diff -up ./include/sound/ac97_codec.h.ad1980 ./include/sound/ac97_codec.h
--- ./include/sound/ac97_codec.h.ad1980	2026-02-01 08:09:53.000000000 +0900
+++ ./include/sound/ac97_codec.h	2026-05-28 20:12:24.696696239 +0900
@@ -267,6 +267,7 @@ struct snd_ac97 {
 			unsigned short codec_cfg[3];	// CODEC_CFG bits
 			unsigned char swap_mic_linein;	// AD1986/AD1986A only
 			unsigned char lo_as_master;	/* LO as master */
+			unsigned char dont_set_losel;	// do not set AC97_AD198X_LOSEL bit (surround) for LINE_OUT/HP_OUT */
 		} ad18xx;
 		unsigned int dev_flags;		/* device specific */
 	} spec;
diff -up ./sound/pci/ac97/ac97_patch.c.ad1980 ./sound/pci/ac97/ac97_patch.c
--- ./sound/pci/ac97/ac97_patch.c.ad1980	2026-02-01 08:09:53.000000000 +0900
+++ ./sound/pci/ac97/ac97_patch.c	2026-05-28 20:12:24.712696266 +0900
@@ -1935,7 +1935,7 @@ static int snd_ac97_ad1888_lohpsel_get(s
 	unsigned short val;
 
 	val = ac97->regs[AC97_AD_MISC];
-	ucontrol->value.integer.value[0] = !(val & AC97_AD198X_LOSEL);
+	ucontrol->value.integer.value[0] = !(val & (ac97->spec.ad18xx.dont_set_losel ? AC97_AD198X_HPSEL : AC97_AD198X_LOSEL));
 	if (ac97->spec.ad18xx.lo_as_master)
 		ucontrol->value.integer.value[0] =
 			!ucontrol->value.integer.value[0];
@@ -1950,7 +1950,7 @@ static int snd_ac97_ad1888_lohpsel_put(s
 	val = !ucontrol->value.integer.value[0];
 	if (ac97->spec.ad18xx.lo_as_master)
 		val = !val;
-	val = val ? (AC97_AD198X_LOSEL | AC97_AD198X_HPSEL) : 0;
+	val = val ? ((ac97->spec.ad18xx.dont_set_losel ? 0 : AC97_AD198X_LOSEL) | AC97_AD198X_HPSEL) : 0;
 	return snd_ac97_update_bits(ac97, AC97_AD_MISC,
 				    AC97_AD198X_LOSEL | AC97_AD198X_HPSEL, val);
 }
@@ -2065,17 +2065,33 @@ static int patch_ad1888(struct snd_ac97
 	if (ac97->subsystem_vendor == 0x1043 &&
 	    ac97->subsystem_device == 0x1193) /* ASUS A9T laptop */
 		ac97->spec.ad18xx.lo_as_master = 1;
+	/*
+	 * C601 does not have surround out jacks.
+	 * It wires SURR_OUT/HP_OUT pins to internal speaker, and
+	 * LINE_OUT pins to line-out AND headphone jacks.
+	 * Setting AC97_AD198X_LOSEL bit will select LINE_OUT to
+	 * surround out, which results in "no sound".
+	 * cf. https://bz-attachments.freebsd.org/attachment.cgi?id=101182
+	 */
+	if (ac97->subsystem_vendor == 0x10cf &&
+	    ac97->subsystem_device == 0x122f) /* Fujitsu/Siemens C601 */
+		ac97->spec.ad18xx.dont_set_losel = 1;
 
 	misc = snd_ac97_read(ac97, AC97_AD_MISC);
 	/* AD-compatible mode */
 	/* Stereo mutes enabled */
 	misc |= AC97_AD198X_MSPLT | AC97_AD198X_AC97NC;
-	if (!ac97->spec.ad18xx.lo_as_master)
+	if (!ac97->spec.ad18xx.lo_as_master) {
+		misc |= AC97_AD198X_HPSEL;
 		/* Switch FRONT/SURROUND LINE-OUT/HP-OUT default connection */
 		/* it seems that most vendors connect line-out connector to
 		 * headphone out of AC'97
 		 */
-		misc |= AC97_AD198X_LOSEL | AC97_AD198X_HPSEL;
+		if (!ac97->spec.ad18xx.dont_set_losel)
+			misc |= AC97_AD198X_LOSEL;
+		else
+			misc &= ~AC97_AD198X_LOSEL;
+	}
 
 	snd_ac97_write_cache(ac97, AC97_AD_MISC, misc);
 	ac97->flags |= AC97_STEREO_MUTES;