diode x17 Two thyristors |
Pwer | AC100V |
Power consumption | 260VA |
External dimensions | Width 460x Height 170x Depth 420 mm |
Weight | 17kg |