SR MBP Static Issue: The Problem, Some Facts, and a $14 Fix

dordal

macrumors member
Original poster
Jun 26, 2007
49
1
I've been doing quite a lot of research on the 'static issue' that affects the new Santa Rosa MacBook Pros, and I have some things to report:

The Problem
The issue has three components, as described in this MacinTouch Report:
- A low hiss that is constant whenever the audio circuitry is on
- Static that occurs whenever anything is playing... even something quiet.
- A series of high-pitched noises that occur somewhat randomly. The best comparison I've seen is that it's like listening to those hearing tests where you raise your hand when you hear a tone.

The problem only occurs with low-impedance headphones (more on this below).

Some Facts
- The problem occurs on ALL Santa Rosa MacBook Pros, 2.2 and 2.4 GHz. It is a design flaw on Apple's part, and returning your machine for a new one will not help. There are plenty of people who say they can't hear the noise, but those people either have high-impedance headphones or speakers, or just don't have very good hearing. :)
- Only Santa Rosa MacBook Pros seem to be affected by this particular static problem. I've seen some reports of other machines having audio issues, but they are always different.
- The 'Audio Update 2007-001' that Apple released about two weeks ago doesn't fix it. It does fix a popping problem on all Intel Macs (including the SR MBPs), so it's worth installing, but that is a different problem than this one.
- It does seem to be an Apple-specific problem; I've been unable to find any other reports of non-Apple Santa Rosa notebooks having the same problem.

The Story on Impedance
The problem only occurs with low-impedance headphones, such as the Shure 3EC or the Etymotic ER-4P, which both have a 1KHz impedance of about 26 ohms. Impedance is a rather complicated subject, but roughly translated it is the resistance that the headphones exhibit to the audio circuitry when they are plugged in. The audio circuitry puts out a certain amount of power; a low resistance means more of that signal to be translated into sound, which means the sound is louder. A high resistance (impedance) means less signal is translated into sound, and the volume is lower at any given power level.

Why does all this matter? Well, because the flaw in the audio circuitry is always there, but is only detectable with lower-impedance headphones (remember, these are louder for a given power level.) The high impedance headphones mask the problems. You've still got the same static; you just can't hear it.

The Fix
The fix is actually surprisingly easy: all you need to do is increase the impedance of your headphones! To do this, you'll need to either buy or make an adapter. I chose to buy one, the Shure Level Attenuator Volume Control EA650. Cheapest I could find it was from some guy on eBay. Shure makes good quality products, and at $14 shipped it's not that expensive. It connects between your computer and your headphones, and only a quarter turn on the volume knob eliminated the hiss and static for me.

You can also make one of your own, following the directions on head-fi.org.

I do hope Apple will own up to this problem and fix the audio on the motherboards, but I don't think it's likely. With the yellow screen and whatnot, they've got bigger fish to fry.
 

LaMerVipere

macrumors 6502a
Jan 19, 2004
971
0
Chicago
THIS HAS BEEN DRIVING ME INSANE.

I listen to music pretty much all night through my Shure E2c's attached to my MacBook Pro and I get all 3 of those audio issues nonstop.

I hope there's a fix for this that doesn't require buying some 3rd party piece of equipment....someday. :cool:
 

mach

macrumors regular
Jun 5, 2007
103
5
2 questions:

- I don't have my MBP yet, but I looked up the specs on my headphones (Sony MDR XD300) and the impedance is 70 ohms. Does this mean I would still hear the audio noise?

- I plan on having my MBP hooked up to my Logitech z-5450s via optical, does this audio issue affect the digital (optical signal I will be using) signal as well?

Thanks for much for this news!
 

iW00t

macrumors 68040
Nov 7, 2006
3,286
0
Defenders of Apple Guild
2 questions:

- I don't have my MBP yet, but I looked up the specs on my headphones (Sony MDR XD300) and the impedance is 70 ohms. Does this mean I would still hear the audio noise?

- I plan on having my MBP hooked up to my Logitech z-5450s via optical, does this audio issue affect the digital (optical signal I will be using) signal as well?

Thanks for much for this news!
If you are getting the optical signal you won't be affected.
 

Tasc

macrumors newbie
Jun 14, 2007
29
0
Thanks for posting this dordal, I think it will help a lot of people including myself. Are most headphones low-impedence? I have used Bose Tri-Ports and the standard apple iPod headphones and hear the static/noise through both of them...
 

dordal

macrumors member
Original poster
Jun 26, 2007
49
1
No, I think most headphones are medium to high imepedance... e.g. 70 to 100 ohms. I would imagine you won't hear much, if any, static with 70 ohm headphones, and almost certainly not with 100 ohms. That's just my guess, though.
 

r1400sch

macrumors member
Jun 10, 2007
33
0
Ah, good thing I haven't gotten around to get the other USB audio solution mentioned..this adaptor is far less bulky.

