Those who want to listen privately to your music program should add this headphone amplifier in the chain of modular preamp. The circuit is kept as simple as possible consistent with high quality performance. This was achieved by using two NE5532 operational amplifiers on a circuit where IC1B is the "master" amplifier in the cable joint inversion of configuration is not already used in the amplifier's control center line. IC1A is the "slave" of the amplifier and is configured as a unity gain buffer: parallel amplifiers to increase the output current capacity of the circuit.
Two headphone outputs are provided by J3 and J4.
The AC gain of the amplifier was deliberately kept low because this module is intended to be connected after the Control Center module, which provides sufficient gain to drive the power amplifier. If you intend to use the headphone amplifier as a standalone device, an AC higher gain may be necessary to cope with a CD player or tuner output. This is achieved by reducing the value of R1 to 1K5. Thus AC gain of 9 is obtained, more than enough for the purpose.
Unlike the two ICs 15V positive and negative regulator used in other modules of this preamp, two devices were used instead of 9V. This is because the NE5532 automatically limits the output voltage at very low loads as 32 Ohm so that the output amplitude of the amplified signal remains the same, whether the circuit is powered by ± 15V to ± 9V. The choice of a source of ± 9 V allows lower power dissipation and better performance of the amplifier near the cutoff point.
The input jack of this amplifier must be connected to the output module main control center. As this output is usually reserved for driving the power amplifier, a second connection (J2) connected in parallel to J1 is provided for this purpose.
As with the other modules in this series, each electronic card can be fitted in a standard: Hammond extruded aluminum cases are well suited to accommodate the tables in this preamp. In particular, instances of size 16 x 10.3 x 5.3 cm or 22 x 10.3 x 5.3 cm look very good when stacked. See below an example of the possible arrangement of the front and back of this module.
Two headphone outputs are provided by J3 and J4.
The AC gain of the amplifier was deliberately kept low because this module is intended to be connected after the Control Center module, which provides sufficient gain to drive the power amplifier. If you intend to use the headphone amplifier as a standalone device, an AC higher gain may be necessary to cope with a CD player or tuner output. This is achieved by reducing the value of R1 to 1K5. Thus AC gain of 9 is obtained, more than enough for the purpose.
Unlike the two ICs 15V positive and negative regulator used in other modules of this preamp, two devices were used instead of 9V. This is because the NE5532 automatically limits the output voltage at very low loads as 32 Ohm so that the output amplitude of the amplified signal remains the same, whether the circuit is powered by ± 15V to ± 9V. The choice of a source of ± 9 V allows lower power dissipation and better performance of the amplifier near the cutoff point.
The input jack of this amplifier must be connected to the output module main control center. As this output is usually reserved for driving the power amplifier, a second connection (J2) connected in parallel to J1 is provided for this purpose.
As with the other modules in this series, each electronic card can be fitted in a standard: Hammond extruded aluminum cases are well suited to accommodate the tables in this preamp. In particular, instances of size 16 x 10.3 x 5.3 cm or 22 x 10.3 x 5.3 cm look very good when stacked. See below an example of the possible arrangement of the front and back of this module.
