Amplifier these recorder can be used in two ways - as a two-channel bridge with a maximum power of 2x25 W or as with a conventional four-load connection and "virtual ground". Power in this case is 4h7Vt. The most famous member of this family - Sony 1253/1853. To work with a subwoofer also need to use a dual-channel configuration.
Fig.1.
Selecting the connection type, as in the previous case, be subject to the sensitivity of heads. A variant for capacitors C1, C2 act as HPF. They may be waived if the application heads provide undistorted reproduction of lower frequencies. Branch constant component produced internal capacitors radio. However, for option B necessarily the presence of two high-pass and low-pass filter for the stereo for the total channel. Their mission - to eliminate the parallel operation of heads at low frequencies. Since the impedance at low frequencies is almost equal to their heads DC resistance, lack of filters can lead to overload the amplifier, designed for a 4 ohm load. For stereo used first order filters (C1, C2), for the total - the second (C3L1R1).
Another variant of the mixed load connection, but within one amplifier channel. It is convenient to connect two or three-way speaker system. LF-head bridging is used, and for the MF / HF or HF - the usual. Mode switch is set to the position for four-configuration.
Fig.2.
Dependence of the power supplied to the heads of fader position is shown in ris.2.b. In the process of regulatory power to the pavement maximum load decreases by 6 dB (4 times), because in the end positions fader scheme reduces to the usual ("left without a signal" shoulder amplifier acts as a "virtual ground"). Note that in the zone of the joint action of the heads, they are parallel-connected, but because these frequencies are affected by the growth of the load impedance due to the inductance of the voice coil, the amplifier is not really an overload occurs.
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