Audio Devices AD-P55
¥ 550,000 (1 unit, released in 1990)
Commentary
AD-5 series monaural power amplifier, the third stage of audio devices.
The AD-P55 is focused on three issues : musical expression, speaker drive, and cost performance.
The single power transistor used for the power stage and constant voltage stabilization circuit is used to improve the sound quality for small signals compared with parallel use.
A constant voltage stabilization circuit is used for all circuits including power stages.
The current supply to the amplifier circuit was generally stabilized up to the drive circuit, but not to the power stage. In the AD-P55, a constant voltage circuit is also used to stabilize the power stage in order to obtain the drive capability for the speaker whose power is higher than the power value.
It is designed to deliver power linearly from 8 Ω to 3 Ω to accommodate low-impedance speakers.
The parts are selected by veteran engineers who have worked for more than 15 years in the design team of audio devices. They are selected from inside and outside of Japan and used for important parts.
Main parts include a large-size R-core power transformer (PAT. P) with special winding, a computer-grade electrolytic capacitor made by Sprag of the United States, and semiconductors made in the United States.
A control amplifier that can be paired with AD-P55 was developed. The model name seems to be AD-C5.
It was scheduled to be released in the spring of 1991. (The actual release has not been confirmed, so please contact the manager if you know.)
Model Rating
| Type | Monaural power amplifier |
| Maximum power output | 40W (8 Ω) 50W (6 Ω) 75W (4 Ω) 100W (3 Ω) |
| Input voltage | 0.85Vrms |
| Input impedance | 20k Ω |
| External dimensions | Width 430x Height 134x Depth 380 mm |
| Weight | 18.5kg |