Add the separate echo buffer option.

apu/bapu/dsp/SPC_DSP.cpp

@@ -959,7 +959,7 @@ VOICE_CLOCK(V9_V6_V3) { voice_V9(v); voice_V6(v+1); voice_V3(v+2); }
 //// Echo
 
 // Current echo buffer pointer for left/right channel
-#define ECHO_PTR( ch )      (&m.ram [m.t_echo_ptr + ch * 2])
+#define ECHO_PTR( ch )      ((Settings.SeparateEchoBuffer) ? (&m.separate_echo_buffer [m.t_echo_ptr + ch * 2]) : (&m.ram [m.t_echo_ptr + ch * 2]))
 
 // Sample in echo history buffer, where 0 is the oldest
 #define ECHO_FIR( i )       (m.echo_hist_pos [i])
@@ -1221,6 +1221,8 @@ void SPC_DSP::soft_reset_common()
 	m.echo_offset        = 0;
 	m.phase              = 0;
 
+    memset(m.separate_echo_buffer, 0, 0x10000);
+
 	init_counter();
 
 	for (int i = 0; i < voice_count; i++)

apu/bapu/dsp/SPC_DSP.h

@@ -202,6 +202,8 @@ private:
 		sample_t* out_end;
 		sample_t* out_begin;
 		sample_t extra [extra_size];
+
+        uint8_t separate_echo_buffer [0x10000];
 	};
 	state_t m;
 

win32/wsnes9x.cpp

@@ -5109,8 +5109,8 @@ INT_PTR CALLBACK DlgEmulatorHacksProc(HWND hDlg, UINT msg, WPARAM wParam, LPARAM
         switch (LOWORD(wParam))
         {
         case IDOK:
-            if ((!Settings.BlockInvalidVRAMAccessMaster == IsDlgButtonChecked(hDlg, IDC_INVALID_VRAM) ||
-                Settings.SeparateEchoBuffer != IsDlgButtonChecked(hDlg, IDC_SEPARATE_ECHO_BUFFER))
+            if (((Settings.BlockInvalidVRAMAccessMaster != !IsDlgButtonChecked(hDlg, IDC_INVALID_VRAM)) ||
+                (Settings.SeparateEchoBuffer != IsDlgButtonChecked(hDlg, IDC_SEPARATE_ECHO_BUFFER)))
                 && !Settings.StopEmulation)
             {