Stereo Tone Control Component List

INTEGRATED CIRCUIT

• TL072 : 2
• TL071 : 1

RESISTORS All 1/4W

• 22K ohm (red, red, orange) : 10
• 10K ohm (Brown, Black, Orange) : 10
• 1K ohm (brown, black, red) : 3
• 100K ohm (brown, black, orange) : 3
• 100 ohm (Coffee, Black, Coffee) : 4
• stereo/dual potentiometers 100K ohm : 3
• stereo/dual potentiometers 10K ohm : 2
• mono/single potentiometers 10K ohm : 2

CAPACITORS

• 1uF/25V electrolytic capacitor : 4
• 10uF/25V electrolytic capacitor : 1
• 4.7uF/25V electrolytic capacitor : 2
• 6.8nF (682) polyester capacitor : 2
• 1.5nF (152) polyester capacitor : 2
• 47nF (473) polyester capacitor : 2
• 1nF (102) polyester capacitor : 2
• 100nF (104) polyester capacitor : 4
• 2200uF x 25 V electrolytic capacitor : 2
• 1uF nonpolar capacitor (105) : 5

Stereo Tone Control PCB Layout and Component Placement

Power Supply Circuit

The power supply type for the stereo tone control is symmetrical and regulated and on its output we use +15 and -15 VDC. The LM7815 will deliver stabilized +15VDC and the LM7915 will deliver stabilized -15 VDC. For symmetrical source, the TL072 VCC range will be 7V up to 36V, so you may use a pair of regulator IC LM7805/LM7905 up to LM7815/7915.
Below is the schematic diagram, pcb design and component layout:

Power supply circuit for bass guitar preamp also included in the PCB design. Simply connect the power supply section to the output of transformer with the secondary 15 + 15 V / 500 mA.

Bass Guitar Preamp Pedal PCB Design

Bass Guitar Preamp Top PCB

Bass Guitar Preamp Top Component Placement

Bass Guitar Preamp Pedal Connection

This is the circuit diagram of mic condenser amplifier. The low-cost and compact mic condenser audio amplifier described right here is deliver good-quality audio of 0.5 watts at 4.5 volts. It could possibly be applied as a part of low-power transmitters, packet radio receivers, intercoms and walkie-talkies.

Transistors T1 and T2 form the mic preamplifier. Resistor R1 gives the required bias for the mic condenser whilst preset VR1 works as gain control for adjusting its gain level. As a way to boost the audio power, the low-level audio output from the preamplifier stage is coupled via coupling capacitor C7 to the audio power amplifier constructed close to BEL1895 IC.

BEL1895 is really a monolithic audio power amplifier IC intended specifically for sensitive AM radio applications that delivers 1 watt into 4 ohms at 6V power supply voltage. It exhibits very low distortion and noise and works above 3V-9V supply voltage, which would make it perfect to be supplied with battery operation. A turn-on pop reduction circuit prevents thud once the power supply is switched on.

Coupling capacitor C7 determines low-frequency response of the amplifier. Capacitor C9 acts as the ripple-rejection filter. Capacitor C13 couples the output accessible at pin 1 towards the loudspeaker. R15-C13 combination acts as the damping circuit for output oscillations. Capacitor C12 presents the boot strapping function.

This circuit is appropriate for low power HAM radio transmitters to supply the important audio power for modulation. With easy modifications it could possibly also be applied to intercom circuits.

