Showing posts with label Guitar FX. Show all posts
Showing posts with label Guitar FX. Show all posts

GUITAR FX

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Guitar Tone Control

Stand-alone, 9V battery powered unit

Three-level input selector, three-band tone control

Device purpose:

This preamplifier was designed as a stand-alone portable unit, useful to control the signals generated by guitar pick-ups, particularly the contact "bug" types applied to acoustic instruments. Obviously it can be used with any type of instrument and pick-up.
It features a -10dB, 0dB and +10dB pre-set input selector to adjust input sensitivity, in order to cope with almost any pick-up type and model.
A very long battery life is ensured by the incredibly low current consumption of this circuit, i.e. less than 800µA.

Parts:

P1,P2_________100K   Linear Potentiometers
P3____________470K   Linear Potentiometer
P4_____________10K   Log. Potentiometer

R1____________150K   1/4W Resistor
R2____________220K   1/4W Resistor
R3_____________56K   1/4W Resistor
R4____________470K   1/4W Resistor
R5,R6,R7_______12K   1/4W Resistors
R8,R9___________3K9  1/4W Resistors
R10,R11_________1K8  1/4W Resistors
R12,R13________22K   1/4W Resistors

C1____________220nF   63V Polyester Capacitor
C2,C8___________4µ7   63V Electrolytic Capacitors
C3_____________47nF   63V Polyester Capacitor
C4,C6___________4n7   63V Polyester Capacitors
C5_____________22nF   63V Polyester Capacitor
C7,C9_________100µF   25V Electrolytic Capacitors

IC1___________TL062   Low current BIFET Dual Op-Amp

J1,J2__________6.3mm. Mono Jack sockets

SW1______________1 pole 3 ways rotary or slider switch
SW2______________SPST Switch

B1_______________9V PP3 Battery

Clip for PP3 Battery

Circuit operation:
IC1A op-amp is wired as an inverting amplifier, having its gain set by a three ways switch inserting different value resistors in parallel to R4. This input stage is followed by an active three-band tone control stage having unity gain when controls are set in their center position and built around IC1B.

Technical data:

Frequency response:20Hz to 20KHz -0.5dB, controls flat.
Tone control frequency range: ±15dB @ 30Hz; ±19dB @ 1KHz; ±16dB @ 10KHz.
Maximum input voltage (controls flat): 900mV RMS @ +10dB input gain; 7.5V RMS @ -10dB input gain.
Maximum undistorted output voltage: 2.5V RMS.
Total Harmonic Distortion measured @ 2V RMS output: <0.012% @ 1KHz; <0.03% @ 10KHz.
THD @ 1V RMS output: <0.01%
Total current drawing: <800µA.
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60 Watt Guitar Amplifier + Tone Control

The following is a circuit of amplifiers are equipped with the appropriate regulatory tone in use to strengthen the electric guitar, using a single-rail supply of about 60V and capacitor-coupling for the speaker . The advantages for a guitar amplifier are the very simple circuitry, even for comparatively high power outputs, and a certain built-in degree of loudspeaker protection, due to capacitor C8, preventing the voltage supply to be conveyed into loudspeakers in case of output transistors' failure.

  Skema Rangkaian Guitar Amplifier + Tone Control

In all cases where Darlington transistors are used as the output devices it is essential that the sensing transistor (Q2) should be in as close thermal contact with the output transistors as possible. Therefore a TO126-case transistor type was chosen for easy bolting on the heatsink, very close to the output pair

R30 must be trimmed in order to measure about half the voltage supply across the positive lead of C7 and ground. A better setting can be done using an oscilloscope, in order to obtain a symmetrical clipping of the output wave form at maximum output power

Note:
To set quiescent current, tide ampare meter in series between supplay with this series, then do the following
  • Set the volume control to the minimum and Trimmer R3 to its minimum resistance.
  • Power-on the circuit and adjust R3 to read a current drawing of about 30 to 35mA.
  • Wait about 15 minutes, watch if the current is varying and readjust if necessary.
List component

R1,R2______________68K 1/4W Resistors
R3________________680K 1/4W Resistor
R4________________220K 1/4W Resistor
R5_________________33K 1/4W Resistor
R6,R16______________2K2 1/4W Resistors
R7__________________5K6 1/4W Resistor
R8,R21____________330R 1/4W Resistors
R9_________________47K 1/4W Resistor
R10_______________470R 1/4W Resistor
R11_________________4K7 1/4W Resistor
R12,R20____________10K 1/4W Resistors
R13_______________100R 1/4W Resistor
R14,R15____________47R 1/4W Resistors
R17,R18,R19_______100K 1/4W Resistors
R22__________________6K8 1W Resistor
R23,R25_____________470R 1/4W Resistors
R24__________________2K 1/2W Trimmer Cermet
R26,R27_______________4K7 1/2W Resistors
R28________________220R 1/2W Resistor
R29__________________2K2 1/2W Resistor
R30_________________50K 1/2W Trimmer Cermet
R31________________68K 1/4W Resistor
R32,R33______________R47 4W Wirewound Resistors


