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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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.


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.

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.

Vintage Guitar Preamp re-design

I have seen this circuit many years ago and I did planned to build this circuit but I never got a chance. This time though let’s try to re-design it to work with lower voltage and use an smaller amplifier for practicing. I am planning to use it for 12V or 9V amp so we need to modify it to work below 9V instead of the 60V supply which is the original design.

About the Ciruit

This circuit is all over the internet now and you can find it in many website. It is quite simple although the biggest problem in building this circuit is the operating voltage which is 60V. I will try to modify it to work with 9V supply. This task should be easy by using simulation software such as simetrix. I’m too lazy to compute so I just modify it by trial and error on the simulation by intelligent guessing of course! The main focus here are the high side resistors such as R3, R6 and R17. The goal is to decrease its value until you will come up with same bias level with the original supply voltage.

There is a small error I spot on this design – C11 should be connected to ground and not on the emitter of Q3. I wonder how they made this error.

Simulation Circuit

Again, I am lazy to match the names of the device on my simulation model so let’s keep it this way. 🙂

I did not included the “Harmonic Modifier” circuit on the simulation circuit because I want to keep it as is.

Bias Levels

I only have noted those points of interest here:

The level at Q3-emitter is around 26V, since our goal is to operate it at 12V, it wont be able to reach 26V when VDD is only 12V. We just need the voltage at this point to be half the supply. Same is true with Q2-emitter voltage.

Frequency Response

Here’s the frequency response of the original circuit.


Here’s the 12V modified version:

There are minimal changes, the base bias of Q1 and Q3 have been modified to make it simple. Added R20 and C7 to make up the gain at low voltage operation.

Simulation result of the modified circuit

The circuit has slightly higher gain. You can try to experiment on the values of the  resistors and capacitors. You can download the simulation file below. Simetrix is used for this simulation. It is a free software.


PCB Design

The PCB design is made using the kicad software, it is also free so anybody can download and use it. The design is very simple because I have no plans to build it for now. I just wanted to share the design for those who want to build this kind of project. You are free to edit it for your own requirements.

The design of the PCB is pretty basic. You can download the PCB project file below so you can edit it based on your requirement.

The best feature of Kicad is that you can view your design in 3D! This is a feature you wont expect on a free software! 🙂



Download Page


Simple USB powered Guitar Amp

Here’s a simple guitar amp that is USB powered. It only has gain control and nothing else. The amp is based on LM386 IC and can only give up to around 200mW when powered via USB. But you can get as much as 700mW when powering it with 9V and using an 8 ohm speaker. There is no volume or tone controls to make the circuit simple but I am planning to to design a USB powered guitar amp with tone controls in the future. But for now, here is the simple version.

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Korg Nutube – vacuum tube sound in a smaller package

Vacuum tubes are now almost obsolete because they are huge and consumes more power than a typical transistor but many guitarist and audiophiles still prefers vacuum tubes over solid state amplifiers mainly because vacuum tubes have warmer sound. Korg now made a modern vacuum tube which is smaller and consumes less power. Now you can enjoy the vacuum tube sound with just using a battery, thanks to its lower current consumption.

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Guitar Preamp Design

If you are a electronic hobbyist and at the same time a guitarist, this project is for you. I have seen many circuits of guitar preamp online but none of them gives you the PCB design and circuit simulations. I already made a version of this project years ago and it works. I also have included simulation files together with the eagle PCB files for you to download if you want to build this project. Take note that the capacitor sizes are not yet taken into account. You will need to edit some few capacitors like the C10 which will be bigger than it is on the board.

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