diff --git a/sndiod/dev.c b/sndiod/dev.c
index 6f8fa83..1f8eb32 100644
--- a/sndiod/dev.c
+++ b/sndiod/dev.c
@@ -619,11 +619,12 @@ dev_mix_adjvol(struct dev *d)
 {
 	unsigned int n;
 	struct slot *i, *j;
-	int weight;
+	int jcmax, icmax, weight;
 
 	for (i = d->slot_list; i != NULL; i = i->next) {
 		if (!(i->mode & MODE_PLAY))
 			continue;
+		icmax = i->opt->pmin + i->mix.nch - 1;
 		weight = ADATA_UNIT;
 		if (d->autovol) {
 			/*
@@ -634,8 +635,9 @@ dev_mix_adjvol(struct dev *d)
 			for (j = d->slot_list; j != NULL; j = j->next) {
 				if (!(j->mode & MODE_PLAY))
 					continue;
-				if (i->opt->pmin <= j->mix.slot_cmax &&
-				    i->mix.slot_cmax >= j->opt->pmin)
+				jcmax = j->opt->pmin + j->mix.nch - 1;
+				if (i->opt->pmin <= jcmax &&
+				    icmax >= j->opt->pmin)
 					n++;
 			}
 			weight /= n;
@@ -1417,76 +1419,72 @@ dev_mmcloc(struct dev *d, unsigned int origin)
 void
 slot_allocbufs(struct slot *s)
 {
-	unsigned int slot_nch, dev_nch;
+	unsigned int dev_nch;
 	struct dev *d = s->dev;
 
 	if (s->mode & MODE_PLAY) {
-		s->mix.bpf = s->par.bps *
-		    (s->mix.slot_cmax - s->opt->pmin + 1);
+		s->mix.bpf = s->par.bps * s->mix.nch;
 		abuf_init(&s->mix.buf, s->appbufsz * s->mix.bpf);
 
-		slot_nch = s->mix.slot_cmax - s->opt->pmin + 1;
 		dev_nch = s->opt->pmax - s->opt->pmin + 1;
 		s->mix.decbuf = NULL;
 		s->mix.resampbuf = NULL;
 		s->mix.join = 1;
 		s->mix.expand = 1;
 		if (s->opt->dup) {
-			if (dev_nch > slot_nch)
-				s->mix.expand = dev_nch / slot_nch;
-			else if (dev_nch < slot_nch)
-				s->mix.join = slot_nch / dev_nch;
+			if (dev_nch > s->mix.nch)
+				s->mix.expand = dev_nch / s->mix.nch;
+			else if (dev_nch < s->mix.nch)
+				s->mix.join = s->mix.nch / dev_nch;
 		}
 		cmap_init(&s->mix.cmap,
-		    s->opt->pmin, s->mix.slot_cmax,
-		    s->opt->pmin, s->mix.slot_cmax,
+		    s->opt->pmin, s->opt->pmin + s->mix.nch - 1,
+		    s->opt->pmin, s->opt->pmin + s->mix.nch - 1,
 		    0, d->pchan - 1,
 		    s->opt->pmin, s->opt->pmax);
 		if (!aparams_native(&s->par)) {
-			dec_init(&s->mix.dec, &s->par, slot_nch);
+			dec_init(&s->mix.dec, &s->par, s->mix.nch);
 			s->mix.decbuf =
-			    xmalloc(s->round * slot_nch * sizeof(adata_t));
+			    xmalloc(s->round * s->mix.nch * sizeof(adata_t));
 		}
 		if (s->rate != d->rate) {
 			resamp_init(&s->mix.resamp, s->round, d->round,
-			    slot_nch);
+			    s->mix.nch);
 			s->mix.resampbuf =
-			    xmalloc(d->round * slot_nch * sizeof(adata_t));
+			    xmalloc(d->round * s->mix.nch * sizeof(adata_t));
 		}
 	}
 
 	if (s->mode & MODE_RECMASK) {
-		s->sub.bpf = s->par.bps *
-		    (s->sub.slot_cmax - s->opt->rmin + 1);
+		s->sub.bpf = s->par.bps * s->sub.nch;
 		abuf_init(&s->sub.buf, s->appbufsz * s->sub.bpf);
 