Now, could any headphones with an in-line volume control do the trick?
 

klharper

macrumors member
May 2, 2007
42
4
Hmm, interesting
Thanks for the info

Essential, the Shure "fix" is just going to lower output and, once again, merely "mask" the problem though, right?

I'm thinking about picking up a pair of 250 ohm cans, which may require a headphone amp... but getting a headphone amp will only make the problem reappear, yea? In which case, going through a headphone amp => Shure Attenuator => high impedance headphones would be incredibly redundant. Right?
hrmm

Ok, just thinking out loud haha.
 

r1400sch

macrumors member
Jun 10, 2007
33
0
Update:
Problem solved!

I went out and got a pair of headphones with an in-line volume control. @ full volume, the static can obviously still be heard. Moved it down to medium rather than high and I don't hear it one bit! Finally I can listen to music besides heavy rock without hearing crap!!

So now everyone just has to make sure they either buy the adaptor or buy MBP compatible headphones.
 

AceOfBass

macrumors member
May 13, 2007
48
0
Wisconsin
hey I don't know if anybody else has had this problem, but after downloading that update about 2 weeks ago my audio line in jack doesn't work now. instead of getting a signal from it, whenever something is plugged in I get a consistent clicking. Anybody else have this problem? If so, does anybody know how to fix it?
 

remcoy

macrumors newbie
Jun 29, 2006
23
5
yes and no

Dordal, you got it partly right. The problem isn't really the MBP though, and it's not the low impedance of the headphones either. It's the high sensitivity rating of the earphones (around 119db/mW). Shure, Etyomotic and other IEM's all use an armature originally designed for use in hearing aids. These are extremely sensitive and unfortunately pick up hiss and noise when used with a lot of different sources.

I assume you don't have an iPod, because that hisses too! Along with every other Mac I've used. Some headphone amps don't even work properly with them and some have a sensitivity switch for just this reason.

The Radio Shack volume adapter does work- sort of. It messed up the sound a little though..

What you need is a proper 75ohm adapter. some people make their own.. That's beyond mine capability.
I've been using the one in this kit for a few years with all my IEM's:
http://www.earphonesolutions.com/uleasutokit.html

It works great. If these companies just added two small 75ohm resistors into the cable of their headphones then we wouldn't be having this problem. I'm sure there is a reason to leave them in the natural state though. There may be a benefit when used with a proper headphone amp..


Anyways: there you go- it's the headphones not the MBP so don't expect a fix on that end.. ever !
 

dordal

macrumors member
Original poster
Jun 26, 2007
49
1
I assume you don't have an iPod, because that hisses too! Along with every other Mac I've used.
Anyways: there you go- it's the headphones not the MBP so don't expect a fix on that end.. ever !
Well, not sure I totally buy that, because my old Powerbook G4 1.5 didn't have any such hissing problems. I tried them side by side.... same power source, same music, same everything. No hiss/static on the PB, plenty on the MBP. So I'd attribute that to Apple lowering the quality of the audio circuit.

What you need is a proper 75ohm adapter. some people make their own.. That's beyond mine capability.
What's a 'proper 75 ohm adapter'? Just two 75 ohm resistors stuck inline with the circuit?
 

remcoy

macrumors newbie
Jun 29, 2006
23
5
You don't get hiss on your iPod?
Anyways, my Shure E500's and Westone UM2's both do this too.
I get loud hiss with loud machine noise on my G5, loud hiss on my MBP SR and on my GF's Macbook, and regular hiss on my old Ti Powerbook (about equal to an iPod)

In my experience, this has always been the case with these kinds of earphones.

Another problem with the high sensitivity, for me at least, is that the volume when listing to music on the Laptops is too loud at only one click up of the volume keys!

Using the 75 ohm adapter.. they handle more like a regular headphone.
--Yes, two 75 resistors I believe.
By 'proper' adapter.. I was just referring to a dedicated one i guess.. The radio shack in-line adapter has a variable resistor i believe? and the volume knob is cr*p ?
 

rogerh

macrumors member
Aug 15, 2006
91
1
hopefully there will be a new revision that fixes this problem, don't really want to buy an adapter.
 

