diff --git a/bin/subcomposer b/bin/subcomposer
--- a/bin/subcomposer
+++ b/bin/subcomposer
@@ -154,7 +154,7 @@ if __name__ == "__main__":
     root.tk_setPalette("#004633")
 
     sc = Subcomposer(root, dmxdummy=0,
-                     numchannels=276 # use this to see all the skyline dims
+                     #numchannels=276 # use this to see all the skyline dims
                      #numchannels=118
                      )
     sc.pack()
diff --git a/light9/dmxchanedit.py b/light9/dmxchanedit.py
--- a/light9/dmxchanedit.py
+++ b/light9/dmxchanedit.py
@@ -134,7 +134,7 @@ class Levelbox(tk.Frame):
         stdfont = tkFont.Font(size=8)
         self.levels = [] # Onelevel objects
 
-        rows = 48
+        rows = 35
         frames = [make_frame(self) for x in range((num_channels // rows) + 1)]
 
         for channel in range(1, num_channels+1):
diff --git a/light9/io/__init__.py b/light9/io/__init__.py
--- a/light9/io/__init__.py
+++ b/light9/io/__init__.py
@@ -55,11 +55,11 @@ class ParportDMX(BaseIO):
             self.parport.outbyte(levels[p-1]*255 / 100)
 
 class UsbDMX(BaseIO):
-    dimmers = 512
-    def __init__(self):
+    def __init__(self, dimmers=72):
         BaseIO.__init__(self)
         self.__name__ = "UsbDMX"
         self.out = None
+        self.dimmers = dimmers
 
     def _dmx(self):
         if self.out is None: