Ubuntu Studio components including Rakarrack A cheap audio interface like Xenyx 302 USB is a worse choice here, since it plays the input sound over the USB mix. It has a mic input and a headphone output. An equalizer and a compressor was applied to the signal, and the processed version came out with a barely noticeable delay.Īn old Philips USB sound card that came with a pair of headphones many years ago. It's not running on a Raspberry pi yet, but I tried it on a laptop. I am trying to build a headphones audio processor with Linux, and today I got a proof of concept running. I better go and check to see how much headphone impedance does vary with frequency... However making a voltage divider with the headset as a part in it, will introduce weird non-linear responses, since headphones vary in impedance depending on frequency. I would really like to have an analogue potentiometer to be able to adjust the volume there, outside of the Pi. And it should be a touch screen so the sliders adjacent to the VU meters can be used. Since Rakarrack already has built in meters for input and output, it's probably better to outfit the Pi with a small screen, and then create a viewport with xrandr that ensures that those meters of Rakarrack are displayed. I could go the route of having a VU meter directly monitoring the input before it reaches the Pi, but that would be a lot of tinkering. So I need an indicator, a VU meter that it is indeed being fed at a good level. However some very practical problems remain, and they would actually remain for whatever solution I would have chosen, namely: How do I know I'm feeding the compressor at the right level? If the input signal is too low, the compressor/limiter may not kick in. It seems clear now that I have succeeded in building a headphones protector with a Raspberry Pi 3B+, Jackd and Rakarrack. Force the pi to always be alert, by telling it so on startup: sudo nano -w /etc/rc.localĮcho "performance" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governorĮcho "performance" > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governorĮcho "performance" > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governorĮcho "performance" > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor
Default configuration to use the USB card: sudo nano -w /etc/nfĤ. DBus security policy (disclaimer: I have no idea what this one does in this context): sudo nano -w /etc/dbus-1/nfģ. Disable the internal audio card by commenting out the "dtparam=audio=on" : sudo nano -w /boot/config.txtĢ. The things I did that were new were the following:ġ. In a quick test this morning it seemed to make a difference although some of the adjustments had already been made. Either the Modep image cannot handle the 3B+ hardware or it cannot handle being on a USB, I guess. It complained about things being on different partitions or something.
Update : Couldn't boot with Modep from a USB stick with a Raspberry Pi 3 B+. Their stuff looks close to what I would like to create except they do guitar effects.įinally, since I have problems with the processing power of the Pi, maybe it's time to look at PureData, maybe the bare bones approach would yield more powerful results, suitable for a headless configuration?
Modep seems to be created by the guys behind the super pedals Mod Duo and Mod Duo X. Review: Blokas PiSound, Audio & MIDI Interface For Raspberry Pi : Ask.Audio At around €100 I will refrain to buy it at this point in time, since I think it is the processing limits of the Pi itself, that sets the limits for me. Buy Pisound - Sound Card & MIDI Interface for Raspberry Pi. Modep is hosted by the Lithuanian Blokas guys who make the Pisound high-quality sound sound card for Pi. There are even two de-essers among the plugins! I suupect though that many of the plugins are made for guitar effects and are hence in mono. I haven't tested it yet, but I am very curious as to how well they solve the optimization issues.
Modep ( Meet MODEP - MOD DUO Emulator for Raspberry Pi) is a ready-made operating system image with almost 200 plugins installed.
Going deeper into the world of Raspberry Pi and sound I have discovered some new options.