We can say that this Multidirectional microphone circuit consists one side of electret four modules, each of them provide power to the capsule through 10K resistor, DC blocked through 1μF capacitor and the resulting AF signal is received at the end of the potentiometer which serves as a reception setting. 100K resistors and transistors form a network FET preamp and summing several signals, which can be applied without any problems on the line input as the microphone channel of the console.

The circuit is powered by a 9V and consumption is very low, so it can be safely operated by a power source or standard 9V battery. In the latter case, remember that proper filtering is the key to good audio quality.

Output cables must be shielded types (mesh) to prevent interference or noise from the sound produced.

It is recommended to mount it in a cabinet or in a circular or pyramidal. Although the first is what gives best results and has a nice aesthetic.

Another recommendation that is not in the scheme is to put a 100nF capacitor between + V and mass within the printed circuit of the apparatus.

The potentiometer allows to adjust the sensitivity of each microphone. This is useful when there are more people on one side than another, or when someone is talking too loudly than others.

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No major difficulties for the realization, but may be difficult to find the SSM2017 and SSM2142. Note that you can easily replace the SSM2019 and SSM2017 directly by replacement it INA217, INA163 or by THAT 1510 or  THAT 1512. Similarly, the SSM2142 can be replaced by DRV134. In all cases, the replacement is made pin to pin and does not require modification of the circuit.

The SSM2017 (or replacement SSM2019 or INA217) allows to make a good preamp with few components. In the schema on the internet is seen where the resistance that determines the gain is the only component in the Annex SSM. No phantom power supply provided (and therefore no protection against power surges), no RF input filter, in short, the ideal scheme for the beginner. The Mono preamp circuit diagram above includes all the “functions” basis, you will be completely free to simplify assembly by excluding one or all of these functions.

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The circuit is divided into two parts. Left – is located in close proximity to the microphone, for example, in his case. The right-hand – anywhere – in the amplifier, a mixer. Connect these two pieces of two-wire, shielded cable.

How does it work? It’s very simple – a signal from a microphone, amplified the left side is fed to the right side, the input stage of which (VT3, VT4) is an accumulator with a phase shift of 180 degrees (the phase of the signal, not of what you think.) Thus, the useful signal coming out of phase two wire folded and its value is doubled. And the nasty in-phase noise are mutually self-destruct.

The input impedance amplifier – about 57 ohms. At assembly, the left side it is desirable to place a metal screen.

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Key Features

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