Showing posts with label guitar. Show all posts
Showing posts with label guitar. Show all posts
Tuesday, December 24, 2013
Electric Guitar Preamplifier
Here is the circuit diagram of a guitar preamplifier that would accept any standard guitar pickup. It is also versatile in that it has two signal outputs. A typical example of using a pick-up attached to a guitar headstock is shown in Fig. 1. The pickup device has a transducer on one end and a jack on the other end. The jack can be plugged into a preamplifier circuit and then to a power amplifier system. The pickup device captures mechanical vibrations, usually from stringed instruments such as guitar or violin, and converts them into an electrical signal, which can then be amplified by an audio amplifier. It is most often mounted on the body of the instrument, but can also be attached to the bridge, neck, pick-guard or headstock.
The first part of this preamplifier circuit shown in Fig. 2 is a single-transistor common-emitter amplifier with degenerative feedback in the emitter and a boot-strapped bias divider to secure optimal input impedance. With the component values shown here, the input impedance is above 50 kilo-ohms and the peak output voltage is about 2V RMS. Master-level-control potentiometer VR1 should be adjusted for minimal distortion. The input from guitar pickup is fed to this preamplifier at J1 terminal. The signal is buffered and processed by the op-amp circuit wired around IC TL071 (IC1). Set the gain using preset VR2. The circuit has a master and a slave control. RCA socket J2 is the master signal output socket and socket J3 is the slave.
Electric Guitar Preamplifier Circuit diagram:
Electric Guitar Preamplifier Circuit diagram:
It is much better to take the signal from J2 as the input to the power amplifier system or sound mixer. Output signals from J3 can be used to drive a standard headphone amplifier. Using potentiometer VR3, set the slave output signal level at J3. House the circuit in a metallic case. VR1 and VR3 should preferably be the types with metal enclosures. To prevent hum, ground the case and the enclosures. A well-regulated 9V DC power supply is crucial for this circuit. However, a standard 9V alkaline manganese battery can also be used to power the circuit. Switch S1 is a power on/off switch.
Source: http://www.ecircuitslab.com/2011/06/electric-guitar-preamplifier.html
Friday, July 12, 2013
100W Guitar Pre Amplifier Rise
Introduction
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.
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.
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.
Tuesday, April 30, 2013
Electric Guitar Violin Preamplifier
Magnetic pick-ups in musical instruments have a relatively high output impedance. This can result in a reduction in treble response when connected via a long cable run or to equipment with a low input impedance. This preamplifier provides a high input impedance and a low impedance output, solving both issues. It has adjustable voltage gain and can run off a battery or DC plugpack. The input signal is AC-coupled to the non-inverting input of IC1a, part of a TL074 quad op amp. This has JFET input transistors and the input impedance is set by a 330kΩ bias resistor which also sets the DC level at this input to half supply (Vcc/2). This is generated by a voltage divider comprising two 10kΩ resistors and bypassed by a 47µF capacitor to reject noise and hum.
IC1a is configured as a non-inverting amplifier with a gain of between 2 and 20, depending on the setting of VR1. IC1a’s output is fed to VR2 via a 22µF capacitor, allowing the output volume to be set. The audio then passes to the non-inverting inputs of the remaining three op amps (IC1b-IC1d) which are connected in parallel to provide a low output impedance; it will drive a load impedance as low as 600Ω. The 100Ω resistors in series with the outputs provide short-circuit protection for the op amps and also prevent large currents from flowing between the outputs in case they have slightly different offset voltages.
The buffered signal is then AC-coupled to two output connectors using 47µF electrolytic capacitors. For Output 1, a 47kΩ resistor sets the output DC level to ground and a 220Ω series resistor provides further short-circuit protection. Output 2 is similar but includes another potentiometer (VR3) to allow its level to be set individually. Note that this means the impedance of Output 2 can be high (up to 2.5kΩ depending on the position of VR3’s wiper). The total harmonic distortion of this circuit is typically less than 0.01% with the gain set to six. If a TL064 is used instead of a TL074, the current drain will decrease but there will be more noise at the output. Finally, the input imped
IC1a is configured as a non-inverting amplifier with a gain of between 2 and 20, depending on the setting of VR1. IC1a’s output is fed to VR2 via a 22µF capacitor, allowing the output volume to be set. The audio then passes to the non-inverting inputs of the remaining three op amps (IC1b-IC1d) which are connected in parallel to provide a low output impedance; it will drive a load impedance as low as 600Ω. The 100Ω resistors in series with the outputs provide short-circuit protection for the op amps and also prevent large currents from flowing between the outputs in case they have slightly different offset voltages.
The buffered signal is then AC-coupled to two output connectors using 47µF electrolytic capacitors. For Output 1, a 47kΩ resistor sets the output DC level to ground and a 220Ω series resistor provides further short-circuit protection. Output 2 is similar but includes another potentiometer (VR3) to allow its level to be set individually. Note that this means the impedance of Output 2 can be high (up to 2.5kΩ depending on the position of VR3’s wiper). The total harmonic distortion of this circuit is typically less than 0.01% with the gain set to six. If a TL064 is used instead of a TL074, the current drain will decrease but there will be more noise at the output. Finally, the input imped
Friday, April 5, 2013
A Frequency Doubler Effect for Electric Guitar
This circuit is a octave shifting that is used for electric guitar is done by rectifying the original signal, just like AC to DC conversion inside your AC-DC power supply adapter. This circuit is use single supply instead of symmetric power supply. This is the figure of the circuit.
