Hi All,
I recently installed the breakout board for improving the bela pepper output. Upon testing, everything seems to work fine and I get audio output but it still seems too low (like a quarter of the amplitude of a normal eurorack vco for example).
I tried writing audioWrite(context, n, ch, -1); to the audiooutput but i only get 0.5v at the audio output (testing with a multimeter on an audio jack) no matter if i send 1 or -1 .
Sorry I am quite new to debugging this kind of thing, but is there a good way to test my installation of the breakout board?
Thanks,

Cheers,

Richard.

    These two behaviours should be mutually exclusive:

    electrowalrus t but i only get 0.5v at the audio output (testing with a multimeter on an audio jack) no matter if i send 1 or -1 .

    and

    electrowalrus everything seems to work fine and I get audio output but it still seems too low (like a quarter of the amplitude of a normal eurorack vco for example).

    The first suggests that the output is fixed independent of the signal being generated while the second indicates that the output does indeed follow the generated signal, albeit with smaller amplitude than expected.

    I suggest you remove the board from Bela and double check all component values and the orientation of the IC first. Then, try applying a known voltage to the differential inputs and verify the resulting output. The schematic is here: https://github.com/BelaPlatform/bela-pepper/wiki/Amplifier-Pepper . The differential gain is 15k/5.6k, that is 2.68. Using the GND (0V) and 3.3V signals available on Bela applying a 3.3V to the + input and 0V to the - input of a channel should give 3.3V * 2.68 = 8.84V output. Conversely, applying 3.3V to the - input and 0V to the + input should give -3.3V * 2.68 = -8.84V at the output. If you verify that this holds true for both channels then the issue may be with the wiring of the pin/socket connector between the Bela cape, the amplifier board and Pepper.

        yeah i've tested it again, and that is what happens. perhaps i am testing wrongly. i am using a multimeter in DC volt mode to test against the other end of a eurorack jack that is in the audio out of the pepper, black lead on the long part of the jack and red lead on the tip of the jack. also when i remove the power from the amplifier board i get the same results (i am unsure why i get audio output). i will double check the components and see if I can unsolder and reflow the joints tomorrow. (a bit difficult with the way the board is attached).

        thanks Robert and Giulio. I have fixed the issue, which was very simply that I had the power hooked up wrongly. I think what threw me off was that there is still audio output even though the op amp was not powered. The module is soooo much more useful to me now the audio output is at a level of other eurorack modules. And still the debugging/learning experience was useful also. I think perhaps a note on the testing page that audio may still output even if the amp is not working maybe be helpful to others, also to double check the power 🙂