The Bells Oberon Mini Keg guitar amp!

I built this Oberon guitar amplifier for my brother's birthday present.

My brother is a bassist and like most guitarist he likes to play his acoustic bass at the beach with his buddies. His bass however is overpowered by acoustic guitars. He wanted a portable amp that would be loud and easy to carry around. I settled on a mini keg as they are durable and easy to acquire. Bells Oberon spelled the perfect keg. Oberon is a sure sign that summer has arrived and what better way to enjoy summer than with some beer and music at the beach. http://www.bellsbeer.com

We decided that using a rechargeable battery would be the best option. My brother works in the construction field, and as you might expect he has a number of cordless tools. With a little trimming I was able to get an entire DeWALT battery charger into the keg. This allows the keg to double as a charger.

The circuit uses the ubiquitous TDA line of chip amps. The tda2050 to be precice.

I followed this datasheet schematic.

I changed R4 for a 1k potentiometer that allowed me to set the gain for a guitar. I also added this simple passive equalizer.

The setup works better than I expected. The sound is deep and loud. My brother loves it and I hope to have video for you guys soon.

Easier to compile Advmame.

How to get advmame on the rasberry pi.

I found a tip about using advmame instead of xmame and decided it was worth a try.
advmame has an awesome configure script that takes all the work out of editing makefiles.
It also runs a lot faster.


First you will need to have some sort of rasberry pi simulator I went with this method.
RPi on Virtual Box

As before
Use the following command to ensure your running on the arm kernal

uname -a

here is my output.

Linux rasberry-pi 3.0.4 #2 mon oct 17 17:39:42 ict 2011 armv61 GNU/Linux

If you dont have X set up install it by using the command

apt-get install lxde xorg python geany

Now we need to install some dependencies to build advmame. You may not need all of these. I put them together from a lot of tinkering.

apt-get install build-essential libgtk2.0-dev libgnome2-dev libsdl1.2-dev

apt-get install libxv-dev libxv1

 

Download the advmame source. I tried 106.1 without success.

wget  http://sourceforge.net/settings/mirror_choices?projectname=advancemame&filename=advancemame/0.106.0/advancemame-0.106.0.tar.gz

extract the archive.

tar -zxvf advancemame-0.106.0.tar.gz

cd advancemame-0.106.0

Now we configure and compile.

./configure

make

make install

 

Pretty easy huh. Thanks to advmame team for all there work. 

Compiling xmame .106 on the Rasberry Pi

How to get mame on the rasberry pi.

Full size screen shot

Please note that it is easier to get advmame up and running. check out my guide here.
First you will need to have some sort of rasberry pi simulator I went with this method.
RPi on Virtual Box
Here are my pre patched files
makefile.unix
unix.mak

Lets get started.
Use the following command to ensure your running on the arm kernal

uname -a

here is my output.

Linux rasberry-pi 3.0.4 #2 mon oct 17 17:39:42 ict 2011 armv61 GNU/Linux

If you dont have X set up install it by using the command

apt-get install lxde xorg python geany

Now we need to install some dependencies to build xmame.

apt-get install build-essential libgtk2.0-dev libgnome2-dev libsdl1.2-dev

apt-get install libxv-dev libxv1

Download and extract xmame .106

wget  http://caltaxcn.googlecode.com/files/xmame-0.106.tar.bz2

tar xvjf xmame-0.106.tar.bz2

cd xmame-0.106

We need to edit the make file so it will compile correctly.

nano makefile.unix

Under reset flags comment out the line
CFLAG =
to
#CFLAG =

Under Choose from some preset CFLAGS. comment out the folowing
# GCC on x86
CFLAGS = -O2
to
# GCC on x86
#CFLAGS = -O2

Under general optimizations uncomment
#CFLAGS += -fno-merge-constantsto
CFLAGS += -fno-merge-constants

and uncomment
# CFLAGS += -fstrict-aliasingto
CFLAGS += -fstrict-aliasing

Under Architecture change
MY_CPU = i386
to
MY_CPU = arm

Save the modified makefile.
now open up the following file.

nano src/unix/unix.mak

and Change the line
CFLAGS.risc_lsb   = -DALIGN_INTS -DALIGN_SHORTS -DLSB_FIRST
to
CFLAGS.arm   = -DALIGN_INTS -DALIGN_SHORTS -DLSB_FIRST
then close and save the file.


At this point you can finally compile xmame. simply type in make

make

on my laptop this takes about 6hrs to compile. once done you can run xmame from this directory.

chmod -x xmame.x11

./xmame.x11 

I hope this gets the ball rolling. I know there is more optimizations to be had.