Soft base with high treble settings is the need of every stereo system. And today I have TL072 jfet operational amplifier-based audio preamp. All the controls are running on a single two channel op amp IC. Simple RC filters are used for the bass and treble audio separation further regulated by operational amplifier. This operational amplifier works on dual power supply. And has a very good bass effect, I made a dedicated PCB of this using JLCPCB prototyping service. You can see the all the details and specs of PCB and circuit below.
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- Dual power supply 7-12volt
- Stereo operation
- Bass, treble control
- Less noisy than other tone controllers
1) TL072 operational amplifier
2) 47K potentiometer
3) 100uf, 47uf, 10uf and 1uf electrolytic capacitor
4) 104, 102, 473, 470, 47pf capacitors
5) 22k, 15k, 10k, 1.5k, 1k resistor
6) Dual power supply
7) Custom PCB from JLCPCB
This is the modified and well tested schematics of this amplifier you can change the 473 capacitor by 153 to increase the bass response. You can choose between the two, soft bass and hard bass. I like soft bass and I am using 473 capacitor. 47k potentiometers are used to control the bass, treble and volume. Here we are using RC filters to control the bass and treble. Operational amplifier is used in inverting mode and by setting the reference to ground.
PCB specifications and design:
I made this schematics in EasyEDA and then export the Gerber files for the PCB. If you want to use the same PCB then download the Gerber files from here. I kept all the control at front side and made the PCB as small as possible. I uploaded these files to JLCPCB and get these amazing looking PCB in just $2.
Soldering and assembly:
I will always suggest first to place small components like resistor and diodes, then go with the capacitors, transistors and integrated circuits. After that place big filtering capacitors and potentiometers. Solder all the component properly because in audio circuit any missed connection or dry solder may generate noise and hum.
Connection with Amplifier:
You can use any stereo type amplifier, there are 3 pin headers given on the top. Two for the input/output and one for the power. It can be directly supplied from transformer linear power supply. Input of the preamp is connected to the Bluetooth module, output is connected to amplifier input stage. And then speakers are connected to the amplifier TDA2030.
Working and testing:
I paired this amplifier with previously made TDA2030 amplifier. The frequency response of the preamp is very good but I was more affected by the bass. The softness in bass made this TL072 amplifier more useable in-home theaters. You can see the quality of audio produced by this through the video embedded here.