- Speaker- 10W, 4Ω
- Power Supply- 9V
It is a class AB stereo audio power amplifier designed for quality hi-fi applications using a TDA2005 module. It is easy to construct and has a minimum of external components. The module has output current protection and thermal protection. This is the data book circuit which produces an excellent sound. The supply voltage required for this kit is 8 - 18V DC at 1 to 2 Amps.
> 8 W RMS / channel, 2 ohm load, 16V DC supply.> 6W RMS / channel, 4 ohm load, 16V DC supply.> 4W RMS / channel, 4 ohm load 12V DC supply.
The optimal supply voltage is around 50V, but this amp work from 30 to 60V. The maximal input voltage is around 0.8 - 1V. In this design the components have a big tolerance, so you can build it almost of the components, which you find at home. The and transistors can be any NPN type power transistor, but do not use Darlington types. The output power is around 60W.
- 1. Error correction in transducer amplifiers by correcting gain.
- Auto ranging in DMM.
- Sensor selection or input type selection in process control.
- Digitally preset power supplies or electronic loads.
- Programmable precision mV or mA sources.
- PC or micro controller or microprocessor based instruments.
- Data loggers and scanners.
| Truth Table | (Control | Input vs | Gain) |
| X,Y (On-switch Pair) | (2) B | (1) A | Gain (Av.) |
| X0,Y0 | 0 | 0 | 1/10 |
| X1,Y1 | 0 | 1 | 1 |
| X2,Y2 | 1 | 0 | 10 |
| X3,Y3 | 1 | 1 | 100 |
The 22 watt amp is easy to build, and very inexpensive. The circuit can be used as a booster in a car audio system, an amp for satellite speakers in a surround sound or home theater system, or as an amp for computer speakers. The circuit is quite compact and uses only about 60 watts.
-
The circuit works best with 4 ohm speakers, but 8 ohm units will do.
-
The circuit dissipates roughly 28 watts of heat, so a good heatsink is necessary. The chip should run cool enough to touch with the proper heatsink installed.
-
The circuit operates at 12 Volts at about 5 Amps at full volume. Lower volumes use less current, and therefore produce less heat.
-
Printed circuit board is preferred, but universal solder or perf board will do. Keep lead length short.
| Part | Total Qty. | Description |
| R1 | 1 | 39K 1/4 Watt Resistor |
| C1,C2 | 2 | 10uf 25V Electrolytic Capacitor |
| C3 | 1 | 100uf 25V Electrolytic Capacitor |
| C4 | 1 | 47uf 25V Electrolytic Capacitor |
| C5 | 1 | 0.1uf 25V Ceramic Capacitor |
| C6 | 1 | 2200uf 25V Electrolytic Capacitor |
| U1 | 1 | TDA1554 Two Channel Audio Amp Chip |
| MISC | 1 | Heatsink For U1, Binding Posts (For Output), RCA Jacks (For Input), Wire, Board |
This is a four channel amplifier ideally suited for use with quadraphonic equipment such as a Sound Blaster Live card. There is no volume control,audio levels being directly controlled from the sound card itself.
Parts List:
D1-D4: 1N4001 (4)
C1,C20: 1000u CAP (2)
C2,C11: 47u CAP (2)
C3,C5,C7,C8,C12,C14,C16,C17,C21,C22: 0.1u CAP (10)
C4,C6,C13,C15: 10u CAP (4)
C9,C10,C18,C19: 2200u CAP (4)
R1,R4,R9,R12: 1M RESISTOR (4)
R2,R6,R10,R14: 100k RESISTOR (4)
R3,R5,R11,R13: 1k RESISTOR (4)
R7,R8,R15,R16: 2R7 RESISTOR (4)
IC1: 7812 (1)
IC2,IC3: LM1778N (2)
SPK1,SPK2,SPK3,SPK4: 8R 2 Watt speakers (4)
Notes:
Construction is straight forward and is suitable for Verobaord. Overall gain is controlled by the ratio R14/R13 and R6/R5. Used with small hifi speakers the volume was too loud for my room so I reduced R14 and R6 to 33k. The zobel network formed by R7,C7,R8,C8,R15,C16,R16,C17 prevents instability which can happen with long speaker wires. The input impedance is high, 1M and if very long input cables are present could pick up noise. Screened cable should be used, in my case I used 10k resistors between points A & C, B & C, D & F, E & F. This provides a DC path to ground and higher noise immunity. If instability does occur, then you will notice sound distortion and the LM1877N will become hot to touch.
Connections: The back of a sound blaster live card has colour coded 3.5mm stereo jacks. The image below shows a close up of the rear of my Sound Blaster Live card. As well as colour coding, each connector has an appropriate marking, for easy connectivity.
The normal output connector is green and the rear speaker connector is black. Creative provide utilities and sound mixer for use with Windows. Under Linux the utility Gamix can be used, which allows independent volume control for all channels.
