The best approach with this problem is to upgrade the OS to the latest kernel.
To upgrade your system use the following commands from a shell terminal:
sudo apt-get update
sudo apt-get dist-upgrade
Restart the OS and your JustBoom card should be available for you to select.
Note: The problem behind this is that only very recent versions of the kernel support our boards and upgrading is by far the easiest way of fixing the issue.
My JustBoom isn’t recognised by the OS I am using
Some OS will not configure the JustBoom cards without some additional configuration.
Generally it will be a question of adding two lines to the config.txt under either /boot or /flash
For DAC and Amp cards:
For Digi cards:
save, reboot and you should be able to select your JustBoom card within your distro preferences.
Note that if there already is a line dtparam=audio=on you should comment it out with a # at the beginning.
My JustBoom Zero board is not playing despite all the software being properly configured
The JustBoom Zero boards can be used with stacking headers or installed directly on the Raspberry Pi Zero. Some stacking headers and some 2×20 male headers on the market though are too thin or too short to provide good contact with the board.
If you are using stacking headers make sure that the pins are squared and are at least 0.6mm in width. If you are soldering the 2×20 male header on the Raspberry Pi Zero make sure that the pins are 0.6mm in width and 6mm in usable height.
Which are the Inputs and which the Outputs on Amp and DAC?
The Inputs and Outputs of the JustBoom DAC and the JustBoom Amp are clearly highlighted in the picture. Please bare in mind that should you combine the two together you can always used the micro USB power input unless you are connecting passive speakers to the Amp. In this case refer to this document which clarifies the specs of the power supply to be used depending on which speakers will you use.
Note: The Input on the Amp is intended to be a Line In type of signal and it is only available when the Amp is used on its own. Do not use this screw terminal when the Amp is stacked on top of the DAC or the DAC HAT.
Note: The polarity of the screw terminal block for the Output on the Amp is also reported in the picture.
What PSU do you recommend for the JustBoom Amps?
We will be listing a few PSU choices on our online shop fairly soon but in the meantime you can choose from this selection:
What are the sampling frequencies and the bit depth supported by the JustBoom cards?
Please bare in mind that some OSs will not allow 24 bit decoding. The majority of today’s Linux Kernels are configured for 16 bit and 32 bit only.
How do I add a header on the DAC HAT so that I can still use the standalone Amp?
The JustBoom DAC HAT comes with the possibility to install a header to replicate the GPIO of the Raspberry Pi. The header can be installed on P2 and can be installed in a standard fashion with it being soldered on the bottom side of the board with the pins made available from the top.
This approach although valid will preclude the installation of the optional standalone Amp. In order to solve this you can install a right angled header by soldering it from the top of the board and with the pins sandwiched between the Raspberry Pi and the JustBoom PCB as shown in the picture.
Routing the GPIO pins in this way can be confusing as the pin numbering is somewhat reversed from one might expect at first glance. We have added a pinout to this picture to help you work out which pin is which.
Note: This configuration can be helpful even when installing a rotary encoder. The pinout reports the default setup of our rotary encoder script.
How do I change the gain on the ALSA mixer to match the tables in the technical guides?
Within the ALSA mixer the first two analogue sliders can either be 0% or 100%. On the Amp HAT for example the first goes from -6dB to 0dB and the second from 0dB to 0.8dB.
Within those tables though you will notice that the recommended gains cannot be entirely matched by simply acting on the two analogue sliders in the ALSA mixer. So that you can more closely reflect gains like -8dB, -1.5dB, +1dB, etc. you will sometimes have to adjust the digital slider to compensate for the analogue ones. This in turn means that you might not be able to push the digital volume to 100% as in some case you might experience clipping and distortion.
As a rule of thumb keep the two analogues to a combination as close as possible to the one we specify and work on the digital slider only.
Can I bridge the channels on my JustBoom Amp?
The JustBoom Amps have not been designed so that a single speaker can be connect to both channels at the same time. Generally people will want to do this s that they can both double the output power and obtain a mono configuration.
