First Singing Test – June 24th

Since my last post, I’ve been busy preparing for our live singing test with volunteers from Ragazzi’s YME Chorus. We distributed 7 test kits consisting of Raspberry Pi 4B’s with HifiBerry DAC+ ADC, a microphone, all necessary cables, etc. The boxes are designed using a custom image to run headless (no monitor, keyboard, or mouse), and are managed remotely using a new cloud service that I’ve been building out (more about this in the future). The idea being that you shouldn’t have to do much more than plug them in and sing. This makes the low-latency audio technology far more accessible to a broader audience by (a) making it a lot easier to get started, and (b) minimizing hardware/software latency so that it works better across more Internet connections.

We completed our first singing test this past Wednesday. Jamulus seemed to work great for everyone, but JackTrip (48k, 128 and stereo) only worked for a few people. Others heard distracting artifacts or in one case, nothing at all. I suspect their upstream bandwidth couldn’t handle the demands, but rather than trying to troubleshoot on this call, we just switched back to Jamulus. I may try JackTrip using mono with larger buffers next time.

We had 6 boxes connected on the first test: 4 boys singing with an accompanist on piano, and myself listening in. Server load was about 1/4 of a single CPU core, which suggests that a high-end EC2 VM could handle about 192 participants.

I recorded the call using Audacity by connecting the output from my RPI to a Focusrite 2i2. Below are two samples (with added reverb) for your listening pleasure. Unfortunately, I had the input level set too high, so you may hear some clipping on the louder parts. Also note that this is the first time these boys have been able to sing together in several months. Especially considering all of this, I’m thrilled with the results!

“Come Again, Sweet Love,” – John Dowland, ed. Philip Lawson
“Siriri,” arr. Daniel R. Afonso, Jr.

We plan to continue testing weekly, while also growing the group of participants throughout the Summer.

2 thoughts on “First Singing Test – June 24th

  1. Great plan, still not very cheap, but avoids the problem of installing and running Jamulus on a regular computer. I work with Jamulus with some choirs, but for a lot of members it is too difficult to work with (especially combining with Zoom). Still I managed to get some people on board with just their plain phone-pods with inbuilt mic. Sounded not too bad. But remote control and a dedicated machine sounds great!
    Question: why do you need a ADC if you have a USB mic?
    Might it be an cheaper idea to make a package with an inbuilt electret condenser mic and a more simple DAC/ADC like https://www.abelectronics.co.uk/p/74/adc-dac-pi-zero-raspberry-pi-adc-and-dac-expansion-board ?

    1. I like the HiFiBerry boards because you get extremely high quality and low latency (1ms) at a reasonable cost. It’s certainly possible to use lower cost options for ADC/DAC, but you’ll likely be trading off one or both of these.

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