Mic condenser amplifier circuit source: “Electronics For You” magazine, December 2001

Vcc – Pin 1 IC1
+12v – Pin 8 IC2, IC3, IC4
-12v – Pin 4 IC2, IC3, IC4
Ground – Pin 8 IC1

IC1 – 4049 CMOS Hex Inverting Buffer
IC2, 3, 4 – 5532 Dual Low-Noise OpAmp
D1, 2 – 1N4001
D3, 4, 5, 6, 7 – 1N4148
All 1uf caps 50v all others 25v unless
marked otherwise.
All resistors 1/4W, 5%

Channel 2 is identicle to Channel 1, and uses IC4b for the clipping meter and IC3 for the input/output driver. The input impedance of the TubeHead is about 20k ohms, which is consistant with most gear like Synths, Effects Processors, Mixers, EQs, and so on. 20k is too low for a proper match with high impedance sources like guitar pickups, but a few minor changes take care of this. To use the Tube Head as a instrument pickup preamp, remove the 47k* resistor and the 20pf capacitor from the feedback loop of the driving Op-Amp. Then change the 47k” resistor to 680k and the 22k resistor in the feedback loop of the driving OpAmp to 100k. Now the Tube Head can be used to warm up a cold sounding guitar amp or just provide a great preamp tone.

Designed/Manufactured by PAiA Electronics

Download Tube Head circuit + components list and explanation in pdf file:

Tube Head Pre-amp Circuit

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Component Parts List:
R1, R3, R4 = 10K
R2 = 1K
R5 = 100K-1M Potensiometer
C1 = 0.1uF
C2 = 4.7uF/16V
IC1 = LM358 dual op-amp single supply
Mic = Electret Microphone

Notes:

• Use R5 to adjust the gain of op-amp LM358.
• The LM358 has dual op-amp module, you may build stereo audio pre-amp using single LM358. These devices consist of two independent, high-gain frequency-compensated operational amplifiers designed to operate from a single supply over a wide range of voltages.

Download PDF document of LM358 datasheet from below link:

LM358 Datasheet

1 file(s) 1.21 MB

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The simple mic pre-Amp based LM358 circuit designed by Tony van Roon

Designed by Don Tillman, this guitar pre-amp circuit design is dedicated for people who don”t like op-amps module. This circuit is a discrete JFET pre-amplifier design, use 2N5457 as the main component. It has low noise, low distortion, low feedback, overloads gracefully, is small, etc.

Overall gain is 3db (2X) or so. It uses about 1/2 ma, so a 9V battery will last a long time, you may also use simple regulated power supply with LM7809. It is possible to add a high boost switch in case you like by having it shunt the 2.2k ohm resistor with a 0.05uF cap (or other value; smaller cap = boosts only higher frequencies, as well as the reverse). You may simply placed in a 10uF capacitor across the 2.2k ohm resistor in order to up the gain.? You don”t like pre-amp circuit with op-amps..? then, just try to build this circuit.

All capacitors with value of 33uF are 16V, while the all others are 50V unless marked otherwise. Resistors marked with “#” are 1% metalfilm resistor type.

The “Drive” LED indicates how hard the tube is being driven. The “Blend” control allows for a mixing of SS and tube coloration. Symmetry controls the relative amounts of even and odd harmonics, CCW the Tube Mic Pre-Amp may sound punchier, while CW it may sound warmer. The 12VAC needed for pin 5 of the 12AX7 can be obtained from point G while pin 4 should be connected to point A.

There are two options for line level signals. First if you know that you”ll be using line level signals all the time with the TMP then you can change the two 33k 1% resistors to 1k 1% types and your done. Alternatively if you want the option of line level or low level signals then you can sacrifice the polarity switch and and rewire it here as shown. Notice that the 47k resistors are again of the 1% variety.

Download the schematics and circuit explanation of Tube Mic Pre-Amp circuit:

Tube Mic Pre Amplifier

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This easy circuit provides good gain to weak audio signals such as electret microphone. Use it in front of an RF oscillator to make an RF transmitter that’s very sensitive to sound. Power supply used for this circuit is wide range from 3VDC to 9VDC, you may choice the middle range about 6VDC to minimize the risk, safety purpose

Components List:

R1 = 10k
R2 = 100k
R3 = 10k
C1 = 0.1uf or if you prefer 104 or 100n
C2 = 0.1uf or if you prefer 104 or 100n
Q1 = 2N3904
MIC1 = a common electret microphone

Dynamic microphones are versatile and ideal for general-purpose use. They use a simple design with few moving parts. They are relatively sturdy and resilient to rough handling. They are also better suited to handling high volume levels, such as from certain musical instruments or amplifiers. They have no internal amplifier and do not require batteries or external power.

