diff --git a/libs/ardour/ardour/source_factory.h b/libs/ardour/ardour/source_factory.h
index 94ceb9c441..db9f6dfd5a 100644
--- a/libs/ardour/ardour/source_factory.h
+++ b/libs/ardour/ardour/source_factory.h
@@ -20,10 +20,14 @@
 #ifndef __ardour_source_factory_h__
 #define __ardour_source_factory_h__
 
+#include <list>
+#include <glibmm/thread.h>
+
 #include <string>
 #include <stdint.h>
 #include <sigc++/sigc++.h>
 #include <boost/shared_ptr.hpp>
+#include <boost/weak_ptr.hpp>
 
 #include <ardour/source.h>
 #include <ardour/audiofilesource.h>
@@ -36,6 +40,8 @@ class Session;
 
 class SourceFactory {
   public:
+	static void init ();
+
 	static sigc::signal<void,boost::shared_ptr<Source> > SourceCreated;
 
 	static boost::shared_ptr<Source> create (Session&, const XMLNode& node, bool async = false);
@@ -45,7 +51,12 @@ class SourceFactory {
 	static boost::shared_ptr<Source> createReadable (Session&, std::string path, int chn, AudioFileSource::Flag flags, bool announce = true, bool async = false);
 	static boost::shared_ptr<Source> createWritable (Session&, std::string name, bool destructive, nframes_t rate, bool announce = true, bool async = false);
 
+	static Glib::Cond*                              PeaksToBuild;
+	static Glib::StaticMutex                        peak_building_lock;
+	static std::list<boost::weak_ptr<AudioSource> > files_with_peaks;
+
   private:
+
 	static int setup_peakfile (boost::shared_ptr<Source>, bool async);
 };
 
diff --git a/libs/ardour/audiosource.cc b/libs/ardour/audiosource.cc
index 5df5e0b23a..0c889da194 100644
--- a/libs/ardour/audiosource.cc
+++ b/libs/ardour/audiosource.cc
@@ -582,9 +582,10 @@ AudioSource::build_peaks_from_scratch ()
 {
 	nframes_t current_frame;
 	nframes_t cnt;
-	Sample buf[frames_per_peak];
+	Sample* buf = 0;
 	nframes_t frames_read;
-	nframes_t frames_to_read;
+	nframes_t frames_to_read = 65536; // 256kB reads from disk, roughly ideal
+
 	int ret = -1;
 
 	{
@@ -599,6 +600,7 @@ AudioSource::build_peaks_from_scratch ()
 		current_frame = 0;
 		cnt = _length;
 		_peaks_built = false;
+		buf = new Sample[frames_to_read];
 		
 		while (cnt) {
 			
@@ -609,7 +611,7 @@ AudioSource::build_peaks_from_scratch ()
 				done_with_peakfile_writes (false);
 				goto out;
 			}
-
+			
 			if (compute_and_write_peaks (buf, current_frame, frames_read, true, false)) {
 				break;
 			}
@@ -617,7 +619,7 @@ AudioSource::build_peaks_from_scratch ()
 			current_frame += frames_read;
 			cnt -= frames_read;
 		}
-		
+
 		if (cnt == 0) {
 			/* success */
 			truncate_peakfile();
@@ -642,6 +644,10 @@ AudioSource::build_peaks_from_scratch ()
 		unlink (peakpath.c_str());
 	}
 
+	if (buf) {
+		delete [] buf;
+	}
+
 	return ret;
 }
 
@@ -719,9 +725,7 @@ AudioSource::compute_and_write_peaks (Sample* buf, nframes_t first_frame, nframe
 				PeakRangeReady (peak_leftover_frame, peak_leftover_cnt); /* EMIT SIGNAL */
 				if (intermediate_peaks_ready) {
 					PeaksReady (); /* EMIT SIGNAL */
-				} else {
-					cerr << "skipped PR @ A\n";
-				}
+				} 
 			}
 
