This document describes how to build a lower-cost version of JackTrip (VS) device. There are two main reasons to do this:
- You have an audio interface, such as a Focusrite Scarlett 2i2 or a Behringer UM2 and want to use it instead of the audio interface built in to the VS device.
- You aren't concerned with having the absolutely best audio quality and the lowest latency, and want to save money.
In order to build this, you will need a reasonably small amount of technical expertise.
Parts List
These parts are suggested examples. You can purchase from other vendors (for example, Sweetwater and Monoprice), or other brands. Prices quoted are in US dollars, not including any sales taxes or shipping costs. All the parts are off-the-shelf and readily available. It should be relatively easy to find everything you need almost anywhere in the world.
Raspberry Pi 4 Model B, with 2GB of RAM
You can buy this for $35, from one of the vendors listed on raspberrypi.org. Amazon has them too, but at higher prices.
Raspberry Pi 4 Case
You can buy this case for $5 at CanaKit or from PiShop.
If you are in an environment with lots of electrical noise you might need to buy a metal case to keep your audio free of hum and noise. Amazon carries an aluminum case made by GeeekPi that also includes a power supply with an on/off switch, some stick-on heatsinks, a fan (which you don’t need to use), a small screwdriver for the screws, and instructions on how to assemble it. Amazon also has a similar package from Vilros that includes the Raspberry Pi, plus a monitor cable. Most of the vendors recommended on raspberrypi.org also sell Raspberry Pi starter packages.
Power Supply
A power supply by itself costs around $8 (a little more if it includes an on/off switch). You should not skimp by using a power supply meant for a phone (even if you have a spare one lying around).
Alternatively, Canakit sells an approved power supply with slightly higher power and a convenient on/off switch on Amazon. If you are going to use an audio interface, it will take its power from a Pi USB port, so it can be nice to have a little extra power.
Micro SD Card
The JackTrip Foundation is now selling Micro SD cards loaded with the JackTrip software. They look like the image below. You can buy them from Amazon. If Amazon is out of stock, or if you just want to create your own card (perhaps because you already have a spare one), this section contains the instructions on how to do that. Otherwise, you can skip to the next section.
The software takes up less than 2GB, but if you are buying a card, the smallest for sale nowadays seem to be 8GB, and 16GB cards are actually less expensive than 8GB ones. You can also use 32GB cards, but if you want to use anything 64GB or larger you will have to reformat it, so stick with something smaller if you can (16GB or 32GB).
Your card should be at least Class 10 (a measure of the speed of the card), as shown by the 10 placed inside the letter C, shown on the SanDisk card in the figure below. Cards like the Samsung, below, which instead have a number placed inside a letter U, are at least Class 10 and will be slightly faster to boot up. Here’s a comparison of various Micro SD cards, including their speed on a Raspberry Pi 4B (for this project, you will be most concerned about boot times).
You should buy a brand of card that is known to be good, as there have been lots of substandard cards sold. SanDisk, Samsung, Lexar, Micro Center, Kingston, Patriot, Pioneer, and Transcend are good brands (in that order). The card shown above by SanDisk can be bought from Amazon for less than $7, and it even includes an adapter card, which you might need. The Samsung card has twice the capacity, is faster, and lasts longer, and Amazon sells it for not much more than the SanDisk card (also including an adapter).
You will need an SD card reader that can take Micro SD cards (or the adapter that allows you to plug a Micro SD card into a regular SD card slot). You will only need this once, so you can possibly borrow it from someone. Amazon sells an inexpensive SD card reader that takes both micro and standard SD cards, and can be used in computers with either USB-A or USB-C ports. Also, some computers (especially laptops) come with a regular sized SD card slot.
To install the software on the Raspberry Pi, you will require a standard computer (Macintosh, Windows, or Linux). Install Balena Etcher onto your computer. Download the JackTrip Studio image from this page, and use Etcher to install it on the Micro SD card using the SD card reader.
USB Audio Adapter or Audio Interface
A big advantage of building your own JackTrip device is that you can use other audio interfaces and adapters, possibly including ones you already have. Here is a list of audio adapter and audio interfaces that have been tested by the JackTrip Foundation to work with the JackTrip software. For this project we are focusing on those using a USB connector. Even when limited to audio interfaces that use USB connectors, there are literally hundreds of them out there, and most of them should work ok.
