diff --git a/components/aes67_tx/aes67_tx.c b/components/aes67_tx/aes67_tx.c
index bcd387d..4ff509f 100644
--- a/components/aes67_tx/aes67_tx.c
+++ b/components/aes67_tx/aes67_tx.c
@@ -22,6 +22,7 @@
 #define MAX_LAG_NS      20000000    // more than 20 ms behind: resync instead of bursting
 #define TONE_HZ         1000
 #define TONE_DBFS       -18.0
+#define WAKE_MARGIN_US  20          // wake just after a packet's last sample is due
 
 static const char *TAG = "aes67_tx";
 
@@ -166,15 +167,23 @@ static int64_t samples_to_ns(int64_t s, int rate)
 }
 
 // 1 kHz tone, phase from the PTP sample index, so every sender's tone lines up.
+// One period is rate / 1000 samples (48 at 48 kHz, 96 at 96 kHz): precomputed table.
 static void tone(int32_t *buf, int frames, int channels, int rate, int64_t s0)
 {
-    static float amp;
-    if (!amp) {
-        amp = (float)(pow(10.0, TONE_DBFS / 20.0) * 2147483647.0);
-    }
+    static int32_t table[96000 / TONE_HZ];
+    static int table_rate;
     int period = rate / TONE_HZ;
+    if (table_rate != rate) {
+        double amp = pow(10.0, TONE_DBFS / 20.0) * 2147483647.0;
+        for (int i = 0; i < period; i++) {
+            table[i] = (int32_t)(amp * sin(2.0 * M_PI * i / period));
+        }
+        table_rate = rate;
+    }
+    int ph = (int)(s0 % period);
     for (int i = 0; i < frames; i++) {
-        int32_t v = (int32_t)(amp * sinf(2.0f * (float)M_PI * (float)((s0 + i) % period) / (float)period));
+        int32_t v = table[ph];
+        ph = ph + 1 == period ? 0 : ph + 1;
         for (int ch = 0; ch < channels; ch++) {
             buf[i * channels + ch] = v;
         }
@@ -216,8 +225,6 @@ static void tx_task(void *arg)
             next = 0;
             if (c.enabled) {
                 fd = open_socket(&c);
-                // wake once per packet time; late wakes are caught up below
-                esp_timer_start_periodic(timer, (uint64_t)c.frames * 1000000ULL / c.rate);
             }
         }
 
@@ -277,6 +284,13 @@ static void tx_task(void *arg)
                 seq++;
                 next += c.frames;
             }
+            // Wake when the next packet's last sample is due (PTP time), not on a free-running
+            // period, so each packet leaves right after it is complete. Re-read the clock:
+            // building and sending took time.
+            aes67_ptp_now_ns(&now);
+            int64_t wait_us = (samples_to_ns(next + c.frames, c.rate) - now) / 1000 + WAKE_MARGIN_US;
+            esp_timer_stop(timer);
+            esp_timer_start_once(timer, wait_us < 50 ? 50 : wait_us > 10000 ? 10000 : wait_us);
         }
         if (new_state != state) {
             state = new_state;