Vocal Adaptor for Bass Guitar Amp Circuit Diagram

These days, music is a major hobby for the young and not-so-young. Lots of people  enjoy  making  music,  and  more  and  more dream of showing off their talents on stage. But one of the major problems often encountered is the cost of musical equipment. How many amateur music groups sing  through an amp borrowed from a guitarist or bass player? 

This is where the technical problems arise not in terms of the .25” (6.3 mm)  jack, but in terms of the sound quality (the words  are barely understandable) and volume (the amp  seems to produce fewer decibels than for a guitar). What’s more, unpredictable feedback may cause damage to the speakers and is very unpleasant on the ear. This cheap little  easy-to-build project can help solve these technical  problems.

Circuit diagram :

Vocal Adaptor for Bass Guitar Amp Circuit Diagram

 

A guitar (or bass guitar) amplifier is designed first and foremost to reproduce the sound of the guitar or bass as faithfully as  possible. The frequency response of the amp doesn’t need to be as wide or as flat as in hi-fi (particularly at the high end), and so this sort of amplifier won’t permit faithful reproduction of the voice. If you build an adaptor to compensate for the amp’s limited frequency response by amplifying in advance the frequencies that are  then attenuated by the amp, it’s possible to  improve the quality of the vocal sound. That’s  just what this circuit attempts to do.


The adaptor is built around the TL072CN low-noise dual FET op-amp, which offers good value for money. The NE5532 can be used with almost the same sound quality, but at (slightly) higher cost. The circuit breaks  down into two stages. The first stage is used to match the input impedance and amplify the microphone signal. For a small 15 W guitar or bass amplifier, the achievable gain is  about 100 (gain = P1/R1). For more powerful amplifiers, the gain can be reduced to  around 50 by adjusting P1. The second stage amplifies the band of frequencies (adjustable using P2 and P3) that are attenuated by the guitar amp, so as to be able to reproduce the (lead)  singer ’s voice as clearly, distinctly, and  accurately as possible. To refine the adaptor and tailor it to your amplifier and speaker, don’t be afraid to experiment with the component values and the type  of capacitors.


The circuit can readily be powered using a 9 V battery, thanks to the voltage divider R4/R5 which converts it into a symmetrical  ±4.5 V supply.

Author : Jérémie Hinterreiter

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Camera Video Amplifier Circuit (Transistorized )

There are occasions  when you want to view your video clips taken in your digital camera on  your TV.You can do so by interfacing the camera video output to video input of your TV.But this times you cant connect directly as it needs some amplification before the signal reaches from camera to television

The video amplifier schematic circuit shown in the figure is a simple PAL video amp, expected to have a 3db bandwidth of 5.5MHz. You can connect your camera to TV through this circuit. So this is a low level transistorized video amplifier stage that accepts 1V (p-p) and outputs 2V(p-p) signal. 

Notes The circuit requires a 5V dc power supply

Sourrced By: Streampowers

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10 to 14W Class A Audio Amplifier Circuit Diagram

I have built this amplifier and it does sound good. It requires a preamp as it hasn't got much gain. It requires big heat sinks and a large transformer and a great power supply and careful wiring, but in the end it is xtremely simple and it sounds very good. The zener diode rejects any ripple coming from the power supply, But you still only want a ripple of 10mV max. The ripple reaching the input is amplified, so the zener diode gets rid of that, but whatever ripple there is will still reach the power stage.

10 to 14W Class A Audio Amplifier Circuit Diagram

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Low Impedance Microphone Amplifier

The circuit is a microphone amplifier for use with low impedance (~200 ohm) microphones. It will work with stabilized voltages between 6-30VDC. If you don't build the impedance adapter part with T1, you get a micamp for higher impedance microphones. In this case, you should directly connect the signal to C7.

•  R1=15k
• R2= 150k
• R3= 2k2
• R4= 820
• R6= 10k
• R7= 10k
• P1= 1M
• C1= 3k9
• C2= 100u
• C3= 22u
• C4= 4u7
• C5= 470u
• C6= 10u
• C7= 100n
• C8= 47u UNIPOLAR
• D1= 1N4148
• U1= TL081
• CN1= SIL6

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44 Watt Mobile Car Stereo Amplifier

Using a mobile phone while driving is dangerous. It is also against the law. However, you can use your mobile phone as a powerful music player with the help of a stereo power amplifier. This does away with the need of a sophisticated in-dash car music system. Most mobile phones have a music player that offers a number of features including preset/manual sound equalisers. They have standard 3.5mm stereo sockets that allow music to be played through standard stereo headphones/sound amplifiers. Nokia 2700 classic is an example.


A car audio amplifier with 3.5mm socket can be designed and simply connected to the mobile phone output via a shielded cable with suitable connectors/jacks (readymade 3.5mm male-to-male connector cable is a good alternative). Fig. 1 shows the circuit of car stereo player. It is built around popular single-chip audio power amplifier TDA1554Q (IC1). The TDA1554Q is an integrated class-B power amplifier in a 17-lead single-in-line (SIL) plastic power package.