 			/* left overs are done */
@@ -833,10 +837,7 @@ AudioSource::compute_and_write_peaks (Sample* buf, nframes_t first_frame, nframe
 		PeakRangeReady (first_frame, frames_done); /* EMIT SIGNAL */
 		if (intermediate_peaks_ready) {
 			PeaksReady (); /* EMIT SIGNAL */
-		} else {
-			cerr << "skipped PR @ B\n";
 		}
-					
 	}
 
 	ret = 0;
diff --git a/libs/ardour/globals.cc b/libs/ardour/globals.cc
index 199d69d42a..e5c9d27d5e 100644
--- a/libs/ardour/globals.cc
+++ b/libs/ardour/globals.cc
@@ -52,6 +52,7 @@
 #include <ardour/audiosource.h>
 #include <ardour/utils.h>
 #include <ardour/session.h>
+#include <ardour/source_factory.h>
 #include <ardour/control_protocol_manager.h>
 
 #ifdef HAVE_LIBLO
@@ -301,6 +302,8 @@ ARDOUR::init (bool use_vst, bool try_optimization)
 
 	setup_hardware_optimization (try_optimization);
 
+	SourceFactory::init ();
+
 	/* singleton - first object is "it" */
 	new PluginManager ();
 	
diff --git a/libs/ardour/source_factory.cc b/libs/ardour/source_factory.cc
index b2774591e4..405f0a064f 100644
--- a/libs/ardour/source_factory.cc
+++ b/libs/ardour/source_factory.cc
@@ -41,28 +41,62 @@ using namespace PBD;
 using namespace sigc;
 
 sigc::signal<void,boost::shared_ptr<Source> > SourceFactory::SourceCreated;
+Glib::Cond* SourceFactory::PeaksToBuild;
+Glib::StaticMutex SourceFactory::peak_building_lock;
+std::list<boost::weak_ptr<AudioSource> > SourceFactory::files_with_peaks;
 
-static void setup_peakfile (boost::weak_ptr<AudioSource> was)
+static void 
+peak_thread_work ()
 {
-	boost::shared_ptr<AudioSource> as (was.lock());
+	PBD::ThreadCreated (pthread_self(), string ("peakbuilder-") + to_string (pthread_self(), std::dec));
 
-	if (!as) {
-		return;
+	while (true) {
+
+		SourceFactory::peak_building_lock.lock ();
+
+		SourceFactory::PeaksToBuild->wait (SourceFactory::peak_building_lock);
+
+		if (SourceFactory::files_with_peaks.empty()) {
+			continue;
+		}
+		
+		boost::shared_ptr<AudioSource> as (SourceFactory::files_with_peaks.front().lock());
+		SourceFactory::files_with_peaks.pop_front ();
+		SourceFactory::peak_building_lock.unlock ();
+		
+		if (!as) {
+			continue;
+		}
+		
+		as->setup_peakfile ();
 	}
+}
 
-	PBD::ThreadCreatedWithRequestSize (pthread_self(), string ("peakbuilder-") + to_string (pthread_self(), std::dec), 1024);
-	as->setup_peakfile ();
-	// PBD::ThreadLeaving (pthread_self());
+void
+SourceFactory::init ()
+{
+	PeaksToBuild = new Glib::Cond();
+
+	for (int n = 0; n < 2; ++n) {
+		Glib::Thread::create (sigc::ptr_fun (::peak_thread_work), false);
+	}
 }
 
 int
 SourceFactory::setup_peakfile (boost::shared_ptr<Source> s, bool async)
 {
 	boost::shared_ptr<AudioSource> as (boost::dynamic_pointer_cast<AudioSource> (s));
+
 	if (as) {
+
 		if (async) {
-			Glib::Thread::create (bind (sigc::ptr_fun (::setup_peakfile), boost::weak_ptr<AudioSource>(as)), false);
+
+			Glib::Mutex::Lock lm (peak_building_lock);
+			files_with_peaks.push_back (boost::weak_ptr<AudioSource> (as));
+			PeaksToBuild->signal ();
+
 		} else {
+
 			if (as->setup_peakfile ()) {
 				error << string_compose("SourceFactory: could not set up peakfile for %1", as->name()) << endmsg;
 				return -1;