diff --git a/atari800/src/votraxsnd.c b/atari800/src/votraxsnd.c
index d70560a..6edf36e 100644
--- a/atari800/src/votraxsnd.c
+++ b/atari800/src/votraxsnd.c
@@ -267,8 +267,8 @@ void VOTRAXSND_Process(void *sndbuffer, int sndn)
 	while (sndn > 0) {
 		int amount = ((sndn > VTRX_BLOCK_SIZE) ? VTRX_BLOCK_SIZE : sndn);
 		votrax_process(votrax_buffer, amount, temp_votrax_buffer);
-		if (bit16) mix((SWORD *)sndbuffer, votrax_buffer, amount, 128/4);
-		else mix8((UBYTE *)sndbuffer, votrax_buffer, amount, 128/4);
+		if (bit16) mix((SWORD *)sndbuffer, votrax_buffer, amount, POKEYSND_volume >> 3);
+		else mix8((UBYTE *)sndbuffer, votrax_buffer, amount, POKEYSND_volume >> 3);
 		sndbuffer = (char *) sndbuffer + VTRX_BLOCK_SIZE*(bit16 ? 2 : 1)*((num_pokeys == 2) ? 2: 1);
 		sndn -= VTRX_BLOCK_SIZE;
 	}
diff --git a/atari800/src/votraxsnd.h b/atari800/src/votraxsnd.h
index 0b26675..6edf36e 100644
--- a/atari800/src/votraxsnd.h
+++ b/atari800/src/votraxsnd.h
@@ -1,15 +1,276 @@
-#ifndef VOTRAXSND_H_
-#define VOTRAXSND_H_
+/*
+ * votraxsnd.c - Atari800 interface to votrax.c
+ *
+ * Copyright (C) 2007-2010 Atari800 development team (see DOC/CREDITS)
+ *
+ * This file is part of the Atari800 emulator project which emulates
+ * the Atari 400, 800, 800XL, 130XE, and 5200 8-bit computers.
+ *
+ * Atari800 is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Atari800 is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Atari800; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+*/
 
+#include <stdio.h>
+#include <stdlib.h>
 #include "atari.h"
-#include "votrax.h"
+#include "util.h"
+#include "votraxsnd.h"
+#ifdef PBI_XLD
+#include "pbi_xld.h"
+#endif
+#ifdef VOICEBOX
+#include "voicebox.h"
+#endif
+#include "pokey.h"
+#include "log.h"
 
-void VOTRAXSND_PutByte(UBYTE byte);
-void VOTRAXSND_Init(int playback_freq, int n_pokeys, int b16);
-void VOTRAXSND_Frame(void);
-void VOTRAXSND_Process(void *sndbuffer, int sndn);
-extern int VOTRAXSND_busy;
-void VOTRAXSND_Reinit(void);
-void VOTRAXSND_ModifyRatio(double factor);
+/* Votrax */
+
+#define VTRX_RATE 24500
+
+static double ratio;
+static int bit16;
+#define VTRX_BLOCK_SIZE 1024
+SWORD *temp_votrax_buffer = NULL;
+SWORD *votrax_buffer = NULL;
+int VOTRAXSND_busy = FALSE;
+static int votrax_sync_samples;
+static int dsprate;
+static int num_pokeys;
+static int samples_per_frame;
+/*if SYNCHRONIZED_SOUND is not used and the sound generation runs in a
+ * separate thread, then these variables are accessed in two different
+ * threads: */
+static int votrax_written = FALSE;
+static int votrax_written_byte = 0x3f;
+
+void VOTRAXSND_PutByte(UBYTE byte)
+{
+	/* put byte to voice box */
+	votrax_sync_samples = (int)((1.0/ratio)*(double)Votrax_Samples((votrax_written_byte&0x3f), (byte&0x3f), votrax_sync_samples));
+	votrax_written = TRUE;
