Hi Fi audio tone control circuit using low noise transistors

If you are looking for a Hi-Fi audio tone control circuit. This may be the best choice for you. Because it uses all low noise transistors.

The circuit is designed to adjust a smooth bass, and treble is soft sound with very low distortion.

Hi Fi preamplifier with tone controls project

Special feature

  • Use low noise transistors
  • Frequency response range: 20Hz-20KHz
  • Total Harmonic Distortion Noise 0.001% at frequencies 20Hz-20KHz
  • Maximum output voltage 14Vrms at frequencies 20Hz-20KHz
  • Input sensitivity is 50mV
  • The increase / decrease rate of bass : +/- 17dB at 20 Hz
  • The increase / decrease rate of treble : +/- 17dB at 20KHz
the schematic circuit diagram


Figure 1 the schematic circuit diagram

How it works

The transistors Q1, Q2, and Q3, Q4 are connected together as the differential amplifier.

Then the output signal of lead C of Q1 and Q3, Next, sent to Q5, Q6, and Q7, Q8, amplifier set.

The bias of Q5, Q6, and Q7, Q8 will be set in class A. To protect a crossover distortion. The C3 capacitor to cut high-frequency interference.

The output of the circuit is in lead C of Q8 through C4 and R14. For, C4 in the circuit using 10uF 100V, we may use 6.8uF 250V instead, No effect on sound quality at lead C of Q6.

The sound output is sent through R, C circuit to adjust the sound through the middle pin of VR3 and VR4 passed through R9 to R17 and R18 lead B of Q4.

Which is negative feedback if VR raised above, the negative feedback signal which is a lot, to make the bass and treble down. If at the center of the output signal will out of directly.

Without adjusting bass and treble. If VR adjusted downward if the feedback is less. the bass-treble will up.

This is the feedback tone control circuit that someone may need more treble was achieved by reducing the R16 from 1K to 100 ohms.

The power supply are positive and negative, by use both 18V DC regulators ICs as LM7818 and LM7918 to apply voltage at +18V and -18V


Parts you will need

1% 0.25W Resistors (Metal film types)
R1, R16, R20: 1K
R2, R3, R15: 4.7K
R4: 1M
R5, R8: 15K
R6, R7: 75K
R9, R17: 100 Ω
R10, R12: 43K
R11, R13: 100 Ωs 0.5W
R14: 330Ω
R18, R19: 10K

Metalized Polypropylene Capacitors (MKT)
C1: 470 pF 50V
C2, C20, C22: 0.1μF 63V
C3: 100 pF 50V
C4: 10μF 100V
C5: 0.0015μF 63V
C6: 0.015μF 63V
C7: 0.047μF 63V
C8: 0.47μF 63V
C9, C10: 220μF 16V
C11, C13, C15, C16: 0.01μF 63V

Electrolytic Capacitors
C12, C14: 220μF 25V
C17, C18: 2200μF 25V
C19, C20: 100μF 25V

Potentiometers
VR1: Volume 100K-MN types
VR2: Dual volume 100K-A types with center trap
VR3, VR4: Dual volume 100K-B types

Semiconductors
Q1, Q2, Q7, Q8: BC550, low noise transistors
Q3, Q4, Q5, Q6: BC560, Low noise transistors
IC1: LM7818, 18V positive DC regulators IC
IC2: LM7918, 18V negative DC regulators IC
D1, D3: Positive full-wave diodes
D2, D4: Negative full-wave diodes

Others parts
transformers, PCB, and more.

The PCB layouts


Figure 2 The PCB layouts

The components layouts


Figure 3 The components layouts

Note:

This projects may not be suitable for a beginner. You should have expertise in electronic medium.

This project worked. Please watch in this video.

Thanks, Jerivall good job!

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Salim Khan

Excellent.

amitronald

i need transistorized diagram of kvt audio booster amplipier

Geller Sarco

is this work? pls. reply?

Geller Sarco

is this work? pls. reply cuz i like this if it’s work.

Lede

I know you can explain it better

richard

hello, i have built some of your projects but now I would like to buy some of the pc boards that go with the projects, how can I buy the pcb’s?

Omait

can you send the simulation and pcb layout files?

Maine

Hello author! Can this be powered by +-15V instead of 18V? Has anyone built this circuit that can confirm if it works?

arindam

Here output are connected speaker??????

pankaj

hi
Hi Fi audio tone control circuit using low noise transistors i see this project and i thing its a good one. i want to know how can i buy this pcb and all components and how much its cost.

Anand

Please make an audio amplifier with image and video

Anand

Please make a simple audio amplifier board with image and video please

Jerivall

I used this preamplifier here, is awesome!

https://www.youtube.com/watch?v=eZFx1fbGIDg&t=13s

thank you!

Krychu

The preamplifier has a lot of noise and I do not know how to get rid of it

Marus

Hi
I wanna build this tone control so can you, please, give me the layout file for pcb ?
Thank you !

Jerivall
V V Ramadoss

The pre amp is made with a different pcb made by me. It produces a constant hum even at volume control minimum. This hum is constant at all volume control position. The pcb is redisned and made by including a 4.7k and 220 mfd decoupling capacitor in both +ve and –ve power supply. This is included only for Q1, Q2, Q3 and for Q4. The hum remains same. when I removed the input to Q5 and Q6 ( by cutting the track to the base) the hum goes off. The amplifier is silent. That means the hum is produced in… Read more »

Garry

Hello.Figure 1 the schematic circuit diagram the input resistor in the circuit is 1k, and on Figure 3 The components layouts 4.7k, is this an error?

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