Here is the schematic for an 8 watt audio amp. This amp can be used as a simple booster, the heart of a more complicated amplifier or used as a guitar amp.
Parts:
C1 - 10uf Electrolytic Capacitor
C2 - 470uf Electrolytic Capacitor
C3 - 0.1uF Disc Capacitor
C4 - 2000uf Electrolytic Capacitor 2200uF
R1 - 2.2 Ohm Resistor Anything Within 10%
R2 - 220 Ohm Resistor Anything Within 10%
IC1 - LM383 8 Watt Amp IC ECG1232
Notes:
- IC1 MUST be installed on a heat sink.
- C3 is for filtering and to prevent oscillation and should not be omitted.
- The circuit can be built on a perf board, universal solder board or PC board, the PC board is preferred. I built the circuit on a perf board and had to add extra inductors, capacitors and resistors to prevent oscillation.
- The circuit draws about 880 ma at 12 V.
- By swapping the values of R1 and R3, you can turn this amplifier into a guitar amp with no preamp required.
- If you can't find 2000uF, then replace C4 with a 2200uF unit.
- If you add a 0.2uF capaciitor in series with a 1 ohm resistor to the output you can prevent oscillation of the circuit under certain conditions.
This amplifier was designed to be self-contained in a small loudspeaker box. It can be feed by Walkman, Mini-Disc and CD players, computers and similar devices having line or headphone output. Of course, in most cases you'll have to make two boxes to obtain stereo. 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 transformer. 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.
Output power: 1.5 Watt RMS @ 8 Ohm, 2.5 Watt @ 4 Ohm, 3.5 Watt @ 2 Ohm (1KHz sinewave)
Sensitivity: 100mV input for 1.5W output @ 8 Ohm
Frequency response: 30Hz to 20KHz –1dB
P1 = 10K Log.Potentiometer
R1,R2 = 33K 1/4W Resistors
R3 = 33R 1/4W Resistor
R4 = 15K 1/4W Resistor
R5,R6 = 1K 1/4W Resistors
R7 = 680R 1/4W Resistor
R8 = 120R 1/2W Resistor
R9 = 100R 1/2W Trimmer Cermet
C1,C2 = 10΅F 63V Electrolytic Capacitors
C3 = 100΅F 25V Electrolytic Capacitor
C4,C7 = 470΅F 25V Electrolytic Capacitors
C5 = 47pF 63V Ceramic Capacitor
C6 = 220nF 63V Polyester Capacitor
C8 = 1000΅F 25V Electrolytic Capacitor
D1 = 1N4148 75V 150mA Diode
Q1 = BC560C 45V 100mA PNP Low noise High gain Transistor
Q2 = BC337 45V 800mA NPN Transistor
Q3 = TIP31A 60V 4A NPN Transistor
Q4 = TIP32A 60V 4A PNP Transistor
SW1 SPST switch
SPKR 3-5 Watt Loudspeaker, 8, 4 or 2 Ohm impedance.
This is a 100 watt basic power amp that was designed to be (relatively) easy to build at a reasonable cost. It has better performance than the standard STK module amps that are used in practically every mass market stereo receiver manufactured today.
The input stage is an LF351 op amp which provides most of the open loop gain as well as stabilizes the quiescent dc voltage. This feeds a level shift stage which references the voltage swing to the (-) rail. The transconductance stage is a darlington, to improve high-frerqency linearity. The 2SC2344 by itself has a rather large collector-base capacitance which is voltage dependent. The MPSA42 presents this with a low-z and has a C(ob) of only a few pf that is effectively swamped by the 33pF pole-splitting cap. The stage is supplied by the 2SA1011 active load (current source) which is about 20 ma. The current to the stage is limited by the 2N3094 to about 70 ma under worst case.
The output is a full complementary darlington with paralleled outputs. Although you could "get away with" only one if only 8 ohm easy-to-drive loads are used, this is not recommended. The use of parallel devices increases the ability to drive reactive loads (which can pull a significant current while the voltage waveform crosses zero and puts a high voltage and a high curent across the transistor simultaneously), gives the amp a higher damping factor, and reduces the maximum current each transistor has to supply to peaks (remember, the gain of a power transistor drops as the current increases).
Compensation is two-pole and one zero. The op-amp's pole and the pole generated by the 33pf cap and the 470 ohm bias resistor of the MPSA42 dominate. (the 33pF gets multiplied by the stage gain.) The 22 pf feedback capacitor provides lead compensation, and is taken from the output of the tranconductance stage rather than the output itself. In this way, the phase lag introduced by the output transistors is not seen by the high-frequency feedback. This intorduces a closed-loop pole which limits the high-frequency response. The two compensation capacitors must be type 1 creamic (NPO) or silver mica - with ZERO voltage coefficient.