+	votrax_written_byte = byte;
+	if (!VOTRAXSND_busy) {
+		VOTRAXSND_busy = TRUE;
+#ifdef PBI_XLD
+		if (PBI_XLD_enabled) {
+			PBI_XLD_votrax_busy_callback(TRUE); /* idle -> busy */
+		}
+#endif
+	}
+}
+
+static void VOTRAXSND_busy_callback_async(int busy_status)
+{
+	return;
+	/* do nothing */
+}
+
+static int votraxsnd_enabled(void)
+{
+	if (
+#ifdef VOICEBOX
+		!VOICEBOX_enabled &&
+#endif
+#ifdef PBI_XLD
+		!PBI_XLD_v_enabled &&
+
+#endif
+		1) return FALSE;
+	else return TRUE;
+}
+
+/* called from POKEYSND_Init */
+void VOTRAXSND_Init(int playback_freq, int n_pokeys, int b16)
+{
+	static struct Votrax_interface vi;
+	int temp_votrax_buffer_size;
+	bit16 = b16;
+	dsprate = playback_freq;
+	num_pokeys = n_pokeys;
+	if (!votraxsnd_enabled()) return;
+	if (num_pokeys != 1 && num_pokeys != 2) {
+		Log_print("VOTRAXSND_Init: cannot handle num_pokeys=%d", num_pokeys);
+#ifdef PBI_XLD
+		PBI_XLD_v_enabled = FALSE;
+#endif
+#ifdef VOICEBOX
+		VOICEBOX_enabled = FALSE;
+#endif
+		return;
+	}
+	vi.num = 1;
+	vi.BusyCallback = VOTRAXSND_busy_callback_async;
+	Votrax_Stop();
+	Votrax_Start((void *)&vi);
+	samples_per_frame = dsprate/(Atari800_tv_mode == Atari800_TV_PAL ? 50 : 60);
+	ratio = (double)VTRX_RATE/(double)dsprate;
+#ifdef VOICEBOX
+	temp_votrax_buffer_size = (int)(VTRX_BLOCK_SIZE*ratio*(VOICEBOX_BASEAUDF+1) + 10); /* +10 .. little extra? */
+#else
+	temp_votrax_buffer_size = (int)(VTRX_BLOCK_SIZE*ratio + 10); /* +10 .. little extra? */
+#endif
+	free(temp_votrax_buffer);
+	temp_votrax_buffer = (SWORD *)Util_malloc(temp_votrax_buffer_size*sizeof(SWORD));
+	free(votrax_buffer);
+	votrax_buffer = (SWORD *)Util_malloc(VTRX_BLOCK_SIZE*sizeof(SWORD));
+
+	VOTRAXSND_busy = FALSE;
+	votrax_sync_samples = 0;
+}
+
+void VOTRAXSND_Reinit(void)
+{
+	if (dsprate) VOTRAXSND_Init(dsprate, num_pokeys, bit16);
+}
+
+/* process votrax and interpolate samples */
+static void votrax_process(SWORD *v_buffer, int len, SWORD *temp_v_buffer)
+{
+	static SWORD last_sample;
+	static SWORD last_sample2;
+	static double startpos;
+	static int have;
+	int max_left_sample_index = (int)(startpos + (double)(len - 1)*ratio);
+	int pos = 0;
+	double fraction = 0;
+	int i;
+	int floor_next_pos;
+
+	if (have == 2) {
+	    temp_v_buffer[0] = last_sample;
+		temp_v_buffer[1] = last_sample2;
+		Votrax_Update(0, temp_v_buffer + 2, (max_left_sample_index + 1 + 1) - 2);
+	}
+	else if (have == 1) {
+	    temp_v_buffer[0] = last_sample;
+		Votrax_Update(0, temp_v_buffer + 1, (max_left_sample_index + 1 + 1) - 1);
+	}
+	else if (have == 0) {
+		Votrax_Update(0, temp_v_buffer, max_left_sample_index + 1 + 1);
+	}
+	else if (have < 0) {
+		Votrax_Update(0, temp_v_buffer, -have);
+		Votrax_Update(0, temp_v_buffer, max_left_sample_index + 1 + 1);
+	}
+
+	for (i = 0; i < len; i++) {
+		SWORD left_sample;
+		SWORD right_sample;
