diff --git a/csdr/chain/__init__.py b/csdr/chain/__init__.py
index 3f0a3b24..6be0ce88 100644
--- a/csdr/chain/__init__.py
+++ b/csdr/chain/__init__.py
@@ -1,14 +1,11 @@
 from pycsdr.modules import Buffer
 
-import logging
-logger = logging.getLogger(__name__)
-
 
 class Chain:
     def __init__(self, *workers):
         self.input = None
         self.output = None
-        self.workers = workers
+        self.workers = list(workers)
         for i in range(1, len(self.workers)):
             self._connect(self.workers[i - 1], self.workers[i])
 
@@ -55,6 +52,35 @@ class Chain:
         else:
             return self.input.getOutputFormat()
 
+    def replace(self, index, newWorker):
+        if index >= len(self.workers):
+            raise IndexError("Index {} does not exist".format(index))
+
+        self.workers[index].stop()
+        self.workers[index] = newWorker
+
+        if index == 0:
+            newWorker.setInput(self.input)
+        else:
+            previousWorker = self.workers[index - 1]
+            if isinstance(previousWorker, Chain):
+                newWorker.setInput(previousWorker.getOutput())
+            else:
+                buffer = Buffer(previousWorker.getOutputFormat())
+                previousWorker.setOutput(buffer)
+                newWorker.setInput(buffer)
+
+        if index < len(self.workers) - 1:
+            nextWorker = self.workers[index + 1]
+            if isinstance(newWorker, Chain):
+                nextWorker.setInput(newWorker.getOutput())
+            else:
+                buffer = Buffer(newWorker.getOutputFormat())
+                newWorker.setOutput(buffer)
+                nextWorker.setInput(buffer)
+        else:
+            newWorker.setOutput(self.output)
+
     def pump(self, write):
         output = self.getOutput()
 
diff --git a/csdr/chain/am.py b/csdr/chain/am.py
index 9f0640fe..550032bc 100644
--- a/csdr/chain/am.py
+++ b/csdr/chain/am.py
@@ -18,6 +18,4 @@ class Am(Demodulator):
         super().__init__(*workers)
 
     def setLastDecimation(self, decimation: Chain):
-        # TODO: build api to replace workers
-        # TODO: replace placeholder
-        pass
+        self.replace(2, decimation)
diff --git a/csdr/chain/fft.py b/csdr/chain/fft.py
index 68d03796..9a5f541f 100644
--- a/csdr/chain/fft.py
+++ b/csdr/chain/fft.py
@@ -1,45 +1,25 @@
 from csdr.chain import Chain
 from pycsdr.modules import Fft, LogPower, LogAveragePower, FftSwap, FftAdpcm
 
-import logging
-logger = logging.getLogger(__name__)
-
 
 class FftAverager(Chain):
     def __init__(self, fft_size, fft_averages):
         self.fftSize = fft_size
-        self.fftAverages = None
-        self.worker = None
-        self.input = None
-        self.output = None
-        self.setFftAverages(fft_averages)
-        workers = [self.worker]
+        self.fftAverages = fft_averages
+        workers = [self._getWorker()]
         super().__init__(*workers)
 
     def setFftAverages(self, fft_averages):
         if self.fftAverages == fft_averages:
             return
-        if fft_averages == 0 and self.fftAverages != 0:
-            if self.worker is not None:
-                self.worker.stop()
-            self.worker = LogPower(add_db=70)
-            if self.output is not None:
-                self.worker.setOutput(self.output)
-            if self.input is not None:
-                self.worker.setInput(self.input)
-        elif fft_averages != 0:
-            if self.fftAverages == 0 or self.worker is None:
-                if self.worker is not None:
-                    self.worker.stop()
-                self.worker = LogAveragePower(add_db=-70, fft_size=self.fftSize, avg_number=fft_averages)
-                if self.output is not None:
-                    self.worker.setOutput(self.output)
-                if self.input is not None:
-                    self.worker.setInput(self.input)
-            else:
-                self.worker.setAvgNumber(avg_number=fft_averages)
-        self.workers = [self.worker]
         self.fftAverages = fft_averages
+        self.replace(0, self._getWorker())
+
+    def _getWorker(self):
+        if self.fftAverages == 0:
+            return LogPower(add_db=-70)
+        else:
+            return LogAveragePower(add_db=-70, fft_size=self.fftSize, avg_number=self.fftAverages)
 
 
 class FftChain(Chain):
diff --git a/csdr/chain/fm.py b/csdr/chain/fm.py
index ebc42ac7..62e535e5 100644
--- a/csdr/chain/fm.py
+++ b/csdr/chain/fm.py
@@ -17,6 +17,4 @@ class Fm(Demodulator):
         super().__init__(*workers)
 
     def setLastDecimation(self, decimation: Chain):
-        # TODO: build api to replace workers
-        # TODO: replace placeholder
-        pass
+        self.replace(2, decimation)