Introduction: Altoids USB Condenser Microphone

Record quality audio at home with a Homebrew USB Condenser Mic! This week, we are hacking a tiny little gadget, the USB soundcard, and turn into a studio quality microphone. It's a microphone that carries the whole package, it has a shock-mount, pop filter, preamp and an internal DAC.

The project was housed on a Retro Altoids container. Its cardioid pickup pattern, smooth frequency response and 16-bit, 44.1/48kHz resolution give you professional audio results no matter what you're recording. The project consists of four main components, the USB soundcard (DAC), the mic preamp, the enclosure and the microphones themselves. Don't worry I made the project as simple as I could so everyone in the DIY community can enjoy making the USB mic project!

Why Make a USB microphone?
USB microphones are made for easy, plug-and-play use. They’re fantastic for podcasters, musicians, voice actors, audio students, tech-reviewers and people who just want something better than the microphone built into their laptop. If you don't have a USB mic, you might want to try a Homebrew version before you buy one! Don't worry, the project fits on a $10 budget! DIY is the most rewarding thing to do!

Perfect For Podcasting:

As podcasting continues to grow in popularity, creators need both audio quality and ease of use. This mic can help you wow your listeners and set yourself apart in a crowded podcasting community.


Video & Sample Audio Coming Soon!

Step 1: Aux Version - Prototype

Sorry guys, I wasn't able to post the 3.5mm aux version of the mic that I've promised. It had flaws and the TL072 chip that I've used was very uncommon. I'll be posting a newer version of the 3.5mm aux mic soon! I usually use the aux mic on my DSLR since all DSLRs support 3.5mm mic jack and not USB ports.

Sample Audio:

If you are curious on how it sounds, I've used it on my "Google Science Fair Entry". The mic was plugged to my Nikon D5300. Please support my GSF project. Thank you! :)

Step 2: Influence

USB microphones are becoming a trend these days. Condenser microphones are a must have for people who loves to records song covers, instrumental covers, video tutorials, product reviews and etc...

Reason Why USB Mics Exist:

A real condenser mic needs a preamp and DAC setup. You are looking at a $500-$2,000 setup. This is the reason why audio companies started to sell consumer "USB Condenser Microphones", they are cheaper, smaller and user friendly. It's the perfect mic for quality-amateur recording.

Advantages Over Traditional Mics:

Companies designed USB mics for them to be able to set a standard. This way, every mic sounds the same no matter how crappy your soundcard is. The mic carries the whole studio recording package! It has an internal preamp and a DAC! Unlike the typical 3.5mm PC mic, USB microphones has a preamp that amplifies the available signal via hardware. It replaced the digital-gain which by the way is the one responsible for that awful grainy noise!

Top USB Condenser Mics (2014):

1st.) Blue Microphones Snowball USB Microphone

2nd.) Blue Microphones Yeti Pro USB Condenser Microphone

3rd.) Audio Technica AT2020USB Studio Condenser Microphone

4th.) CAD U37 USB Studio Condenser Recording Microphone

5th.) Audio-Technica ATR2500-USB Cardioid Condenser USB Microphone

6th.) Samson Meteor Mic USB Studio Microphone (Cardioid)

Why Not Buy A USB Mic From The Shelf ?

Consumer USB mics are extremely overpriced, even if they lye at the $50 price range! You don't believe me? Watch this video! You'll be surprised of what you'll see inside.

Step 3: The Design

The project consists of four main components, the USB soundcard (DAC), the mic preamp, the enclosure and the microphones themselves. All plays a great role in recording quality sound.

The Bad Reputation Of Electret Condenser Mic:

Over the years, hobbyists imprinted the idea that ECMs are the worst sounding mics. Yes they are cheap, it's one of the main reasons why people think ECMs are crappy. The truth is, ECMs are actually good microphones. Not only can it perceive a wide frequency response of 10Hz-50kHz but they are also affordable for the general public. Have you tried these mics? I bet they sound bad! Yes they sometimes do. The reason behind this inconsistent performance of ECMs is not because of the mics themselves, rather it's the unstandardized design of soundcards. Some soundcards are less sensitive to the ECM's sound, that's why we try to increase the mics sensitivity via software by going to the control panel. Gaining volume by software results to the increase of noise, the hissing sound that you hear.

The Solution:

After watching teardown videos on the leading brand-models of USB condenser mics, I was able to find a solution to the problem. A $10 homebrew version of the $100+ consumer USB mic. A USB soundcard was added to make sure that everyone has a uniform soundcard. The USB soundcard also did a great job in isolating the mic from the hostile internals of the laptop, this reduced the hissing sound. An adjustable hardware preamp was added to prevent the user from using the digital mic gain, this reduced the hissing 10x-50x. A two types of foams were added inside the altoids container to act as a pop-filter and shock mount.

Why Not Use Low Noise Op-Amps?

I wanted to make this project doable for everyone. Honestly, I prefer the TL072 low noise Op-Amp, but it is really hard to come by. I chose the single stage design because the parts are widely available. I'm 100% sure that you can find them in your local RadioShack store. For those people who prefers to buy online, Digikey and Newmark (a.k.a Element14) is a great source of discrete components.

Electret Condenser Mic Preamp Design:

This is the initial design of my single stage ECM preamp. The build is pretty simple, low noise and efficient. The potentiometer can be replaced with a 100k version of the pot, this would let you increase the mics sensitivity even more. You will also notice that I have two electret mics wired in parallel, this is done to increase the available signal without using a higher preamp gain, it helps a lot in reducing noise.