Fig. 1: Circuit of mobile car stereo player

IC TDA1554Q contains four 11W identical amplifiers with differential input stages (two inverting and two non-inverting) and can be used for single-ended or bridge applications. The gain of each amplifier is fixed at 20 dB. Here it is configured as two 22W stereo bridge amplifiers. The amplifier is powered from the 12V car battery through RCA socket J2. Diode D1 protects against wrong-polarity connection. LED1 indicates the power status.

Connect stereo sound signal from the 3.5mm headset socket of the mobile phone to audio input socket J1. When you play the music from your mobile, IC1 amplifies the input. The output of IC1 is fed to speakers LS1 and LS2 fitted at a suitable place in your car. Electrolytic capacitor C5 connected between pin 4 of IC1 and GND improves the supply-voltage ripple rejection. Components R2 and C4 connected at mute/standby pin (pin 14) of IC1 eliminate the switch on/off plop. The circuit is quite compact. A good-quality heat-sink assembly is crucial for IC1. Fig. 2 shows the stereo socket and stereo jack.

Fig. 2: (a) 3.5mm stereo socket and (b) 3.5mm stereo jack

Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Small dimensions of the power amplifier make it suitable for being enclosed in a plastic (ABS) case with vent holes. Signal input socket, speaker output terminals, on/off switch, indicator, fuse holder and power supply socket are best located on the front panel of the enclosure as shown in Fig. 3.[link]

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Low Distortion Audio Amplifier Circuit Diagram

This is an unusual circuit for an ultra-low distortion power amp. According to my original notes the circuit is dated January 1977 so the circuit is not exactly modern but it is still sufficiently different to be interesting. The circuit was designed and sold as a card by a purveyor of surplus components but, even using mostly manufacturer's rejected transistors, we managed to get about 0.02% total harmonic distortion at 30 watts with a ±25v power supply into 8 ohms.: no bad figure even in these days of MOSFET and ICs. In 1977 anything below 0.1% was considered excellent. And this figure was pretty repeatable without doing much selection.

The problem of course is that since I haven't touched this amplifier for many a year I have absolutely no idea what modern transistor types one should use for it but they are not critical: output transistors and drivers need to be the correct type but the other transistors can be small signal types - as long as they can handle the full voltage between + and - supplies.

 Low Distortion Audio Amplifier Circuit Diagram

Tr1 and Tr2 are a long-tailed pair (LTP to save typing). It is quite common to have a LTP in an audio amp but this is different: this is a complimentary LTP. As far as I am aware no one else had used a complimentary LTP at the time, though I have since seen it used in one other circuit. So I guess the circuit is unique to the author. One of the things that limits the performance of a conventional LTP is that the tail source loads the common emitters. In a complementary LTP this can't happen as there is no tail current source so that all the current of one transistor has to flow through the other. 

Tr2's collector current flows into D1 and D2 which develop a voltage: this is used to bias Tr8 as a constant current source for Tr4's collector. The fact that Tr4 is working at a constant current defines its base-emitter voltage which must be developed across R4. This defines a current in R4 and this is the current that the LTP must operate at - so the ring of four transistors (Tr1, 2, 3, & 4) is self biasing and all transistors work at their best with minimum unwanted loads and biasing detracting from the performance. Tr4 is actually one of the most critical transistors: in the original circuit it was selected for Vce greater than 75v. Most Texas BC212s passed easily. Lower voltage transistors caused an increase in distortion level. 

There is always a down side to any circuit: in the conventional LTP the base-emitter voltages tend to cancel each other out. In the complimentary LTP they add so there is a drop of about 1.2v between the two bases: this must be cancelled in the biasing chain and, since this circuit was designed for operation over a wide range of supply voltage, I had to be a little clever. Because of the constant current operation of the LTP and the constant voltage drop across D1 & D2, there is also a constant voltage across R14. This drop is used to lift up the bottom of the biasing chain (R1 and R11) so that the output sits at around half supply voltage, over a wider supply range. 

D3 and D4 develop a bias voltage so that the output transistors are at the correct point, slightly conducting, to minimise crossover distortion. 

The output transistors are complimentary (the original design used MJE2011 and MJE2021) and are driven by complimentary drivers: PNP driving NPN and vice versa. This arrangement is not only pleasingly symmetrical but gives better performance that the more common Darlington arrangement - the full gain of all the transistors is used and there is more internal feedback and less voltage drop. 

The output current is monitored in the two resistors R7 and R22 (180 milliohms). The current limiting is unusual in that it works inside the input ring at an earlier stage than normal. This has an advantage that the current limiting transistors do not load the drive circuitry - which will introduce distortion. The slight down side is that there may be a slight tendency to oscillation when in current limit. R3 and R14 are necessary to restrict the current availability when the current limit engages. R5 and R19 are present to make the current limit vary with the voltage across the power transistors to avoid the second breakdown region of power transistors. 

