diff --git a/src/emu/sound/disc_flt.c b/src/emu/sound/disc_flt.c
index 73c49e46b5d..6986f851691 100644
--- a/src/emu/sound/disc_flt.c
+++ b/src/emu/sound/disc_flt.c
@@ -73,6 +73,7 @@ struct dst_rcdisc_context
 	double exponent0;
 	double exponent1;
 	double v_cap;		/* rcdisc5 */
+	double v_diode;		/* rcdisc3 */
 };
 
 struct dst_rcdisc_mod_context
@@ -360,9 +361,21 @@ static DISCRETE_STEP(dst_op_amp_filt)
 		{
 			/* Millman the input voltages. */
 			i  = context->iFixed;
-			i += (DST_OP_AMP_FILT__INP1 - context->vRef) / info->r1;
-			if (info->r2 != 0)
-				i += (DST_OP_AMP_FILT__INP2 - context->vRef) / info->r2;
+			switch (context->type)
+			{
+				case DISC_OP_AMP_FILTER_IS_LOW_PASS_1M:
+					i += (DST_OP_AMP_FILT__INP1 - DST_OP_AMP_FILT__INP2) / info->r1;
+					if (info->r2 != 0)
+						i += (context->vP - DST_OP_AMP_FILT__INP2) / info->r2;
+					if (info->r3 != 0)
+						i += (context->vN - DST_OP_AMP_FILT__INP2) / info->r3;
+					break;
+				default:
+					i += (DST_OP_AMP_FILT__INP1 - context->vRef) / info->r1;
+					if (info->r2 != 0)
+						i += (DST_OP_AMP_FILT__INP2 - context->vRef) / info->r2;
+					break;
+			}
 			v = i * context->rTotal;
 		}
 
@@ -373,6 +386,11 @@ static DISCRETE_STEP(dst_op_amp_filt)
 				node->output[0] = context->vC1 * context->gain + info->vRef;
 				break;
 
+			case DISC_OP_AMP_FILTER_IS_LOW_PASS_1M:
+				context->vC1 += (v - context->vC1) * context->exponentC1;
+				node->output[0] = context->vC1 * context->gain + DST_OP_AMP_FILT__INP2;
+				break;
+
 			case DISC_OP_AMP_FILTER_IS_HIGH_PASS_1:
 				node->output[0] = (v - context->vC1) * context->gain + info->vRef;
 				context->vC1 += (v - context->vC1) * context->exponentC1;
@@ -470,6 +488,7 @@ static DISCRETE_RESET(dst_op_amp_filt)
 	switch (context->type)
 	{
 		case DISC_OP_AMP_FILTER_IS_LOW_PASS_1:
+		case DISC_OP_AMP_FILTER_IS_LOW_PASS_1M:
 			context->exponentC1 = RC_CHARGE_EXP(info->rF * info->c1);
 			context->exponentC2 =  0;
 			break;
@@ -634,6 +653,7 @@ static DISCRETE_RESET(dst_rcdisc2)
  * input[2]    - Resistor0 value (initialization only)
  * input[4]    - Resistor1 value (initialization only)
  * input[5]    - Capacitor Value (initialization only)
+ * input[6]    - Diode Junction voltage (initialization only)
  *
  ************************************************************************/
 #define DST_RCDISC3__ENABLE	(*(node->input[0]))
@@ -641,6 +661,7 @@ static DISCRETE_RESET(dst_rcdisc2)
 #define DST_RCDISC3__R1		(*(node->input[2]))
 #define DST_RCDISC3__R2		(*(node->input[3]))
 #define DST_RCDISC3__C		(*(node->input[4]))
+#define DST_RCDISC3__DJV	(*(node->input[6]))
 
 static DISCRETE_STEP(dst_rcdisc3)
 {
@@ -653,15 +674,31 @@ static DISCRETE_STEP(dst_rcdisc3)
 	if(DST_RCDISC3__ENABLE)
 	{
 		diff = DST_RCDISC3__IN - node->output[0];
-		if( diff > 0 )
+		if (context->v_diode > 0)
 		{
-			diff = diff - (diff * context->exponent0);
-		} else if( diff < 0)
-		{
-			if(diff < -0.5)
-				diff = diff - (diff * context->exponent1);
-			else
+			if( diff > 0 )
+			{
 				diff = diff - (diff * context->exponent0);
+			} else if( diff < 0)
+			{
+				if(diff < -context->v_diode)
+					diff = diff - (diff * context->exponent1);
+				else
+					diff = diff - (diff * context->exponent0);
+			}
+		} 
+		else
+		{
+			if( diff < 0 )
+			{
+				diff = diff - (diff * context->exponent0);
+			} else if( diff > 0)
+			{
+				if(diff > -context->v_diode)
+					diff = diff - (diff * context->exponent1);
+				else
+					diff = diff - (diff * context->exponent0);
+			}
 		}
 		node->output[0] += diff;
 	}
@@ -679,6 +716,7 @@ static DISCRETE_RESET(dst_rcdisc3)
 
