This is the circuit diagram of Octaver-Fuzz Guitar Effects Unit that easy to. Above schematic diagram was extracted from ETI-Canada, January 1980. The transistor Q1 is MPS6515, The diode DI and D2 are 1N4148. The IC is any low noise dual op-amp, shown on above scheme is the 4558. Switching could be improved with a full bypass mod.

The (Guitar Effects Unit) GEU is good sounding octave fuzz, with an optional mode of just fuzz. The fuzz is a fully rectified signal and is quite chewy. For some the Fuzz alone might not be loud enough, this can be fixed by increasing the value of the 820 ohm resistor and lowering the 39k one. Or one could just replace both with a normal volume potensiometer for a more standard approach. The “struzz” is the fuzz with an octave higher signal mixed in. Good for signal notes and leads.

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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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As shown in the Sound level meter schematic diagram of the entire system is in the integrated circuit LM3915, and beyond that there are only a a few passive components. Because the impedance of the speaker in which the measurements were made affecting the outcome, and therefore provided a button to select the load impedance, it may be 4 or 8 ohm.

These Sound level meter devices must be connected, if possible, the terminal itself and baffle not on the amplifier to prevent effect of cable length and voltage drop that is not covered under the measure.

Parts list :

Resistors : 10K (2), 18K, 390K, 2.7K
Diode : Led (10)
IC : LM3915
Battery : 9V

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