Wiring & diagram Info: 100w

Showing posts with label 100w. Show all posts

Friday, November 14, 2014

100W AUDIO AMPLIFIER USING TDA7294

TDA7294 is an integrated, monolithic, Class AB audio amplifier designed specifically for Hi-Fi applications. The IC has a DMOS output stage and can deliver 100W RMS into an 8Ohm speaker at +/-38V dual supply. The TDA7294 has low noise, low distortion, good ripple rejection and can be operated from a wide range of supply voltages. The IC has built in short circuit protection and thermal shutdown circuitries. The IC is available in multiwatt 15V and multiwatt 15H packages.

Description

In the circuit TDA7294 is configured to provide 100W output power into an 8Ohm loudspeaker at +/- 38V supply. C8 is the input coupling capacitor and the input is applied to the non-inverting input (Pin3) of the IC. C3 and C9 are power supply filter capacitors while C10 and C4 are bypass capacitors. C2 is the bootstrap capacitor. RC network comprising of R1 and C1 improves the high frequency stability of the amplifier and also prevents oscillations. R2 and C6 sets the mute time constant while R3 and C5 sets the standby time constant. S1 and the mute switch and S2 are the standby switch. R5 is the input resistance and the amplifiers input impedance has a direct relationship to its value. R4 and R6 is used for setting type closed loop gain and with the used value, gain is 30dB. C2 is a feedback capacitor and it also provides DC decoupling.

Circuit Diagram

Notes

The supply voltage range is +/- 10V to =/-40V DC.
Heat sink is required and its thermal resistance should be around 0.038 degree Celsius/Watt.
Use an 8 Ohm 150W speaker as the load.
For 100W output the supply voltage must be +/-38VDC.
The power supply must be well filtered and free of ripples.
If ripples are present in the power supply it may cause oscillations.
VM = 1.5V is the mute ON threshold and VM=3.5V is the mute OFF threshold.
VSTBY = 1.5V is the standby on threshold and VSTBY = 3.5V is the standby OFF threshold.
Typical input resistance of TDA7294 is 100KiloOhm.
Frequency response is 20Hz to 20KHz.
145 degree Celsius is the threshold for thermal shutdown. Slew rate of TDA7294 is 10V/microsecond and the open loop voltage gain is 80 dB.
Quiescent current of TDA7294 is approximately 30mA and its maximum value is 65mA.

Saturday, October 18, 2014

Simple 100W Guitar Pre Amplifier Circuit Diagram

This is a simple Simple 100W Guitar Pre-Amplifier Circuit Diagram. Guitar amplifiers are always an fascinating challenge. The tone controls, gain & overload characteristics are individual, & the ideal combination varies from guitarist to the next, & from guitar to the next. There is no amp that satisfies everyones requirements, & this offering is not expected to be an exception. The preamp is now at Revision-A, & although the whole schematic of the new version is not shown below, the essential characteristics are not changed - it still has the same tone control "stack" & other controls, but now has a second op amp to reduce output impedance & improve gain characteristics.

One major difference from any "store bought" amplifier is that in case you build it yourself, you can alter things to fit your own needs. The ability to experiment is the key to this circuit, which is although introduced in complete form, there is every expectation that builders will make modifications to suit themselves.

The amp is rated at 100W in to a four Ohms load, as this is typical of a "combo" type amp with 8 Ohm speakers in parallel. Alternatively, you can run the amp in to a "quad" box (four x 8 Ohm speakers in series parallel - see Figure five in Project 27b, the original editorial) and will get about 60 Watts. For the adventurous, two quad boxes and the amp head will provide 100W, but will be much louder than the twin. This is a common combination for guitarists, but it does make it hard for the sound man to bring everything else up to the same level.

The Pre-Amplifier

A picture of the Revision-A preamp is shown below. Youll see that theres dual op amps, but the schematic only shows. This is the main part of the Rev-A update - the output section now has gain (which is basically selected), and a better buffered low output impedance. The remainder of the circuit is unchanged.

Guitar Pre-Amplifier Board

The preamp circuit is shown in Figure one, and has a few fascinating characteristics that separate it from the "normal" - assuming that there is such a thing. This is simple but elegant design, that provides excellent tonal range. The gain structure is designed to provide a immense amount of gain, which is ideal for those guitarists who like to get that fully distorted "fat" sound.

However, with a couple of simple changes, the preamp can be tamed to suit any style of playing. Likewise, the tone controls as shown have sufficient range to cover very anything from an electrified violin to a bass guitar - The response can be limited in the event you wish (by experimenting with the tone control capacitor values), but I recommend that you try it "as is" before making any changes.

