COUNTERPOINT SA-4
¥ 1,000,000 (1 unit, released in 1984)
¥ 900,000 (1 unit, date unknown)
Commentary
A bulb-type monaural power amplifier developed using the latest electronic technology.
The SA-4 is an OTL (output transformer-less) power amplifier without the output transformer used in general tube type power amplifiers.
OTL amplifiers are available in the SEPP and SRPP types with one power supply, the SEPP type with two positive and negative power supplies, and the OCL (output capacitor-less) type with no output capacitor and two positive and negative power supplies to keep the midpoint at 0 potential. The SA-4 uses an OCL configuration with a direct coupling between the output tube and speaker, and does not include an output transformer or an output capacitor.
This eliminates the negative effects of the output transformer, such as winding resistance, leakage inductance, and stray capacitance of the winding.
To prevent the DC component from flowing into the speaker instead of the output capacitor, the SA-4's unique servo amplifier system is installed. When the DC flow exceeds the allowable level of 30 mV to 90 mV stored in the IC, this servo amplifier operates and instantly cuts off the SA-4 and the speaker. This prevents damage to the speaker.
An auxiliary system coupled with a condenser that cuts frequencies below 16 Hz is also installed.
The output stage consists of eight 6LF6 units.
The power supply section is equipped with a strong power supply capable of stably supplying 1 kw.
The front panel is equipped with an ammeter and meter selector for bias adjustment and a semi-fixed トリマーポ tension meter to check the current bias and idle current of each outlet tube.
In addition to the silver model, there was also a black model.
Model Rating
| Type | Tube type monaural power amplifier |
| Output | 140W (8 Ω) 280W (16 Ω) |
| Frequency bandwidth | 0.1 Hz to 50 kHz |
| Distortion factor | 0.1% or Less (Maximum Output) 0.02% (at 20W output) |
| Vacuum tube used | ECC83 6LF6x8 6FS5x2 |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 200W (in normal use) |
| External dimensions | Width 480x Height 170x Depth 480 mm |
| Weight | 26kg |
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