Portable stereo speaker
+ +1 General
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- DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE +COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE +DESIGNS AT YOUR OWN RISK. + + +
- This design is released under Creative Commons Zero (CC0) license. + + +
- Author:
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- Svjatoslav Agejenko + +
- Homepage: https://svjatoslav.eu + +
- Email: svjatoslav@svjatoslav.eu + +
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+ - See also: + + +
2 Project description
++I had pair of good compact stereo speakers lying uselessly around as +well as secondhand TDA2030 Chinese knockoff audio amplifier chips. +Also I wanted to test modular construction approach: motherboard with +shared bus and functionality realized via pluggable modules. So I +built stereo speaker: +
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+Indicator on the front panel shows available power within the +system. Ideally it should be at the maximum. It drops when batteries +run empty or when consumed power (too loud music) is greater than +onboard power supply or batteries can handle. It has on/off switch and +stereo audio input. Audio input impedance is about 100 ohms. +
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+Idea for the holes on the top and smaller ones on the bottom back is +to enable air flow for passive cooling. +
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+Entire construction is made of parts, no larger than +120x120x120mm. Maximum for my printer. +
+3 Battery holder
++Device is powered by 4 times AA NiMH batteries (1.2V each). +
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+I happened to have AA battery adapters lying around with different +bottom hole configurations. Therefore this weird hole design: +
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+Download: +
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- FreeCAD file + +
- STL file + +
+Result:
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+Attaches to the back of the body:
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4 20V up-step module
++Battery pack voltage is routed through main on/off switch on the front +panel, and then it goes to the 20V up-step module. +
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+It uses ready made upstep module, but adds extra voltage filtering via +inductor and capacitors. +
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5 Main board
++Voltage upstep above sits on top of main board (motherboard). It has +uniform central bus that spans all connectors. +
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+First row of the main board is special IO terminal (for connecting +speakers, front panel, etc..) +
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+Remaining rows are for connecting boards: +
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+To provide structural support, main board is attached to frame: +
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+Download: +
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- FreeCAD file + +
- STL file + +
+And boards plugged into main board are fixed at the top, using clip: +
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+Download: +
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- FreeCAD file + +
- STL file + +
+Result: +
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6 Mono audio amplifier module
++Design uses scavenged secondhand Chinese TDA2030 audio amp +clones. Each chip is mono audio amplifier. Therefore 2 almost +identical audio amp modules had to be built, one for left speaker, one +for right. +
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+I like to build on top of prototype PCBs. Gives results much faster +for one-off projects. Before soldering, I solve component layout on +paper: +
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+Result - front: +
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+Result - back: +
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+Here copper tape is used as improvised heatsink. +
+7 Speakers
++High frequency small speaker and medium frequency bigger speaker are +combined. +
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+Capacitor acts as high-pass filter on top of tiny PCB: +
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+Speaker enclosure: +
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+Download: +
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- FreeCAD file + +
- STL file + +
+Speaker enclosure cover: +
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+Download: +
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- FreeCAD file + +
- STL file + +
+Result: +
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8 Front panel
++Initial idea was really simple panel: +
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- on/off switch + +
- system power indicator + +
- stereo audio input + +
+But, since I'm using "agile" approach, during load-testing, it become +clear that active fan based cooling would be nice (when playing loud +music). I found tiny cooler fan that needs 5 volts to operate. Also I +need to power backlight for power indicator. For both of these cases, +I decided to add another voltage up-step module (target voltage output +set to 6V). This time directly on the front panel. +
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+Front panel case: +
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+Electronics fits inside: +
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+Front view: +
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+And attaches to the remaining components: +
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9 Extra capacitors
++Another thing that become clear during load-testing: output +power/volume can be further enhanced by adding high power capacitors +to even out load on primary 20V up-step module. +
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+Download: +
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- FreeCAD project + +
- STL file + +
+Extra caps are mounted on top of the speaker and electrically attached +to the main board. +
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10 Center box
++Last physical part, to attach it all together: central body. +
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+Front:
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+Back:
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+Download: +
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- FreeCAD file + +
- STL file + +
11 Conclusions / TODO
++These things could be done better: +
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- Instead of using undersized heatsinks on the audio amplifiers and +need for active cooling as a consequence, it would be better to try +to mount audio amplifier chip on top of speaker metallic body. It +would provide plenty of cooling and reduces power losses within +cable, since amplifier would be as close to the speaker as possible. + + +
- I used agile design. That is, implemented functionality ad-hoc. If I +had done design in advance, then I could have had smarter connector +layout between main board and front panel. That is: Instead of +multiple smaller cables, one wide (multi connector) cable. + + +
- Screw holes are too close to the edges on the front panel. + + +
- It would be better if screw heads were slightly buried within +construction body. + +
+Overall, it was good learning experience and I was able to test +various ideas on it. Will add cooler later :) +
+ + ++Photo of initial PSU + audio amp test: +
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