The points shown connecting terminals 1-2 and 6-7 are 'scratch-through tracks'. 1 and 2 are the power and signal earths: to keep distortion in a stereo system to a minimum the currents in these must never share the same path so in a stereo system four earth wires are run to the system's common earth point - a 'spider' common earth - and this means breaking the link. The link between 6 & 7 is in the feedback path and there are times when this can usefully be broken - one 'cheapskate' was to fit a tone control circuit here (see below). It works fine but is a bit of an insult to such a low-distortion design!. A third break point is in the collector of Tr2. Breaking this shuts down the amplifier completely and safely. Is a thermal switch is to be fitted, this is the place. 

Overall negative feedback is in two parts: D.c. is fed back via R13: there is 100% d.c. feedback. A.c. feedback is via R12 and R17. Note the output capacitor is inside this feedback loop (speaker connects between terminal 5 and negative) which extends the low frequency response. 

Another feature is the accessibility of both ends of the output coupling capacitor: being designed for a junk shop, they didn't want to use expensive capacitors! So for extra bass performance an additional capacitor can easily be connected. 

The circuit can also be driven as a low input impedance: break 6-7, short pin 8 to C4's positive and apply input to pin 6. In this mode the input distortion is actually better: my original notes show as low as 0.01%!

When building a low-distortion amplifier, layout is vital. In fact to get distortion around 0.02% requires a lot of skill and experience. The problem is that the current in the output stage alternates between the two power transistors so is a 'rectified' version of the input. Now there is no such thing as a 'wire'. Any real piece of wire or copper track is a resistor with associated inductance and capacitance. If the high current, rectified output signal mixes in the same 'piece of wire' with the input signal the distortion in the rectified output current will feed into the input and cause the overall distortion to rocket. This is something which cannot properly be taught but has to be experienced. A skilled audio engineer will spend his lifetime learning about it. 

Source by : 4qdtec

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22 Watt Stereo Amplifier Circuit Diagram

This 22 Watt Stereo Amplifier Circuit Diagram.This circuit is very basic to build and puts out great power for your car or home. Keep all leads as short as possible.

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Supply Instrumentation Amplifier Circuit Diagram

The OP284 is a low noise dual op amp with a bandwidth of 4MHz and rail-to-rail input/output operation. These properties make it ideal for low supply voltage applications such as in a two op amp instrumentation amplifier as shown in the diagram. The circuit uses the classic two op amp instrumentation topology with four resistors to set the gain. The transfer equation of the circuit is identical to that of a non-inverting amplifier. Resistors R2 and R3 should be closely matched to each other as well as to resistors (R1+P1) and R4 to ensure good common-mode rejection (CMR) performance. It is advisable to use resistor networks for R2 an and R3, because these exhibit the necessary relative tolerance matching for good performance.

 Supply Instrumentation Amplifier Circuit Diagram

Potentiometer P1 is used for optimum d.c. CMR adjustment, and capacitor C1 is used to optimize a.c. CMR. With circuit values as shown, circuit CMR is better than 80 dB over the frequency range of 20 Hz to 20 kHz. Circuit referred-to-input (RTI) noise in the 0.1 Hz to 10 Hz band is exemplary at 0.45 µVpp. Resistors R5 and R6 protect the inputs of the op amps against over-voltages. Capacitor C2 may be included to limit the bandwidth. Its value should be adjusted depending on the required closed-loop bandwidth of the circuit. The R4-C2 time constant creates a pole at a frequency, f3dB, equal to f3dB=1/2πR4C2. With a value of C2 of 12 pF, the bandwidth is about 500 kHz. The amplifier draws a current of about 2mA. 

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Low Power Wireless Audio Power Amplifier

Battery-Powered portable unit, Suitable for all type Televisions

Using this low-cost project one can reproduce audio from TV without disturbing others. It does not use any wire connection between TV and Loud Speaker. In place of a pair of wires, it uses invisible infra-red light to transmit audio signals from TV to Loud speakers, Without using any lens a range of up to 6 meters is possible. Range can be extended by using lenses and reflectors with IR sensors comprising transmitters and receivers.

Transmitter's operation:

IR transmitter uses two-stage transistor amplifier to drive two series-connected IR LEDs. An audio output transformer (T1) is used (in reverse) to couple audio output from TV to the IR transmitter. Transistors Q1 and Q2 amplify the audio signals received from TV through the audio transformer. Low impedance output windings (lower gauge or thicker wires) are used for connection to TV side while high-impedance windings are connected to IR transmitter. This IR transmitter can be powered from a 9V mains adapter or a 9V battery. Red LED (D1) in transmitter circuit functions as a Zener diode (0.65V) as well as supply-on indicator.

Transmitter diagram:

Wireless Audio Power Amplifier Transmitter Circuit Diagram

Receiver's operation:

IR receiver uses popular op-amp IC µA741 and audio-frequency amplifier IC LM386 along with phototransistor L14F1 (Q3) and some discrete components. The sound generated by TV set is transmitted through IR LEDs, received by phototransistor Q3 and fed to pin 2 of IC µA741 (IC1). Its gain can be varied using potmeter P2. The output of IC µA741 is fed to IC LM386 (IC2) via capacitor (C7) and potmeter P3. The sound produced is heard through the receiver’s loudspeaker. Potmeter P3 is used to control the volume of loudspeaker SPKR (8-ohm, 1W).

