// feedforward
Impulse i => Delay delay => dac;
// feedback
delay => OneZero lowpass => delay;

// set delay
500::samp => delay.delay;
// set lowpass zero position
-1 => lowpass.zero;
// set feedback gain
.99 => lowpass.gain;

// fire!
5 => i.next;
// advance time
10::second => now;