By the question from a reader-driven, it is a sensible addition to a vehicle audio system, especially if you will, a crossover and other low-level amplifiers used. The circuit includes two audio preamplifier, with a maximum gain of 21dB (which can be reduced, because it may be too high) for many applications.
Also provided is a country that “artificial” ( “field” for American readers) that can be used to provide power center of the crossovers, and other accessories – like a parametric equalizer or even a simple graphic equalizer.
Circuit Detail
The input impedance is at least 15K (it is much more than that for most control settings), and the output impedance of 100 ohms – low enough to drive any line input.
The schematic for the preamp
The preamplifier circuit is quite conventional, and the need is AC coupled everywhere. The artificial soil is represented by two resistors (R1 and R2) is grounded “exactly 1 / 2 the supply voltage derivatives. This is theoretically 13.8 in all cars, since this is the correct charging voltage for a 12V battery.
To reduce the maximum profit, you simply reduce the values of R105 and R205. For example, the reduction will be the 4k7 to a maximum gain of 3 (10 dB), which in reality is probably sufficient.
Note 1 – There are a series of filters, because the vehicle is now well known, very strong. In some cases it may be necessary to replace R3 with a module adapted noise filter, inductor, or both.
The artificial soil was obtained before the “6V” administration, and is used instead of connecting the real world for additional circuits. It may (will) not be necessary in some cases …
Add input and output capacitors to the additional circuit
Reversing the polarity of the entry into force polarized output capacitors. The + ve lead of all electrolytic capacitors must be connected to the system with lead-ve as an entry, exit or chassis ground, if necessary.
In addition, electrolytic capacitors should be in feedback circuits that are connected with the earth, the real world are connected, not the artificial world, or performance may suffer.
For example, I provided for the circuit of the equalizer for my subwoofer and a parametric equalizer (Project 28), with necessary modifications indicated. The same principle applies to other networks or crossover signal processing circuit.
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