Receiver diagram:

Wireless Audio Power Amplifier Transmitter Circuit Diagram

Parts:

P1 = 10K
P3 = 10K
P2 = 1M

R1 = 4.7K
R2 = 22K
R3 = 100R
R4 = 10R-1W
R5 = 10K
R6 = 10K
R7 = 15K
R8 = 15K
R9 = 100K
R10 = 680R-1W
R11 = 1K
R12 = 10R-1W

C1 = 220uF-25V
C2 = 220uF-25V
C3 = 10uF-25V
C4 = 220uF-25V
C5 = 220uF-25V
C6 = 100nF-63V
C7 = 100nF-63V
C8 = 100nF-63V
C9 = 100nF-63V

D1 = Red LED
D2 = IR LEDs
D3 = IR LEDs

Q1 = BC547
Q2 = BD140
Q3 = L14F1

IC1 = uA741 Opamp
IC2 = LM386

J1 = Audio input Jack
T1 = Audio Transformer
SPKR = 1W-8ohm

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Subwoofer Lowpass Filter using uA741 Single Op-Amp Ic

This is the simplest Sub woofer Low Pass filter Circuit using uA741 single op amp ic. The circuit is very low cost with respect to their work. The cut off frequency of this circuit is 25Hz to 80Hz maximum. Using this circuit , you can easily design a 2.1 Sub-woofer Speaker System at your own Home. The circuit contains very few components.In Pakistan, the cost of this circuit with PCB is Rs:45 The same circuit is working in my own hand made sub-woofer system. So Try this

Subwoofer Lowpass Filter using uA741 Single Op-Amp Ic  

Parts List: 

R1,R3,R4 = 10K 1/4W
R2=100K 1/4W
CY1,CY2 = 0.22uF Polyester
C1,C2 = 10uF/25V Electrolytic
IC1 = uA741A Single Op-Amp Ic + 8 Pin Ic Socket
3 Pin Male & Female Connector x 2
2 Pin Male & Female Connector x 1
PCB as in required size 4.5 cm x 3.4 cm

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2 Watt Audio Amplifier Circuit Diagram

This amplifier was designed to be self-contained in a small loudspeaker box. It can be feed by Walkman, Mini-Disc, iPod and CD players, computers and similar devices fitted with line or headphone output. Of course, in most cases you will have to make two boxes to obtain stereo.

Circuit Diagram:

Parts:

P1 = 10K
R1 = 33K
R2 = 33K
R3 = 33R
R4 = 15K
R5 = 1K
R6 = 1K
R7 = 680R
R8 = 120R-1/2W
R9 = 100R-1/2W Trimmer Cermet
C1 = 10µF-63V
C2 = 10µF-63V
C3 = 100µF-25V
C4 = 470µF-25V
C5 = 47pF-63V
C7 = 470µF-25V
C6 = 220nF-63V
C8 = 1000µF-25V
D1 = 1N4148
Q1 = BC560C
Q2 = BC337
Q3 = TIP31A
Q4 = TIP32A
SW1 = SPST switch
SPKR = 3-5 Watt Loudspeaker

Circuit Operation:

The circuit was deliberately designed using no ICs and in a rather old-fashioned manner in order to obtain good harmonic distortion behavior and to avoid hard to find components. The amplifier(s) can be conveniently supplied by a 12V wall plug-in adapter. Closing SW1 a bass-boost is provided but, at the same time, volume control must be increased to compensate for power loss at higher frequencies. In use, R9 should be carefully adjusted to provide minimal audible signal cross-over distortion consistent with minimal measured quiescent current consumption; a good compromise is to set the quiescent current at about 10-15 mA. To measure this current, wire a DC current meter temporarily in series with the collector of Q3.

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5 Watt Class-A Audio Amplifier Circuit Diagram

This solid-state push-pull single-ended Class A circuit is capable of providing a sound comparable to those valve amplifiers, delivering more output power (6.9W measured across a 8 Ohm loudspeaker cabinet load), less THD, higher input sensitivity and better linearity. Voltage and current required for this circuit are 24V and 700mA respectively, compared to 250V HT rail and 1A @ 6.3V filament heating for valve-operated amplifiers. The only penalty for the transistor operated circuit is the necessity of using a rather large Heatsink for Q2 and Q3 (compared to the maximum power delivered).In any case, the amount of heat generated by this circuit can be comparable to that of a one-valve amplifier. An optional bass-boost facility can be added, by means of R5 and C5.

