Bass Bump Headphone Amp
Build this circuit to boost low frequencies and make your MP3s go boom.
Jeffrey Braverman
Time Required: A Weekend Cost: $80–$100
ROSS HERSHBERGER
has worked as a mainframe programmer, tooling machinist, restorer of vintage tube amps, custodial equipment technician, and several other unlikely jobs. Since 2012 he has worked as a YAG Laser Field Service Engineer for the North American division of Trumpf GmbH.
THE BASS BUMP HEADPHONE AMP WILL IMPROVE ALL YOUR PRIVATE MUSIC LISTENING. The custom bass-enhancement circuit lets you boost the music’s critical low-frequency spectrum to your taste, and it has enough power to give clear sound and punchy dynamics through most any headphones, or even small speakers.
This amp sounds better than the headphone driver circuits in most smartphones and MP3 players because it has a lower source impedance and much higher drive current. This means the sound from your headphones is unaffected by long cables or impedance mismatches. Build one and you’ll hear the difference right away.
You’ll solder the circuit on a twin perfboard to create two identical channels — left and right — each adjusted by its own bass control potentiometer. Each channel splits the low from the high frequencies at about 100Hz, passes the low through the adjustable boost, then recombines them before feeding them into the amplifier chip. At the output, a Zobel network keeps the impedance low at high frequencies and damps any oscillations. It’s all done with a handful of resistors, capacitors, and two LM386 audio amplifier chips. All the parts are easily sourced at RadioShack.
I chose the LM386 because it’s easy to build with — it’s widely available, will run on a single power supply as low as 5V, and requires few external components. There are higher-performance amp chips, but they’d require a dual power supply, making the circuits much more complex. The LM386 performs well and keeps it simple.
The Bass Bump Headphone Amp is powered by a rechargeable battery for mobile use, but you can also power it via USB using a custom cable. We can show you how to make that too. 
Put some bottom in it! Full instructions and schematic at makezine.com/bassbump-headphone-amp
Share it: #bassbumpheadphoneamp
MonoBox Powered Speaker
A mobile amplified speaker for any smartphone or music player.
Infrared String Bass
Build an optical pickup and rock this unique 4-string bass guitar.
Raygun Vector Weapon
Pew pew! Build this sound toy from scratch or from our kit (makershed.com #MSVWP).