100W Guitar Power Amplifier

The power amp board has remained unchanged since it was first published in 2002. It certainly isn't broken, so there's no reason to fix it. The photo below shows a fully assembled board (available as shown as M27). Using TIP35/36C transistors, the output stage is deliberately massive overkill. This ensures reliability under the most arduous stage conditions. No amplifier can be made immune from everything, but this does come close.

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The power amp (like the previous version) is loosely based on the 60 Watt amp previously published (Project 03), but it has increased gain to match the preamp. Other modifications include the short circuit protection - the two little groups of components next to the bias diodes (D2 and D3). This new version is not massively different from the original, but has adjustable bias, and is designed to provide a "constant current" (i.e. high impedance) output to the speakers - this is achieved using R23 and R26. Note that with this arrangement, the gain will change depending on the load impedance, with lower impedances giving lower power amp gain. This is not a problem, so may safely be ignored.

Should the output be shorted, the constant current output characteristic will provide an initial level of protection, but is not completely foolproof. The short circuit protection will limit the output current to a relatively safe level, but a sustained short will cause the output transistors to fail if the amp is driven hard. The protection is designed not to operate under normal conditions, but will limit the peak output current to about 8.5 Amps. Under these conditions, the internal fuses (or the output transistors) will probably blow if the short is not detected in time.

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. BC559

2. BC549

3. BD139

4. BD140

5. TIP35C

6. TIP36C

Guitar Pre-Amplifier

A photo of the Revision-A preamp is shown below. You'll see that there are two dual opamps, but the schematic only shows one. This is the main part of the Rev-A update - the output section now has gain (which is easily selected), and a better buffered low output impedance. The remainder of the circuit is unchanged. Full details of the new version are available on the secure site for those who purchase the PCBs.


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The preamp circuit is shown in Figure 1, and has a few interesting 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 huge 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 just about any style of playing. Likewise, the tone controls as shown have sufficient range to cover almost anything from an electrified violin to a bass guitar - The response can be limited if you wish (by experimenting with the tone control capacitor values), but I suggest that you try it "as is" before making any changes.





Download this schematic diagram.



semiconductor datasheet component. (PDF Format)

1. TL072
2. BC549

The circuit diagram for a 4 bit TTL counter, a type of state machine.

A circuit diagram (also known as an electrical diagram, wiring diagram, elementary diagram, or electronic schematic) is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified standard symbols, and the power and signal connections between the devices. Arrangement of the components interconnections on the diagram does not correspond to their physical locations in the finished device.

Unlike a block diagram or layout diagram, a circuit diagram shows the actual wire connections being used. The diagram does not show the physical arrangement of components. A drawing meant to depict what the physical arrangement of the wires and the components they connect is called "artwork" or "layout" or the "physical design."

Circuit diagrams are used for the design (circuit design), construction (such as PCB layout), and maintenance of electrical and electronic equipment.

Download this schematic diagram.

Semiconductor datasheet download. (PDF Format)

1. 74SL107D

2. 74LS08D

For detail, please visit http://en.wikipedia.org

Christmas Decoration Project

This project flashes 18 LEDs at three different rates and you can use these to create a Christmas decoration of your choice. The circuit is kept simple (and cheap!) by using the 4060B IC which is a counter and oscillator (clock) in one package. The circuit requires a 9V supply, such as a PP3 battery. It will not work with lower voltages and a higher voltage will destroy the LEDs.

The preset variable resistor can be used to adjust the oscillator frequency and this determines the flash rate of the LEDs. The IC limits the current to and from its outputs so the LEDs can be safely connected without resistors in series to limit the current. The stripboard part of the circuit is easy to build but the wiring for the LEDs needs care so detailed instructions are provided below.

Download this schematic diagram.

Parts Required

• resistors: 10k, 470k
• preset: 47k (this could be 100k if necessary)
• capacitor: 0.1µF
• 4060B IC
• 16-pin DIL socket for IC
• LEDs × 18, 5mm diameter, any mix of colours: red, orange, amber, yellow or green
• on/off switch
• battery clip for 9V PP3
• stripboard 13 rows × 18 holes

Download list datasheet semiconductor parts. (PDF Format)

1. CD4060B

Voltage Regulator 5V-20V Project.

If you are looking for a low drop voltage regulator that is able to provide a power supply

of 1A with an output voltage of between 5V and 20V DC, National Semiconductor LM2941 Low Dropout Adjustable Regulator is one that you can choose to use. It has a typical dropout voltage of 0.5V which means that the input supply need only have to be 0.5V DC more than the desired output voltage. Its other features include internal short circuit current limit and reverse battery protection. As shown in the schematic below, the regulator has 5 pins which consists of the ON/OFF control, Input Voltage, Output Voltage, Ground and Adjustable pins. ON/OFF is used for the purpose of switching on and off of the regulator. The capacitors C1 and E1 are to be placed as close as possible to the regulator.

Download this schematic diagram.

The output of the circuit can be varied by varying the value of potentiometer VR1 from 5V DC to 20V DC. The input voltage is limited from 5.5V DC to 30V DC. Resistor R1 must be greater than 1K. The value of the VR1 that needs to be set is calculated from the formula given below:

VR1 = R1[(Vout/1.275) - 1] ohm

If R1=1K, Vout = 5V, VR1 should be set to 2.9K ohm.