Step 4: Parts & Materials

Discrete Electronic Components:

- 2N3904 General Purpose NPN Transistor

- Electret Condenser Microphone (2x)

- 10uF Electrolytic Capacitor (2x)

- 4.7K Ohm ¼ Resistor (optional)

- 10K Ohm ¼ Resistor (2x)

- 10K Ohm Potentiometer


- USB Soundcard/ DAC (with microphone input)

- Altoids Tin Container (Instructable Version)

- ¼ inch bolt-thread

- Gorilla Glue
- Super Glue

Tools & Equipment:

- Portable/ Cordless Drill

- Rotary Tool (Dremel)

- 30W Soldering Iron

- Rotary Tool Bits

- Hot Gluegun

Step 5: Marking the Altoids Tin Container

Use a coin and ruler to mark the guidelines for the cut-out. Be sure to leave a margin, the mesh needs a surface to be glued on.

Step 6: Grinding the Altoids Container

Snips are bad for cutting small pieces of metal so go get your trusty rotary tool (dremel) then grind off the marked surface of your altoids container.

Tip: The sanding drum works great for grinding the round edges!

Step 7: Clean the Container

Be sure to give your Altoids container a rinse. Metallic dusts, acquired from grinding, can short and ruin your circuitry.

Step 8: Finding & Prepping the Mesh

Finding A Mesh:

I can bet the most common question that people are going to ask is "Where can I find or buy a mesh?". You can find/ buy metal mesh from broken speakers. Junkshops have tons of them!

Preparing The Mesh:

Use your scissors to cut the mesh. My mesh isn't wide enough to cover the whole panel so I had to cut them in half in order for it to cover the holes. The round edges can be made by cutting the mesh having a coin as a guide.

Step 9: Gluing the Mesh

Drop some hot glue then swiftly mount the mesh in place.

For some reason I prefer contact adhesive although they cure for more than an hour so I started all over again and used hot glue instead.

Step 10: Installing the Tripod Mount

At first I thought I needed a special thread for the tripod's screw. After doing some trial and error on my workspace, I found out that a 1/4" bolt-thread screws-in perfectly on the tripod's screw!

How Do I Glue It?

I tried to mount the thread with a few drops of superglue, it turns out that the superglue wasn't strong enough. I finally decided to use "Gorilla Glue", it works great, it literally does the toughest jobs in planet Earth!

Step 11: Dismantle and Desolder the USB Soundcard

Carefully open the USB soundcard's enclosure. Any knife would do in opening the enclosure. Just make sure that you don't hit the components inside. Now desolder the two audio jacks, the LED and the Male USB plug.

Step 12: Replacing the USB Plug

Like all USB microphones in the market, your homebrew USB mic needs a female printer cable USB port. The type of USB port that you would find on your Arduino Uno. Having trouble in the USB port conversion? Kindly refer to the USB pin-map above.

Why not use the original male USB plug?

Simple, you don't want to have that bulging male USB plug on your Altoids mic.

Step 13: File a Hole for the USB Port

The best way to make a square hole for the USB port is by drilling a 6.5mm hole on the Altoids container.

It's not square yet! Okay, now get the narrowest file you have then file your way until you achieve a square hole.

Step 14: Hot Glue the USB Soundcard

Now hot glue the USB soundcard in place. Make sure that the PCB doesn't touch the Altoids container's conductive surface.

Step 15: Install the Electret Condenser Mic

1st.) Peel off the cotton of the electret mic, this makes it more sensitive from sound.

2nd.) Solder both mics in parallel. Observe proper polarity!

3rd.) Cut two square pieces of packaging foam then hot glue both mics on each foam.

Step 16: Install the Trimmer Pot

Drill a hole then superglue the trimmer resistor in place.

What's the 4.7k resistor for? It lets the trimmer pot have a minimum resistance of 4.7k and a max of 14.7k You can omit this.

Step 17: Build the Circuit

1st.) Carefully read the schematic diagram in step #2.

2nd.) Solder the preamp's components on a perfboard.

3rd.) Connect the trimmer pot to the assembled preamp.

4th.) Connect the USB soundcard to your preamp circuit.


Still having a hard time? Go back to step#2, the diagram explains it all :)

Step 18: Hot Glue the Circuit

Apply a thick blob of hot glue. Hold the circuit until the hot glue cools down. Don't push it to much, you don't want the circuit to short because the conductive container.

Step 19: Cut Foams - for Built-In Pop Filter

Cut the foam in half then cover both mics with it. This works as a pop-filter and prevents the Altoids container from echos.

Step 20: Plug the USB Cable

The moment of truth! Plug the USB mic to your PC!

Step 21: Plug-And-Play Quick Setup

Wait for the computer to recognize the USB mic.

Set To Zero Digital Gain:

To reduce noise, you will have to slide the digital gain to zero. Windows usually sets zero as the default gain. To make sure, go to Control Panel > Hardware & Sound > Manage Audio Devices > Recording Tab > Your Microphone > Levels... You will find a gain slider make sure it's set to zero.

Disable The USB Soundcard's Audio Out:

It's important that you disable the audio-output of the USB soundcard. Otherwise your computer will use your USB soundcard as the default audio output and not your built-in soundcard. To set this, go to Control Panel > Hardware & Sound > Manage Audio Devices > Playback Tab > Right Click On Your Microphone > Properties > Device Usage (dropbox menu) > Disable This Device. This will let you disable the USB soundcard's audio-out while leaving the mic-in functional.


I hope you like the project! If you do, please vote for me in the "Gadget Hacking Contest". I would like to give my dad a GoPro Hero 3 for his upcoming birthday. Thank you! :)

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