These audio devices are divided into several kinds: Audio Adapters (sometimes called external sound cards), Audio Interfaces (more expensive), and USB mixers (also expensive).
Audio Adapters
Audio adapters are designed as external sound cards for computers. These are meant for gaming and listening to music, and are quite popular, so they are relatively inexpensive (around $5 to $30). I’ve compiled data on latency and noise floor for these adapters.
On most of these, the microphone input is strictly mono, but using a (stereo) TRS jack. Unless otherwise noted, the input and output volumes are adjusted using the JackTrip web app, and the adapter supplies bias power, so it can be used with condenser microphones.
A. Sabrent Aluminum USB External Stereo Sound Adapter
Pros: low cost, metal case (assuming you buy the aluminum version, which is the same price as the plastic case), reasonable latency, and includes a USB extension cable. Tested and it works just fine.
Cons: some people complain that it sounds scratchy. This might be because it has high gain on the microphone, which can cause it to overload and clip the JackTrip server. Try turning down the “Input Volume” on the web app to around 50 to 60 and see if that solves the problem.
B. UGREEN USB Audio Adapter External Stereo Sound Card
A little more expensive than the Sabrent. Lower noise, so you can set the Input Volume on the web app to around 80.
C. DuKabel USB Audio Adapter for Gaming Headset
Similar in price to the Sabrent. Metal case, Cloth braided cables. Has high gain but poor noise floor, so try setting the Input Volume on the web app to around 60. If you turn it up higher, you will hear noise (hiss).
D. StarTech.com USB Sound Card w/SPDIF Digital Audio & Stereo Mic
More expensive, but additional capabilities. Has multiple sample rates (44.1/48/96 KHz), SPDIF digital output, a simple equalizer and the mic input is true stereo. It also has a physical output volume control (and the output volume can also be adjusted from the JackTrip web app).
Audio Interfaces
High quality audio interfaces typically include XLR microphone connectors, switchable phantom power (so you can use high quality condenser mics), clipping indicators, and level controls for both the microphone inputs and headphone output. Most audio interfaces include multiple inputs; for example, if you want an input for a musical instrument in addition to a microphone input for your voice. These run from $50 on up to more than a thousand dollars. If you use one of these, you will set your volume levels on the interface, not using the JackTrip web app.
A very popular audio interface. It is currently selling for $170 on Amazon (the price has been going up due to heavy demand during the pandemic).
$100 on Amazon.
Around $45 on Amazon. Handles one mic and one instrument pickup.
USB Mixers
These are mixers that can connect to a computer using USB. We have not tested any of these ourselves, but the Behringer XR18 is said to work. It has 18 inputs, and costs over $500.
Estimated Cost
You can build this JackTrip device yourself with the Sabrent audio adapter for around $56. For comparison, the existing JackTrip device sold on Amazon costs $160, (including the power supply). That’s less than half the cost. And it can be even less if you already have some parts (like an audio interface or adapter). And you don’t need to buy the headphone adapter cable to convert the two RCA jacks to a stereo TRS connector (saving you an additional $5), because the Sabrent audio adapter has a TRS headphone jack.
Another advantage of this is that you can customize it to your needs. For example, if you just want to practice together, or jam with friends, the low-cost Sabrent audio adapter will work just fine. Besides, if you need higher quality later, you can upgrade to a powerful audio interface.
Other Accessories
Like with the stock JackTrip device, you will need some additional things before you can play music together remotely. The recommended accessories for the existing JackTrip device are listed in the JackTrip device documentation. This document mainly explains a few differences, and suggestions for low-cost but good quality alternative accessories.
Also consult this article, "Setting up Your JackTrip Studio" for more detailed information.
Ethernet Cable
You will need an Ethernet cable. It needs to be long enough to reach your Internet modem and router. Do not use WiFi.
Headphones
Do not use wireless (e.g., Bluetooth) headphones. As mentioned, you may not need the adapter cable.
If you use the Sabrent audio adapter, then headphones with a 3.5mm TRS plug will plug in directly. If you use an audio interface, most of them use a ¼ inch (6.35mm) TRS jack, so you will need an inexpensive adapter.
Alternatively, you can use wired earbuds, not wireless, and preferably ones that do not include a built-in microphone.