Sopranino

macrumors 6502
Sep 27, 2006
348
0
Alberta, Canada
I've been doing quite a lot of research on the 'static issue' that affects the new Santa Rosa MacBook Pros, and I have some things to report:

The Problem
The issue has three components, as described in this MacinTouch Report:
- A low hiss that is constant whenever the audio circuitry is on
- Static that occurs whenever anything is playing... even something quiet.
- A series of high-pitched noises that occur somewhat randomly. The best comparison I've seen is that it's like listening to those hearing tests where you raise your hand when you hear a tone.

The problem only occurs with low-impedance headphones (more on this below).

Some Facts
- The problem occurs on ALL Santa Rosa MacBook Pros, 2.2 and 2.4 GHz. It is a design flaw on Apple's part, and returning your machine for a new one will not help. There are plenty of people who say they can't hear the noise, but those people either have high-impedance headphones or speakers, or just don't have very good hearing. :)
- Only Santa Rosa MacBook Pros seem to be affected by this particular static problem. I've seen some reports of other machines having audio issues, but they are always different.
- The 'Audio Update 2007-001' that Apple released about two weeks ago doesn't fix it. It does fix a popping problem on all Intel Macs (including the SR MBPs), so it's worth installing, but that is a different problem than this one.
- It does seem to be an Apple-specific problem; I've been unable to find any other reports of non-Apple Santa Rosa notebooks having the same problem.

The Story on Impedance
The problem only occurs with low-impedance headphones, such as the Shure 3EC or the Etymotic ER-4P, which both have a 1KHz impedance of about 26 ohms. Impedance is a rather complicated subject, but roughly translated it is the resistance that the headphones exhibit to the audio circuitry when they are plugged in. The audio circuitry puts out a certain amount of power; a low resistance means more of that signal to be translated into sound, which means the sound is louder. A high resistance (impedance) means less signal is translated into sound, and the volume is lower at any given power level.

Why does all this matter? Well, because the flaw in the audio circuitry is always there, but is only detectable with lower-impedance headphones (remember, these are louder for a given power level.) The high impedance headphones mask the problems. You've still got the same static; you just can't hear it.

The Fix
The fix is actually surprisingly easy: all you need to do is increase the impedance of your headphones! To do this, you'll need to either buy or make an adapter. I chose to buy one, the Shure Level Attenuator Volume Control EA650. Cheapest I could find it was from some guy on eBay. Shure makes good quality products, and at $14 shipped it's not that expensive. It connects between your computer and your headphones, and only a quarter turn on the volume knob eliminated the hiss and static for me.

You can also make one of your own, following the directions on head-fi.org.

I do hope Apple will own up to this problem and fix the audio on the motherboards, but I don't think it's likely. With the yellow screen and whatnot, they've got bigger fish to fry.
Thanks for your research dordal. You confirmed my suspicions that the hiss was impedance related. I have the same audio artifacts present when using low impedance earbuds (16 ohms) or headphones (26 ohms) but it is not present when using a pair of AKG K271 Studio Headphones which have an impedance of 55 ohms.

I hadn't noticed this issue before as I generally use just the AKG's. Due to this issue the local Apple store tech replaced the logic board which didn't really fix the issue but, due to the new logic board being faulty, introduced a couple of other errors. Another logic board was ordered, it came in DOA. Apple is now replacing my computer with a new one. I am hoping that the new one has the audio problem rectified.

Sopranino
 

Sopranino

macrumors 6502
Sep 27, 2006
348
0
Alberta, Canada
Sopranino-

Did the new machine fix the problem?

D
It hasn't arrived yet, I'll post the results once it's come in.

Your information on the impedance was very informative and has helped a lot of people.

I've started a poll in an attempt to determine the scope of the issue. You can find the poll here Do you have audio hiss?

So far the numbers are pretty close to even after about 55 polls.

Sopranino
 

jamerson9

macrumors newbie
Feb 11, 2007
11
0
Ultimate Ears series earphones comes with an sound attenuator for use on airplanes and other unfamiliar devices. It did remove the hiss, however it does reduce the volume considerable, so I have to keep the volume up to the max. Wish there was a better solution.
 

hibera

macrumors newbie
Oct 16, 2007
5
0
What is the latest update on this issue?
Has anyone got a replaced system board and did it fix the problem?
What about the computers that are shipping now, are they affected as well?
 

Stuma

macrumors newbie
Dec 11, 2007
1
0
Same problem here on new Aluminum iMac. Just using too sensitive headphones I guess. Thanks for the tips.
 

Nakamura

macrumors newbie
Dec 9, 2007
28
0
Oxfordshire, England
If I renember (and not too excited about my MacBook Pro) I will test this out with my new macbook pro (should be delivered tomorrow). I have Sennheiser CX-300's that pick up noise if I just nock the cable, this is going to be fun :(.