diff --git a/csdr/chain/__init__.py b/csdr/chain/__init__.py
index 33ec232..bab0c0b 100644
--- a/csdr/chain/__init__.py
+++ b/csdr/chain/__init__.py
@@ -35,3 +35,23 @@ class Chain(Flow):
             return
         self.output = buffer
         self.workers[-1].setOutput(buffer)
+
+    def pump(self, write):
+        if self.output is None:
+            self.setOutput(Buffer())
+
+        def copy():
+            run = True
+            while run:
+                data = None
+                try:
+                    data = self.output.read()
+                except ValueError:
+                    pass
+                if data is None or (isinstance(data, bytes) and len(data) == 0):
+                    run = False
+                else:
+                    write(data)
+
+        return copy
+
diff --git a/owrx/fft.py b/owrx/fft.py
index 141ca45..3346f0f 100644
--- a/owrx/fft.py
+++ b/owrx/fft.py
@@ -1,5 +1,5 @@
 from owrx.config import Config
-from csdr import csdr
+from csdr.chain.fft import FftChain
 import threading
 from owrx.source import SdrSource, SdrSourceEventClient
 from owrx.property import PropertyStack
@@ -9,7 +9,7 @@ import logging
 logger = logging.getLogger(__name__)
 
 
-class SpectrumThread(csdr.output, SdrSourceEventClient):
+class SpectrumThread(SdrSourceEventClient):
     def __init__(self, sdrSource):
         self.sdrSource = sdrSource
         super().__init__()
@@ -17,7 +17,7 @@ class SpectrumThread(csdr.output, SdrSourceEventClient):
         stack = PropertyStack()
         stack.addLayer(0, self.sdrSource.props)
         stack.addLayer(1, Config.get())
-        self.props = props = stack.filter(
+        self.props = stack.filter(
             "samp_rate",
             "fft_size",
             "fft_fps",
@@ -26,45 +26,56 @@ class SpectrumThread(csdr.output, SdrSourceEventClient):
             "csdr_dynamic_bufsize",
             "csdr_print_bufsizes",
             "csdr_through",
-            "temporary_directory",
         )
 
-        self.dsp = dsp = csdr.dsp(self)
-        dsp.nc_port = self.sdrSource.getPort()
-        dsp.setBuffer(self.sdrSource.getBuffer())
-        dsp.set_demodulator("fft")
+        self.dsp = None
 
-        self.subscriptions = [
-            props.wireProperty("samp_rate", dsp.set_samp_rate),
-            props.wireProperty("fft_size", dsp.set_fft_size),
-            props.wireProperty("fft_fps", dsp.set_fft_fps),
-            props.wireProperty("fft_compression", dsp.set_fft_compression),
-            props.wireProperty("temporary_directory", dsp.set_temporary_directory),
-            props.wireProperty("fft_voverlap_factor", dsp.set_fft_voverlap_factor),
+        self.subscriptions = []
+        self.subscriptions += [
+            # these props require a restart
+            self.props.wireProperty("fft_size", self.restart),
+            self.props.wireProperty("fft_compression", self.restart),
         ]
 
-        dsp.csdr_dynamic_bufsize = props["csdr_dynamic_bufsize"]
-        dsp.csdr_print_bufsizes = props["csdr_print_bufsizes"]
-        dsp.csdr_through = props["csdr_through"]
         logger.debug("Spectrum thread initialized successfully.")
 
     def start(self):
+        if self.dsp is not None:
+            return
+
+        self.dsp = FftChain(
+            self.props['samp_rate'],
+            self.props['fft_size'],
+            self.props['fft_voverlap_factor'],
+            self.props['fft_fps'],
+            self.props['fft_compression']
+        )
         self.sdrSource.addClient(self)
+
+        self.subscriptions += [
+            # these props can be set on the fly
+            self.props.wireProperty("samp_rate", self.dsp.setSampleRate),
+            self.props.wireProperty("fft_fps", self.dsp.setFps),
+            self.props.wireProperty("fft_voverlap_factor", self.dsp.setVOverlapFactor),
+        ]
+
+        threading.Thread(target=self.dsp.pump(self.sdrSource.writeSpectrumData)).start()
+
         if self.sdrSource.isAvailable():
-            self.dsp.start()
-
-    def supports_type(self, t):
-        return t == "audio"
-
-    def receive_output(self, type, read_fn):
-        threading.Thread(target=self.pump(read_fn, self.sdrSource.writeSpectrumData)).start()
+            self.dsp.setInput(self.sdrSource.getBuffer())
 
     def stop(self):
+        if self.dsp is None:
+            return
         self.dsp.stop()
+        self.dsp = None
         self.sdrSource.removeClient(self)
-        for c in self.subscriptions:
-            c.cancel()
-        self.subscriptions = []
+        while self.subscriptions:
+            self.subscriptions.pop().cancel()
+
+    def restart(self, *args, **kwargs):
+        self.stop()
+        self.start()
 
     def getClientClass(self):
         return SdrSource.CLIENT_USER
@@ -73,7 +84,10 @@ class SpectrumThread(csdr.output, SdrSourceEventClient):
         if state in [SdrSource.STATE_STOPPING, SdrSource.STATE_FAILED]:
             self.dsp.stop()
         elif state == SdrSource.STATE_RUNNING:
-            self.dsp.start()
+            if self.dsp is None:
+                self.start()
+            else:
+                self.dsp.setInput(self.sdrSource.getBuffer())
 
     def onBusyStateChange(self, state):
         pass