Microphone
You can use (less expensive but good sounding) microphones meant for use with video cameras (and still cameras that can also take video). These mics have the advantage that they are generally designed to work with more distant sounds, so they are more sensitive. They almost always use the same 3.5mm TRS connector used by the Sabrent, and many other audio adapters, so they can just be plugged in, with no adapter needed.
There are many such microphones. One good example is this MouKey video microphone sold by Amazon, which costs around $20, and includes a foam cover so it can be used for singing. It also includes a "deadcat windscreen" (to avoid wind noise when used outdoors), and a shock mount that can fit onto the hot shoe of a camera or onto a standard tripod. You can use an inexpensive desktop camera tripod to hold it. This mic sounds very good for its size and price.
Note that this mic will not work with the existing Virtual Studio device (unless you modify it), because it requires bias power. But it will work fine with most Audio Adapters discussed in this article.
Some video mics are stereo (two mics in one!). If you use an audio adapter like the StarTech.com USB Sound Card, it will work in true stereo!
One downside of microphones meant for cameras is that they tend to have very short cables. But you can use longer, inexpensive 3.5mm TRS cables instead.
Of course, you can also use many other styles and brands of microphones. Depending on their connector, you might need an adapter cable. And if you are using an audio interface (like the Focusriteor Presonus) or mixer, those have balanced XLR jacks for the microphone, so you might want to use a microphone with an XLR connector.
Building your JackTrip Studio device
Building your own JackTrip device is actually surprisingly easy, even if you don’t have many technical skills. If you did not buy a Micro SD card with the software already installed, follow the instructions in the section on the Micro SD card.
Tools you will need
If your case has screws (some don’t) and doesn’t come with a screwdriver, you may need a relatively small one. That's it.
Steps
If you purchase the Micro SD card with the JackTrip software already installed, you don’t need to perform the first two steps.
- Insert the Micro SD card into the Raspberry Pi board. Depending on your metal case, you may need to do this after you assemble the board into the case.
- Assemble your Raspberry Pi, using the instructions that come with the case.
- Plug in your audio adapter or audio interface to a USB port. The Raspberry Pi has both “SuperSpeed” USB 3.0 ports (which are light blue) and regular USB 2.0 ports (which are white or black). Either type will work just fine for audio, but you should use a USB 3.0 port (for slightly lower latency).
- Plug in your microphone and headphones into the connectors on your audio adapter or audio interface.
- Follow the instructions in “Step 2. Plugging it all in” and "Step 3. Registering and connecting".
Setting Audio Levels
An important step in getting various USB audio devices to work well is to set your audio levels correctly. If you are using an audio interface, you will control both the input and output volumes using knobs on that device. Otherwise, this is done using the JackTrip web app, at app.jacktrip.com.
The Input Volume slider controls the mic input of your audio adapter, and thus the volume of your microphone. Different microphones will have different output levels. For example, the MouKey microphone suggested earlier has a fairly high output, and if the Input Volume control is set too high it can overload the signal, causing scratching or popping sounds. If this happens, using the web app, turn down the Input Volume and/or turn off the Boost switch.
The Output Volume slider controls the headphone output of your audio adapter, and thus the volume you hear in your headphones. If you need more volume, using the web app, turn up the Output Volume and/or turn on the Boost switch.
Depending on your audio adapter and your headphones, you may still need more volume, in which case you have a couple of options. You can use a different audio adapter, including switching to an audio interface which has its own input and output volume controls (in which case you will not use the web app to set these levels).
Alternatively, you can buy a headphone amplifier (around $20 or so). Most headphone amplifiers can drive more than one set of headphones, in case you want to have more than one person playing or listening to music over the internet. The Behringer HA400 can drive up to four headphones with individual volume controls, and sells for $24 on Amazon. It uses 6.35mm (¼ inch) TRS connectors instead of 3.5mm, so you will probably need some inexpensive adapters. The Rockville RHPA4 is slightly more expensive, but it takes either 6.35mm (1/4 inch) or 3.5mm (1/8 inch) headphone connectors, so you won't need to buy any adapters.
Setting proper levels is especially important when you have people playing together who are using different USB audio devices, different microphones, or are standing at different distances from their microphones. Each player will need to set their own Input volume so everyone can be heard equally.
Further Reading
JackTrip documentation for Virtual Studio.
Information about latency, lag, and jitter.
If you are confused about connector types (like TRS, XLR, RCA, etc.) Sweetwater has a nice guide to the common ones. Also see this article about balanced versus unbalanced cables.