Audio Database

A501
Commentary

A power amplifier kit developed as the first of A500 series.

The A501 is designed to switch between four modes : class A / AB stereo and class A / AB monaural.

It is equipped with a duo-beta circuit and assumes an amplifier with excellent naked characteristics. By combining an appropriate amount of NFB and DC servo, it ensures a plump mid-high range and a tight low range, and achieves a well-balanced sound quality.

All stages are push-pull configuration. Low-distortion cascode bootstrap differential input is used for the first stage, complimentary service push-pull circuit is used for the pre-driver stage, and Darlington connection is used for the driver stage.

A large audio heat pipe with higher heat radiation efficiency than conventional heat sinks is used, and a large 350 VA transformer and a large 15,000 μ F capacitor are used in the power supply.

Magnetic distortion is reduced by the configuration that does not use metal chassis.

The A501Limited is a kit with the same circuit structure and luxurious parts. It uses a glass epoxy 70 μ m copper-foil substrate, copper-foil Styrol capacitor, audio electrolytic capacitor with sound quality measures, and oxygen-free copper wire / AC cord.

There was a CR part set for A501Limited for A501.

* The panel design of A501 seems to be different between the early stage and the later stage, and until around 1981, it was the design at the bottom of the page.

Model Rating
Type Power amplifier kit
Mode Stereo A Class Stereo AB class Mono A Class Monaural AB class
Operation Pure A-class AB Class Up to 25W pure A-class
Class AB for 25W or more		 AB Class
Effective output (8 Ω load) 25W+25W 100W+100W 100W 300W
Total harmonic distortion factor (8 Ω load at rated output) Not more than 0.007% 0.01% or less Not more than 0.04% Not more than 0.05%
Frequency characteristic DC ~ 200 kHz -1dB DC ~ 100 kHz -1dB
Input sensitivity 430mV 850mV 430mV 740mV
SN ratio (IHF-A, input short) 105 dB or more 115 dB or more 110 dB or more 120 dB or more
Attachment Input level control
A class / AB class changeover switch
Stereo / monaural changeover switch
Speaker protection circuit with DC drift detection
Overcurrent protection circuit
Power consumption 190W Up to 400W Up to 250W Up to 650W
External dimensions Width 445x Height 143x Depth 304 mm
Weight 10.5kg
Sold Separately A501 Limited Kit CR501L (¥ 44,000)