PGA gain in supercollider

RafaeleAndrade

Sorry Giulio , when I run this code on the ssh terminal, I get a different response than in the bela platform terminal, here is the print screen for you

giuliomoro

RafaeleAndrade

giuliomoro running this code and rebooting doesnt give me any progress as well :/

giuliomoro

you should run the code one line at a time or put semicolons in between. Use the below (note the single >, which you didn't use in the latest screenshot )

echo "CPPFLAGS+=-DGEMMULTI_REVA3_NOREWORK" > /root/Bela/CustomMakefileTop.in;
touch /root/Bela/core/Gem_Multi_Codec.cpp /root/Bela/include/BelaContextManager.h;
make -C /root/Bela lib;

RafaeleAndrade

giuliomoro Running this code isn't making the channels from 2 to 8 be hearable but some different things happen on this visual monitor:

giuliomoro

Run my code, do the channels show up in the scope? By the way, are you plugging them into the jacks or straight into the pins?

RafaeleAndrade

giuliomoro I’ve been testing this configuration for the last few hours and I wanted to give you a detailed update, as I’ve realized something very specific is happening.
Initially, I thought it was a syntax problem in SuperCollider. When I ran a single channel (like Channel 8, the Arduino mic), it worked perfectly. However, as soon as I added more channels or tried to use multipliers, the output would immediately mute.
After further testing, I’ve discovered that this is likely a headroom/gain threshold issue in the new image. It seems the system is preventing me from setting any gain louder than -6dB (which is the 0.5 multiplier in SuperCollider). If I keep everything at or below 0.5, it works; if I go above that, it mutes.
I’m currently stuck because I need to be able to set a louder gain for my inputs, but the system is muting them as if they are hitting a hard limit. I would appreciate your guidance on how to resolve this—is there a setting in the new image I can adjust to regain that headroom?

P.S. I did try the latest code you sent me and it is currently running on my Bela, but it hasn't resolved this specific muting behavior.

RafaeleAndrade

giuliomoro I checked the SuperCollider console output, and it shows the ADC level is 0 dB and the DAC level is 0 dB. I also looked for the "ADC Level" adjustment in the Bela IDE Settings tab that we used to have, but it seems to be missing in this new image.

giuliomoro

While the program is running you can open the audio tab in the IDE to observe the audio inputs and adjust the input gain. Can you see reasonable input levels there and do they respond to changes in the input?

Also,

Run my code, do the channels show up in the scope? By the way, are you plugging them into the jacks or straight into the pins?

RafaeleAndrade

giuliomoro
I am not using the jacks or the pins, I made my own PCB.

Here is the code you asked:

RafaeleAndrade

giuliomoro

On this screenshot I have the levels at 0 dB. That prevents of some channels being muted in the beginning. Few things I notice:

Channel 0 and 1 can go up to 30dB, if doing so they will mute other channels if starting at 10dB
Channels 2,3,4,5,6,7 can go until 9 dB , if I place 10dB they get muted

I would like to have 8 channels (0 to 7) 15dB of gain on the start. Is that possible on the new bela?

giuliomoro

Try using the wing with the on-board jacks; things should work fine there.

When using an external PCB and plugging directly into the pins, you need extra AC-coupling circuitry unless your input signal is already AC-coupled. At the very least you'd need a series capacitor (1µF) between your signal and the + input. Additionally, it would be good to add a 1µF capacitor from the - input to ground. Do NOT short the - input to ground.

RafaeleAndrade

giuliomoro Thank you, Giulio! Could you just tell me if it's even possible to add 15 dB of gain on these inputs before I remove the whole PCB and all the wiring? I am afraid that I'm going into a rabbit hole and in the end, it's not even doable.

giuliomoro

yes it is, there's 42dB of gain available on channels 2-9

giuliomoro

before tearing apart the PCB, I recommend you remove your PCB, put on the input wing with the jacks and test the inputs there. You can even use the signals on the sockets with the wing on, if you prefer pins to jacks: they are already AC-coupled. If that fixes the issue then most likely what you are missing is the capacitors I described above.

What pickups are you using ? Is their output AC- or DC-coupled?

RafaeleAndrade

giuliomoro Okay, I will try it tomorrow! I am using the Nu Cyfi pickups , it behaves as an AC audio signal.

since I have 16 of it in total and bela can only receive 8 channels, I use a resistor of 1k to combine 2 pickup signals into one (as advised by the maker of the pickups), which works but unfortunately remove some loudness of it.

RafaeleAndrade

giuliomoro Hi Giulio, I tested this morning with 2 pickups at the channel 2 and I can confirm the problem was the capacitors. I could boost up to 40dB this time.

I will be busy finding a way to connect these 2 capacitors on my PCB Design, meantime. could you confirm if I should follow these steps to set this new gain at the startup of bela? Will these setting also be triggered if I update the code on the fly ?

Access bela:ssh root@bela.local
Create /root/.bela first with: sudo mkdir -p /root/.bela
Create a file with: nano /root/.bela/belaconfig
Write on the file: CL=-I2,10,3,10,4,10,5,10,6,10,7,10
for sc users: Use the adcLevel hack( s.options.adcLevel = 1) on sc patch. The gain of the first two channels can be set via pgaGainLeft/Right from the scd file.
reboot

giuliomoro

those steps should work yes; you won't need to reboot the board, just restart the program.

RafaeleAndrade

giuliomoro it worked! Mistery solved!

« Previous Page