ROTEL RB-2000
¥ 110,000 (around the late 1970 s?)
Commentary
DC power amplifier with class AB operation.
The circuit configuration is as follows : first stage dual FET differential amplifier 3-stage cascade bootstrap pure complimentary service push-pull + Darlington connection, all stages direct connect OCL type DC-amplifier configuration.
We carefully select low-noise type dual FETs with excellent thermal and electrical characteristics to maintain the pair characteristics required for the first stage DC amplifier.
All stages have DC configuration, eliminating capacitors from signal systems and NF loops.
As for the drift of the midpoint potential which is a problem, the stability of the midpoint potential of the differential amplifier is improved, and the DC balance is stabilized by the circuit technology.
Taking advantage of the good sound quality of class A amplifier, it adopts class AB operation system which can obtain large output.
Normal operation is class A operation, and it is automatically switched to class B operation when a large signal requires a large power.
We have achieved a low distortion rate by focusing on materials and parts as well as printed circuit board design and shielding cord placement.
The power supply section uses a large toroidal core transformer with high efficiency, excellent regulation, and low leakage flux.
As protection circuits, an Electro-Carry Control ASO (Safe Operating Area) circuit and a DC feedback power limit circuit are mounted. The electro-carry control ASO circuit operates as a relay to protect the amplifier transistors and speakers, and the DC feedback power limit circuit operates quickly against overload to protect the transistors.
In addition, the RB-2000 is equipped with a special relay and in-rush absorber for the in-rush current at the time of power-on, which is a problem with large output amplifiers, to improve safety and reliability.
It is equipped with a peak power meter. Unlike normal meters, this meter displays peak power that rises quickly and returns slowly. This makes it easy to read peak power.
In addition, the scale is a logarithmic compression type, making it possible to display accurately from small output to large output.
It is equipped with two input terminals : a DC direct connection terminal and an input capacitor terminal that can maintain sound quality and characteristics while cutting DC components.
Uses gold-plated terminals.
The front panel is an EIJ standard rack mount type.
Model Rating
| Type | Stereo power amplifier |
| Rated Output (Both channel drive) | 140W/ch (4 Ω, 1 kHz) 120W/ch (8 Ω, 20 Hz to 20 kHz) |
| Total harmonic distortion factor | 0.01% (20 Hz ~ 20 kHz, at Rated Output) |
| Cross modulation distortion factor | 0.015% (8 Ω at rated output) |
| Frequency Characteristics (1W/ch, 8 Ω) | DCin : DC ~ 100 kHz + 0 -1dB AC in : 5 Hz ~ 100 kHz + 0 -1dB |
| Input Sensitivity / Impedance | 1.5V/50k Ω |
| Damping factor (8 Ω) | 60 (20 Hz to 20 kHz) 100(1kHz) |
| S/N ratio (IHF-A network short) | 110dB |
| Crosstalk (10 kHz) | 65dB |
| Slew rate | 40 V / μ S |
| Square wave rise time | 2 μ S |
| Maximum Power Consumption | 900W |
| External dimensions | Width 482x Height 143x Depth 430 mm |
| Weight | 18kg |