Despite doubling the power is not possible with our cards you can still apply a workaround that allows a mono configuration off of either the left or the right channel can be found in our tutorials section. Note that the guide is only applicable for the JustBoom Amp HAT and Amp Zero.
What is P3 on the JustBoom Amp HAT and how can I use it?
Certain type of installations may require a PSU that provide connections via screw terminals or by directly soldering on a PCB. The P3 connector offers the same characteristics of the barrel one. It is also ideal because it offers a more stable mechanical connection. You can get the cable ready made from our online shop, Pi Supply.
Can I use 6 ohm speakers with the JustBoom Amps?
You can certainly use 6 ohm speakers with the JustBoom Amps, simply follow the link to our technical guide and apply the same recommendations as for the 4 ohm ones.
How do I change the gain in Kodi to match the tables in the technical guides?
When playing a video in Kodi in the playback control bar you can bring up the settings by clicking on the cog in the bottom right corner of the screen. Select “Audio and subtitle settings” then change “Volume” or “Volume Amplification” according to the information contained in JustBoom Amps Use Cases and Usage Configurations.
You may not be able to get exactly the same values so simply aim for one which is close enough.
How do I use the Soft Mute on the JustBoom Amp HAT?
The Soft Mute available on the JustBoom Amp HAT will help prevent popping of the speakers during startup and minimise power usage when nothing is played.
To enable this feature you will need to move J4 in the “Soft Mute” position. This makes so that the board starts muted. In order to control the mute/unmute you will have to configure pin15/GPIO22 as output. Bringing the pin to low will mute whereas high will unmute.
On the JustBoom Player for example the card will start muted and you will be able to control it for example using the gpio command as follows:
Which outputs get disabled when plugging the headphones?
The following table summarises what happens to the JustBoom DAC boards when the headphones are plugged in.
Note the only case in which plugging the jack in disables an output is with the JustBoom DAC HAT with the JustBoom Standalone Amp stacked on top.
Can I use the official Raspberry Pi Touchscreen with the JustBoom boards?
The official Raspberry Pi Touchscreen has been designed to either be independently powered by its own micro USB power supply or to provide power to the Raspberry Pi via it’s control board. The JustBoom Amp HAT has also been designed to back-power the Raspberry Pi and when combining the three things together you should make sure to connect them as shown in the picture. Essentially you will have to use two separate PSUs one for the touchscreen and one for the JustBoom Amp HAT and Raspberry Pi. Finally use a jumper cable between the boards to ensure good grounding is provided. As you cannot directly access the ground pins on the Raspberry Pi header you will have to use pin 4 on J2 of the JustBoom Amp HAT instead.
The need for two PSUs is so that power requirements for both the touch screen and the JustBoom are both fulfilled and not exceeded.
With regards to using the Raspberry Pi Touchscreen with the JustBoom DAC and Digi simply follow the assembly instructions provided by the Raspberry Pi foundation. Connect the power to the Raspberry Pi via either using a short USB to micro USB cable or solder the J2 connector on JustBoom DAC and Digi if using the jumper wires.
How do I add a volume control for my JustBoom Digi?
The JustBoom Digi HAT and Zero by default do not offer a volume control and that’s because generally speaking that’s not the way these type of cards should be used. The “role” to control the volume is delegated to the Amp to which you should normally connect them too.
In some circumstances though it might be useful to create a mechanism that will allow to increase an decrease the volume of the signal coming out of the Digis.
The Playback LED indicates whether the channels are in use or not. When the LED is on that generally means that the player is actually playing something.
Depending on the software distribution you are using this is not always true because some players will maintain the channels in use although muted in software to reduce the noise on the outputs. The lines are in fact more subject to interference when no signal is reproduced. In essence then the LED is the hardware flag to say whether the channels are in “reproduction mode” or not.
The JustBoom HATs come with the Playback LED already mounted on board. For the DAC and Digi the LED is red whereas for the Amp it is green as the red LED has been used to indicate whether the power line is active.
On the JustBoom DAC Zero and Digi Zero the LED can be installed as a separate option, follow this guide to know more.
Note that the JustBoom Amp Zero doesn’t come with the option of installing the LED.