Audio Database

BA-2000
Commentary

This is a high output stereo power amplifier that not only faithfully reproduces the original music but also reproduces the sound of the music itself.

In the final stage, a parallel push-pull system is adopted, in which two high-output transistors with the same characteristics are used for each channel. Since the current flowing through each transistor is reduced to 1/2, operating points with good linearity can be selected, stable high output can be obtained continuously, and low distortion rate can be obtained over a wide range.

The circuit configuration is further refined from the pure complimentary service OCL circuit directly connected to all stages. The pre-drive stage is a 2-stage class A amplifier with active load, and the drive stage is a parallel push-pull type with 3-stage Darlington connection.
The differential amplifier uses a newly developed dual transistor with the same operating point and temperature characteristics to improve the stability of the midpoint potential. At the same time, the DC balance is made more stable by combining a constant current circuit and a current mirror circuit.
In addition, high-quality parts such as ultra-low-noise transistors, low-leak capacitors with low loss and leakage current, fuse resistors, non-flammable resistors, and varistors are actively to determine sound quality not only by physical characteristics but also by rigorous listening tests.

The power supply section uses an independent two winding toroidal transformer and consists of a high-capacity silicon rectifier and a high-capacity electrolytic capacitor.
± 2 power supplies are supplied independently to the pre-drive and drive stages, and a stabilized power supply circuit is provided to the pre-drive stage that employs a constant current circuit.

The output transistor is protected by a current limiter circuit that detects the safe operating area (ASO) and a temperature detection circuit using a positive star. The speaker is protected by a DC detection circuit combined with a relay. The indicator on the front panel lights red while these protective functions are in operation.
For the inrush current when the power supply is turned on, which is a problem with large output amplifiers, special relays and prevention circuits are provided to improve safety.

It is equipped with a large power meter with excellent tracking ability that can check the output level and left / right balance. This power meter is an effective value display type with a logarithmic compression circuit, and follows pulse signals and signals at small output power.
This indication range can be switched to three levels of x1, x1/10 and x1/100, and can read from 0.001W to 110W and from -34dB to + 3 dB.

The driver stage, output stage, and power supply part are completely separated from each other and block configuration is adopted. In addition to preventing mutual interference and influence of each block stage, shield wires are eliminated as much as possible by connecting each block at the shortest distance.

In order to effectively dissipate the heat generated by the output transistor, large chimney type heat sink utilizing the chimney effect is adopted.
This heat sinker employs four convective radiators with an envelope volume of 1,200c. c., and takes full advantage of the chimney effect, which has a kind of forced air cooling function that absorbs cold air from the lower part.

Model Rating
Type Stereo power amplifier
Effective output (both channel operation)
20 Hz to 20 kHz : 110W + 110W (4 Ω, THD 0.05%)
110W + 110W (8 Ω, 0.03% THD)
1kHz: 110W + 110W (4 Ω, 0.03% THD)
110W + 110W (8 Ω, THD 0.01%)
Output Bandwidth (IHF) 5 Hz ~ 50 kHz (8 Ω, THD 0.05%)
Total harmonic distortion factor
At 1W output : 0.03% or Less (4 Ω)
0.02% or Less (8 Ω)
At rated output : 0.05% or Less (4 Ω)
0.03% or Less (8 Ω)
Cross modulation distortion factor 0.03% or less (70 Hz : 7 kHz = 4 : 1, SMPTE)
Frequency response (at 1W output) 5 Hz to 100 kHz + 0 -1dB
Channel separation 75 dB or More (1 kHz)
Signal-to-noise ratio 115 dB or more (IHF, A-network, short circuit)
Input Sensitivity / Impedance 1000mV/50k Ω (1 kHz)
Power consumption 245W (rated)
910W maximum
Maximum external dimensions Width 460x Height 176x Depth 415 mm
Weight 18.3kg