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.

lm386 headphone amp.

Just another amp build. nothing special about the circuit. the Power supply on the other hand is a different story. I picked up a little iphone speaker box from the dollar store that took only one aa battery. after tearing it apart i found a little opamp and a buckboost converter. the converter takes 1.5volts from the battery and turns it into 5volts that the op amp requires. So for 1 dollar I got a switch, battery snaps, and a dc-dc converter.

For a better write up on this type of amp go here

Taming those charging cables with a usb breakout board.

I'm sure there are those out there like me, that have a ton of usb charging cables. In my case theres my phone, my girlfriend's iphone, my tablet, her nook, and my camera. Thats 5 different devices using 3 different types of cables. On top of that the iphone wont respond to all usb chargers.It seems Apple will take every step to try and insure that you only use their chargers if your not using a computer.

So I put together a box that contains five usb sockets including one for the iphone. its a pretty easy thing to put together just paralleling the connection from one port to the other and attaching that to a usb cable.

Now the iphone port took a little more effort. With the iphone expect to see some voltage on the data lines of the usb port. So a couple of voltage dividers are required to trick the iphone into charging.

Heres the schematic:

Now we have all the ports we need. Everything is tucked in a nice wooden box that looks a whole lot better than a mess of wires.
I will write up the box build soon.

360 VGA output with 3.5mm audio jack

I recently had an xbox given to me. The only problem no video cable. I decided to see If I could hook it up to a computer monitor.

The older 360s have the capability to output rgb vga video signals. One simply has to connect the correct pins on the video connector to a db15 connector. I used some old hard drive ribbon cable to make the connections.

I added a pin socket to the cable to so I could unconnect the setup if necessary. the arrow in the picture is pointing to the solder bridging the two pins together. this tells the xbox that the cable is connected and to use vga mode

on the other end is a db15 video connector and headphone jack.

The setup works great. I can enjoy 360 game at 1080p and it looks amazing. If you would like to try the same thing here are some links to get you started

http://www.engadget.com/2006/11/14/how-to-turn-a-standard-xbox-360-video-cable-into-a-vga-cable-fo/
http://pinouts.ru/Video/VGA15_pinout.shtml
http://thingiverse-production.s3.amazonaws.com/assets/bf/9f/44/73/28/Xbox_360-HandC-V1_4.pdf



LM386 Noise

After some experiments I concluded that the radioshacks version of the lm386 is extreamly noisy. lm386 .7watt and 1 watt versions from digikey are far better sounding and seem to eliminate the white noise that can be heard from the radio shack equivelent.

Getting android 2.3.3 on the cobe kyros 7015a

Getting this working on the device seemed to be alot bigger of a problem then I would of liked. After trying to follow the guide layed out here. I ended up formating the flash and not writting the new data. The nand patch file provided by the megaupload link at the bottom didnt match the internal nand found in my tablet. Knowing that if I powered off the device with an empty flash would leave me with a brick I did all I could to get this working until I found just the file I needed.  http://www.szltp.com/download/download36.html The page is in chinese so I recommend using google to translate it. simply use the files in the Download as outlined in the tutorial above and it should work. DONOT use the megaupload link.

Another tip for those that had trouble. If your tablet enters fastboot mode after resetting, you can get it back into fwdn mode by holding down the home key and pressing the reset button.