Limiter circuit-Based Audio Op-Amp

This audio peak limiter employs a FET as a variable resistance to attenuate the input signal according to a control voltage (CV). It offers unusually good performance with low cost and component count. A TL072 dual opamp (U1) provides the circuit gain and full wave peak detection.

Skema Rangkaian Audio Limiter Berbasis Op-Amp


If desired, a LED VU meter may be used here instead, and with proper calibration will give a good indication of the peak attenuation at any time. This option will require some experimentation from the constructor, and further details are up to the individual to work out.

The 4.7K resistor and 1uF capacitor (R14 and C5) determine the attack time, which is about 5ms as shown. R12 and C5 determine the release or recovery time, and as shown this is approximately 1 second.

R11, C3 C4 and R13 form the distortion cancelling circuit, and as can be seen, the control voltage impedance is very low compared to the distortion cancellation impedance, so the circuit's attack time is not compromised. The values of resistance and capacitance have been optimised for the least distortion across the audio band, at 0.3% THD typical for frequencies above around 500 Hz, at 1.65V RMS output level. Below 500 Hz, the distortion rises gently with decreasing frequency, but also falls with lower voltages. Distortion is negligible at any voltage level below the limiting threshold.

Be careful of values for R14 of less than 1k, as the opamp will be unable to supply the current needed to charge C5. R13 (3k) is easily made using a 1k2 and 1k8 resistor in series. C5 needs to be a low leakage capacitor - either a low leakage electrolytic or a tantalum. A standard electro is inappropriate for this circuit.

In addition, always keep R12 a minimum of 10 times R14 ... for example, if R14 were to be 1k, the minimum value for R12 will be 10k. This would be a very fast limiter indeed

Subwoofer Controller circuit

Subwoofer controller is quite simple, an input buffer provides phase switching and ensures that the input impedance of the source does not affect the filter performance, and this is nowfollowed by a 12dB/octave high pass filter. The phase reverse switch is used so that the sub can be properly phased to the rest of the system. If the mid-bass disappears as you advance the level of control, then the phase is wrong, so just switch to the opposite position.Contribute a better translation

The board has only one input, so if you plan to use a normal stereo feed supplying a single P48 board, you'll need to sum the two stereo outputs. This is easily accomplished by using a pair of resistors - the value should be between 2.2k and 4.7k. If this is done, replace R1 with either a 100 ohm resistor or a wire link.

Skema Rangkaian subwoofer Controller

VR1 is used to change the gain of the second integrator. The level through the controller can be set to make sure that there is no distortion - there can be a huge amount of gain at low frequencies, and if the gain is too high, distortion is assured!

The high-pass filter is designed as a peaking type, and gives a response that is almost perfect down to 20Hz. The lowest frequency can be tailored by changing C1, C2, C3 and C4. As shown, the response peaks at 18Hz, but you can use 68nF to increase this to 27Hz, or 47nF for 39Hz. See Table 1 for the full range of values.

The integrators (U2B and U2A) include shelving resistors (R8 and R11), and the capacitor / resistor networks (C3-R9, C4-R12) allow the HF attenuation to be halted at a specific frequency.

Important:

The unity gain frequency is important in only one respect - it will determine the internal gain of the system, and needs to be set based on the input signal level. If the unity gain frequency is set to (say) maximum (68Hz) and you have a 1V RMS input, then a 1V RMS input at 20Hz will severely clip the integrators. The setting for VR1 is determined by the input sensitivity of your power amplifier(s) used on the main system. It is probably easier to experiment a little than try to measure everything.

Circuit Condenser Mic Pre-Amp

Microphone amplifier circuit is simple, consisting of 2 levels. with wide dynamic regions, small noise, and can with a long cable about 50 meters.

Skema rangkaian Pre-Amp mic condenser


Note:
all capacitor (elco) using 25-volt
to avoid the buzzing sound, use a good regulator supplay
This circuit can provide voltage 6-20volt

This circuit uses low noise transistors are type types: BC 650 C but the transistor is hard to find, so you can replace it with 109 BC is no less good. This condenser mic element in it is a very sensitive microphone, and to use this mic condenser required voltage between 2-10 volts, for that we can resistors in series with 1K-10 K ohms, in the picture above the tide 1k ohms

Pin BC109
Emitter
Base
ollector, connected to the case

BC109 limiting values

collector-base voltage 30 V
collector-emitter voltage 20 V
emitter-base voltage 5 V
collector current (DC) 100 mA
peak collector current 200 mA
peak base current 200 mA
total power dissipation Tamb £ 25 °C - 300 mW
storage temperature 65 +150 °C
junction temperature 175 °C
operating ambient temperature -65 +150 °C
DC current gain (hFE) IC = 10 mA; VCE = 5 V 100 -- 270

The series of Audio Noise Reduction (DNR system)

This circuit can be use to audio noise reduction for use with audio playback systems. The DNR system is noncomplementary, meaning it does not require encoded source material. The system is compatible with virtually all prerecorded tapes and FM broadcasts. Psychoacoustic masking, and an adaptive bandwidth scheme allow the DNR to achieve 10 dB of noise reduction. DNR can save circuit board space and cost because of the few additional components required.