 	context->state = 0;
 	context->t = 0;
+	context->v_diode = DST_RCDISC3__DJV;
 	context->exponent0 = RC_CHARGE_EXP(DST_RCDISC3__R1 * DST_RCDISC3__C);
 	context->exponent1 = RC_CHARGE_EXP(RES_2_PARALLEL(DST_RCDISC3__R1, DST_RCDISC3__R2) * DST_RCDISC3__C);
 }
diff --git a/src/emu/sound/disc_mth.c b/src/emu/sound/disc_mth.c
index 7d7221e173e..6419e8b9128 100644
--- a/src/emu/sound/disc_mth.c
+++ b/src/emu/sound/disc_mth.c
@@ -1872,8 +1872,10 @@ static DISCRETE_RESET(dst_op_amp)
 			context->exponent = disc_info->sample_rate * info->c;
 	}
 
-	if (info->r3 >= 0)
+	if (info->r3 > 0)
 		context->i_fixed = (info->vP - OP_AMP_NORTON_VBE) / info->r3;
+	else
+		context->i_fixed = 0;
 }
 
 
diff --git a/src/emu/sound/disc_wav.c b/src/emu/sound/disc_wav.c
index 7c666cebfda..21868c7b54a 100644
--- a/src/emu/sound/disc_wav.c
+++ b/src/emu/sound/disc_wav.c
@@ -479,7 +479,7 @@ static DISCRETE_STEP(dss_lfsr)
 
 		/* output the lfsr reg ?*/
 		if (context->out_lfsr_reg)
-			node->output[1] = context->lfsr_reg;
+			node->output[1] = (double) context->lfsr_reg;
 
 	}
 	if(!DSS_LFSR_NOISE__ENABLE)
diff --git a/src/emu/sound/discrete.c b/src/emu/sound/discrete.c
index f92a299e9fe..fe50f12f07e 100644
--- a/src/emu/sound/discrete.c
+++ b/src/emu/sound/discrete.c
@@ -141,7 +141,7 @@ static const discrete_module module_list[] =
 	/* from disc_wav.c */
 	/* Generic modules */
 	{ DSS_COUNTER     ,"DSS_COUNTER"     , 1 ,sizeof(struct dss_counter_context)     ,dss_counter_reset     ,dss_counter_step     },
-	{ DSS_LFSR_NOISE  ,"DSS_LFSR_NOISE"  , 1 ,sizeof(struct dss_lfsr_context)        ,dss_lfsr_reset        ,dss_lfsr_step        },
+	{ DSS_LFSR_NOISE  ,"DSS_LFSR_NOISE"  , 2 ,sizeof(struct dss_lfsr_context)        ,dss_lfsr_reset        ,dss_lfsr_step        },
 	{ DSS_NOISE       ,"DSS_NOISE"       , 1 ,sizeof(struct dss_noise_context)       ,dss_noise_reset       ,dss_noise_step       },
 	{ DSS_NOTE        ,"DSS_NOTE"        , 1 ,sizeof(struct dss_note_context)        ,dss_note_reset        ,dss_note_step        },
 	{ DSS_SAWTOOTHWAVE,"DSS_SAWTOOTHWAVE", 1 ,sizeof(struct dss_sawtoothwave_context),dss_sawtoothwave_reset,dss_sawtoothwave_step},
diff --git a/src/emu/sound/discrete.h b/src/emu/sound/discrete.h
index e670943f2ea..27f68b9d95b 100644
--- a/src/emu/sound/discrete.h
+++ b/src/emu/sound/discrete.h
@@ -287,7 +287,7 @@
  * DISCRETE_OP_AMP_FILTER(NODE,ENAB,INP0,INP1,TYPE,INFO)
  * DISCRETE_RCDISC(NODE,ENAB,IN0,RVAL,CVAL)
  * DISCRETE_RCDISC2(NODE,SWITCH,INP0,RVAL0,INP1,RVAL1,CVAL)
- * DISCRETE_RCDISC3(NODE,ENAB,INP0,RVAL0,RVAL1,CVAL)
+ * DISCRETE_RCDISC3(NODE,ENAB,INP0,RVAL0,RVAL1,CVAL, DJV)
  * DISCRETE_RCDISC4(NODE,ENAB,INP0,RVAL0,RVAL1,RVAL2,CVAL,VP,TYPE)
  * DISCRETE_RCDISC5(NODE,ENAB,IN0,RVAL,CVAL)
  * DISCRETE_RCINTEGRATE(NODE,INP0,RVAL0,RVAL1,RVAL2,CVAL,vP,TYPE)
@@ -2249,7 +2249,26 @@
  *  vRef >-----------------------'  |/
  *
  *          --------------------------------------------------
+  *
+ *     DISC_OP_AMP_FILTER_IS_LOW_PASS_1M
+ *          First Order Low Pass Filter
  *
+ *                              c1
+ *                      .-------||---------.
+ *                      |                  |
+ *          r1          |       rF         |
+ *  IN0 >--ZZZZ--.      +------ZZZZ--------+
+ *               |      |                  |
+ *          r2   |      |           |\     |
+ *  VP  >--ZZZZ--+------+--------+  | \    |
+ *               |               '--|- \   |
+ *          r3   |                  |   >--+----------> Netlist Node
+ *  VN  >--ZZZZ--'               .--|+ /
+ *                               |  | /
+ *  IN1 >------------------------'  |/
+ *
+ *          --------------------------------------------------
+ * 
  *     DISC_OP_AMP_FILTER_IS_HIGH_PASS_1
  *          First Order High Pass Filter
  *
@@ -2482,7 +2501,10 @@
  *                        |                 |
  *    ENAB       -0------>|                 |
  *                        |    diode  R2    |
- *    INPUT1     -1------>| -+-|<|--ZZZZ-+- |---->   Netlist node
+ *    JV         -5------>| -+-|>|--ZZZZ-+- |---->   Netlist node (JV < 0)
+ *                        |                 |
+ *                        |    diode  R2    |
+ *    INPUT1     -1------>| -+-|<|--ZZZZ-+- |---->   Netlist node (JV > 0)
  *                        |  |           |  |
  *    RVAL1      -2------>|  '-ZZZZ-+----'  |
  *                        |     R1  |       |
@@ -2499,16 +2521,19 @@
  *                      input node (or value),
  *                      R1 resistor value in OHMS,
  *                      R2 resistor value in OHMS,
- *                      capacitor value in FARADS)
+ *                      capacitor value in FARADS,
+ *                      diode junction voltage)
  *
+ * The polarity of the diode junction voltage determines the polarity of the diode.
+ * 
  *  Example config line
  *
- *     DISCRETE_RCDISC3(NODE_11,NODE_10,10,100,220,CAP_U(1))
+ *     DISCRETE_RCDISC3(NODE_11,NODE_10,10,100,220,CAP_U(1), 0.5)
  *
  *  When enabled by NODE_10, C charges from 10v as indicated by RC
  *  of 100R & 1uF.
  *
- * EXAMPLES: see Tank8
+ * EXAMPLES: see Tank8, bzone
  *
  ***********************************************************************
  *
@@ -3460,6 +3485,7 @@ enum
 #define DISC_OP_AMP_FILTER_IS_BAND_PASS_1M	0x30
 #define DISC_OP_AMP_FILTER_IS_HIGH_PASS_0	0x40
 #define DISC_OP_AMP_FILTER_IS_BAND_PASS_0	0x50
+#define DISC_OP_AMP_FILTER_IS_LOW_PASS_1M	0x60
 
