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Simple car preamplifier and artificial e introduce the princ

2015-01-12 18:29  
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This article is a simple car preamplifier and artificial e principle of the introduction. In the  pre-amplifier  circuit is completely conventional, need to be AC-coupled throughout. Artificial Earth derived tw1o resistors (R1 and R2), it will set the "Earth" is precisely at 1/2 supply voltage. This is nominally 13.8 v all the cars, because it is the right charging voltage of 12 volt battery. Reduce the maximum gain, only reduce the value of R105 and R205. For example, reducing the 4 k7 will provide a maximum gain of 3 (10 db), which in reality may be sufficient. There are a lot of filtering, because the vehicle supplies are notoriously noisy. In some cases it may be necessary to use a suitable replacement R9 noise filter module, or an inductor. Artificial Earth get "6 v" terminal, and is used instead of the real earth you connect additional circuits. It may (will) be necessary in some cases, either ... add input and output capacitance increases the circuit reverse polarity of the current polarization of the input / output capacitors. Ve lead electrolytic chemical must be connected to the circuit all, ve lead as input, output, or chassis earth is appropriate. In addition, an electrolytic capacitor in the feedback circuit is connected to the earth should be connected to the actual earth, not man-made earth, or performance may be affected. As an example, I have included the parameters of the circuit for me to tie the game to tie the game and fittings Subwoofer (Item 28), you need to modify the display. The same principle also applies to cross netw1orks or any other signal processing circuits. This is a useful complement to a car audio system, especially if one wants to use a crossover circuits and other low-level of the amplifier. tw1o circuit includes audio preamplifier, earn up to 21 db (which can be reduced, because it may be too high for many applications). Also provides a "Sputnik" ("land" we readers), which can be used to provide a center voltage of cross-border vehicles and other complementary - such as a parametric equalizer, or even a simple graphic equalizer. Input impedance is a minimum 15 k (it will be more than this for most control settings), the output impedance of 100 ohms - low enough to make any line-level input.



p32 fig1 simple car preamplifier and artificial e

Figure 1 – The Circuit For The Preamp

p32 fig2 simple car preamplifier and artificial e

Figure 2 – Modified Version Of Project 28

As can be seen, all the original earth connections except the one new one (the “Vehicle Chassis” connection) go to the artificial earth. If this is not done, the circuit simply will not work, as it will be trying to function with the input at the same potential as the negative supply terminal on the opamp.

One word of warning – if the device you are connecting to the artificial earth is expected to have significant AC or DC earth currents (> 10mA), this system will not work. It is designed for low current (preamp) type applications only. A higher powered version could be developed from the basics presented here, but as long as speaker type currents are kept away, this design should be quite acceptable.

By the way, the above circuit would be an ideal addition to almost any car sub-woofer installation, leaving out the upper midrange and treble controls (they are not useful for a sub).Alternatively, you could have tw1o of the 35-150Hz controls, which will give much better control of the lower bass region. The 120-550Hz control is likely to be useful to eliminate unwanted peaks (or dips) over the crossover region. You may want to lower the frequency, by increasing the value of one or both capacitors for this control. Doubling the value of either cap will halve the frequency (i.e. from 60 to 225Hz).