Here’s a simple electronic stereo audio selector switch that can be used for arduino. You can directly connect the pin 1, 16, 3 and 18 to arduino for selecting the source. This pin can accept as low as 2V for logic high according to its datasheet so no need for level shifter.
Category: Audio
Simple Guitar Headphone amplifier with overdrive and aux input
Here’s a simple guitar headphone guitar amplifier project that you can use for practicing. The headphone amplifier uses a LM386 that can be able output up to 0.7W than can be use also for small speakers. It also has an auxiliary input that can be used to connect your phone or an MP3 player for you to jam and play along with the song you are playing. It has a simple built-in overdrive channel.
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Guitar Phaser Effects Pedal
Here’s a phaser guitar effects schematic from an electronics magazine. I have build it some years ago but unfortunately I lost it so I cannot share the prototype. Anyway if I have time in the future, I might build 1.
Alexan Overdrive FX kit review
So I purchased a guitar overdrive effects kit from Alexan just for fun. If you are looking for a cheap DIY effects for your guitar, this one is for you.
Schematic
The design is not a true-bypass configuration, meaning the signal is still passing on the buffer circuit in bypass mode. What is bad about that? Well the buffer circuit cuts of some of the low frequencies of your signal and it also adds some noise to it.
At bypass mode, the low frequency cut off is just small and negligible. It cuts -3dB at around 30Hz.
Tone Control Response
Below is the simulation I made and compared it to Ibanez Tube Screamer FX pedal. Volume and gain set to maximum and the tone control set to 0%, 50% and 100%. As you can see, gain on the alexan overdrive is lower due to passive tone control design used. It also has more aggressive low frequency roll-off, which mean the alexan has thinner sound.
On the other hand, alexan has more gain on the overdrive circuit because it uses a 1M gain potentiometer rather than the 500k used in ibanez tube screamer. But do you need that high gain? I don’t think so, higher gain means higher noise.
Mic Preamp With bass treble Tone Control for videoke
If you are looking for a mic preamp with bass and treble control, you may consider this one. I designed it for my future mixer build. I am planning to build one someday when I am not too busy.
ABOUT THE CIRCUIT
The circuit is only on design stage, not yet done any prototype but it is working on my simulation. This is an improved version of the preamp on my audio mixer design I posted.
The rolloff on the 10k-20kHz range is caused by the capacitor C8. This is done to make sure the system will not allow any radio frequency to pass especially AM radio signals. If you want that roll-off to be more aggressive, you can increase it. Treble frequency is set by C3 and C4 while C2 is for setting the bass frequency. Increasing those capacitor values will decrease the frequency. For instance you want the bass to have more boost on the lower end frequency, just increase the value of C2.
Gain is set by R1, if you want more gain, increase R1 value. Potentiometer used are 100k, using 50k or lower will decrease the boost and cut range by around 3dB.
Simulation Results
All range: bass and treble at 0%, 50% and 100%
Bass control (0%-100% at 10% increment)
Treble control (0%-100% at 10% increment)
Bass Guitar 2 band eq active preamp circuit
Here’s a simple 2 band Equalizer circuit for your bass guitar. Can be powered by 9V battery.
About the circuit
The circuit it made up with 2 opamps from TL072 IC. You can use OPA2272 for better performance. The volume control is not included on the circuit but it is connected after the pickup. VR1 is a trimmer resistor meaning it is only for gain trimming which is adjusted once and forget it. you can replace it with a fixed resistor once you determine the best value.
Simulation Result
Frequency response graph of bass and treble at 0%-100% , 10% increment.
DIY TPA3116D2 100W amplifier with Bluetooth, MP3 and FM for home and car audio
So here’s a little cheap amplifier project that you can build for your home or car audio which only cost you around 600 pesos.
Bill of Materials
- TPA3116D2 amplifier module – Php 201 – shopee link
- Bluetooth/FM/MP3 module – Php 178 – shopee link
- Enclosure from DEECO – Php 145
- Others(wires,switches) – Php 50
Total is around 574 pesos only!
Note that power supply is not yet included. I am using it with my hybrid solar power which has an output of 12V which good enough for watching TV and some soft music. Power supply module will cost around 500 pesos, be sure to buy a 24V power supply instead of 12V to have the highest output power possible. At 12V, it can only deliver about half of its power capability. You can use a boost converter to increase the voltage from 12V to 26V to be able to get the maximum power output of this amplifier from a 12V power supply. Boost converter like this one on shopee.
I built it mainly for my home audio but this can also be used for car audio.
Youtube Video build:
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2 Band Tone Control
Here’s an improve tone control with 12dB boost on 80Hz for better super bass experience.
About the Circuit
The circuit is made up of 2 opamps TL072. This can be changed to other general purpose opamps like LM358. First stage opamp gain is set to 1, if you need more gain, you will need to decrease R2. If you want to use it for Mic, use 1k for R2.
Take note that there is no capacitor in series with the output, this is only for simulation, in reality you will need to add capacitor at the output to cancel out the DC offset on the output.
Want more Bass?
This circuit can already deliver +12dB boost at 80Hz but if that is not enough for you, you may want to decrease value of R3 and R4 for higher bass boost. Decreasing it to 3.3k will give you a bass boost of around 17dB at 80Hz! That would be too much and take note that you may need more power for that.