 #define DISC_OP_AMP_FILTER_TYPE_MASK		(0xf0 | DISC_OP_AMP_IS_NORTON)	// Used only internally.
 
@@ -4292,7 +4318,7 @@ enum
 #define DISCRETE_OP_AMP_FILTER(NODE,ENAB,INP0,INP1,TYPE,INFO)           { NODE, DST_OP_AMP_FILT , 4, { ENAB,INP0,INP1,NODE_NC }, { ENAB,INP0,INP1,TYPE }, INFO, "DISCRETE_OP_AMP_FILTER" },
 #define DISCRETE_RCDISC(NODE,ENAB,INP0,RVAL,CVAL)                       { NODE, DST_RCDISC      , 4, { ENAB,INP0,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL,CVAL }, NULL, "DISCRETE_RCDISC" },
 #define DISCRETE_RCDISC2(NODE,SWITCH,INP0,RVAL0,INP1,RVAL1,CVAL)        { NODE, DST_RCDISC2     , 6, { SWITCH,INP0,NODE_NC,INP1,NODE_NC,NODE_NC }, { SWITCH,INP0,RVAL0,INP1,RVAL1,CVAL }, NULL, "DISCRETE_RCDISC2" },
-#define DISCRETE_RCDISC3(NODE,ENAB,INP0,RVAL0,RVAL1,CVAL)               { NODE, DST_RCDISC3     , 5, { ENAB,INP0,NODE_NC,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL0,RVAL1,CVAL }, NULL, "DISCRETE_RCDISC3" },
+#define DISCRETE_RCDISC3(NODE,ENAB,INP0,RVAL0,RVAL1,CVAL,DJV)           { NODE, DST_RCDISC3     , 6, { ENAB,INP0,NODE_NC,NODE_NC,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL0,RVAL1,CVAL,DJV }, NULL, "DISCRETE_RCDISC3" },
 #define DISCRETE_RCDISC4(NODE,ENAB,INP0,RVAL0,RVAL1,RVAL2,CVAL,VP,TYPE) { NODE, DST_RCDISC4     , 8, { ENAB,INP0,NODE_NC,NODE_NC,NODE_NC,NODE_NC,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL0,RVAL1,RVAL2,CVAL,VP,TYPE }, NULL, "DISCRETE_RCDISC4" },
 #define DISCRETE_RCDISC5(NODE,ENAB,INP0,RVAL,CVAL)                      { NODE, DST_RCDISC5     , 4, { ENAB,INP0,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL,CVAL }, NULL, "DISCRETE_RCDISC5" },
 #define DISCRETE_RCDISC_MODULATED(NODE,INP0,INP1,RVAL0,RVAL1,RVAL2,RVAL3,CVAL,VP)	{ NODE, DST_RCDISC_MOD, 8, { INP0,INP1,NODE_NC,NODE_NC,NODE_NC,NODE_NC,NODE_NC,NODE_NC }, { INP0,INP1,RVAL0,RVAL1,RVAL2,RVAL3,CVAL,VP }, NULL, "DISCRETE_RCDISC_MODULATED" },
diff --git a/src/mame/audio/bzone.c b/src/mame/audio/bzone.c
index f21a83c44a2..773df7d8478 100644
--- a/src/mame/audio/bzone.c
+++ b/src/mame/audio/bzone.c
@@ -22,6 +22,7 @@ D0  explosion enable        gates a noise generator
 #include "streams.h"
 #include "bzone.h"
 