Schematic diagram:

Circuit Notes:

• This dynamic microphone amplifier circuit has a total gain of 200 times.
• If you use 200? microphones R4 must be 220? and C1 is 4.7uF.
• For the best performance, use metal film resistor, MKM type for unpolar capacitor and tantalum type for bipolar capacitor. Use stabled and regulated power supply.

With a 3mVpp input signal the output will be 800mVpp. The maximum output voltage was 10Vpp when the input is 50mVpp. The frequencies domain is between 50Hz and 100KHz.

Schematic diagram:

Pre-Amp + Tone Control Components List:

Resistors:
R1, R2__________________ 220R
R3, R4__________________ 4K7
R5______________________ 2K2
R6______________________ 1K

Capacitors:
C1, 2, 7, 8, 17_________ 10 uF ecap
C3, 4___________________ 47 nF
C5, 6___________________ 15 nF
C9______________________ 220 nF poly
C10_____________________ 100 uF 25V
C11, 12, 13, 14, 16_____ 100 nF
C15_____________________ 1000 uF 35V
C18, 19_________________ 10 nF

Misc.:
IC1_____________________ TDA 1524A
IC2_____________________ LM 7812
P1______________________ 50k linear switch pot
P2, 3, 4________________ 50k linear pot
X1, 2, 3, 4_____________ RCA jack
D1______________________ Diode 1N4004
L1______________________ Red LED

Circuit Works:

All signal processing is done within the TDA1524A by voltage controlled amplifiers and voltage controlled filters. The IC provides a fixed voltage (~ 3.8V DC) at pin 17, and this is used by all the variable resistors to provide an adjustable DC voltage to the appropriate control pins.

Current sensing is used to provide a flat response when R5 is connected to pin 17, and a loudness contour when disconnected. 100 nF capacitors are used on each pot to decouple any AC signals from the control inputs. 10 uF capacitors are used to couple both input and output audio signals whilst blocking DC. R1 and R2, are to ensure stability with capacitive loads. R3 and R4 make sure there are no DC spikes at the output sockets if the load is switched. C3 and C4 control the loudness contour. C5 and C6 control the treble turn-over frequency. C18 and C19 have been added to roll off the gain above 70 kHz. Low volume settings coupled with treble boost was causing HF instability in some instances. This should no longer be a problem.

C15, 16, 17 provide power supply filtering. D1 provides protection in case of incorrect supply polarity. The LED is a power on indicator and may be omitted if not required, or preferably mounted on the enclosure. If you are not using a switch pot, you can connect an external switch across the P1 switch pins, or connect a wire link there and switch the power supply.

The power supply is critical to the noise? performance of the pre-amp. An on board regulator is provided to reduce mains hum. If you wish to use it with a car or other 12V battery, then you should omit the 7812 regulator, and place a wire link between the regulator input and output pin positions on the PC board. Do not short to earth! This will be necessary because the regulator must have an input voltage at least 2-3V greater than it”s output, for it to maintain regulation. However the regulator will not be necessary with a battery supply.

If using a plug pack, it”s output voltage should be 15 to 18V DC. Because most plug packs have poor regulation, one rated at 12V DC will often be around 15V when lightly loaded. The current drain of the pre-amp is less than 50 mA, so many 12 V unregulated supplies may be adequate if you have one. Replace D1 with a wire link if necessary, making sure you have the supply polarity correct!

If you are using a 15-20V supply for your power amplifier, you can use that as your pre-amp supply as well. Make sure you test the voltage first in all cases.

Download the Pre-Amp + Tone Control Circuit Manual in PDF:

Preamp and Tone Control with TDA1524A Manual

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Download TDA1524A Stereo-tone/volume control circuit:

TDA1524A Datasheet

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