Figure 1 - Guitar Pre-Amplifier

From Figure one, you can see that the preamp makes use of a dual op amp as its only amplification. The lone transistor is an emitter follower, & maintains a low output impedance after the master volume control. As shown, with a typical guitar input, it is feasible to receive a fat overdrive sound by winding up the volume, & then setting the master for an appropriate level. The general frequency response is deliberately limited to prevent extreme low-end waffle, & to cut the extreme highs to help reduce noise & to limit the response to the normal requirements for guitar. In case you use the TL072 op amp as shown, you may find that noise is an issue - at high gain with lots of treble boost. I strongly recommend that you use an OPA2134 - a premium audio op amp from Los angels Instruments (Burr-Brown division), you will then find this possibly the quietest guitar amp you have ever heard (or not heard :-). At any gain setting, there is more pickup noise from my guitar than circuit noise - & for the prototype one used carbon resistors!

Notes:
one - IC pin outs are industry standard for dual op amps - pin four is -ve supply, and pin 8 is +ve supply.
two - Op amp supply pins must be bypassed to earth with 100nF caps (preferably ceramic) as close as feasible to the op amp itself.
three - Diodes are 1N4148, 1N914 or similar.
four - Pots ought to be linear for tone controls, & log for volume and master.

The power supply section (bottom left corner) connects directly to the main +/-35V power amp supply. Use one Watt zen-er diodes (D5 and D6), and make positive that the zen-er supply resistors (R18 and R19, 680 ohm one Watt) are kept away from other parts, as they will get warm in operation. Again, the preamp PCB accommodates the supply on the board.

The pin connections shown (either huge dots or "port" symbols) are the pins from the PCB. Normally, all pots would be PCB types, and mounted directly to the board. For a do-it-yourself project, that would limit the layout to that imposed by the board, so all connections use wiring. It may look a bit hard, but is simple and looks fine when the unit is done. Cable ties keep the wiring tidy, and only a single connection to the GND point ought to be used(several are provided, so select that suits your layout. VCC is +35V from the main supply, and VEE is the -35V supply.

In the event you dont require all the gain that is available, basically increase the worth of R6 (the first 4k7 resistor) - for even less noise and gain, increase R11 (the second 4k7) as well. For more gain, decrease R11 - I recommend a maximum of 2k2 here.

If the bright switch is bright ( much treble), increase the 1k resistor (R5) to tame it down again. Reduce the worth to get more bite. The tone control arrangement shown will give zero output if all controls are set to maximum - this is unlikely to be a common requirement in use, but be aware of it when testing.

The diode network at the output is designed to permit the preamp to generate a "soft" clipping characteristic when the volume is turned up. Because of the diode clipping, the power amp needs to have an input sensitivity of about 750mV for full output, otherwise it wont be feasible to get full power even with the Master gain control at the maximum setting.

Make positive that the input connectors are isolated from the chassis. The earth isolation parts in the power supply help to prevent hum ( when the amp is connected to other mains powered equipment).

If issues are encountered with this circuit, then you have made a wiring mistake .. period. A golden rule here is to check the wiring, then keep on checking it until you find the error, since I can assure you that if it does not work properly there is at least mistake, & probably more.

The input, effects & output connections are shown in Figure 1B.

Figure 1B - Internal Wiring

The connections shown are similar (ok, virtually identical :-) to those used in my prototype. Noise is low, & probably might have been lower if I had made the amp a tiny bigger. All connectors must be fully insulated types, so there is no connection to chassis. This is important ! You will notice from the above diagram that I didnt include the "loop breaker" circuit shown in the power supply diagram. For my needs, it is not necessary, for your needs, I shall let you pick. In case you select to make use of it, then the earth (chassis) connection marked * (next to the input connectors) must be left off. A few important points The main 0 volt point is the connection between the filter caps.

This is the reference for all zero volt returns, including the 0.1 ohm speaker feedback resistor. Dont connect the feedback resistor directly to the amps GND point, or you will generate distortion & feasible instability. The supply for the amp & preamp must be taken directly from the filter caps - the diagram above is literal - that means that you follow the path of the wiring as shown. Although mentioned above, you might well ask why the pots dont mount directly to the PCB to save wiring. Simple . Had I done it that way, you would require to make use of the same type pots as I designed for, & the panel layout would must be the same , with the exact same spacings. I figured that this would be limiting, so wiring it is. The wiring actually doesnt take long & is simple to do, so is not an issue. I didnt include the "Bright" switch in Figure 1B for clarity. I expect that it will cause few issues.

Monday, September 15, 2014

100W subwoofer amplifier

General Description:

This is the circuit diagram of a fully transistorized sub woofer amplifier that can produce an output of 100W.There are seven transistors including four in the output stage. The transistors Q1 and Q2 form the preamplifier stage. Transistors Q4 to Q7 form the output stage. Since no ICs are used the circuit is very robust and can be easily assembled on a general purpose PCB.

Circuits features:

The circuit can be powered from a +35V/-35V, 5A dual power supply.
Use a 100W, 12 inch sub woofer at the output.
All electrolytic capacitors must be rated 100V.
The transistor Q4 to Q7 must be fitted with heat sinks.

Circuit Diagram:

100W subwoofer amplifier circuit