Raspbian lite + jconvolver + volume control configuration?

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Raspbian lite + jconvolver + volume control configuration?

Postby Prefader » Mon Sep 09, 2019 6:35 pm

Greetings all,

I'm new to the forums, but I'm a long-time linux user and tinkerer.

My band and I are working on a project to reduce or eliminate our stage volume. Our favorite method so far is to utilize headless raspberry pis with USB interfaces and jconvolver loaded up with cabinet IRs. Latency has been phenomenally low (<3ms!) for such a low-power system, and we're very happy with the tones we've been able to achieve using free IRs found around the web.

One of our guitarists would very much like to use a reverb in conjunction with the cabinet IR. This is not a problem and is working beautifully, with one exception: he needs level control for the reverb. As jack does not provide signal processing, I'm left to find a plugin or other solution. Unfortunately, I've not had much luck finding anything that will run headless (no gui). The alternatives are proving to be beyond my current skillset.

Does anyone know of any simple solutions for this?

I've attempted to use an alsa loopback device with softvol, but I've not had any luck in getting alsamixer to actually show me a volume control. Admittedly, it's been a very long time since I've had to actually configure alsa, and I'm struggling to understand how to write an asound.conf that gives me the desired results.

Any help is greatly appreciated, and I'll update with configuration files when I'm able to get to one of the rpis, if necessary.

## UPDATE ##
I found jackminimix and libosctools, which seem like they'll do the trick. I'll report back my finding after some testing.

Here is the current setup:


Code: Select all

#set governor to performance
echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

#start jack server
JACK_DRIVER_DIR=/usr/local/lib/jack jackd -R -d alsa -d hw:1 -r 48000 -n 2 -p 64 &
sleep 5

#start jconvolver
jconvolver /home/pi/Ampeg_8x10_e602_A107.conf &

sleep 5

#setup jconvolver routing
jack_connect em:capture_2 jconvolver:verb.in.L
jack_connect em:capture_2 jconvolver:verb.in.R
jack_connect em:capture_2 jconvolver:cab.in.L
jack_connect em:capture_2 jconvolver:cab.in.R
jack_connect jconvolver:verb.out.L jconvolver:cab.in.L
jack_connect jconvolver:verb.out.R jconvolver:cab.in.R
jack_connect jconvolver:cab.out.L em:playback_1
jack_connect jconvolver:cab.out.R em:playback_2

and the jconvolver config:

Code: Select all

#                in  out   partition    maxsize
# ---------------------------------------------
/convolver/new    4    4         64     250000
#              num   port name     connect to
# -----------------------------------------------
/input/name     1     verb.in.L
/input/name     2     verb.in.R
/input/name     3     cab.in.L
/input/name     4     cab.in.R
/output/name    1     verb.out.L
/output/name    2     verb.out.R
/output/name    3     cab.out.L
/output/name    4     cab.out.R
#                in out  gain  delay  offset  length  chan      file 
# ----------------------------------------------------------------------
/impulse/read     1   1    0.04  0      0       0       1     Spring_reverb_48k.wav
/impulse/read     2   2    0.04  0      0       0       2     Spring_reverb_48k.wav
/impulse/read     3   3    1     0      0       0       1     Ampeg_8x10_e602_A107_48k.wav
/impulse/read     4   4    1     0      0       0       1     Ampeg_8x10_e602_A107_48k.wav

As you can see, I'm cutting the gain WAY back on the reverb to get the mix the way I'd like. I would much prefer to stick a volume control in between "jconvolver:verb.out.X" and "jconvolver:cab.in.X"

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Re: Raspbian lite + jconvolver + volume control configuration?

Postby Prefader » Tue Sep 17, 2019 4:38 pm

I have a working solution!

jackminimix and the liblo-tools package provide everything I need. Once the project is nearing completion, I'll start a new thread with details on what I end up with.

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Digital Larry
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Joined: Thu Jan 09, 2014 5:25 am

Re: Raspbian lite + jconvolver + volume control configuration?

Postby Digital Larry » Tue Sep 17, 2019 9:33 pm

I am interested to hear about it.

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Joined: Sat Sep 07, 2019 3:23 pm

Re: Raspbian lite + jconvolver + volume control configuration?

Postby Prefader » Wed Sep 18, 2019 1:45 pm

It might be a little while. ;)

As with most things, getting a pile of parts working together is one thing. Making it all useful to the end user is another thing entirely.

Right now I'm trying to teach myself enough python to cobble together software to make button presses and knob turns do the things I want. I'm progressing well, but will eventually need to bundle all of this up into a form factor suitable to stick on a pedalboard. I'm aiming to get all of this done with under $100 in hardware, including the pi. Best guess says I'm at least 2 months away, given family/work/leisure duties. Once I get to the point where I'm building the hardware into an enclosure, I'll start a thread about the project.

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