diff --git a/us144mkii_playback.c b/us144mkii_playback.c
index 0234993..af31d86 100644
--- a/us144mkii_playback.c
+++ b/us144mkii_playback.c
@@ -256,6 +256,22 @@ void playback_urb_complete(struct urb *urb)
 	}
 	urb->transfer_buffer_length = total_bytes;
 
+	/* A stuck PLL can produce all-zero-length packets, which makes the
+	 * device underflow and output persistent noise. Force a minimal
+	 * nominal packet if that happens.
+	 */
+	if (total_bytes == 0) {
+		tascam->freq_q16 = div_u64(((u64)tascam->current_rate << 16), 8000);
+		tascam->phase_accum = 0;
+		frames = min((u32)(tascam->current_rate / 8000), (u32)MAX_FRAMES_PER_PACKET);
+		if (frames == 0)
+			frames = 1;
+		urb->iso_frame_desc[0].offset = 0;
+		urb->iso_frame_desc[0].length = frames * PLAYBACK_FRAME_SIZE;
+		total_bytes = urb->iso_frame_desc[0].length;
+		urb->transfer_buffer_length = total_bytes;
+	}
+
 	/* Ghost Playback: Send Silence */
 	if (!atomic_read(&tascam->playback_active)) {
 		if (tascam->running_ghost_playback) {
@@ -342,9 +358,22 @@ void feedback_urb_complete(struct urb *urb)
 				u8 *d = urb->transfer_buffer + urb->iso_frame_desc[p].offset;
 				u32 val = (urb->iso_frame_desc[p].actual_length >= 3) ? (d[0] + d[1] + d[2]) : (d[0] * 3);
 				u32 target = (val << 16) / 24;
-				tascam->freq_q16 = (tascam->freq_q16 * PLL_FILTER_OLD_WEIGHT +
-				target * PLL_FILTER_NEW_WEIGHT) / PLL_FILTER_DIVISOR;
-				tascam->feedback_synced = true;
+				u32 nominal = div_u64(((u64)tascam->current_rate << 16), 8000);
+				u32 min_freq = nominal - (nominal >> 2);
+				u32 max_freq = nominal + (nominal >> 2);
+
+				/* Ignore transient bad feedback that would drive the PLL to
+				 * zero or an unrealistic value and cause DAC underflow noise.
+				 */
+				if (tascam->current_rate > 0 && target >= min_freq && target <= max_freq) {
+					tascam->freq_q16 = (tascam->freq_q16 * PLL_FILTER_OLD_WEIGHT +
+					    target * PLL_FILTER_NEW_WEIGHT) / PLL_FILTER_DIVISOR;
+					if (tascam->freq_q16 < min_freq)
+						tascam->freq_q16 = min_freq;
+					else if (tascam->freq_q16 > max_freq)
+						tascam->freq_q16 = max_freq;
+					tascam->feedback_synced = true;
+				}
 			}
 		}
 	}