iPod Color 60GB, circuit findings...

[discord]

Quote:

Originally Posted by Vinnie R. Hi Bob, The Pollini track sounds perfect with my 16-ohm Sony headphones, volume cranked up to max (very loud!)....not a trace of distortion. Regarding the serial and model number: JQ5353----- M9830LL Version 1.2

I listened to the Pollini track on my color ipod and didn't hear any distortion on it using my MS-1.

4j5291
MA079LL

 

[Spad]

I also hear no distortion with my 60 photo with a variety of low impedance headphones. Hasn't this always been a rather random problem?

Does anyone know the original source for the Pollini sample?

 

[shuy]

it wld be GREAT to know that the problem is fixed. i'm currently deciding between a zen micro and ipod nano, and sound quality is my main deciding criteria.

 

[mjg]

e4's and ipod photo 60 gig....
i thought i heard the problem once with some piano, though ithink it might of been in my head...

i can't really detect this problem.
I'll try that test track though.

 

[Bob_McBob]

It's been very random because a lot of the people who have done testing (mainly on ilounge) have used the stock iPod earbuds to pronounce their iPods perfect. I can barely hear the distortion with them, but it is there. It's more pronounced with my MS-1s (if only because the sound is much clearer), and it's truly godawful with my er6is.

 

[Vinnie R.]

Quote:

Originally Posted by shuy it wld be GREAT to know that the problem is fixed. i'm currently deciding between a zen micro and ipod nano, and sound quality is my main deciding criteria.

All,

Has anyone found the iPod Nano to even have the distortion problem?

If not, this really makes me believe that the problem IS an oscillating opamp problem. I can tell from pics that the iPod Nano does not have the opamps. As far as I know, the only iPods that have the opamps are the iPod Color 20Gb and 60Gb. I'm starting to feel more and more confident that this is a hardware design issue with the opamp output circuit (marginal design, where some have the problem and some do not, based on the tolerances of the parts used).

I'm at the point now where I seriously doubt that the problem has anything to do with the color screen or the video output on the headphone jack, unless iPod Nano users are experiencing the distortion problem...

If someone wants to send their iPod Color with the distortion issue to me to look at and most likely fix, let me know. I would need the headphones that make it distort, and a test track that always shows the problem. I'm pretty confident that I can fix the problem by bypassing the opamp circuit...

Regards,

Vinnie Rossi
Red Wine Audio, Inc.

 

[Vinnie R.]

The iPod certainly has a bass rolloff problem.

I used test tones and found that with the stock 32-ohm headphones, the bass sounds like it starts rolling off at 100Hz. It has to be at least 3dB down at around 50Hz. This is an easy fix...replace those caps with at least 220uF caps....

 

[Spad]

Quote:

Originally Posted by Vinnie R. All, Has anyone found the iPod Nano to even have the distortion problem?

I've heard no distortion at all with my Nano. I've been using PX100s mostly, but I've also checked it with SA5Ks and ER-4Ps. My listening includes lots of classical piano ripped at 192 AAC. The only difference I hear between the 60 and the Nano is that the Nano has more power.

 

[Wodgy]

Quote:

Originally Posted by Vinnie R. The iPod certainly has a bass rolloff problem. I used test tones and found that with the stock 32-ohm headphones, the bass sounds like it starts rolling off at 100Hz. It has to be at least 3dB down at around 50Hz. This is an easy fix...replace those caps with at least 220uF caps....

Vinnie, the caps are 220 uF caps. The bass rolloff corner frequency is much lower if you actually measure it, rather than trying to guess it with the stock crappy earbuds. You could also just do the math.

Of course, if you had done the math, you'd know that 220uF caps are not sufficient. You need at least double that to reduce the bass rolloff.

Also, I doubt the distortion on a small number of early iPod Photos is caused by oscillating op-amps. Once an op-amp begins to oscillate, it usually doesn't stop until the device is powered off. Also, if it was oscillation, you'd see increasing DC offset before the output coupling caps.

 

[Bob_McBob]

Quote:

Originally Posted by Wodgy Also, I doubt the distortion on a small number of early iPod Photos...

My iPod isn't an early photo model, it's one of the new 20GB "iPod with color screen" models, and I bought it at the end of July. The original Photo models were released at the end of October last year, giving Apple plenty of time to correct any early problems. Apparently it's not very high on their agenda.

 

[Wodgy]

Interesting. Regardless, if it distorts, it's defective and you should get it replaced with a new one. Here in the US, you can bring it to an Apple Store, they'll check it out, and give you a new one on the spot. It's probably the same policy in Canada. Next time you're in Toronto, go to the Apple Store and get it swapped with a new one.

 

[Bob_McBob]

I'm definitely leaning towards that option now that I've had credible confirmation that not all colour iPod have the distortion problem. I will be in Toronto next weekend, so I may give it a try. However, I've heard several stories of people having their iPods replaced, only to receive a new or refurbished unit with the same problem.

 

[Vinnie R.]

Quote:

Originally Posted by Wodgy Vinnie, the caps are 220 uF caps. The bass rolloff corner frequency is much lower if you actually measure it, rather than trying to guess it with the stock crappy earbuds. You could also just do the math. Of course, if you had done the math, you'd know that 220uF caps are not sufficient. You need at least double that to reduce the bass rolloff. Also, I doubt the distortion on a small number of early iPod Photos is caused by oscillating op-amps. Once an op-amp begins to oscillate, it usually doesn't stop until the device is powered off. Also, if it was oscillation, you'd see increasing DC offset before the output coupling caps.

Hi Wodgy,

My 20GB iPod caps are NOT 220uF, they are 100uF ("107" marked on the cap). Doing the math, with my 16-ohm headphones the 3dB corner freq should be approx. 99.47Hz. With the stock 32-ohm headphones, it should be approx. 49.73Hz...

With 32-ohm headphones, 220uF ARE pretty sufficient, give a corner of 22.6Hz. Also, I said "at least" 220uF caps...

You're probably right about the oscillation, but what people are saying is at least distortion, which AFAIK, nobody has detected with the iPods that don't have the opamps.

Regards,

Vinnie

 

[AlanY]

Quote:

Originally Posted by Vinnie R. My 20GB iPod caps are NOT 220uF, they are 100uF ("107" marked on the cap). Doing the math, with my 16-ohm headphones the 3dB corner freq should be approx. 99.47Hz. With the stock 32-ohm headphones, it should be approx. 49.73Hz...

They went down to 100uF? That's really insufficient.

 

[Mercuttio]

I too was one of the people on iLounge that had a distorting 60 gigabyte color... and I ditched it in favor of the nano.

Distortion on mine was quite severe with Shure E2cs, and still noticable with the nasty white stock phones. I simply assumed the problem to be the signal from the TV out shorting the L and R channels, because the nano has excellent sound with no TV out.

Interestingly, (and I'm not sure how accurate this is) someone did a test on the sound quality of the nano here:

Nano Sound Quality Tests

See what you think, I'd love to know if he was accurate with his findings.