The rectifying is done by four 1N4148 silicon diodes, configured as full-wave rectifier bridges. Because the bridge is inserted inside the negative feedback of the operational amplifier (op-amp) U1B, the nonlinear characteristic of the diodes around the turn-on point (the forward bias voltage) is compensated by the op-amp’s feedback mechanism. As the result, the output of the rectifier looks like coming from ideal diode with no bias voltage needed. The pre-amp gain can be adjusting by R3 potentiometer between clean and slightly overdriven, hear the effect, and set as you want.
The R4 pot is provided to adjust the processed signal so the output level after the frequency doubling is equal to the level before entering this analog effect processor. Make R7, R8, and C3 layout as close as possible to the pin 10 of the LM324 IC (U1C) with shortest possible wiring to minimize capturing any noise. This voltage (at pin 10 U1) is the reference for internal “virtual ground” coming out from U1C output (pin 8). Make sure that the PCB tracks for this “virtual ground” (pin 8 U1) are wider than other signal tracks to give consistent reference for all op-amps. Make sure C4 and C5 have the shortest possible connection to the power pins (pin 4, pin 11) and the “virtual ground” line (pin 8).
The rectifying is done by four 1N4148 silicon diodes, configured as full-wave rectifier bridges. Because the bridge is inserted inside the negative feedback of the operational amplifier (op-amp) U1B, the nonlinear characteristic of the diodes around the turn-on point (the forward bias voltage) is compensated by the op-amp’s feedback mechanism. As the result, the output of the rectifier looks like coming from ideal diode with no bias voltage needed. The pre-amp gain can be adjusting by R3 potentiometer between clean and slightly overdriven, hear the effect, and set as you want.
The R4 pot is provided to adjust the processed signal so the output level after the frequency doubling is equal to the level before entering this analog effect processor. Make R7, R8, and C3 layout as close as possible to the pin 10 of the LM324 IC (U1C) with shortest possible wiring to minimize capturing any noise. This voltage (at pin 10 U1) is the reference for internal “virtual ground” coming out from U1C output (pin 8). Make sure that the PCB tracks for this “virtual ground” (pin 8 U1) are wider than other signal tracks to give consistent reference for all op-amps. Make sure C4 and C5 have the shortest possible connection to the power pins (pin 4, pin 11) and the “virtual ground” line (pin 8).
Thursday, April 4, 2013
Mini Portable Guitar Amplifier
Can be fitted into a packet of cigarettes, Also suitable as Fuzz-box
This small amplifier was intended to be used in conjunction with an electric guitar to do some low power monitoring, mainly for practice, either via an incorporated small loudspeaker or headphones. The complete circuit, loudspeaker, batteries, input and output jacks can be encased in a small box having the dimensions of a packet of cigarettes, or it could be fitted also into a real packet of cigarettes like some ready-made units available on the market.
This design can be used in three different ways:
- Loudspeaker amplifier: when powered by a 9V alkaline battery it can deliver about 1.5W peak output power to the incorporated loudspeaker.
- Headphone amplifier or low power loudspeaker amplifier: when powered by a 3V battery (2x1.5V cells) it can drive any headphone set type at a satisfactory output power level or deliver to the incorporated loudspeaker about 60mW of output power. This configuration is useful for saving battery costs.
- Fuzz-box: when powered by a 3V battery (2x1.5V cells) and having its output connected to a guitar amplifier input the circuit will behave as a good Fuzz-box, showing an output square wave with marked rounded corners, typical of valve-circuits output when driven into saturation.
Circuit diagram:
Mini Guitar Amplifier Circuit Diagram
Parts:
R1__________22K 1/4W Resistor
C1__________10µF 25V Electrolytic Capacitor
C2__________100nF 63V Polyester or Ceramic Capacitor
C3__________220µF 25V Electrolytic Capacitor
IC1_________TDA7052 Audio power amplifier IC
J1,J2_______6.3mm Stereo Jack sockets (switched)
SPKR_______8 Ohm Loudspeaker (See Notes)
B1_________9V PP3 Battery or 3V Battery (2 x 1.5V AA, AAA Cells in series etc.)
Clip for PP3 Battery or socket for 2 x 1.5V AA or AAA Cells
Notes:
- For the sake of simplicity and compactness, this unit employs a dual bridge IC amplifier and a few other parts. For the same reason no volume or tone controls are provided as it is supposed that the controls already existing on the electric guitar will serve satisfactorily to the purpose.
- No power switch is used: the battery voltage will be applied to the circuit when the input plug will be inserted in the input jack socket J1. For this purpose be sure that the input plug is a common 1/4 inch guitar mono jack plug and J1 is a 1/4 inch stereo jack socket.
- The output jack socket J2 must be a switched stereo type. The changeover switching is arranged in such a way that, when a common headphones stereo jack plug is inserted into the socket, the loudspeaker will be disabled and the mono output signal will drive both the headsets in series, allowing full headphone reproduction. When used as a Fuzz-box output, a mono jack plug must be inserted into J2.
- If the amplifier is intended to be encased in a packet of cigarettes, standard loudspeaker diameter should be 57 or 50mm.
Technical data:
Max output power: 1.5W @ 9V supply - 8 Ohm load; 60mW @ 3V supply - 8 Ohm load
Frequency response: Flat from 20Hz to 20kHz
Total harmonic distortion @ 100mW output: 0.2%
Max input voltage @ 3V supply: 8mV RMS
Minimum input voltage for Fuzz-box operation: 18mV RMS @ 3V supply
Current consumption @ 400mW and 9V supply: 200mA
Current consumption @ 250mW and 9V supply: 150mA
Current consumption @ 60mW and 3V supply: 80mA
Quiescent current consumption: 6mA @ 9V, 4mA @ 3V supply
Fuzz-box current consumption: 3mA @ 3V supply
Copyright: www.redcircuits.com
Saturday, March 30, 2013
Fender Guitar Manual Wiring Diagram Schematics Parts
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