-		slot_nch = s->sub.slot_cmax - s->opt->rmin + 1;
 		dev_nch = s->opt->rmax - s->opt->rmin + 1;
 		s->sub.encbuf = NULL;
 		s->sub.resampbuf = NULL;
 		s->sub.join = 1;
 		s->sub.expand = 1;
 		if (s->opt->dup) {
-			if (dev_nch > slot_nch)
-				s->sub.join = dev_nch / slot_nch;
-			else if (dev_nch < slot_nch)
-				s->sub.expand = slot_nch / dev_nch;
+			if (dev_nch > s->sub.nch)
+				s->sub.join = dev_nch / s->sub.nch;
+			else if (dev_nch < s->sub.nch)
+				s->sub.expand = s->sub.nch / dev_nch;
 		}
 		cmap_init(&s->sub.cmap,
 		    0, ((s->mode & MODE_MON) ? d->pchan : d->rchan) - 1,
 		    s->opt->rmin, s->opt->rmax,
-		    s->opt->rmin, s->sub.slot_cmax,
-		    s->opt->rmin, s->sub.slot_cmax);
+		    s->opt->rmin, s->opt->rmin + s->sub.nch - 1,
+		    s->opt->rmin, s->opt->rmin + s->sub.nch - 1);
 		if (s->rate != d->rate) {
 			resamp_init(&s->sub.resamp, d->round, s->round,
-			    slot_nch);
+			    s->sub.nch);
 			s->sub.resampbuf =
-			    xmalloc(d->round * slot_nch * sizeof(adata_t));
+			    xmalloc(d->round * s->sub.nch * sizeof(adata_t));
 		}
 		if (!aparams_native(&s->par)) {
-			enc_init(&s->sub.enc, &s->par, slot_nch);
+			enc_init(&s->sub.enc, &s->par, s->sub.nch);
 			s->sub.encbuf =
-			    xmalloc(s->round * slot_nch * sizeof(adata_t));
+			    xmalloc(s->round * s->sub.nch * sizeof(adata_t));
 		}
 
 		/*
@@ -1497,13 +1495,13 @@ slot_allocbufs(struct slot *s)
 	         */
 		if (s->sub.resampbuf) {
 			memset(s->sub.resampbuf, 0,
-			    d->round * slot_nch * sizeof(adata_t));
+			    d->round * s->sub.nch * sizeof(adata_t));
 		} else if (s->sub.encbuf) {
 			memset(s->sub.encbuf, 0,
-			    s->round * slot_nch * sizeof(adata_t));
+			    s->round * s->sub.nch * sizeof(adata_t));
 		} else {
 			memset(s->sub.buf.data, 0,
-			    s->appbufsz * slot_nch * sizeof(adata_t));
+			    s->appbufsz * s->sub.nch * sizeof(adata_t));
 		}
 	}
 
