You have a good power amplifier and speaker. You are listening to music. But the sound is very light. The problem has many reasons. One reason for the problem is the input signal is too low. You may need a preamplifier using IC. It will make the input signal is higher. Then, You will listen a good music so happy.
Why preamplifier using IC
There are many reasons. You should IC in preamp. I will show you.
Small—In one ICs have many transistors and more parts. For example, the internal structure of 741 op-amp. There is 20 transistor!
Source: Operational amplifier
High gain—when there are many the transistor so many gains.
Easy—just add two resistors you so a good audio amplifier.
Inexpensive—Now IC is low price than a transistor in the same working.
Do you want to use IC?
In the list below, I show using three IC.
- First, the famous 741 OP-AMP, it is cheap and easy to get at all store near you.
- Second, the low noise NE5532 preamplifier—Dual Low-Noise High-Speed Audio Operational Amplifier. So good for audio working
- Third, the LM382 OP-AMP, Low Noise Dual Preamplifier.
Universal Preamplifier using 741
This is a mono preamplifier circuit. Which it can use with various inputs. For example, microphone, tuner, CD and AUX.
In the circuit above, IC741 is set into inverting amplifier mode. When a signal flows to AF in through C1 and R1 to pin 2 of IC1. Then, the signal goes out of pin 6. R4 acts as feedback resistors.
Both resistors R2, R3, and Capacitor C2 are set the voltage to improve the gain of IC1. VR1 adjusts the amplitude of an output signal sent to the AF OUT.
If you want to build this circuit. We recommend buying this kit. Easy to and cheap!
Source: Universal Mono Pre-Amplifier Kit
This is a multi-purpose NE5532 Preamplifier circuit. It is easy to use. The input signal is the various types of up to 4 inputs. As follows:
- Microphone has a sensitive signal about 50 mV.
- Cassette player—See less, too ancient— has a sensitive signal about 100 mV.
- FM tuner has sensitive signal of about 300 mV.
- CD player sensitive signal about 500 mV.
This circuit can increase the output signal up to about 1 Vrms. Which it is a signal strong signal enough to drive the main power amplifier.
This circuit uses NE5532 Low-Noise High-Speed Audio Operational Amplifier. The internal structure has Dual op-amp in 8 DIP pinout. So, easy to use in Dual Opamp in a stereo system. You can use the legs to rest the image structure IC NE5532.
Principle of working
When the input signal comes through the R1 and C1. They are coupling and filter the signal to pin 3 (input) of IC1.
The IC1 is set in non-inverting mode. So, the input and output have in phase the same. And, the output gains at pin 1 depends on R3, R4, R5, R6, and R2.
Next, You can choose only one input channel by rotating switch-S1. Which each input channel has a different amplitude.
For example, if selected to a position of the Microphone signal. Its amplitude is about 50 mV.
We can calculate the gain of output.
AV = (R3/R2) 1 = 21 times.
Then, the input amplitude times AV answer the output voltage. Each position of the input always become into the output amplitude about 1 Vrms.
Simple op-amp Preamplifier circuit using LM382
If your music so light. It has many reasons that the sound of the speaker is so low volume. It may need a preamplifier. Here is simple op-amp preamplifier circuit using LM382. It can amplify the low signals to higher, before entering to an input of the amplifier.
In the circuit, it usesLM382— Low Noise Dual Preamplifier— and a few components, So small circuit. We can select a sound general signal from AUX and MAG, Pressing S1a.
The S1 is TPDT switch – Trible – pole, Double-throw. The S1b also choose both signals. It connects the RC networks.
This circuit requires only a single power supply, from 10V to 40V. It is a very wide voltage range.
Note: We do not use the MAG input. So we may cut it out.
The others detail, see in the circuit.
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