Your attention is invited to the pre amplifier with the tonestack. Amplifier this initial level, but its simplicity the parameters he is quite decent.

Main features are as follows: Nominal output voltage, 1
Input sensitivity, mV:
1 250
2 20
3 3
Signal/noise ratio, dB -70
Total harmonic distortion, % 0,5
Operating frequency range, 20 Hz...20000
The range of adjustment of timbre, dB at a frequency of:
31.5 Hz +/-15
18 kHz +/-15
The voltage, V +/-12

Looking scheme:
Pre-amplifier CRUD

As mentioned above, the amplifier is assembled on the chip CRUD. The feedback circuit is enabled tone control. Adjustment of the high frequencies involved resistor R11, and low - R6. Well, resistor R10 is regulated by the level of the output signal.

The power amplifier requires stable. The stabilizer can be done in two ways - parametric voltage on Zener (1) and stabilizer on chips (2).

The first advantage of the scheme is that the maximum input voltage is practically unlimited in size is enough to pick up the resistors R1 and R2, whereas the integral of the input voltage stabilizers should not exceed 30 volts.

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