Vocal Removal/Accompaniment Extraction/Karaoke Circuit - CXA1642P

Vocal Removal/Accompaniment Extraction/Karaoke Circuit - CXA1642P
1. Introduction
The CXA1642P is a vocal removal IC manufactured by Sony for use in audio equipment, CDs, etc.
This chip is now discontinued; those purchased online are either salvaged or from existing
stock. It is packaged in DIP-8, making it compact and convenient.
2. Vocal Removal Principle
Vocal Removal Methods
There are generally two methods for vocal removal: stereo removal and band-
stop filter removal. The band-stop filter method reduces the energy of a certain frequency range to zero, thus eliminating that frequency range of sound in the original signal.
This example uses stereo vocal removal.
 
Basic Principle of Stereo Vocal Removal
The basic principle of stereo vocal removal is that two signals with the same amplitude but opposite phase add up to zero.
The reason people perceive stereo music is that the accompaniment in the left and right channels differs in frequency, amplitude, and phase. Since vocals are always placed in the center during mixing, the amplitude and phase of the vocals in the left and right channels are basically the same, meaning the vocals are essentially identical in both channels.
Therefore, by inverting the sound of one channel and then superimposing the other channel, the vocals can be canceled out, leaving only the accompaniment.
 
Disadvantages
: 1. This method will eliminate elements with similar properties to vocals, such as drums and bass in the accompaniment.
2. The input music must be stereo; if a single-channel music input is used, vocals cannot be eliminated.
3. The resulting sound is a single-channel mixed music.
 
3. Theory and Practice:
If you don't have a PCB but can use AU for theory, it's simple.
First, import an audio file, then separate its left and right channels
into L/R.
Then, open one channel and use the phase inversion effect (not reverse, but the L channel).
Then, create a new multitrack and mix the inverted L channel with the separated R channel.
The result will be a sound without vocals, only the accompaniment and harmonies.
4. Circuit:
As mentioned in the previous sound cancellation method, this method will eliminate elements with similar properties to vocals, such as drums and bass in the accompaniment, which are low-frequency instruments.
Therefore, we only need to create a low-pass filter on one channel of the original music to obtain the bass, and then mix the music with the bass after the vocals have been removed to better preserve the low-frequency part.
The CXA1642P has already integrated this function internally.
The drawback also mentions that the noise-removed output is a single-channel mixed music;
the left channel is inverted and mixed to the right channel, resulting in the right channel accompaniment. Therefore, by adding another channel, inverting the right channel, and then mixing it with the left channel, a stereo accompaniment can be produced. Thus, two CXA1642Ps are sufficient.
However, since it is a stereo effect produced by mixing two mono channels, the stereo effect is weak or almost non-existent.
A 5V to 9V boost circuit was previously commonly used, such as the SX1308
. 5. The actual effect
is playing "The Tower of Flowers," noise-removed,
with microphone effects and reverb: https://oshwhub.com/aknice/pt2399