+#if !BZONE_DISCRETE
 #define OUTPUT_RATE (6000*4)
 
 
@@ -295,4 +296,293 @@ DEVICE_GET_INFO( bzone_sound )
 	}
 }
 
+#else
 
+#include "sound/discrete.h"
+#include "sound/pokey.h"
+
+#define BZ_NOISE_CLOCK		12000		/* FIXME */
+
+/*************************************
+ *
+ *  Discrete Sound Defines
+ *
+ *************************************/
+
+#define BZ_INPUT			NODE_01		/* at M2 LS273 */
+#define BZ_INP_EXPLO		NODE_SUB(10, 0)
+#define BZ_INP_EXPLOLS		NODE_SUB(10, 1)
+#define BZ_INP_SHELL		NODE_SUB(10, 2)
+#define BZ_INP_SHELLLS		NODE_SUB(10, 3)
+#define BZ_INP_ENGREV		NODE_SUB(10, 4)
+#define BZ_INP_SOUNDEN		NODE_SUB(10, 5)
+#define BZ_INP_STARTLED		NODE_SUB(10, 6)
+#define BZ_INP_MOTEN		NODE_SUB(10, 7)
+
+#define TTL_OUT 5
+
+#define BZ_R5			RES_K(1)
+#define BZ_R6			RES_K(4.7)
+#define BZ_R7			RES_K(1)
+#define BZ_R8			RES_K(100)
+#define BZ_R9			RES_K(22)
+
+//#define RT			(1.0/BZ_R5 + 1.0/BZ_R6 * 1.0/BZ_R7)
+
+#define BZ_R10			RES_K(100)	
+#define BZ_R11			RES_K(250)
+#define BZ_R12			RES_K(33)
+#define BZ_R13			RES_K(10)
+#define BZ_R14			RES_K(22)
+#define BZ_R15			RES_K(1)
+#define BZ_R16			RES_K(1)
+#define BZ_R17			RES_K(22)
+#define BZ_R18			RES_K(10)
+#define BZ_R19			RES_K(33)
+
+#define BZ_R20			RES_K(33)
+#define BZ_R21			RES_K(33)
+#define BZ_R25			RES_K(100)
+#define BZ_R26			RES_K(33)
+#define BZ_R27			RES_K(330)
+#define BZ_R28			RES_K(100)
+#define BZ_R29			RES_K(22)
+
+#define BZ_R32			RES_K(330)
+#define BZ_R33			RES_K(330)
+#define BZ_R34			RES_K(33)
+#define BZ_R35			RES_K(33)
+
+#define BZ_C9			CAP_U(4.7)
+
+#define BZ_C11			CAP_U(0.015)
+#define BZ_C13			CAP_U(10)
+#define BZ_C14			CAP_U(10)
+
+#define BZ_C21			CAP_U(0.0047)
+#define BZ_C22			CAP_U(0.0047)
+#define BZ_C29			CAP_U(0.47)
+
+/*************************************
+ *
+ *  Discrete Sound static structs
+ *
+ *************************************/
+
+
+static const discrete_lfsr_desc bzone_lfsr =
+{
+	DISC_CLK_IS_FREQ,
+	16,			          	/* Bit Length */
+	0,			          	/* Reset Value */
+	3,			          	/* Use Bit 10 (QC of second LS164) as F0 input 0 */
+	14,			          	/* Use Bit 23 (QH of third LS164) as F0 input 1 */
+	DISC_LFSR_XOR,			/* F0 is XOR */
+	DISC_LFSR_NOT_IN0, 		/* F1 is inverted F0*/
+	DISC_LFSR_REPLACE,	  	/* F2 replaces the shifted register contents */
+	0x000001,		      	/* Everything is shifted into the first bit only */
+	DISC_LFSR_FLAG_OUTPUT_SR_SN1, /* output the complete shift register to sub node 1*/
+	15		          	/* Output bit */
+};
+
+static const discrete_op_amp_filt_info bzone_explo_0 = 
+{
+		BZ_R18 + BZ_R19, 0, 0, 0, 		/* r1, r2, r3, r4 */
+		BZ_R33,							/* rF */
+		BZ_C22, 0, 0,					/* c1, c2, c3 */
+		0,								/* vRef - not used */
+		22, 0							/* vP, vN */
+};
+
+static const discrete_op_amp_filt_info bzone_explo_1 = 
+{
+		BZ_R18, 0, 0, 0, 				/* r1, r2, r3, r4 */
+		BZ_R33,							/* rF */
+		BZ_C22, 0, 0,					/* c1, c2, c3 */
+		0,								/* vRef - not used */
+		22, 0							/* vP, vN */
+};
+
+static const discrete_op_amp_filt_info bzone_shell_0 = 
+{
+		BZ_R13 + BZ_R12, 0, 0, 0, 		/* r1, r2, r3, r4 */
+		BZ_R32,							/* rF */
+		BZ_C21, 0, 0,					/* c1, c2, c3 */
+		0,								/* vRef - not used */
+		22, 0							/* vP, vN */
+};