C1,C4,C5,C6________10µF 63V Electrolytic Capacitors
C2_________________47µF 63V Electrolytic Capacitor
C3_________________47pF 63V Ceramic Capacitor
C7_________________15nF 63V Polyester Capacitor
C8_________________22nF 63V Polyester Capacitor
C9________________470nF 63V Polyester Capacitor
C10,C11,C12________10µF 63V Electrolytic Capacitors
C13_______________220µF 63V Electrolytic Capacitor
C14,C15,C17,C18________47µF 63V Electrolytic Capacitors
C16________________100µF 25V Electrolytic Capacitor
C19_________________33pF 63V Ceramic Capacitor
C20_______________1000µF 50V Electrolytic Capacitor
P1,P2______________10K   Potentiometers
P3_________________10K   Potentiometer

D1,D2____________BAT46   100V 150mA Schottky-barrier Diodes
D3_________________LED

Q1,Q3____________BC546    NPN Transistors
Q2_______________BC556    PNP Transistor
Q4,Q5____________BD139    80V 1.5A NPN Transistors
Q6_____________MJ11016   120V 30A NPN Darlington Transistor
Q7_____________MJ11015   120V 30A PNP Darlington Transistor

J1,J2___________6.3mm. Mono Jack sockets
SW1,SW2___________SPST Switches
SPKR______________speakers  8 or 4 Ohm with Minimum power 75W
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Guitar and Bass Sustain Unit


We have all heard that wonderful sound of a guitar, where the note just hangs there seemingly forever (or at least until next Thursday).  Sustain can be obtained by turning the amp up full, but the rest of the band will just kill you - they need to be able to hear themselves too!  This little project is best used in the effects loop of a guitar amp (if it has one - not all do).  It can be used direct from the guitar, but the effect is not as good, since it is designed for relatively high levels (around 1 Volt).
The circuit is very simple to build, and mine is on a piece of Veroboard.  Because it can easily be built as a pedal or even into a guitar amp (such as that described in Project 27), I do expect to make PCBs available in the not too distant future depending on demand, and these may have a few additional functions as well. 

Here is not a lot to it, but the LED and LDR (Light Dependent Resistor) are critical - they must be completely enclosed in a light proof enclosure of some kind.  Vactrol make some very nice little LDR opto-isolators, but unfortunately they are not easy to get, and are fairly expensive.  The next best thing is a couple of pieces of black heatshrink tubing.  The LED and LDR must be as close to each other as possible, and a flat topped LED is recommended if you can get one. 
Note the rather unusual earth (ground) connection.  This is not a mistake in the drawing.  U2A is used to buffer the 1/2 supply voltage created by R3 and R4, and instead of using the 12V supply negative as earth, the output of U2A is used instead.  This gives a balanced supply from a single voltage source.  Note that the AC/DC adapter (plug pack or wall wart - select the term you are most comfortable with :-) must not be used to power other equipment as well, since this may cause problems.  If you wish, a conventional +/-15V supply may be used instead, and U2A will not be used.  Note that if a +/-15V supply is used, you must increase the value of R13 to about 3.3k to limit LED current to around 10mA.
All resistors are 1/4 or 1/2 Watt, and may be 1% or 5%.  R1 and R2 should be metal film for lowest noise.  Although the TL072 is suggested for the audio path, other opamps may be used as well.  Likewise, the LM1458 can also be substituted if you like.  Caps are 16V types, but higher voltage units can be used if desired.  D7 is a power on indicator, and D6 is there to prevent damage to the circuit if the polarity of the applied 12V DC is incorrect.  Be warned that the AC/ DC adapter will be damaged if the polarity is wrong, and it is left connected for any length of time.
VR1 is a simple volume control, and is used to set the output level.  VR2 is the limiting threshold control - as it is adjusted to a higher setting, the volume will decrease.  You may wish to wire the pot "backwards", so that maximum output is obtained when VR2 is set to the fully clockwise position.
U1A is the gain control stage.  Maximum gain as shown is unity, but R2 can be increased if you find that the gain is too low.  When the signal level is high enough for D1 - D4 to conduct, the LED illuminates, and reduces the gain of the input stage.  Any further increase of input voltage will just cause the LED to glow brighter, which reduces the gain.  In this way, a constant output level is maintained, since as the input signal reduces, so does the LED brightness and the stage gain increases again.
The connections shown will be fine for most purposes, but some LDRs may give distortion at low frequencies.  A 100uF cap in parallel with the LED will probably help if this is a problem.  LDRs typically have a slow "release" time.  After illumination, they take some time to return to their full dark resistance.  This characteristic is exploited here, to allow a very simple circuit with an almost perfect attack and release time for musical instrument use.

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