@@ -1671,9 +1669,9 @@ found:
 	s->mode = mode;
 	aparams_init(&s->par);
 	if (s->mode & MODE_PLAY)
-		s->mix.slot_cmax = s->opt->pmax;
+		s->mix.nch = s->opt->pmax - s->opt->pmin + 1;
 	if (s->mode & MODE_RECMASK)
-		s->sub.slot_cmax = s->opt->rmax;
+		s->sub.nch = s->opt->rmax - s->opt->rmin + 1;
 	if (s->opt->mmc) {
 		s->xrun = XRUN_SYNC;
 		s->tstate = MMC_STOP;
diff --git a/sndiod/dev.h b/sndiod/dev.h
index 361e446..ba784aa 100644
--- a/sndiod/dev.h
+++ b/sndiod/dev.h
@@ -47,7 +47,7 @@ struct slot {
 		unsigned int vol;		/* volume within the vol */
 		struct abuf buf;		/* socket side buffer */
 		int bpf;			/* byte per frame */
-		int slot_cmax;			/* slot source chans */
+		int nch;			/* number of play chans */
 		struct cmap cmap;		/* channel mapper state */
 		struct resamp resamp;		/* resampler state */
 		struct conv dec;		/* format decoder params */
@@ -59,7 +59,7 @@ struct slot {
 		struct abuf buf;		/* socket side buffer */
 		int prime;			/* initial cycles to skip */
 		int bpf;			/* byte per frame */
-		int slot_cmax;			/* slot destination chans */
+		int nch;			/* number of rec chans */
 		struct cmap cmap;		/* channel mapper state */
 		struct resamp resamp;		/* buffer for resampling */
 		struct conv enc;		/* buffer for encoding */
diff --git a/sndiod/sock.c b/sndiod/sock.c
index 82f7f64..1296adb 100644
--- a/sndiod/sock.c
+++ b/sndiod/sock.c
@@ -627,7 +627,7 @@ sock_setpar(struct sock *f)
 			rchan = 1;
 		else if (rchan > NCHAN_MAX)
 			rchan = NCHAN_MAX;
-		s->sub.slot_cmax = s->opt->rmin + rchan - 1;
+		s->sub.nch = rchan;
 #ifdef DEBUG
 		if (log_level >= 3) {
 			sock_log(f);
@@ -638,7 +638,7 @@ sock_setpar(struct sock *f)
 			log_puts(" -> ");
 			log_putu(s->opt->rmin);
 			log_puts(":");
-			log_putu(s->sub.slot_cmax);
+			log_putu(s->opt->rmin + s->sub.nch - 1);
 			log_puts("\n");
 		}
 #endif
@@ -648,14 +648,14 @@ sock_setpar(struct sock *f)
 			pchan = 1;
 		else if (pchan > NCHAN_MAX)
 			pchan = NCHAN_MAX;
-		s->mix.slot_cmax = s->opt->pmin + pchan - 1;
+		s->mix.nch = pchan;
 #ifdef DEBUG
 		if (log_level >= 3) {
 			sock_log(f);
 			log_puts(": playback channels ");
 			log_putu(s->opt->pmin);
 			log_puts(":");
-			log_putu(s->mix.slot_cmax);
+			log_putu(s->opt->pmin + s->mix.nch - 1);
 			log_puts(" -> ");
 			log_putu(s->opt->pmin);
 			log_puts(":");
@@ -1013,13 +1013,13 @@ sock_execmsg(struct sock *f)
 				log_puts(", play ");
 				log_puti(s->opt->pmin);
 				log_puts(":");
-				log_puti(s->mix.slot_cmax);
+				log_puti(s->opt->pmin + s->mix.nch - 1);
 			}
 			if (s->mode & MODE_RECMASK) {
 				log_puts(", rec ");
 				log_puti(s->opt->rmin);
 				log_puts(":");
-				log_puti(s->sub.slot_cmax);
+				log_puti(s->opt->rmin + s->sub.nch - 1);
 			}
 			log_puts(", ");
 			log_putu(s->appbufsz / s->round);
@@ -1122,14 +1122,10 @@ sock_execmsg(struct sock *f)
 		m->u.par.sig = s->par.sig;
 		m->u.par.le = s->par.le;
 		m->u.par.msb = s->par.msb;
-		if (s->mode & MODE_PLAY) {
-			m->u.par.pchan = htons(s->mix.slot_cmax -
-			    s->opt->pmin + 1);
-		}
-		if (s->mode & MODE_RECMASK) {
-			m->u.par.rchan = htons(s->sub.slot_cmax -
-			    s->opt->rmin + 1);
-		}
+		if (s->mode & MODE_PLAY)
+			m->u.par.pchan = htons(s->mix.nch);
+		if (s->mode & MODE_RECMASK)
+			m->u.par.rchan = htons(s->sub.nch);
 		m->u.par.rate = htonl(s->rate);
 		m->u.par.appbufsz = htonl(s->appbufsz);
 		m->u.par.bufsz = htonl(SLOT_BUFSZ(s));