diff --git a/Components/6560/6560.cpp b/Components/6560/6560.cpp
index 1377ea9fc..7bb013ebb 100644
--- a/Components/6560/6560.cpp
+++ b/Components/6560/6560.cpp
@@ -95,9 +95,14 @@ static uint8_t noise_pattern[] = {
 	0xf0, 0xe1, 0xe0, 0x78, 0x70, 0x38, 0x3c, 0x3e, 0x1e, 0x3c, 0x1e, 0x1c, 0x70, 0x3c, 0x38, 0x3f,
 };
 
-#define shift(r) _shift_registers[r] = (_shift_registers[r] << 1) | (((_shift_registers[r]^0x80)&_control_registers[r]) >> 7);
-#define increment(r) _shift_registers[r] = (_shift_registers[r]+1)%8191;
-#define update(r, m, up) _counters[r]++; if((_counters[r] >> m) == 0x7f) { up(r); _counters[r] = _control_registers[r]&0x7f; }
+#define shift(r) _shift_registers[r] = (_shift_registers[r] << 1) | (((_shift_registers[r]^0x80)&_control_registers[r]) >> 7)
+#define increment(r) _shift_registers[r] = (_shift_registers[r]+1)%8191
+#define update(r, m, up) _counters[r]++; if((_counters[r] >> m) == 0x80) { up(r); _counters[r] = (unsigned int)(_control_registers[r]&0x7f) << m; }
+// Note on slightly askew test: as far as I can make out, if the value in the register is 0x7f then what's supposed to happen
+// is that the 0x7f is loaded, on the next clocked cycle the Vic spots a 0x7f, pumps the output, reloads, etc. No increment
+// ever occurs. It's conditional. I don't really want two conditionals if I can avoid it so I'm incrementing regardless and
+// testing against 0x80. The effect should be the same: loading with 0x7f means an output update every cycle, loading with 0x7e
+// means every second cycle, etc.
 
 void Speaker::get_samples(unsigned int number_of_samples, int16_t *target)
 {
diff --git a/Components/6560/6560.hpp b/Components/6560/6560.hpp
index 3b14c40be..b445c5dd3 100644
--- a/Components/6560/6560.hpp
+++ b/Components/6560/6560.hpp
@@ -68,7 +68,11 @@ template <class T> class MOS6560 {
 
 			// show only the centre
 			_crt->set_visible_area(_crt->get_rect_for_area(16, 237, 11*4, 55*4, 4.0f / 3.0f));
-			_speaker->set_input_rate(255681.75);	// assuming NTSC; clock rate / 4
+		}
+
+		void set_clock_rate(double clock_rate)
+		{
+			_speaker->set_input_rate((float)(clock_rate / 4.0));
 		}
 
 		std::shared_ptr<Outputs::CRT::CRT> get_crt() { return _crt; }
diff --git a/Machines/Commodore/Vic-20/Vic20.cpp b/Machines/Commodore/Vic-20/Vic20.cpp
index cbe58f3f4..408ae8735 100644
--- a/Machines/Commodore/Vic-20/Vic20.cpp
+++ b/Machines/Commodore/Vic-20/Vic20.cpp
@@ -181,11 +181,19 @@ void Machine::set_region(Commodore::Vic20::Region region)
 	{
 		case PAL:
 			set_clock_rate(1108404);
-			if(_mos6560) _mos6560->set_output_mode(MOS::MOS6560<Commodore::Vic20::Vic6560>::OutputMode::PAL);
+			if(_mos6560)
+			{
+				_mos6560->set_output_mode(MOS::MOS6560<Commodore::Vic20::Vic6560>::OutputMode::PAL);
+				_mos6560->set_clock_rate(1108404);
+			}
 		break;
 		case NTSC:
 			set_clock_rate(1022727);
-			if(_mos6560) _mos6560->set_output_mode(MOS::MOS6560<Commodore::Vic20::Vic6560>::OutputMode::NTSC);
+			if(_mos6560)
+			{
+				_mos6560->set_output_mode(MOS::MOS6560<Commodore::Vic20::Vic6560>::OutputMode::NTSC);
+				_mos6560->set_clock_rate(1022727);
+			}
 		break;
 	}
 }
@@ -193,6 +201,7 @@ void Machine::set_region(Commodore::Vic20::Region region)
 void Machine::setup_output(float aspect_ratio)
 {
 	_mos6560.reset(new Vic6560());
+	_mos6560->get_speaker()->set_high_frequency_cut_off(1600);	// There is a 1.6Khz low-pass filter in the Vic-20.
 	set_region(_region);
 
 	memset(_mos6560->_videoMemoryMap, 0, sizeof(_mos6560->_videoMemoryMap));
diff --git a/Outputs/Speaker.hpp b/Outputs/Speaker.hpp
index 261965912..72e595aa9 100644
--- a/Outputs/Speaker.hpp
+++ b/Outputs/Speaker.hpp
@@ -72,10 +72,20 @@ class Speaker {
 			set_needs_updated_filter_coefficients();
 		}
 
-		Speaker() : _buffer_in_progress_pointer(0), _requested_number_of_taps(0) {}
+		/*!
+			Sets the cut-off frequency for a low-pass filter attached to the output of this speaker; optional.
+		*/
+		void set_high_frequency_cut_off(float high_frequency)
+		{
+			_high_frequency_cut_off = high_frequency;
+			set_needs_updated_filter_coefficients();
+		}
+
+		Speaker() : _buffer_in_progress_pointer(0), _requested_number_of_taps(0), _high_frequency_cut_off(-1.0) {}
 
 	protected:
 		std::unique_ptr<int16_t> _buffer_in_progress;
+		float _high_frequency_cut_off;
 		int _buffer_size;
 		int _buffer_in_progress_pointer;
 		int _number_of_taps, _requested_number_of_taps;
@@ -114,7 +124,7 @@ template <class T> class Filter: public Speaker {
 			if(_coefficients_are_dirty) update_filter_coefficients();
 
 			// if input and output rates exactly match, just accumulate results and pass on
-			if(_input_cycles_per_second == _output_cycles_per_second)
+			if(_input_cycles_per_second == _output_cycles_per_second && _high_frequency_cut_off < 0.0)
 			{
 				while(input_cycles)
 				{
@@ -215,7 +225,17 @@ template <class T> class Filter: public Speaker {
 			_buffer_in_progress_pointer = 0;
 
 			_stepper.reset(new SignalProcessing::Stepper((uint64_t)_input_cycles_per_second, (uint64_t)_output_cycles_per_second));
-			_filter.reset(new SignalProcessing::FIRFilter((unsigned int)_number_of_taps, (float)_input_cycles_per_second, 0.0, (float)_output_cycles_per_second / 2.0f, SignalProcessing::FIRFilter::DefaultAttenuation));
+
+			float high_pass_frequency;
+			if(_high_frequency_cut_off > 0.0)
+			{
+				high_pass_frequency = std::min((float)_output_cycles_per_second / 2.0f, _high_frequency_cut_off);
+			}
+			else
+			{
+				high_pass_frequency = (float)_output_cycles_per_second / 2.0f;
+			}
+			_filter.reset(new SignalProcessing::FIRFilter((unsigned int)_number_of_taps, (float)_input_cycles_per_second, 0.0, high_pass_frequency, SignalProcessing::FIRFilter::DefaultAttenuation));
 
 			_input_buffer.reset(new int16_t[_number_of_taps]);
 			_input_buffer_depth = 0;