diff --git a/src/dartsort/cluster/gaussian_mixture.py b/src/dartsort/cluster/gaussian_mixture.py
index 7cfa9dc5..f8b9cc9c 100644
--- a/src/dartsort/cluster/gaussian_mixture.py
+++ b/src/dartsort/cluster/gaussian_mixture.py
@@ -2102,14 +2102,15 @@ def fit(
         self.register_buffer("mean", mean_full)
         if je_suis and res.get("W", None) is not None:
             self.register_buffer("W", W_full)
-        self.pick_channels(achans, res["nobs"])
+        nobs = res["nobs"] if je_suis else None
+        self.pick_channels(achans, nobs)
 
-    def pick_channels(self, active_chans, nobs):
+    def pick_channels(self, active_chans, nobs=None):
         if self.channels_strategy == "all":
             self.register_buffer("channels", torch.arange(self.n_channels))
             return
 
-        if not active_chans.numel():
+        if not active_chans.numel() or nobs is None:
             return
 
         amp = torch.linalg.vector_norm(self.mean[:, active_chans], dim=0)
diff --git a/src/dartsort/util/noise_util.py b/src/dartsort/util/noise_util.py
index 6b5627ee..8af79869 100644
--- a/src/dartsort/util/noise_util.py
+++ b/src/dartsort/util/noise_util.py
@@ -3,12 +3,14 @@
 import numpy as np
 import pandas as pd
 import torch
-from linear_operator import operators
+from linear_operator import operators, settings
 from scipy.fftpack import next_fast_len
 from tqdm.auto import trange
 
 from ..util import drift_util, spiketorch
 
+settings.
+
 
 class FullNoise(torch.nn.Module):
     """Do not use this, it's just for comparison to the others."""
@@ -407,7 +409,9 @@ def marginal_covariance(
             return res
         if channels == slice(None):
             if self._full_cov is None:
-                self._full_cov = self._marginal_covariance()
+                fcov = self._marginal_covariance()
+                fcov = operators.CholLinearOperator(fcov.cholesky())
+                self._full_cov = fcov
                 self._logdet = self._full_cov.logdet()
             if device is not None and device != self._full_cov.device:
                 self._full_cov = self._full_cov.to(device)