When I feel like playing electric guitar at home I always use my Marshall MS-2 mini amp, but I’ve always been sad about it’s pathetic little speaker (8 ohm, 0.8 watt). I felt it could do better. I had a leftover Sony XPlod 4 ohm, 120 watt car speaker doing nothing, so I tested it on the amp: sounds sweet! This speaker has a huge magnet compared to the standard speaker and is very clear and crisp especially when you play clean.
Testing the new speaker
I’m not really an electronics wiz or anything; so I just connected the speaker wires to the existing wires to the standard speaker and played some; the speaker functioned properly. Of course to do this, you need to open up the Marshall. Take note that this can be VERY dangerous on “regular” amps, since they run on mains power, this little one runs on 9 volts, so it won’t kill you.
Unsolder the existing speaker
With a hot soldering iron I unsoldered the leads to the speaker and the leads to the battery compartment, pretty straightforward; take note to remember which wires go where! It also pays to get the hot wire and earth wire correctly; the earth wire is usually black or has a black marking.
Connect the car speaker
I disassembled the Marshall amp; it has a little circuit board with the input, volume, tone and on/off/overdrive switch on it. It’s connected to a small slave circuit board which houses the aux input and the 9 volt DC connector. From this board wires run to the speaker and the battery compartment. The Sony Xplod speaker came with a cable with small plugs on it; a bigger one and a smaller one which fit snugly on the speaker terminals. I cut the cable shorter, added heat shrink tubing, tinned the copper, soldered them to the correct wires on the amp and shrunk the heat shrink tubing to protect the soldered connections.
Building a case
This speaker is too big to fit into the old amp enclosure itself, so I decided to house all of it in a bigger box. I found an old wine box in my shed which was big enough to house the speaker. I cut it in a square shape and used regular wood glue and clamps to glue all the wood to one sturdy box (these boxes are usually stapled together). I cut a round hole in the front to accommodate the speaker. Found some black cardboard at a local store and glued this to the back and front and sides so it looks the part. Made a square hole in the top so I could relocate the amp control plate and a smaller hole in the back to protrude the aux input and DC connector. I cut a piece of plastic from an old dvd case to make a new control plate to attach the pot meters and input connector to and protrude the LED. I used some black tape to make the insides of the openings look good. When everything was screwed in place and all the wires connected it was time to screw the speaker and it’s protective cover in place. I had salvaged the tiny Marshall logo off of the amp, which is held in place by two tiny plastic pins and located it in the cover grid, melting the pins on the inside to secure it. Looking good!
I still plan to put some protective corners on it, but I couldn’t find nice ones at the local DIY store.. so stay tuned for an update. I also want to be able to tilt it slightly backwards. Meanwhile I’m enjoying great TONE on my couch! This is a neat little practice amp after all, pity they used such a crappy speaker!
Stay tuned for more luthier geek blogs!