Skema Rangkaian Peredam Noise Audio (DNR system )

PCD layout DNR system

Features
Non-complementary noise reduction, “single ended”
Low cost external components, no critical matching
Compatible with all prerecorded tapes and FM
10 dB effective tape noise reduction CCIR/ARM
weighted
Wide supply range, 4.5V to 18V
1 Vrms input overload
Applications
Automotive radio/tape players
Compact portable tape players
Quality HI-FI tape systems
VCR playback noise reduction
Video disc playback noise reduction
Note:
The circuit system should always be placed before tone and volume controls. Placing DNR system after tone or volume control won’t work because any adjustment of these controls would alter the noise floor seen by the DNR control path.

Audio Stereo Channel Selector circuit

This circuit serves for connecting the stereo outputs from Four Different channels as inputs and only one of Them is selected to the output at any one time.

When the circuit switch on, channel A (AR and AL) is selected. If no audio is present in channel A, the circuit Waits for Some time and then Selects the next channel (channel B). This search operation continues Until it detects an audio signal in one of the channels. The inter-channel delay time or the wait Can be adjusted with the help of preset VR1. If still longer time is needed, May replace one capacitor C1 with of higher value.

To manually skip over from one active channel to another active channel, simply push the skip switch (S1), until the desired channel input gets selected. The selected channel (A, B, C, or D) is indicated by the glowing of corresponding LED (LED11, 12, 13, or 14 ).

Skema rangkaian audio channel selector stereo


IC CD4066 contains 4 analog switches, These switches are connected to four separate channels. These analogue switches are controlled by IC CD4017 outputs. CD4017 is a 10-bit ring counter IC. Since only one of its outputs is high at any instant, only one switch will be closed at a time. IC CD4017 is configured as a 4-bit ring counter by connecting the fifth output Q4 (pin 10) to the reset pin. Capacitor C5 in conjunction with resistor R6 forms a power-on-reset circuit for IC2, so that on initial switching on of the power supply, output Q0 (pin 3) is always high . The clock signal to CD4017 is provided by IC1 NE555 which acts as an astable multivibrator when transistor T1 is in cut- off state.

IC5 KA2281 is used here for not only indicating the audio levels of the selected stereo channel, but also for forward biasing transistor T1. As soon as a specific threshold audio level is detected in a selected channel, pin 7 and/or pin 10 of IC5 goes low . This low level is coupled to the base of transistor T1, through diode-resistor combination of D2-R1/D3-R22. As a result, transistor T1 conducts and causes output of IC1 to remain low as long as the selected channel output exceeds the preset audio threshold level.

Presets VR2 and VR3 have been included for adjustment of individual audio threshold levels of left and right stereo channels, as desired. Once the multivibrator action of IC1 is disabled, output of IC2 does not change further. Hence, searching through the channels continues until it receives an audio signal exceeding the preset threshold value. The skip switch S1 is used to skip a channel even if audio is present in the selected channel. The number of channels can be easily extended up to ten, by using additional 4066 ICs.

Megabass Circuit

The following is megabass circuit schematic (rangkaian megabass) . The megabass circuit is a modified Baxandall tone control with no bass cut and no treble control. It boosts frequencies from about 30Hz to 160Hz can boost by 14dB.

Skema Rangkaian megabass

Note:
The input capacitor can be replaced with a .01uf cap if you wish.
The 10pf capacitor is optional and will start rolling off everything over 15kHz. 5pf will double this to 31kHz.
The tone control requires a low impedence input. If you already have a low impedence input, the input buffer can be removed. However, the output is inverted.
The opamp is not critical. A 4558 would be just fine.
I do not show the parts for the +4.5 reference. Here is the +4.5 voltage divider I used.

IC A4558 Pinning

The A4558 is a monolithic Integrated Circuit designed for dual operational amplifier.

Absolute maximum ratings of A4558 Ap-amp
Supply voltage VCC 20 or ±10 V
Differential input voltage VIND 20 V
Input voltage VIN ±10 V
Power Dissipation PD 300 mW
Operating temperature Topr -45 ~ +85 °C
Storage temperature Tstg -55 ~ +150 °C