In many modern audio systems, whether it be a music center, a home theater or even a portable speaker for a phone, there is an equalizer, or, in other words, a timbral block. With its help, you can adjust the frequency response of the signal, i.e. change the amount of high or low frequencies in the signal. Sound blocks exist active, built, most often, on microcircuits. They require power, but they do not weaken the signal level. Another type of tone blocks is passive, they slightly weaken the overall signal level, but they do not require power and do not introduce any additional distortions into the signal. That is why in high-quality sound equipment, passive timbral blocks are most often used. In this article, we will look at how to make a simple 2-way timbral block. It can be combined with a home-made amplifier, or used as a separate device.
The circuit contains only passive elements (capacitors, resistors). Two variable resistors are used to adjust the level of high and low frequencies. It is advisable to use film capacitors, however, if there are none at hand, ceramic ones will do. For each channel, you need to assemble one such circuit, and in order for the adjustment to be the same in both channels, use dual variable resistors. The circuit board laid out in this article already contains this circuit in a duplicate, i.e. has an entrance under both the left and right channels.
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The circuit does not contain active components, so it can easily be soldered by wall mounting directly on the terminals of variable resistors. If you want, you can solder the circuit on the circuit board, as I did. A few photos of the process:
After assembly, you can check the operation of the circuit. A signal is applied to the input, for example, from a player, computer or telephone, the circuit output is connected to the amplifier input. Rotating variable resistors, you can adjust the level of low and high frequencies in the signal. Do not be surprised if in extreme positions the sound is “not very” - a signal with completely attenuated low frequencies, or, conversely, overestimated, is unlikely to be pleasant to hear. With the help of the timbral block, you can compensate for the uneven frequency response of the amplifier or speakers, and choose the sound to your taste.
The finished tone block scheme must be placed in a shielded case, otherwise the background cannot be avoided. As a case, you can use a conventional tin can. Pull out the variable resistors and put handles on them. At the edges of the banks must install jack 3.5 connectors for input and output sound.
The bank itself should be connected with the minus of the circuit to create a protective shield, then the signal wire will not catch external interference. The case may be plastic, but in this case, it must be glued with aluminum tape from the inside, which can also be connected with the minus of the circuit.