The amp was designed to run 2 channels off a +/- 55 volt unregulated supply, reducing to +/- 48 volts under full load. It used a 40-0-40 volt, 5 amp toroid transformer, a bridge rectifier, and 10,000 uf of filter cap per side. If a standard EI transformer is used, a 6-amp rated unit should be used. With this power supply, it produces 100 watts continuous, both channels driven into 8 ohms resistive with no clipping. Dynamic headroom is about a db and a half. For more headroom, unloaded voltages to +/- 62 volts can be used with no circuit modification.
By the way, the schematic is in Postscript.
Limitations:
With no modifications the amp will drive 4-ohm speaker systems with no current limiting. The short-circuit current limit is set to about 4.5 amps peak, which will handle conventional speaker loads.(It will, of course, produce higher peak currents as the output voltage swing approaches the rail.) If you are going to be running some of those high-end speakers with impedance minima of half an ohm, or that stay reactive throughout most of the audio band ( ie, 0.5 +j3.2 ohms) you will probably already own a better amp than this. If the higher-power Motorola power transistors are used, it will drive a 2-ohm resistive load without problems (except heat).
I have never heard any slew-induced distortion on this amp with a CD player's band-limited (22KHz) signal. I suppose that real high-end freaks could pick it to pieces by hitting it with a TTL square wave mixed with a 19KHz stereo pilot tone and crank it up. I guarantee that there will be spurs all over the spectrum, but who listens to that?
Possible Modifications:
The Toshiba output transistors (2SD424/2SB554 pair) shoud not be used with supply voltages above +/-60 volts. If you plan on cranking it up, use more in parallel or use the 250 watt Motorola pairs (MJ15024/MJ15025). If very low impedances are expected, raise the bias in the transconductance stage to give more base drive to the output darlingtons or add another current gain stage. Higher-Beta (and faster) power transistors can't handle reactive loads worth a crap. Don't substitute high-fT parts unless you are sure they have adequate second-breakdown capability.
The NE5532 op-amp can be used in the input stage. If more than one are used off the +/-15 volt shunt regulators (balanced ins, anti-slew Bessel filters, etc.) the 2.7K dropping resistors may need to be reduced to say, 1.8K ohm to maintain regulation. The 2.7K resistors will allow up to 4 LF351 type op amps off the regulator (I used a quad 347 for balanced inputs to avoid hum in a DJ setup).
Construction tips:
The output transistors and thermal compensator (2SC1567) will need to be mounted on a common heat sink - a finned unit measuring 5 in. high by 8 in. wide with 1.25 in fins should do nicely for one channel. (They look nice if you make the sides of the case out of them). Most normal applications won't require more cooling than this. The reason the 2SC1567 was chosen for the output bias regulator is because it is fully insulated - the ECG version will require additional mounting hardware. TO-3 hardware for the outputs is cheap and easy to get.
The driver transistors and voltage amps (2SC3344/2SA1011 pairs) will all require heatsinking as well. Individual TO-220 heat sinks on the circuit board will suffice - the voltage amps dissipate about 1.4 watts each. A common piece of 1/8 in. thick 1 in. wide X 4in. long angle aluminum will suffice for all 4 on each channel, but bear in mind that it must be oriented to take advantage of natural convection, and the transistors must be insualted.
Keep the imput grounds separate from everything else, and return them at ONE point. Failure to do so WILL result in high distortion (5% or so), or even oscillation.
The output stage bias should be set to about 25 milliamps in the output transistors. This value takes a while to stabilize, and you may have to monitor it over an hour or so during initial setup. To measure it, measure the voltage across the emitter resistor and use Ohm's law. This way, you can check the current sharing in the parallel output transistors at the same time and change them if there is a serious discrepancy. With parts of the same date code, they should not be off by more than 10% after it has warmed up. Higher output stage biases can be used, but it takes more care in setting it. If you want an idle current of more than 50 milliamps per side, increase the value of the emitter resistors.
Initial Checkout:
DO NOT just plug something like this in! A seemingly insignificant error can set your house on fire! (As well as blow out $30 worth of transistors in a microsecond.) A variac will work in theory, but the amp may latch to the rail if the supply drops too low. I suggest the use of a ballast resistor - a 60 to 100 watt light bulb in series with the AC mains. You get a bright flash when the caps charge, and then it goes (almost) out as the idling supply current reaches its nominal low value. The amplifier will then work normally at low volumes. If the amp draws too much current for whatever reason, the lightbulb will glow brightly, increase resistance, and limit the power to the circuit. Usually, there will either be a mis-wire (use your DMM) or oscillation (will show up on a scope or RF power measuring device). If the bulb goes dim-bright-dim-bright... then the amp is marginally stable and the grounding layout should be checked. Compensation capacitor values may need to be adjusted if any significant changes were made. Mine is stable the way it is.