diff --git a/owrx/source/direct.py b/owrx/source/direct.py
index d11d83b..e4a5eaf 100644
--- a/owrx/source/direct.py
+++ b/owrx/source/direct.py
@@ -1,5 +1,9 @@
 from abc import ABCMeta
 from owrx.source import SdrSource, SdrDeviceDescription
+from csdr.chain import Chain
+from typing import Optional
+from pycsdr.modules import Buffer
+from pycsdr.types import Format
 
 import logging
 
@@ -38,16 +42,30 @@ class DirectSource(SdrSource, metaclass=ABCMeta):
         ]
 
     def getCommand(self):
-        return super().getCommand() + self.getFormatConversion() + self.getNmuxCommand()
+        return super().getCommand() + self.getNmuxCommand()
 
     # override this in subclasses, if necessary
-    def getFormatConversion(self):
-        return []
+    def getFormatConversion(self) -> Optional[Chain]:
+        return None
 
     # override this in subclasses, if necessary
     def sleepOnRestart(self):
         pass
 
+    def getBuffer(self):
+        if self.buffer is None:
+            source = self._getTcpSource()
+            buffer = Buffer(source.getOutputFormat())
+            source.setWriter(buffer)
+            conversion = self.getFormatConversion()
+            if conversion is not None:
+                conversion.setReader(buffer.getReader())
+                # this one must be COMPLEX_FLOAT
+                buffer = Buffer(Format.COMPLEX_FLOAT)
+                conversion.setWriter(buffer)
+            self.buffer = buffer
+        return self.buffer
+
 
 class DirectSourceDeviceDescription(SdrDeviceDescription):
     pass
diff --git a/owrx/source/fifi_sdr.py b/owrx/source/fifi_sdr.py
index cf6e3e7..4bf3bdd 100644
--- a/owrx/source/fifi_sdr.py
+++ b/owrx/source/fifi_sdr.py
@@ -1,6 +1,9 @@
 from owrx.command import Option
 from owrx.source.direct import DirectSource, DirectSourceDeviceDescription
 from subprocess import Popen
+from csdr.chain import Chain
+from pycsdr.modules import Convert, Gain
+from pycsdr.types import Format
 
 import logging
 
@@ -20,8 +23,8 @@ class FifiSdrSource(DirectSource):
     def getEventNames(self):
         return super().getEventNames() + ["device"]
 
-    def getFormatConversion(self):
-        return ["csdr convert_s16_f", "csdr gain_ff 5"]
+    def getFormatConversion(self) -> Chain:
+        return Chain([Convert(Format.COMPLEX_SHORT, Format.COMPLEX_FLOAT), Gain(Format.COMPLEX_FLOAT, 5.0)])
 
     def sendRockProgFrequency(self, frequency):
         process = Popen(["rockprog", "--vco", "-w", "--freq={}".format(frequency / 1e6)])