If R1=1K, Vout = 20V, VR1 should be set to 14.7K ohm

Datasheet semiconductor component download. (PDF Format)

1. LM2941CT

Electronic Timer Switch.

This electronic timer switch project is a good project to build to simulate the presence of occupants in a house. In these days when security is becoming more of a concern when no one is at home, having this device will deter the thief from breaking in. When power up, after 60 minutes, the relay will turn ON for 100 secs, OFF for the next 100 secs, and ON again for 100 secs before OFF again for the next 60 mins. This sequence will be repeated. A device such as a lamp that is connected to the relay will turn ON and OFF according to this timing.

Schematic Diagram

The schematic of the project is as shown below.

Download this schematic diagram.




Parts List

Download datasheet semiconductor component. (PDF Format)

1. CD4060B
2. IN4148
3. IN4003
4. 2SC2002

Vox Amplifier model AC100 Schematic Diagram

Vox Amplifier model AC100 circuit diagram






Download this schematic diagram.





For detail this circuit, visit schematics.ca

Resistor color code

The calculator above will display the value, the tolerance and performs a simple check to verify if the calculated resistance matches one of the EIA standard values. Select the first 3 or 4 bands for 20%, 10% or 5% resistors and all 5 bands for precision (2% or less), 5-band resistors. Hover above the tolerance for min. and max. range values.

If you want to find out the color bands for a value, use the tool on the left. Enter the value, select the multiplier (Ω, K or M), the desired precision and hit 'Display resistor' or ENTER. You can also type in resistor values in shorthand notation like 1k5, 4M7 or 100R.

Standard EIA Decade Resistor Values:

E6 series: (20% tolerance)
10, 15, 22, 33, 47, 68

E12 series: (10% tolerance)
10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82

E24 series: (5% tolerance)
10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91

E48 series: (2% tolerance)
100, 105, 110, 115, 121, 127, 133, 140, 147, 154, 162, 169, 178, 187, 196, 205, 215, 226, 237, 249, 261, 274, 287, 301, 316, 332, 348, 365, 383, 402, 422, 442, 464, 487, 511, 536, 562, 590, 619, 649, 681, 715, 750, 787, 825, 866, 909, 953

E96 series: (1% tolerance)
100, 102, 105, 107, 110, 113, 115, 118, 121, 124, 127, 130, 133, 137, 140, 143, 147, 150, 154, 158, 162, 165, 169, 174, 178, 182, 187, 191, 196, 200, 205, 210, 215, 221, 226, 232, 237, 243, 249, 255, 261, 267, 274, 280, 287, 294, 301, 309, 316, 324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432, 442, 453, 464, 475, 487, 491, 511, 523, 536, 549, 562, 576, 590, 604, 619, 634, 649, 665, 681, 698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 959, 976

E192 series: (0.5, 0.25, 0.1 and 0.05% tolerance)
100, 101, 102, 104, 105, 106, 107, 109, 110, 111, 113, 114, 115, 117, 118, 120, 121, 123, 124, 126, 127, 129, 130, 132, 133, 135, 137, 138, 140, 142, 143, 145, 147, 149, 150, 152, 154, 156, 158, 160, 162, 164, 165, 167, 169, 172, 174, 176, 178, 180, 182, 184, 187, 189, 191, 193, 196, 198, 200, 203, 205, 208, 210, 213, 215, 218, 221, 223, 226, 229, 232, 234, 237, 240, 243, 246, 249, 252, 255, 258, 261, 264, 267, 271, 274, 277, 280, 284, 287, 291, 294, 298, 301, 305, 309, 312, 316, 320, 324, 328, 332, 336, 340, 344, 348, 352, 357, 361, 365, 370, 374, 379, 383, 388, 392, 397, 402, 407, 412, 417, 422, 427, 432, 437, 442, 448, 453, 459, 464, 470, 475, 481, 487, 493, 499, 505, 511, 517, 523, 530, 536, 542, 549, 556, 562, 569, 576, 583, 590, 597, 604, 612, 619, 626, 634, 642, 649, 657, 665, 673, 681, 690, 698, 706, 715, 723, 732, 741, 750, 759, 768, 777, 787, 796, 806, 816, 825, 835, 845, 856, 866, 876, 887, 898, 909, 920, 931, 942, 953, 965, 976, 988

http://www.hobby-hour.com

10 Band Graphic Equalizer

Download this schematic diagram.




This is 10 band graphic equalizer for one channel (mono) audio system. You need build 2 similiar circuits for 2 channel (stereo) audio system.

This equalizer build based on TL074 low noise JFET op-amp which will give you high quality audio output.

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300W Subwoofer Power Amplifier

There are some important updates to this project, as shown below. Recent testing has shown that with the new ON Semi transistors it is possible to obtain a lot more power than previously. The original design was very conservative, and was initially intended to use 2SA1492 and 2SC3856 transistors (rated at 130W) - with 200W (or 230W) devices, some of the original comments and warnings have been amended to suit.




Download this schematic diagram.





Datasheet semiconductor component. (PDF Format)

1. MPSA42
2. MJE15032
3. MJE15033
4. MJL4302A
5. MJL4281A
6. IN4004