Stereo audio distributor

This is a stereo audio distributor 1 in / 3 out. The term has developed a bit much, given that it only get the basic diagram of a doc from one of the TL072 manufacturers.

However, It have adapted slightly to take advantage of editing a version for single power supply (single, for example a car battery 12 V) and another version for dual power supply(balanced, for example + / -12 V)

The general block can see that the structure of audio distributor is very simple.

A first stage, called AMP, can have a high input impedance and have a low output impedance. This first stage, whose primary purpose is to bring the gain even if it is possible (despite the name given AMP), followed by three output stages in parallel:AMP1, AMP2 and AMP3 This provides three separate outputs BF, able to attack each of the amplifiers, recorders, or other audio equipment.

The diagram shows two identical modules, for use in stereo. Of course you can use onlyhalf for use in mono. The following description is based on the first module consists of U1 (top module on the diagram)

Single or dual supply?
The scheme has been adapted to allow a single circuit board, using a single supply ordual power The choice is made by the introduction of two jumpers (per channel), according to the following configuration:
  • PSU simple: set up the jumpers SW1, SW4, SW5 and SW8, and do not wire thepower supply decoupling capacitors C6 to C9.
  •  PSU dual set up the jumpers SW2, SW3, SW6 and SW7, and wire the power supplydecoupling capacitors C6 to C9.
In the first case, the two input terminals of the op amp U1: A is brought to a positive DC potential equal to half the supply voltage, through resistors R4 and R5. In the second case, the two input terminals of the op amp U1: A is brought to a zero potential, themass, still through resistors R4 and R5. Similarly, in the first case the negative supply terminal of the op amp is grounded, whereas in the latter case, it is brought to a negative potential.
Note that the potential + V "half power supply" is provided by the pair of resistors R2 and R3, equal to values, which form a resistive divider bridge The common point of the bridge, there is a good half of the power supply voltage. It is around this voltage we canconsider as a virtual ground, the input signals are centered, in order to receive the maximum dynamic range.
Decoupling capacitors for power supply: it should be placed as close as integrated circuits. If you are unable, make sure at least that the connections between these capacitors and integrated circuits are wide and generously covered with solder. More 

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