BassBox 550W

Bass Guitar Amplifier with small weight and great sound

I spend much time, for find solution for "big sound in small box". I tried several retail solutions for it (ToneHammer 500, some amplifiers by Ashdown and Bugera), but none of them didn't give me a sound quality, which I require. And I start look forward about creation something light and powerfull. And I made it. My friends call it - "half-kilo in half-kilo", means 500W in 0,5Kg. Of course a weight is bigger than 500 gramm, but it's still less than 1Kg.


Preamplifier: j-fet based preamplifier with 3 band EQ.
Ouput Amplifier: Class-D, 550W/4R and 350W/8R with 0,5% THD
Dimensions: 222x165x56mm
Weight: about 1 kg
Features: Serial/Parallel output switch, Line output post-preamp, LinkOut output.


Preamp based on classic j-fet preamplier, builded on ultra-low-noise j-fet transistors (2SK30A by Toshiba). Only two gain stages with classic 3 band eq between them. I spend much time for choose the appropriate gain multiply, which will be provide required amplitude level, with enhanced 2nd and 4th harmonics for more tube-like sound. For last version it provide a very warm and round tube-like sound.

Ouptut amplier was produced by Connex Electronics (look here). It class D amplifier, which contain amplifier and power supply on same board. You need just connect 230V (or 120V) to module and give a signal on input. Module has a small size, about 150x50x40mm, and can be used for different applications.

This amplifier can deliver 500W on 4R at less than 0.1% THD. The maximum output power of the high power version IRS500SMPS Amplifier module at 1% THD, supplied at 230V mains voltage is 627W.

Output amplifier has small noise level on input, and big input headroom - I try put on it signal with amplitude about 4,5-5V - and on output still get not-cutted waves. Of course module has all needed protection systems (overgain, overinput, overheat, output short circuit)

So, I think - it's more than enough for bass guitar.

Below you can download all needed information and tips for build the same amplifier by yourself.

Download project files


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