 Circuit diagram:

Parts:

P1 = 47K
R1 = 100K
R2 = 12K
R3 = 47K
R4 = 8.2K
R5 = 1.5K
R6 = 2.7K
R7 = 100R
R8 = 100R
R9 = 560R-1/2W
R10 = 1R-1/2W
Q1 = BC560
Q2 = BD439
Q3 = BD439
C1 = 10uF-63V
C2 = 10uF-63V
C3 = 47uF-25V
C4 = 100uF-35V
C5 = 150nF-63V
C6 = 220uF-25V
C7 = 220uF-25V
C8 = 1000uF-25V
SPKR = 5W-8R Speaker

Notes:

• If necessary, R2 can be adjusted to obtain 13V across C8 positive lead and negative ground.
• Total current drawing of the circuit, best measured by inserting the probes of an Avo-meter across the positive output of the power supply and the positive rail input of the amplifier, must be 700mA. Adjust R8 to obtain this value if necessary.
• Q2 and Q3 must be mounted on a finned Heatsink of 120x50x25mm. Minimum dimensions.
• Add R5 and C5 if the bass-boost facility is required.

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AC Mains Short-Circuit Protector Circuit Diagram

The simple short circuit and overload protector design presented here can be used for protecting valuable mains operated gadgets like amplifiers, TV sets, DVD players or any other similar appliance.Normally all sophisticated gadgets today incorporate an in built short circuit protector arrangement, yet still adding a more comprehensive external protection device could only benefit the connected system.

Moreover, for gadgets such as amplifiers which are home built this protection device could prove to be very effective and useful. Also for an hobbyist who prefers building electronic gadgets at home could be greatly benefited with the present idea.

The presented short circuit protector design works on a very basic principle and costs not more than a couple of dollars.

Let's learn the functioning details of the proposed circuit.

On applying power, the high current from the 220V input is dropped sufficiently by C1, rectified by D1 and filtered by C2 to feed the gate of the triac T1.

The triac conducts and switches ON the connected transformer primary thus switching ON the load which in this case is a power amplifier.

The transistor Q1 along with R1, R2 forms a current sensor stage.

R2 specifically is chosen such that it develops adequate voltage across itself at the specified dangerous high current threshold.

As usual the formula for determining R2 = 0.6/current(A)

As soon as the triggering voltage accumulates across R2, Q1 activates and sinks the gate voltage of the triac to ground making it switch off.

The regulation continues as long as the short or overload condition is not removed.

The above short circuit regulation ensures that the current level above the specified dangerous level is restricted safeguarding the precious devices associated with the connected amplifier.

If a latching feature is required for the above design, the emitter Q1 can be configured with an SCR and the SCR can be used for latching and switching off the triac.

AC Mains Short-Circuit Protector Circuit Diagram

Parts List

R1 = 100 ohms
R2 = see text
R3 = 1k
R4 = 10k
C1 = 0.33/400V
C2 = 1uf/250V
Q1 = BC547
Z1 = 12V/1 watt zener diode
T1 = BT136 or as per current rating
TR1 = As per load requirement specs.

Source By Swagatam homemadecircuits

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Class one Headphone Amplifier Circuit Diagram

Class one Headphone Amplifier Circuit diagram. This circuit is derived from the Portable Headphone Amplifier featuring an NPN/PNP compound pair emitter follower output stage. An improved output driving capability is gained by making this a push-pull Class-A arrangement. Output power can reach 427mW RMS into a 32 Ohm load at a fixed standing current of 100mA. The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability. Sourced Link

Class one Headphone Amplifier Circuit diagram :

Class-A Headphone Amplifier Circuit diagram

The above mentioned shunt-feedback configuration also allows the easy addition of frequency dependent networks in order to obtain an useful, unobtrusive, switchable Tilt control (optional). When SW1 is set in the first position a gentle, shelving bass lift and treble cut is obtained. The central position of SW1 allows a flat frequency response, whereas the third position of this switch enables a shelving treble lift and bass cut.

Note:

• Before setting quiescent current rotate the volume control P1 to the minimum, Trimmer R6 to zero resistance and Trimmer R3 to about the middle of its travel.
• Connect a suitable headphone set or, better, a 33 Ohm 1/2W resistor to the amplifier output.
• Connect a Multimeter, set to measure about 10Vdc fsd, across the positive end of C5 and the negative ground.
• Switch on the supply and rotate R3 in order to read about 7.7-7.8V on the Multimeter display.
• Switch off the supply, disconnect the Multimeter and reconnect it, set to measure at least 200mA fsd, in series to the positive supply of the amplifier.
• Switch on the supply and rotate R6 slowly until a reading of about 100mA is displayed.
• Check again the voltage at the positive end of C5 and readjust R3 if necessary.
• Wait about 15 minutes, watch if the current is varying and readjust if necessary.

Parts List :

P1          : 22K  Dual gang Log Potentiometer 
R1          : 15K 
R2          : 220K
R3          : 100K
R4          : 33K 
R5          : 68K 
R6          : 50K 
R7          : 10K 
R8,R9       : 47K 
R10,R11     : 2R2 
R12         : 4K7
R13         : 4R7
R14         : 1K2
R15,R18     : 330K
R16         : 680K
R17,R19     : 220K
R20,R21     : 22K
C1,C2,C3,C4 : 10µF/25V 
C5,C7       : 220µF/25V
C6,C11      : 100nF
C8          : 2200µF/25V
C9,C12      : 1nF
C10         : 470pF
C13         : 15nF
D1          : LED
D2,D3       : 1N4002 
Q1,Q2       : BC550C 
Q3          : BC560C  
Q4          : BD136   
Q5          : BD135   
IC1         : 7815
T1          : 15CT/5VA Mains transformer
SW1         : 4 poles 3 ways rotary Switch 
SW2         : SPST slide or toggle Switch