+
+static const discrete_op_amp_filt_info bzone_shell_1 = 
+{
+		BZ_R13, 0, 0, 0, 				/* r1, r2, r3, r4 */
+		BZ_R32,							/* rF */
+		BZ_C21, 0, 0,					/* c1, c2, c3 */
+		0,								/* vRef - not used */
+		22, 0							/* vP, vN */
+};
+
+static const discrete_555_desc bzone_vco_desc =
+{
+	DISC_555_OUT_DC,
+	5.0,
+	DEFAULT_555_CHARGE,
+	1.0 // Logic output
+};
+
+static const discrete_mixer_desc bzone_eng_mixer_desc =
+{
+	DISC_MIXER_IS_RESISTOR,
+	{BZ_R20, BZ_R21, BZ_R34, BZ_R35},	
+	{0, 0, 0, 0},
+	{0, 0, 0, 0},
+	0, 0,
+	BZ_C29,
+	0, /* no out cap */
+	0, TTL_OUT		/* inputs are logic */
+};
+
+static const discrete_mixer_desc bzone_final_mixer_desc =
+{
+	DISC_MIXER_IS_RESISTOR,
+	{BZ_R28, BZ_R25, BZ_R26, BZ_R27},	
+	{0, 0, 0, 0},
+	{0, 0, 0, 0},
+	0, BZ_R29,
+	0,
+	0, /* no out cap */
+	0, 1
+};
+
+/*************************************
+ *
+ *  Discrete Sound Blocks
+ *
+ *************************************/
+
+static DISCRETE_SOUND_START(bzone)
+
+	/************************************************/
+	/* Input register mapping for galaxian          */
+	/************************************************/
+	DISCRETE_INPUT_DATA(BZ_INPUT)
+
+	/* decode the bits */
+	DISCRETE_BITS_DECODE(NODE_10, BZ_INPUT, 0, 7, 5.7)// TTL_OUT)		/* QA-QD 74393 */
+	DISCRETE_ADJUSTMENT_TAG(NODE_11, 0, RES_K(250), DISC_LINADJ, "R11")
+
+	
+	/************************************************/
+	/* NOISE                                        */
+	/************************************************/
+	
+	/* 12Khz clock is divided by two by B4 74LS109 */
+	DISCRETE_LFSR_NOISE(NODE_30, 1, 1, BZ_NOISE_CLOCK / 2, 1.0, 0, 0.5, &bzone_lfsr)
+
+	/* divide by 2 */
+	DISCRETE_COUNTER(NODE_31, 1, 0, NODE_30, 1, DISC_COUNT_UP, 0, DISC_CLK_ON_R_EDGE)
+
+	DISCRETE_BITS_DECODE(NODE_32, NODE_SUB(30,1), 11, 14, 1)		/* to NAND LS20, J4 */
+	/* 11-14 */
+	DISCRETE_LOGIC_NAND4(NODE_33,1,NODE_SUB(32,0),NODE_SUB(32,1),NODE_SUB(32,2),NODE_SUB(32,3))
+	/* divide by 2 */
+	DISCRETE_COUNTER(NODE_34, 1, 0, NODE_33, 1, DISC_COUNT_UP, 0, DISC_CLK_ON_R_EDGE)
+	
+	/************************************************/
+	/* Explosion                                    */
+	/************************************************/
+
+	/* FIXME: +0.7 for diode */
+	DISCRETE_RCDISC5(NODE_40, NODE_34, BZ_INP_EXPLO, BZ_R17 + BZ_R16, BZ_C14)
+	DISCRETE_MULTIPLY(NODE_41, 1, BZ_R16 / (BZ_R17 + BZ_R16), NODE_40)
+	
+	/* one of two filter configurations active */
+	DISCRETE_LOGIC_INVERT(NODE_42, 1, BZ_INP_EXPLOLS)
+	DISCRETE_OP_AMP_FILTER(NODE_43, BZ_INP_EXPLOLS,  0, NODE_41, 
+			DISC_OP_AMP_FILTER_IS_LOW_PASS_1M, &bzone_explo_1)
+	DISCRETE_OP_AMP_FILTER(NODE_44, NODE_42,  0, NODE_41, 
+		DISC_OP_AMP_FILTER_IS_LOW_PASS_1M, &bzone_explo_0)
+	DISCRETE_ADDER2(NODE_45, 1, NODE_43, NODE_44)
+		
+	/************************************************/
+	/* Shell                                        */
+	/************************************************/
+	/* FIXME: +0.7 for diode */
+	DISCRETE_RCDISC5(NODE_50, NODE_31, BZ_INP_SHELL, BZ_R14 + BZ_R15, BZ_C9)
+	DISCRETE_MULTIPLY(NODE_51, 1, BZ_R15 / (BZ_R14 + BZ_R15), NODE_50)
+
+	/* one of two filter configurations active */
+	DISCRETE_LOGIC_INVERT(NODE_52, 1, BZ_INP_SHELLLS)
