| 摘要 |
PURPOSE:To make effective use of an amplifier, by switching an amplifier circuit for 4-speaker drive for inverted phase amplification in 2-speaker drive, in the switching of 4 and 2-speaker driving. CONSTITUTION:When a variable resistor RV is adjusted to zero sound volume for back speakers RRS and RLS and front speakers FRS and FLS only are driven, a contact SV is turned on when the RV is fully turned and a current by a voltage +B flows to a coil CL of a relay RY to switch contacts S1-S3. That is, the contact S1 is switched from a capacitor C2 to a capacitor C3, the contact S2 is switched from ground to a capacitor C7, and the contact S3 is switched from the capacitor C7 to a free terminal respectively. In 4-speaker drive, an in- phase signal is inputted to an amplifier AMP, but in 2-speaker drive, an inverting phase signal by a transistor Q is inputted to the AMP. Thus, an inverted phase amplifying output signal is applied to the speaker FRS via the capacitors C6 and C7. |