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Mobile Automotive Stereo Player Circuit Diagram

Mobile Automotive Stereo Player Circuit diagram. Using a mobile phone while driving is dangerous. It is also against the law. However, you can use your mobile phone as a powerful music player with the help of a stereo power amplifier. This does away with the need of a sophisticated in-dash car music system. Most mobile phones have a music player that offers a number of features including preset/manual sound equalisers. They have standard 3.5mm stereo sockets that allow music to be played through standard stereo headphones/sound amplifiers. Nokia 2700 classic is an example. 

Mobile Automotive Stereo Player Circuit diagram :

Mobile Car Stereo Player Circuit Diagram

A car audio amplifier with 3.5mm socket can be designed and simply connected to the mobile phone output via a shielded cable with suitable connectors/jacks (readymade 3.5mm male-to-male connector cable is a good alternative). Fig. 1 shows the circuit of car stereo player. It is built around popular single-chip audio power amplifier TDA1554Q (IC1). The TDA1554Q is an integrated class-B power amplifier in a 17-lead single-in-line (SIL) plastic power package. 

IC TDA1554Q contains four 11W identical amplifiers with differential input stages (two inverting and two non-inverting) and can be used for single-ended or bridge applications. The gain of each amplifier is fixed at 20 dB. Here it is configured as two 22W stereo bridge amplifiers. The amplifier is powered from the 12V car battery through RCA socket J2. Diode D1 protects against wrong-polarity connection. LED1 indicates the power status.

Stereo Jack :

(a) 3.5mm stereo socket and (b) 3.5mm Stereo Jack 

Connect stereo sound signal from the 3.5mm headset socket of the mobile phone to audio input socket J1. When you play the music from your mobile, IC1 amplifies the input. The output of IC1 is fed to speakers LS1 and LS2 fitted at a suitable place in your car. Electrolytic capacitor C5 connected between pin 4 of IC1 and GND improves the supply-voltage ripple rejection. Components R2 and C4 connected at mute/standby pin (pin 14) of IC1 eliminate the switch on/off plop. The circuit is quite compact. A good-quality heat-sink assembly is crucial for IC1. Fig. 2 shows the stereo socket and stereo jack.

Proposed enclosure

Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Small dimensions of the power amplifier make it suitable for being enclosed in a plastic (ABS) case with vent holes. Signal input socket, speaker output terminals, on/off switch, indicator, fuse holder and power supply socket are best located on the front panel of the enclosure as shown in Fig. 3. 

Author : T.K. Hareendran - Copyright : EFY

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Battery-powered Headphone Amplifier

Low distortion Class-B circuitry 6V Battery Supply Battery-powered Headphone Amplifier Circuit diagram Some lovers of High Fidelity headphone listening prefer the use of battery powered headphone amplifiers, not only for portable units but also for home "table" applications. This design is intended to fulfil their needs and its topology is derived from the Portable Headphone Amplifier featuring an NPN/PNP compound pair emitter follower output stage. 

An improved output driving capability is gained by making this a push-pull Class-B arrangement. Output power can reach 100mW RMS into a 16 Ohm load at 6V supply with low standing and mean current consumption, allowing long battery duration. The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability.

Battery-powered Headphone Amplifier Circuit diagram :

Battery-powered Headphone Amplifier Circuit diagram

Notes:

• For a Stereo version of this circuit, all parts must be doubled except P1, SW1, J2 and B1.
• Before setting quiescent current rotate the volume control P1 to the minimum, Trimmer R6 to maximum resistance and Trimmer R3 to about the middle of its travel.
• Connect a suitable headphone set or, better, a 33 Ohm 1/2W resistor to the amplifier output.
• Switch on the supply and measure the battery voltage with a Multimeter set to about 10Vdc fsd.
• Connect the Multimeter across the positive end of C4 and the negative ground.
• Rotate R3 in order to read on the Multimeter display exactly half of the battery voltage previously measured.
• Switch off the supply, disconnect the Multimeter and reconnect it, set to measure about 10mA fsd, in series to the positive supply of the amplifier.
• Switch on the supply and rotate R6 slowly until a reading of about 3mA is displayed.
• Check again the voltage at the positive end of C4 and readjust R3 if necessary.
• Wait about 15 minutes, watch if the current is varying and readjust if necessary.
• Those lucky enough to reach an oscilloscope and a 1KHz sine wave generator, can drive the amplifier to the maximum output power and adjust R3 in order to obtain a symmetrical clipping of the sine wave displayed.

