diff --git a/src/kyupy/wave_sim.py b/src/kyupy/wave_sim.py
index 2f3d77d..878c49e 100644
--- a/src/kyupy/wave_sim.py
+++ b/src/kyupy/wave_sim.py
@@ -76,8 +76,14 @@ class WaveSim(sim.SimOps):
           final values in the waveforms are still valid.
         """
 
-        self.simctl_int = np.zeros((1, sims), dtype=np.int32)
-        self.simctl_int[0] = range(sims)
+        self.simctl_int = np.zeros((2, sims), dtype=np.int32)
+        """Per-simulation delay configuration.
+
+        * ``simctl_int[0]`` delay dataset or random seed for picking a delay
+        * ``simctl_int[1]`` 0: seed parameter specifies dataset, 1: simctl_int[0] specifies dataset, 2: simctl_int[0] + seed param. is a random seed for picking a delay dataset
+        """
+        self.simctl_int[0] = range(sims)  # unique seed for each sim by default, zero this to pick same delays for all sims.
+        self.simctl_int[1] = 2  # random picking by default.
 
         self.nbytes = sum([a.nbytes for a in (self.c, self.s, self.c_locs, self.c_caps, self.ops, self.simctl_int)])
 
@@ -137,10 +143,15 @@ def _wave_eval(lut, z_idx, a_idx, b_idx, c_idx, d_idx, cbuf, c_locs, c_caps, sim
     overflows = int(0)
 
     if len(delays) > 1:
-        _rnd = (seed << 4) + (z_idx << 20) + simctl_int[0]
-        for _ in range(4):
-            _rnd = int(0xDEECE66D) * _rnd + 0xB
-        delays = delays[_rnd % len(delays)]
+        if simctl_int[1] == 0:
+            delays = delays[seed]
+        elif simctl_int[1] == 1:
+            delays = delays[simctl_int[0]]
+        else:
+            _rnd = (seed << 4) + (z_idx << 20) + simctl_int[0]
+            for _ in range(4):
+                _rnd = int(0xDEECE66D) * _rnd + 0xB
+            delays = delays[_rnd % len(delays)]
     else:
         delays = delays[0]