• Depending on the sample set used, it can be a grand
piano, a mellotron, a drum set, or anything else you can
come up with a sample set for.
• Uses .wav sample files that are 16 or 24 bits at a 44.1
kHz (CD quality) sample rate; either mono or stereo.
• Has buttons for incrementing and decrementing the
current voice, a button for rebooting the RPi 3, and an
(as yet unused) function button.
While the mellotron device I present here is a decent
simulation, it doesn’t reproduce all of the subtleties of
playing a real mellotron nor does it have its
issues/problems. It does work for me in the recordings I
do, and that is its intended purpose.
A schematic diagram of the SamplerBox electronics is
shown in Figure 5. To make the hardware function, the
following steps are required:
1. Connect the components as shown on the
2. Download the Raspberry Pi software image from
the article link. The file is called
Lindley_SamplerBox_Image.iso.zip. Unzip the file.
3. Copy the .iso file to the micro SD card. How this is
done depends on the computer you will be using.
Instructions for each type of computer are available at
http://elinux.org/RPi_Easy_SD_Card_Setup as well as
many other places on the Web.
4. Insert the SD card, insert the USB DAC/sound card,
connect a set of headphones to the sound card output,
insert the USB Flash drive containing the sample sets, then
connect up your MIDI device either using a traditional
MIDI cable or (for newer MIDI keyboards) a USB cable.
5. Connect the USB power supply to the RaspPi. If all
is well, you should see a welcome message (refer ahead to
Figure 9) on the LCD display; if you press a key on the
keyboard, you should hear sounds. If you do, you should
be good to go.
6. If your USB Flash drive has multiple sample sets
available, you should be able to click the increment and
decrement buttons to change the selected set. Be sure to
wait until the sample set is completely loaded before
playing the keyboard.
7. You may need to adjust one or both the contrast
and brightness trimmers to make text displayed on the
NOTE: Sometimes the USB DAC/sound card does not
initialize correctly on power-up which results in no sound
when the keyboard is played. If this happens, press the
reboot button and the RaspPi will reboot. Since the power
is already up and stable, the USB sound card will initialize
September 2017 29
■ FIGURE 4. Mellotron internals: mechanical marvel
or monstrosity? (Eric Haller; originally posted to Flickr as changing the
tape cartridge on the mellotron, CC BY-SA 2.0,
■ FIGURE 5. Schematic diagram.