+	DISCRETE_OP_AMP_FILTER(NODE_53, BZ_INP_SHELLLS,  0, NODE_51, 
+			DISC_OP_AMP_FILTER_IS_LOW_PASS_1M, &bzone_shell_1)
+	DISCRETE_OP_AMP_FILTER(NODE_54, NODE_52,  0, NODE_51, 
+		DISC_OP_AMP_FILTER_IS_LOW_PASS_1M, &bzone_shell_0)
+	DISCRETE_ADDER2(NODE_55, 1, NODE_53, NODE_54)
+
+	/************************************************/
+	/* Engine                                       */
+	/************************************************/
+	
+	
+	DISCRETE_TRANSFORM2(NODE_60, BZ_INP_ENGREV, 0.0, "01=")
+	// FIXME: from R5 .. R7
+	DISCRETE_MULTIPLEX2(NODE_61, 1, NODE_60, 2.5, 4.2)
+	DISCRETE_RCDISC3(NODE_62, 1, NODE_61, BZ_R8, BZ_R9, BZ_C13, -0.5)
+	
+	/* R11 taken from adjuster port */
+	DISCRETE_555_ASTABLE_CV(NODE_63, 1, BZ_R10, NODE_11, BZ_C11, NODE_62, &bzone_vco_desc)
+
+	/* two LS161, reset to 4 resp 6 counting up to 15, QD and ripple carry mixed */
+	DISCRETE_COUNTER(NODE_65, BZ_INP_MOTEN, 0, NODE_63, 11, DISC_COUNT_UP, 0, DISC_CLK_ON_R_EDGE)
+	DISCRETE_TRANSFORM2(NODE_66, NODE_65, 3, "01>") /* QD */
+	DISCRETE_TRANSFORM2(NODE_67, NODE_65, 11, "01=") /* Ripple */
+	
+	DISCRETE_COUNTER(NODE_68, BZ_INP_MOTEN, 0, NODE_63, 9, DISC_COUNT_UP, 0, DISC_CLK_ON_R_EDGE)
+	DISCRETE_TRANSFORM2(NODE_69, NODE_68, 1, "01>") /* QD */
+	DISCRETE_TRANSFORM2(NODE_70, NODE_68, 9, "01=") /* Ripple */
+	
+	DISCRETE_MIXER4(NODE_75, 1, NODE_66, NODE_67, NODE_69, NODE_70, &bzone_eng_mixer_desc)
+	
+	/************************************************/
+	/* FINAL MIX                                    */
+	/************************************************/
+
+	/* not sure about pokey output levels - bleow is just a estimate */
+	DISCRETE_INPUTX_STREAM(NODE_85, 0, 5.0/32767.0 * 4, 0)
+
+	DISCRETE_MIXER4(NODE_280, 1, NODE_45, NODE_55, NODE_75, NODE_85, &bzone_final_mixer_desc)
+	DISCRETE_OUTPUT(NODE_280, 32767.0/5.0 * 2)
+	//DISCRETE_WAVELOG1(NODE_55, 32767.0/22)
+	//DISCRETE_WAVELOG2(NODE_30, 32767.0/5.0, NODE_31, 32767.0/5.0)
+
+DISCRETE_SOUND_END
+
+static const pokey_interface bzone_pokey_interface =
+{
+	{ DEVCB_NULL },
+	DEVCB_INPUT_PORT("IN3")
+};
+
+WRITE8_DEVICE_HANDLER( bzone_sounds_w )
+{
+	discrete_sound_w(device, BZ_INPUT, data);
+
+	output_set_value("startled", (data >> 6) & 1);
+    sound_global_enable(data & 0x20);
+}
+
+
+MACHINE_DRIVER_START( bzone_audio )
+
+	MDRV_SPEAKER_STANDARD_MONO("mono")
+	
+	MDRV_SOUND_ADD("pokey",  POKEY, BZONE_MASTER_CLOCK / 8)
+	MDRV_SOUND_CONFIG(bzone_pokey_interface)
+	MDRV_SOUND_ROUTE_EX(0, "discrete", 1.0, 0)
+
+	MDRV_SOUND_ADD("discrete", DISCRETE, 0)
+	MDRV_SOUND_CONFIG_DISCRETE(bzone)
+
+	MDRV_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
+MACHINE_DRIVER_END
+
+#endif
diff --git a/src/mame/audio/tank8.c b/src/mame/audio/tank8.c
index 920f189b35f..1ed2258c4cf 100644
--- a/src/mame/audio/tank8.c
+++ b/src/mame/audio/tank8.c
@@ -212,7 +212,7 @@ DISCRETE_SOUND_START(tank8)
 	DISCRETE_DIVIDE(NODE_110,1,TANK8_BUGLE_DATA1,7875.0)
 	DISCRETE_DIVIDE(NODE_111,1,TANK8_BUGLE_DATA2,7875.0)
 	DISCRETE_SQUAREWAVE2(NODE_112,TANK8_BUGLE_EN,3.4, NODE_110, NODE_111,1.7,0)
-	DISCRETE_RCDISC3(NODE_113,1, NODE_112, RES_K(10),RES_K(1),CAP_U(0.1))
+	DISCRETE_RCDISC3(NODE_113,1, NODE_112, RES_K(10),RES_K(1),CAP_U(0.1), 0.5)
 	DISCRETE_CRFILTER(TANK8_BUGLE, 1, NODE_113, RES_K(47), CAP_U(.01))
 
