Apple MD094LL/A Audio Built-in Speakers Have Distorted Sound, L14, Is normal during playback

5.	Inspect microphone cable	Yes	Replace rear housing	L14
	routing and verify if cable is		(microphone cable not
	pinched or damaged.		available separately).
		No	Go to step 6.
6.	Record sound sample using	Yes	Microphone circuitry OK.
	GarageBand or iMovie. Verify if		Return system to user.
	sound quality of sound sample
		No	Replace logic board.	M09
	is normal during playback.

Audio: Built-in Speakers Have Distorted Sound

Unlikely cause: LCD display, power supply, hard drive, optical drive, fans

Quick Check

Symptoms	Quick Check
Audio: Built-in Speakers Have	1. Go to System Preferences > Sound > Output.
Distorted Sound	Verify that sound output device is set to internal
• No audio from one or both	speakers and that balance control is set to the
speakers.	center position.

•Audio from speakers distorted 2. Obtain known-good high-quality sound file or use iTunes Store sound samples to evaluate sound quality. Verify suspect sound files on another system to determine if distortion is caused by computer or sound file.

3.Set volume control to mid-range. Overdriving built-in speakers can cause distortion.

Deep Dive

Check		Result	Action	Code
1.	Go to System Preferences >	Yes	LEFT speaker and amplifier
	Sound > Output. Set speaker		circuitry OK. Go to step 2.
	balance 100% to LEFT speaker
	and play a known-good sound	No	Distortion detected in LEFT
	file. Verify if sound is generated		speaker. Set Balance slider to
	by LEFT speaker and that sound		middle position. Go to step 3.
	quality is acceptable.
2.	Set speaker balance 100%	Yes	RIGHT speaker and amplifier
	to RIGHT speaker and play a		circuitry OK. Set Balance slider
	known-good sound file. Verify		to middle. Go to step 3.
	if sound is generated by RIGHT
	speaker and that sound quality	No	Distortion detected in RIGHT
	is acceptable.		speaker. Go to step 4.

2010-09-09 iMac (27-inch, Mid 2010) Symptom Charts — Input/Output Devices  97