Technical data:

Output power (1KHz sinewave):
    16 Ohm: 100mW RMS
    32 Ohm: 60mW RMS
    64 Ohm: 35mW RMS
    100 Ohm: 22.5mW RMS
    300 Ohm: 8.5mW RMS
Sensitivity:
    160mV input for 1V RMS output into 32 Ohm load (31mW)
    200mV input for 1.27V RMS output into 32 Ohm load (50mW)
Frequency response @ 1V RMS:
    flat from 45Hz to 20KHz, -1dB @ 35Hz, -2dB @ 24Hz
Total harmonic distortion into 16 Ohm load @ 1KHz:
    1V RMS (62mW) 0.015% 1.27V RMS (onset of clipping, 100mW) 0.04%
Total harmonic distortion into 16 Ohm load @ 10KHz:
    1V RMS (62mW) 0.05% 1.27V RMS (onset of clipping, 100mW) 0.1%
Unconditionally stable on capacitive loads

Source : Streampowers

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DC- 2 Audio Amplifier Circuit Diagram

DC-Coupled Audio Amplifier Circuit Diagram. Designs for audio amplifiers with DC coupling to the load are not often encountered these days, even though they offer definite advantages. One advantage is that there is no need for the complication of a second (symmetric) power supply; another is good frequency and phase response. Also, no special electrolytic capacitors are needed for voltage stabilisation, and switch-on ‘thump’ is much reduced. To try to rescue this class of circuit from obscurity the author has designed a headphone amplifier working along the lines illustrated in Figure 1.

DC-Coupled Audio Amplifier Circuit Diagram 

It consists of a voltage divider, a voltage follower and the loudspeaker in the headphones, whose other side is connected to the junction of two electrolytic capacitors, providing the virtual earth. The potential at this point is, of course, half the supply voltage. All we need to do now is suitably couple in the audio signal to be amplified. Figure 2 shows a practical realisation of this idea in the form of a stereo headphone amplifier. The amplifier itself consists of IC1 and P1, R3 and R4 (giving a gain of 11).

This part of the circuit demands no further explanation, and the same goes for the voltage divider mentioned above, formed by R1a and R1b. The signal is coupled in via the potentiometers. C2 and R2 have a special purpose: C2 connects the bottom end of the potentiometers (ground for the input signal) to the virtual earth. However, this capacitor creates a feedback path which can lead to oscillation of the amplifier under some circumstances. R2 damps this tendency to oscillate.

DC-Coupled Audio Amplifier Circuit Diagram 2

It is possible to calculate suitable values for these components, but it is better to determine them by experiment. C2 must be sufficiently large that stray electric fields do not cause unacceptable hum at the output. R2 must be sufficiently large that the voltage at the amplifier’s virtual earth stabilises quickly enough after switch-on. The polarity of the electrolytic is unimportant as no significant voltage appears across the network. It is possible to try the circuit out with the C2/R2 network shorted and observe the behaviour of the circuit at switch-on using an oscilloscope. Depending on the degree of asymmetry in the circuit, the voltage at the virtual earth point can take a considerable time to stabilise.

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Hybrid Headphone Amplifier Circuit Diagram

Potentially, headphone listening can be technically superior since room reflections are eliminated and the intimate contact between transducer and ear mean that only tiny amounts of power are required. The small power requirement means that transducers can be operated at a small fraction of their full excursion capabilities thus reducing THD and other non-linear distortions. This design of a dedicated headphones amplifier is potentially controversial in that it has unity voltage gain and employs valves and transistors in the same design. Normal headphones have an impedance of 32R per channel. The usual standard line output of 775 mV to which all quality equipment aspires will generate a power of U2 / R = 0.7752 / 32 = 18 mW per channel across a headphone of this impedance.

Hybrid Headphone Amplifier Circuit Diagram

An examination of available headphones at well known high street emporiums revealed that the sensitivity varied from 96 dB to 103db/mW! So, in practice the circuit will only require unity gain to reach deafening levels. As a unity gain design is required it is quite possible to employ a low distortion output stage. The obvious choice is an emitter follower. This has nearly unity gain combined with a large amount of local feedback. Unfortunately the output impedance of an emitter follower is dependent upon the source impedance. With a volume control, or even with different signal sources this will vary and could produce small but audible changes in sound quality.

To prevent this, the output stage is driven by a cathode follower,based around an ECC82 valve (US equivalent: 12AU7).

This device, as opposed to a transistor configuration, enables the output stage to be driven with a constant value, low impedance. In other words, the signal from the low impedance point is used to drive the high impedance of the output stage, a situation which promotes low overall THD. At the modest output powers required of the circuit, the only sensible choice is a Class A circuit. In this case the much vaunted single-ended output stage is employed and that comprises of T3 and constant current source T1-T2.

The constant current is set by the Vbe voltage of T1 applied across R5 With its value of 22R, the current is set at 27 mA. T3 is used in the emitter follower mode with high input impedance and low output impedance. Indeed the main problem of using a valve at low voltages is that it’s fairly difficult to get any real current drain. In order to prevent distortion the output stage shouldn’t be allowed to load the valve. This is down to the choice of output device. A BC517 is used for T3 because of its high current gain, 30,000 at 2 mA! Since we have a low impedance output stage, the load may be capacitively coupled via C4. Some purists may baulk at the idea of using an electrolytic for this job but he fact remains that distortion generated by capacitive coupling is at least two orders of magnitude lower than transformer coupling.