+		SWORD interp_sample;
+		pos = (int)(startpos + (double)i*ratio);
+		fraction = startpos + (double)i*ratio - (double)pos;
+		left_sample = temp_v_buffer[pos];
+		right_sample = temp_v_buffer[pos+1];
+		interp_sample = (int)(left_sample + fraction*(double)(right_sample-left_sample));
+		v_buffer[i] = interp_sample;
+	}
+	floor_next_pos = (int)(startpos + (double)len*ratio);
+	startpos = (startpos + (double)len*ratio) - (double)floor_next_pos;
+	if (floor_next_pos == max_left_sample_index)
+	{
+		have = 2;
+		last_sample = temp_v_buffer[floor_next_pos];
+		last_sample2 = temp_v_buffer[floor_next_pos+1];
+	}
+	else if (floor_next_pos == max_left_sample_index + 1) {
+		have = 1;
+		last_sample = temp_v_buffer[floor_next_pos];
+	}
+	else {
+		have = (floor_next_pos - (max_left_sample_index + 2));
+	}
+}
+
+/* 16 bit mixing */
+static void mix(SWORD *dst, SWORD *src, int sndn, int volume)
+{
+	SWORD s1, s2;
+	int val;
+
+	while (sndn--) {
+		s1 = *src;
+		s1 = s1*volume/128;
+		s2 = *dst;
+		src++;
+		val = s1 + s2;
+		if (val > 32767) val = 32767;
+		if (val < -32768) val = -32768;
+		*dst++ = val;
+		if (num_pokeys == 2) {
+			dst++;
+		}
+	}
+}
+
+/* 8 bit mixing */
+static void mix8(UBYTE *dst, SWORD *src, int sndn, int volume)
+{
+	SWORD s1, s2;
+	int val;
+
+	while (sndn--) {
+		s1 = *src;
+		s1 = s1*volume/128;
+		s2 = ((int)(*dst) - 0x80)*256;
+		src++;
+		val = s1 + s2;
+		if (val > 32767) val = 32767;
+		if (val < -32768) val = -32768;
+		*dst++ = (UBYTE)((val/256) + 0x80);
+		if (num_pokeys == 2) {
+			dst++;
+		}
+	}
+}
+
+void VOTRAXSND_Frame(void)
+{
+	if (!votraxsnd_enabled()) return;
+#ifdef VOICEBOX
+	if (VOICEBOX_enabled && VOICEBOX_ii) {
+		double factor = (VOICEBOX_BASEAUDF+1.0)/(POKEY_AUDF[3]+1.0);
+		ratio = (double)VTRX_RATE/(double)dsprate * factor;
+		samples_per_frame = ((double)dsprate/(double)(Atari800_tv_mode == Atari800_TV_PAL ? 50 : 60)) / factor;
+	}
+#endif
+	votrax_sync_samples -= samples_per_frame;
+	if (votrax_sync_samples <= 0 ) {
+		votrax_sync_samples = 0;
+		VOTRAXSND_busy = FALSE;
+#ifdef PBI_XLD
+		PBI_XLD_votrax_busy_callback(FALSE); /* busy -> idle */
+#endif
+	}
+}
+
+void VOTRAXSND_Process(void *sndbuffer, int sndn)
+{
+	if (!votraxsnd_enabled()) return;
+
+	if(votrax_written) {
+		votrax_written = FALSE;
+		Votrax_PutByte(votrax_written_byte);
+	}
+	sndn /= num_pokeys;
+	while (sndn > 0) {
+		int amount = ((sndn > VTRX_BLOCK_SIZE) ? VTRX_BLOCK_SIZE : sndn);
+		votrax_process(votrax_buffer, amount, temp_votrax_buffer);
+		if (bit16) mix((SWORD *)sndbuffer, votrax_buffer, amount, POKEYSND_volume >> 3);
+		else mix8((UBYTE *)sndbuffer, votrax_buffer, amount, POKEYSND_volume >> 3);
+		sndbuffer = (char *) sndbuffer + VTRX_BLOCK_SIZE*(bit16 ? 2 : 1)*((num_pokeys == 2) ? 2: 1);
+		sndn -= VTRX_BLOCK_SIZE;
+	}
+}
 
-#endif /* VOTRAXSND_H_ */