 	/************************************************/
diff --git a/src/mame/drivers/bzone.c b/src/mame/drivers/bzone.c
index c86bafc6312..2a5827449d4 100644
--- a/src/mame/drivers/bzone.c
+++ b/src/mame/drivers/bzone.c
@@ -206,14 +206,12 @@
 #include "video/avgdvg.h"
 #include "machine/mathbox.h"
 #include "machine/atari_vg.h"
-#include "sound/pokey.h"
 #include "rendlay.h"
 #include "bzone.h"
 
-#include "bzone.lh"
+#include "sound/pokey.h"
 
-#define MASTER_CLOCK (XTAL_12_096MHz)
-#define CLOCK_3KHZ  (MASTER_CLOCK / 4096)
+#include "bzone.lh"
 
 
 static UINT8 analog_data;
@@ -308,7 +306,11 @@ static ADDRESS_MAP_START( bzone_map, ADDRESS_SPACE_PROGRAM, 8 )
 	AM_RANGE(0x1810, 0x1810) AM_DEVREAD("mathbox", mathbox_lo_r)
 	AM_RANGE(0x1818, 0x1818) AM_DEVREAD("mathbox", mathbox_hi_r)
 	AM_RANGE(0x1820, 0x182f) AM_DEVREADWRITE("pokey", pokey_r, pokey_w)
+#if BZONE_DISCRETE
+	AM_RANGE(0x1840, 0x1840) AM_DEVWRITE("discrete", bzone_sounds_w)
+#else
 	AM_RANGE(0x1840, 0x1840) AM_WRITE(bzone_sounds_w)
+#endif
 	AM_RANGE(0x1860, 0x187f) AM_DEVWRITE("mathbox", mathbox_go_w)
 	AM_RANGE(0x2000, 0x2fff) AM_RAM AM_BASE(&vectorram) AM_SIZE(&vectorram_size) AM_REGION("maincpu", 0x2000)
 	AM_RANGE(0x3000, 0x7fff) AM_ROM
@@ -419,6 +421,11 @@ static INPUT_PORTS_START( bzone )
 	PORT_BIT( 0x20, IP_ACTIVE_HIGH, IPT_START1 )
 	PORT_BIT( 0x40, IP_ACTIVE_HIGH, IPT_START2 )
 	PORT_BIT( 0x80, IP_ACTIVE_HIGH, IPT_UNUSED )
+
+#if BZONE_DISCRETE
+	PORT_START("R11")
+	PORT_ADJUSTER( 50, "Engine Frequency" )
+#endif
 INPUT_PORTS_END
 
 
@@ -543,12 +550,12 @@ static const pokey_interface redbaron_pokey_interface =
  *
  *************************************/
 
-static MACHINE_DRIVER_START( bzone )
+static MACHINE_DRIVER_START( bzone_base )
 
