Cello RHAPSODY
¥ 2,200,000 (released in 2003)
Commentary
A 2-channel / 3-channel power amplifier developed as the first product of the new cello inherited by Matthew James.
There were 2 types of variations, 2 channel configuration and 3 channel configuration.
J-FET dual mono configuration is used for the input stage.
This circuit has a wide dynamic range and is designed to be robust against overloads. This problem has been solved after careful consideration of voltage, current and frequency.
In the driver stage and output stage, distortion is minimized even at a small signal level, and distortion components under actual operating conditions are minimized as much as possible.
The output stage achieves stable operation by minimizing the amount of NF and making the circuit configuration simple.
Six pairs of 250W metal-case bipolar transistors are used for each channel.
The position on the semiconductor and heat sink and the choice of the heat sink itself are determined through trial and error in order to eliminate the effect of temperature change.
The power transistors are mounted on metal hardware, compression washers, and a composite graphite-metal gasket that provides excellent thermal conductivity and is designed to maximize the performance of each device.
Consideration is also given to the placement of the power transformer to minimize the influence of the transformer on other parts.
A thick nickel-plated copper bus bar is used in some cases to more efficiently distribute power between the ground and the amplifier.
The output signal from the amplifier is input to the bus bar through a 10 AWG gauge silver wire using capton as insulation.
The power supply section uses a special high-temperature filter capacitor with a high-current terminal.
Equipped with a microprocessor protection circuit.
This processor protects the amplifier from speaker cable shorts, overheating, DC and overvoltages, as well as soft start, mute and analysis capabilities.
The chassis is machined out of aircraft-grade hard aluminum.
The legs are made of hardened stainless steel and are treated with an Almoloy coating to further increase the hardness through a low-temperature multi-state process. This reduces the cross-modulation distortion that occurs when the amplifier vibrates over a wide range and is effective even at 0.5 Hz. In addition, the mounting position is also taken into consideration to prevent the slight floor vibration from affecting the amplifier.
XLR connector is used for input terminal.
Remote trigger terminal is mounted.
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Model Rating
| Type | 2ch/3ch Power Amplifier |
| Effective power | 200W/ch (8 Ω) 400W/ch (4 Ω) |
| Total harmonic distortion factor | Maximum 0.25% (at 250W/ch, 8 Ω load) Maximum 0.5% (400W/ch, 8 Ω load) |
| Cross modulation distortion factor | Less than 0.1% (SMPTE) |
| Gain | 23dB |
| Input impedance | 10k Ω |
| NOISE | 100 dB or less (at full power, C-curve correction) |
| Power consumption | 1500W at full power |
| External dimensions | Width 435x Height 260x Depth 620 mm |
| Weight | 47kg(2ch) 50kg(3ch) |