Marbles with external quantizer

HBIII · October 21, 2020, 5:35am

Hi everyone,

I have been using marbles for a while now, and noticed I am having an issue with running it through an external quantizer. Say I am running x2 into the cv input of the quantizer and t2 into the trigger input of the quantizer and the output of the quantizer to 1v/o of an oscillator. Whenever the quantizer is triggered I can hear the old note for a split second until it becomes the new note (kind of a short glissando-ish sound). Two different quantizers have given me the same result. I am able to fix it if I clock marbles through pams new workout and then clock the quantizer with a separate clock from pams that is slightly delayed from the one going to marbles. But if there is something else I can do to fix this (or if I am doing something wrong with marbles) without adding extra modules and connections I would love to know.

Thanks so much for any help!

abortivechronicles · October 21, 2020, 6:04am

sounds like you might need a trigger delay. MI Stages et.al

HBIII · October 21, 2020, 6:52pm

So you are telling me the solution to my problem, as is usual in eurorack, is that I need another module ;-).

abortivechronicles · October 22, 2020, 7:13am

I’m not sure there is any alternative.

From my limited understanding of these things is that the quantizer is not processing the signal quick enough.

You could sell the quantizer and buy one that works faster, thereby cleverly bypassing the rule of needing another module!

HBIII · October 22, 2020, 7:54am

Haha, well one of the “quantizers” is an arbhar in wavetable mode using the v/oct and strike input, so I am definitely not getting rid of that one. Other is a regular quantizer that I am thinking I can replace with a uo_c (that has a trigger delay setting to take care of this kind of thing). Is there any kind of trigger delay setting in marbles itself? I wish I had an oscilloscope so I could look at when the x2 cv output is changing and when the t2 triggers…

pichenettes · October 22, 2020, 8:33am

Sequencers whose CV outputs are laggy compared to their GATE outputs are a pet-peeve of mine, so I made sure that things are compensated in Marbles: the GATE and the CV outputs are changing state and settling at the same time.

Here is a scope trace (green = CV, yellow = GATE):

One thing to check: maybe turn STEPS slightly after 12 o’clock, so that you are 100% sure that the portamento/slew-limiting that happens on the first half of STEPS’ course is not active.

If it doesn’t help, here’s a firmware version with a longer delay for the gate outputs. Maybe your quantizer has a very low triggering threshold, or doesn’t take into account the fact that its CV input probably takes longer to sample than its GATE input.

marbles.wav.zip (684.8 KB)

pichenettes · October 22, 2020, 8:37am

You can change the +2 to whatever maximum delay time you want to allow (this line just makes room in the buffer to store the delayed values):

github.com

pichenettes/eurorack/blob/master/marbles/io_buffer.h#L55


const size_t kNumParameters = 8;

class IOBuffer {
 public:
  struct Block {
    uint16_t adc_value[kNumParameters * 2];
    bool input_patched[kNumInputs];
    
    stmlib::GateFlags input[kNumInputs][kBlockSize];
    uint16_t cv_output[kNumCvOutputs][kBlockSize];
    bool gate_output[kNumGateOutputs][kBlockSize + 2];
  };
  
  struct Slice {
    Block* block;
    size_t frame_index;
  };

  typedef void ProcessFn(Block* block, size_t size);

  IOBuffer() { }

And the gate delay itself is modified here:

github.com

pichenettes/eurorack/blob/master/marbles/marbles.cc#L64


#define PROFILE_INTERRUPT 0
#define PROFILE_RENDER 0

using namespace marbles;
using namespace std;
using namespace stmlib;

const bool test_adc_noise = false;

const int kSampleRate = 32000;
const int kGateDelay = 2;

ClockInputs clock_inputs;
ClockSelfPatchingDetector self_patching_detector[kNumGateOutputs];
CvReader cv_reader;
Dac dac;
DebugPort debug_port;
GateOutputs gate_outputs;
HysteresisQuantizer deja_vu_length_quantizer;
IOBuffer io_buffer;
NoteFilter note_filter;

The unit is samples (31.25µs).

Depending on how slow your quantizer is to react, you might have to use a larger delay than I did.

HBIII · October 23, 2020, 12:42am

Wow, thank you so much for this, I never imagined that I would get the scope images, custom firmware, and code to edit if needed. I am really speechless, this is amazing, I have been needing to update marbles with the newest firmware anyway. So happy about this !