Simulation
Flat response ( bass and treble set to 50%)
there is roll off at both ends but it is only around -1dB which is fine. The roll off on the 20kHz is intended to reduce AM interference. This can be reduced by reducing C7 value. While the roll off at the lower end is needed to reduce subwoofer excessive movement. For music listening, the 20Hz to around 50Hz frequency is not important because almost no instrument is playing on that range of frequency. You can further decrease that roll off at 20Hz by decreasing value of C1.
100% Bass and Treble
0% Bass and 0% Treble Vs Set to both maximum
PCB Design
Please do take note that the simulation part numbering is not the same on the PCB part numbering. In example R1 on the simetrix simulation file is not the same R1 on the PCB file.
For PCB design, I used only single layer PCB so it will be easy to build for anyone. But in order to do this, I needed to add some 0 ohm resistors as jumpers. Just use wires for these 0 ohm resistors, these are R13, R14 and R20 on the schematic.
3D Render from Kicad Software
Downloads
You can download the kicad project file and simetrix simulation file here:
Simple USB powered Audio Mic Mixer
Here’s a simple Mic mixer that can be Powered with 5V. There is currently 3 channels on the circuit but you can add more if needed.
About the Circuit
The circuit is made up with BJT common emitter configuration. OPAMPS that can operate at low voltage are hard to find at a local electronic stores. The very common TL072 opamps can still operate at 5V at a very limited output voltage swing.
The circuit provides ~29dB gain, you can reduce that gain by increasing the value of the emitter resistors(R8,R9, and R11).
R3 and C1 is a filter for the power supply. C1 can be increased to reduce the noise if your power supply is noisy. R3 can also be increase up to around 100 ohms for better filtering.
You can connect this circuit to the USB audio interface circuit in this post so you can have this connected to you PC for recording.
Simulation
On the simulation below I used waveform generator with sinewave output at 100mV at frequencies 100Hz, 200Hz and 500Hz respectively. The volume setting is set at 30%, 10% and 10% respectively.
Build this Simple but amazing USB Audio interface for only $5
In case you want to connect your audio mixer or electronic piano or any other line level audio equipments to your computer or laptop for recording, here is a simple USB audio interface circuit that does the job. It is based of PCM29XX IC from TI. This is used in many analog audio mixers with usb interface such as the Behringer Xenyx USB mixer series.
About USB audio interface circuit
This circuit is USB powered. The IC has 16bit delta sigma ADC and DAC and capable of up to 48kHz sampling rate. it has stereo line level input and outputs.The crystal needed is 12MHz.
Quick PCB design
Here is a simple PCB layout that I designed using kicad software.
3D Render
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Prototype
Since I needed this circuit for my recording may piano and guitar covers, I built my own using universal PCB. This is what I used on my guitar and piano covers on my youtube channel here.
There’s no need for drivers, it installs automatically when you plug it in. It has 16bit ADC/DAC with up to 48kHz sampling which is good enough for recording. 16bit/48kHz might not sound great but it is actually good. This chip is used by Behringer on some of their Xenyx USB mixer and also on their cheap usb audio interface. The audio quality is not the best but it is better than those cheap USB sound card on the market. This is good enough for recording for you youtube content.
Video
Here is the actual video of my prototype in action.
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USB audio interface Parts list
| Ref | Value | Part |
| C1 | 1u | 16V electrolytic capacitor |
| C2 | 0.1u | ceramic capacitor |
| C3 | 4.7u | 16V electrolytic capacitor |
| C4 | 4.7u | 16V electrolytic capacitor |
| C5 | 1u | 16V electrolytic capacitor |
| C6 | 1u | 16V electrolytic capacitor |
| C7 | 1u | 16V electrolytic capacitor |
| C8 | 1u | 16V electrolytic capacitor |
| C9 | 1u | 16V electrolytic capacitor |
| C10 | 1u | 16V electrolytic capacitor |
| C11 | 4.7u | 16V electrolytic capacitor |
| C12 | 4.7u | 16V electrolytic capacitor |
| C13 | 22p | ceramic capacitor |
| C14 | 22p | ceramic capacitor |
| D1 | LED | :LED |
| J1 | USB_B | :USB connector |
| J2 | Input | 3pin JST connector |
| J3 | output | 3pin JST connector |
| R1 | 2.2 ohms | Resistor SMD or 1/4W or 1/8W |
| R2 | 1M | Resistor SMD or 1/4W or 1/8W |
| R3 | 1M | Resistor SMD or 1/4W or 1/8W |
| R4 | 1.5k | Resistor SMD or 1/4W or 1/8W |
| R5 | 22 ohms | Resistor SMD or 1/4W or 1/8W |
| R6 | 22 ohms | Resistor SMD or 1/4W or 1/8W |
| R7 | 1M | Resistor SMD or 1/4W or 1/8W |
| R8 | 1M | Resistor SMD or 1/4W or 1/8W |
| R9 | 1M | Resistor SMD or 1/4W or 1/8W |
| R10 | 220 ohms | Resistor SMD or 1/4W or 1/8W |
| U1 | PCM2902C | USB interface IC |
| X1 | CRYSTAL | 12MHz Crystal |
The parts list does not include input and output connectors, you may opt to use RCA or phone jack connector.
I am planning to build an improve version of this device and sell it online so stay tuned! Subscribe to my youtube channel and facebook page to keep you updated! 🙂