The rest of the circuitry is used to condition the various voltages used by the circuit. In order to obtain a linear output the valve grid needs to be biased at half the supply voltage. This is the function of the voltage divider R4 and R2. Input signals are coupled into the circuit via C1 and R1. R1, connected between the voltage divider and V1’s grid defines the input impedance of the circuit. C1 has sufficiently large a value to ensure response down to 2 Hz. Although the circuit does a good job of rejecting line noise on its own due to the high impedance of V1’s anode and T3’s collector current, it needs a little help to obtain a silent background in the absence of signal.

The ‘help’ is in the form of the capacitance multiplier circuit built around T5. Another BC517 is used here to avoid loading of the filter comprising R7 and C5. In principle the capacitance of C5 is multiplied by the gain of T5. In practice the smooth dc applied to T5’s base appears at low impedance at its emitter. An important added advantage is that the supply voltage is applied slowly on powering up. This is of course due to the time taken to fully charge C5 via R7. No trace of hum or ripple can be seen here on the ‘scope. C2 is used to ensure stability at RF. The DC supply is also used to run the valve heater. The ECC82 has an advantage here in that its heater can be connected for operate from 12.6 V. To run it T4 is used as a series pass element. Base voltage is obtained from the emitter of T5. T4 has very low output impedance, about 160 mR and this helps to prevent extraneous signals being picked up from the heater wiring. Connecting the transistor base to C5 also lets the valve heater warm up gently. A couple of volts only are lost across T4 and although the device runs warm it doesn’t require a heat-sink.

Author: Jeff Macaulay - Copyright: Elektor Electronics

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SRPP Headphone Amplifier Circuit Diagram

Mention valve amplifiers and many designers go depressive instantly over the thought of a suitable output transformer. The part will be in the history books forever as esoteric, bulky and expensive because, it says, it is designed and manufactured for a specific valve constellation and output power. There exist thick books on valve output transformers, as well as gurus lecturing on them and winding them by hand. However, with some concessions to distortion (but keeping a lot of money in your pocket) a circuit configuration known as SRPP (series regulated push-pull) allows a low-power valve amplifier to be built that does not require the infamous output transformer. SRPP is normally used for preamplifier stages only, employing two triodes in what looks like a cascade arrangement.



 SRPP Headphone Amplifier Circuit Diagram

Here we propose the use of two EL84 (6BQ5) power pentodes in triode SRPP configuration. The reasons for using the EL84 (6CA5) are mainly that it’s cheap, widely available and forgiving of the odd overload condition. Here, two of these valves are SRPP’d into an amplifier that’s sure to reproduce that ‘warm thermionic sound’ so much in demand these days.

Before describing the circuit operation, it must be mentioned that construction of this circuit must not be attempted unless you have experience in working with valves at high voltages, or can rely on the advice and assistance of an ‘old hand’. As a safety measure, two anti-series connected zener diodes are f it ted at the amplifier output. These devices protect the output (i.e. your head-phones and ears) against possibly dangerous voltages at switch-on,or when output capacitor C3 breaks down.

The power supply is dimensioned for two channels, i.e. a stereo version of the amplifier. The values in brackets are for Elektor readers on 120 VAC power. Note the doubled values of fuses F1 and F3 in the AC primary circuits. The PSU is a conventional design, possibly with the exception of the 6.3 V heater voltage being raised to a level of about +80 V through voltage divider R7-R8. This is done to prevent exceeding the maximum cathode-heater voltage specified for the EL84 (6CA5). R6 is a bleeder resistor emptying the reservoir capacitors C8 and C9 in a quick but control-led manner when the amplifier is switched off. Rectifier diodes D3–D6 each have an anti-rattle capacitor across them.

In the amplifier, assuming the valves used have roughly the same emission, the half-voltage level of about +145 V exists at the junction of the anode of V1 and the control grid of V2. The SRPP is no exception to the rule that high quality, (preferably) new capacitors are essential not just for reproducibility and sound fidelity, but also for safety.

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Reliable 6 Watt Hi Fi Audio Amplifier Using TDA2613

A 6 watt audio amplifier circuit using TDA2613 is shown here. TDA2613 is an integrated Hi-Fi  audio amplifier IC from Philips Semiconductors. The IC is switch ON / switch OFF click proof, short circuit proof, thermally protected and is available in 9 pin single in line plastic package. In the given circuit, TDA2613 is wired to operate from a single supply.

Capacitor C4 is the input DC decoupler while capacitors C5, C6 are power supply filters. Input audio is fed to the non inverting input through capacitor C4. Inverting input and Vp/2 pins of the IC are tied together and connected to ground through capacitor C3. Capacitor C2 couples the speaker to the ICs output and the network comprising of capacitor C1 and resistor R1 improves the high frequency stability.

Reliable 6 Watt Hi Fi Audio Amplifier Circuit diagram

Notes.

• Assemble the circuit on good quality PCB.
• Supply voltage (Vs) can be anything between 15 to 24V DC.
• Heat sink is necessary for TDA2613.
• Do not give more than 24V to TDA2613.

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