Accuphase F-25
¥ 360,000 (released in December 1992)
Commentary
The Dividing Network combines the balanced transmission circuit that Accuphase has developed over many years with a GIC filter, the first of its kind in the Divider.
The F-25 has a structure in which a filter amplifier and a line amplifier are unitized, and can be easily attached and detached from the front panel.
The basic configuration is 2-way and comes with one filter amplifier and two line amplifiers as standard equipment. When upgrading by increasing the number of channels, an optional line amplifier and filter amplifier can be added.
By unitization, crosstalk between channels is reduced.
The crossover frequency is selected by connecting the frequency board directly to the filter amplifier via the connector, which enables the shortest distance connection. There are 21 standard frequency boards ranging from 70 hz to 12.5 khz.
The filter curve used to divide the frequency uses Gaussian characteristics.
This type of filter is also used in high-performance measuring instruments such as FET analyzers. Compared with conventional Butterworth characteristics, it has higher impulse reproducibility and faithfully reproduces the original waveform.
The filter has three levels of attenuation : -12dB/octave, -18dB/octave, and -24dB/octave.
A GIC (Generalized Immortality Converter) is used for the filter circuit that produces the cutoff characteristics.
This filter is a circuit that uses only CR to realize a filter that could only be assembled with LC until now. Compared with Salenkey circuit, a typical conventional feedback filter circuit, this filter does not pass through an amplifier in the passband, so the purity of the signal can be maintained. Also, by selecting a constant, the frequency accuracy and attenuation of the filter can be maintained accurately.
The output circuit has a balanced configuration, and each balanced output with two outputs is fed back with a feed back so that the balanced output can be perfectly balanced. In the case of unbalanced connection, only one output needs to be connected to ground, making an ideal output balance circuit.
In order to realize this circuit with more stable operation, the main circuits are modularized on a alumina ceramics substrate with excellent heat conduction.
The input / output connection is fully balanced with excellent transmission capability, especially when combined with a high-efficiency horn, which has the advantage of less noise interference.
Unbalanced input and output can be selected with switches on the rear panel. Since one of the balanced inputs and outputs is grounded, the same sound quality can be obtained when balanced or unbalanced.
In addition, a phase switch is provided for each channel so that the output balance connection can be switched without adding an inversion circuit, so that sound quality is not impaired.
The output amplifier unit is equipped with a precision attenuator that can select 1 dB steps and ∞ from 0 to -20dB, independent on left and right.
This regulator uses a mirror-finished resistor with a particularly low distortion factor. The resistor rotates and the brush part is fixed and directly exposed to the outside as a terminal, reducing the metal joint part and reducing sound quality degradation.
A dedicated switch is installed in the woofer output on the rear panel to support sub-woofer and 3D systems.
It is equipped with a muting circuit to protect it from shock noise even if it is carelessly inserted or removed during operation.
.jpg)
.jpg)
.jpg)
.jpg)
.jpg)
.jpg)
.jpg)
.jpg)
Model Rating
| Type | Channel divider | ||||||||||||||||||||||||||||||||||||||||||||
| Maximum Input Level (Distortion Factor 0.01% or less, 20 Hz to 20 kHz) | Balanced : 7.0 v, XLR type Unbalanced : 7.0 v, RCA |
||||||||||||||||||||||||||||||||||||||||||||
| Total Harmonic Distortion Factor (20 Hz to 20 kHz, 2.0 V output) | 0.003% | ||||||||||||||||||||||||||||||||||||||||||||
| Frequency Response (Single Channel Equivalent Band) | 20 Hz ~ 20 kHz + 0 -0.2 dB 0.5 Hz ~ 300 kHz + 0 -3.0 dB |
||||||||||||||||||||||||||||||||||||||||||||
| Gain | 0dB | ||||||||||||||||||||||||||||||||||||||||||||
| Crossover frequency | Change by replacement of crossover board Standard frequency : 21 points |
||||||||||||||||||||||||||||||||||||||||||||
| Crossover characteristic | -3.0 dB + / - 5% | ||||||||||||||||||||||||||||||||||||||||||||
| Slope characteristic | -12dB/oct., -18dB/oct., -24dB/oct. Switch-over type |
||||||||||||||||||||||||||||||||||||||||||||
| Input impedance | Balanced : 40k Ω (20k Ω / 20k Ω) Unbalanced : 20k Ω |
||||||||||||||||||||||||||||||||||||||||||||
| Output impedance | Balanced : 50 Ω (25 Ω / 25 Ω) Unbalanced : 50 Ω |
||||||||||||||||||||||||||||||||||||||||||||
| S/N (output 0.5 v, IHF-A corrected) | 100dB | ||||||||||||||||||||||||||||||||||||||||||||
| Minimum load impedance | Balanced : 600 Ω Unbalanced : 600 Ω |
||||||||||||||||||||||||||||||||||||||||||||
| Level adjustment | 0 dB to -20.5 dB, 1 dB step and ∞ Each band is left and right independent |
||||||||||||||||||||||||||||||||||||||||||||
| Power supply voltage | AC100V/117V/220V/240V, 50Hz/60Hz | ||||||||||||||||||||||||||||||||||||||||||||
| Power consumption | 32W | ||||||||||||||||||||||||||||||||||||||||||||
| Maximum external dimensions | Width 475x Height 170x Depth 380 mm | ||||||||||||||||||||||||||||||||||||||||||||
| Weight | 16.0kg | ||||||||||||||||||||||||||||||||||||||||||||
| Sold Separately | Line amplifier unit LA-25 (¥ 50,000) Filter Amplifier Unit DN-25 (¥ 50,000) Frequency board (¥ 15,000 each)
|
.jpg)