ERROR 404

Category Audio

This page includes achievement in Audio :

Amplifier 2x70W


In the music channel, there is an essential element is the power amplifier.

The amplifier that I present below has the advantage of being easy to perform and is very robust to poor handling. This amplifier is realized using an integrated component of Philips (the TDA7294). This component can provide 70 watts RMS and its price does not exceed 8 €. Peripheral components are few. The power amplifier is realized using a symmetrical power 2x25V (for HP 4 ohm) or 2x40V (for HP 8 ohms).

The scheme is based on the datasheet. However, I removed the STBY and MUTE functions. When energized, the amplifier is operating. I used this amp on the first sound system for many years without it asks me wrong.

Component List :
Download files :

Amplifier 2x100W


Here's a new version of the amplifier shown above. The difference lies in the use of the TDA7293 is the superior version of the TDA7294. The new device is capable of providing 100W RMS.

In this version, I kept the protective STBY and MUTE. However, they are activated automatically. From the food, the component waits a few seconds and turns.

Schematic diagram :
Board layout:
Component List :
Download files :

Small mixer


Another essential element for a DJ is a DJ mixer. That I propose does not pretend to be a professional table, but can simply mix two channels without further adjustment.

You can connect any device to line output (CD player, MP3, PC, K7, radio ...). The output can be connected directly to an amplifier or a preamp / EQ. A first potentiometer adjusts the level of channel A and a second level of the channel B.

Download files:
available soon ...

Pitch correction



The picture does not exactly match the artwork.
Indeed, a new version of the artwork can be downloaded.

A simple assembly for adjusting the pitch of a microphone, a guitar or any other sound source. This correction adjusts to all voltage levels (3 mV for a microphone, line input for 1V) with a volume knob.

This correction has 3 separate fixes: the highs, lows and mids. His diet must be done using a small-block area between 8 and 16V DC or 9V battery.

The 4 knobs can be soldered onto the board which limits the connection problems and parasites. A single setting is to: select R2 and the volume knob as follows :

Type of devices R2 P_vol
Micro 330K 220K
Electric guitar 220K 220K
Line Out 2.2K 4.7K
Headphone 2.2K 4.7K

Schematic :
Component List :
Download files:

Active filter for subwoofer


A simple assembly for adjusting the pitch of a microphone, a guitar or any other sound source. This correction adjusts to all voltage levels (3 mV for a microphone, line input for 1V) with a volume knob.

Download files:

RIAA preamp


Even if the digital era is now installed, the fact remains that we need to listen his old LPs, for example switch to MP3.

The small fitting that I present below allows equipment connected to the sound from a turntable to the spend on an amplifier or the sound card in your PC.

This assembly is powered with a 9V battery. You can try to feed it with a power adapter but it will effectively filter feeding to avoid hearing the hum.

I recommend using a 9V: consumption is very small, self assembly is very large.

Photo preamp :
Principle of operation :

A turntable delivers a signal of a few mV, we must amplify the signal to reach the standard level 0 dB (775 mV rms). However, amplification should not be linear. Indeed, the records have the unfortunate tendency to reduce dramatically the low frequencies. We must therefore make a preamplifier to amplify the low frequencies more strongly. It is the purpose of this assembly which is built around an audio PDO.

You can use another reference to AOP but the quality could be affected. Indeed, the NE5532 is the Rolls Royce of audio PDO and its price does not exceed 2€ !

Artwork and layout :


Component List:
Download File :
Réalization :

Start with the IC with the method of your choice (see section TIP for the realization of CIs). Then implanted resistors and capacitors, and finish with the NE5532.

Once all of the welded components, connect your turntable to the preamp and then to your amp (or sound card). Connect the 9 V battery, the devices must operate when energized.

The music is .....