A while ago I was doing some fairly trivial repairs on a Philips portable radio/CD/cassette player. It had a sticker on it claiming that this particular product features something called Dynamic Bass Boost. From the outside this means an extra switch, that when turned on, causes the music to sound better (well, different). It appears that this is
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just another marketing name for a filter that tries to compensate for the frequency response of the human ear (sometimes it`s called Loudness, my Sony calls it Dynamic Sound Generator). The idea is that the ear is less sensitive to low and high end of the spectrum and that the sensitivity varies with the volume. So to compensate you insert a filter into the audio amplifier with a transfer function that matches the inverted ear sensitivity function. I was curious how exactly that filter is implemented, so I disassembled the radio a bit further than it was strictly necessary for repairs and had a look at the circuits. Judging by the patent application I was expecting something complicated, with active filters and such. This little passive filter circuit is all there is behind that button. It`s implemented on a small circuit board that`s attached directly to the rotary logarithmic potentiometer for volume adjustment (R1 and R2 on the picture) and is duplicated for each channel. Input is marked Ui and output is Uo. The button merely shorts C2 to the ground. Unfortunately, the capacitors and resistors didn`t have any recognizable markings on them, so I wasn`t able to simply read their values. Instead of measuring each component separately, I measured the circuit`s frequency response using a signal generator with frequency sweep and a digital oscilloscope with a Fourier transform: The potentiometer has a tap at around on third of...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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