 	/* basic machine hardware */
-	MDRV_CPU_ADD("maincpu", M6502, MASTER_CLOCK / 8)
+	MDRV_CPU_ADD("maincpu", M6502, BZONE_MASTER_CLOCK / 8)
 	MDRV_CPU_PROGRAM_MAP(bzone_map)
-	MDRV_CPU_PERIODIC_INT(bzone_interrupt, (double)MASTER_CLOCK / 4096 / 12)
+	MDRV_CPU_PERIODIC_INT(bzone_interrupt, (double)BZONE_MASTER_CLOCK / 4096 / 12)
 
 	MDRV_MACHINE_START(bzone)
 
@@ -564,15 +571,25 @@ static MACHINE_DRIVER_START( bzone )
 	/* Drivers */
 	MDRV_MATHBOX_ADD("mathbox")
 
-	/* sound hardware */
-	MDRV_SPEAKER_STANDARD_MONO("mono")
+MACHINE_DRIVER_END
 
+static MACHINE_DRIVER_START( bzone )
+
+	MDRV_IMPORT_FROM(bzone_base)
+
+	/* sound hardware */
+#if BZONE_DISCRETE
+	MDRV_IMPORT_FROM(bzone_audio)
+#else
+	MDRV_SPEAKER_STANDARD_MONO("mono")
+	
 	MDRV_SOUND_ADD("pokey",  POKEY, MASTER_CLOCK / 8)
 	MDRV_SOUND_CONFIG(bzone_pokey_interface)
 	MDRV_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
 
 	MDRV_SOUND_ADD("custom", BZONE, 0)
 	MDRV_SOUND_ROUTE(ALL_OUTPUTS, "mono", 0.50)
+#endif
 MACHINE_DRIVER_END
 
 
@@ -582,7 +599,7 @@ static MACHINE_DRIVER_START( bradley )
 	MDRV_IMPORT_FROM(bzone)
 
 	/* sound hardware */
-	MDRV_SOUND_REPLACE("pokey", POKEY,  MASTER_CLOCK / 8)
+	MDRV_SOUND_REPLACE("pokey", POKEY,  BZONE_MASTER_CLOCK / 8)
 	MDRV_SOUND_CONFIG(bzone_pokey_interface)
 	MDRV_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
 MACHINE_DRIVER_END
@@ -591,10 +608,10 @@ MACHINE_DRIVER_END
 static MACHINE_DRIVER_START( redbaron )
 
 	/* basic machine hardware */
-	MDRV_IMPORT_FROM(bzone)
+	MDRV_IMPORT_FROM(bzone_base)
 	MDRV_CPU_MODIFY("maincpu")
 	MDRV_CPU_PROGRAM_MAP(redbaron_map)
-	MDRV_CPU_PERIODIC_INT(bzone_interrupt, (double)MASTER_CLOCK / 4096 / 12)
+	MDRV_CPU_PERIODIC_INT(bzone_interrupt, (double)BZONE_MASTER_CLOCK / 4096 / 12)
 
 	MDRV_MACHINE_START(redbaron)
 
@@ -608,11 +625,14 @@ static MACHINE_DRIVER_START( redbaron )
 	MDRV_VIDEO_START(avg_bzone)
 
 	/* sound hardware */
-	MDRV_SOUND_REPLACE("pokey", POKEY, 1500000)
+	MDRV_SPEAKER_STANDARD_MONO("mono")
+
+	MDRV_SOUND_ADD("pokey", POKEY, 1500000)
 	MDRV_SOUND_CONFIG(redbaron_pokey_interface)
 	MDRV_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
 
-	MDRV_SOUND_REPLACE("custom", REDBARON, 0)
+	MDRV_SOUND_ADD("custom", REDBARON, 0)
+
 	MDRV_SOUND_ROUTE(ALL_OUTPUTS, "mono", 0.50)
 MACHINE_DRIVER_END
 
diff --git a/src/mame/includes/bzone.h b/src/mame/includes/bzone.h
index bb04bdcfb2c..6ed7c926cc2 100644
--- a/src/mame/includes/bzone.h
+++ b/src/mame/includes/bzone.h
@@ -4,6 +4,10 @@
 
 *************************************************************************/
 
+#define BZONE_DISCRETE		(1)
+
+#define BZONE_MASTER_CLOCK (XTAL_12_096MHz)
+#define BZONE_CLOCK_3KHZ  (MASTER_CLOCK / 4096)
 
 /*----------- defined in drivers/bzone.c -----------*/
 
@@ -12,11 +16,17 @@ extern UINT8 rb_input_select;
 
 /*----------- defined in audio/bzone.c -----------*/
 
+#if BZONE_DISCRETE
+
+WRITE8_DEVICE_HANDLER( bzone_sounds_w );
+
+MACHINE_DRIVER_EXTERN( bzone_audio );
+#else
 WRITE8_HANDLER( bzone_sounds_w );
 
 DEVICE_GET_INFO( bzone_sound );
 #define SOUND_BZONE DEVICE_GET_INFO_NAME(bzone_sound)
-
+#endif
 
 /*----------- defined in audio/redbaron.c -----------*/