iPod Color 60GB, circuit findings...

[Vinnie R.]

I posted this on iLounge in regards to the iPod Color distortion issue:

All,

Just curious, have you tried going to:

iPod>Photos>Slideshow Settings> TV Out

and turning OFF the TV Out? I'm pretty sure the "TV Out"
signal goes to the headphone jack (the 4th pin in the headphone connector), and if that is the case, maybe when it is ON, it is causing the distortion. Maybe some of you have it OFF and are hearing no distortion, and some of you have it ON and are hearing distortion. Maybe it is as simple as that?

Hope this helps,

Vinnie

 

[Bob_McBob]

I did try doing that, but unfortunately it didn't make any difference.

 

[Vinnie R.]

Quote:

Originally Posted by Bob_McBob I did try doing that, but unfortunately it didn't make any difference.

Ok, thanks for trying.

Would I be able to hear this problem with my stock 60Gb and the stock earbuds that come with the unit, or do I need lower impedance headphones?

When I open the unit again, I'd like to remove the video connection to the headphone jack and see if this cures the problem.

I'm also curious if the video pin inside the headphone jack is shorting onto the L or R sections of the headphone plug to cause the distortion.

I wonder how tight the mechanical tolerances are on these plugs and jacks? I think an integrated headphone/composite video jack is a crappy idea on Appple's part.

I'm glad I bought the 60Gb because I want to help solve this problem for you guys. Personally, I don't use the headphone out (I am just interested in the line out), but I can see how it really sucks to have distortion on the headphone out and that alone makes me what to solve this problem for you guys...

Regards,

Vinnie

 

[Vinnie R.]

One more thing... are we all positive that the problem has to do the video out circuitry feeding into the headphone jack, or is this speculation?

Since the iPod Color models use the opamp output (that I mentioned at the top of this thread), it is possible that the design is poor and there is an oscillation problem. The 20Gb, 4th Gen iPod (black and white) does not use these opamps, nor do any of the other iPods as far as I know.

Just want to make sure that I am on the correct trail in hunting for the animal.

Keep the faith!

Vinnie

 

[Bob_McBob]

The video output theory is pure speculation, and possibly quite wrong. It's mainly based on the fact that the only apparent difference between the colour models and the regular 4Gs is the ability to output video. Your internal findings on your 60GB seem to indicate there are quite a lot of hardware differences in place.

I'm listening to the Pollini track on my iPod with the stock earbuds, and it's difficult to make out because the sound is so muddy. It comes through as a bit of a quiet scratching/hissing noise throughout, but I don't think you can make any meaningful judgements with these headphones. I can definitely understand why the vast majority of iPod users simply wouldn't hear the problem. The distortion is much easier to hear with my MS-1s, and absolutely unbearable with my er6is.

Note to self: check volume level before pressing play

.

 

[chrisfromalbany]

Quote:

Originally Posted by Vinnie R. All, I spent a while checking out the motherboard of my new 60GB iPod Color. Here is what I've found: -- After the Wolfson 8975 dac, BOTH the line out and headphone outputs are sent into their own Analog Devices stereo opamps. My 20GB iPod (black and white), that I performed the iMod on, uses the same Wolfson 8975 dac, does not use the Analog Devices opamps. I knew they sounded a little different connected to my home stereo! I suspect that the 60GB iPod Color will do a better job driving lower impedance headphones (due to the additonal drive that the opamp will provide), but I haven't tried it. The coupling caps used in the signal path of the headphone output circuit do not have their values written on them, so I'm not sure if they are larger enough to avoid the bass rolloff problem that many of you have experienced. Has anyone experieced bass rolloff with the 60GB iPod Color? I already found these caps to be too small in the 20GB iPod, which will definitely results in bass rolloff with headphones of 32-ohms or lower impedance. -- From the pics of the insides of the iPod Nano, it looks like the Analog Devices opamps are not used and the circuit is just like my 20GB iPod. The dac is a Wolfson 8975G (not sure what the "G" stands for), but they appear to have the same pin out for the line out and headphone outputs. Again, I'm not sure if the coupling caps in the headphone out circuit are too small, but they can easily be changed with larger SMD caps to give a full bass response with low impedance headphones if they are too small. Hope some of you find this information to be useful. Regards, Vinnie

Question Vin,

Are there any other DAPs out their that use a better DAC then the ipod.. (Wolfson 8975 dac)

 

[Vinnie R.]

Quote:

Originally Posted by Bob_McBob The video output theory is pure speculation, and possibly quite wrong. It's mainly based on the fact that the only apparent difference between the colour models and the regular 4Gs is the ability to output video. Your internal findings on your 60GB seem to indicate there are quite a lot of hardware differences in place.

Thanks for the info...this is important. I wasn't sure if someone proved that the problem was because of the video, or if this was just a guess.

My guess is that the problem is an oscillating opamp, and as I mentioned, the iPod Color has the opamp, while the others do not.

The only way for me to prove it is to replicate the problem with the stock unit, and then bypass the opamp in the headphone output and see if the problem is still present. I have some 16-ohm headphones. The problem is that I don't get any distortion at all when using them!

 

[Vinnie R.]

Quote:

Originally Posted by chrisfromalbany Question Vin, Are there any other DAPs out their that use a better DAC then the ipod.. (Wolfson 8975 dac)

I'm not sure. Even if I knew the dacs used in other DAPs and looked up the specs in the datasheets, I have found that better specs doesn't always equal better sound. It is very subjective I suppose...

What I can say is that the Wolfson 8975 is a fantastic sounding dac, and it is hard to really gauge how nice it sounds until you take the outputs from this chip directly out of the unit using a high quality coupling cap (I really like Black Gate NX HiQ caps for this application). The stock caps are junk, and there is a lot of crap in path...as usual

 

[Bob_McBob]

Quote:

Originally Posted by Vinnie R. The only way for me to prove it is to replicate the problem with the stock unit, and then bypass the opamp in the headphone output and see if the problem is still present. I have some 16-ohm headphones. The problem is that I don't get any distortion at all when using them!

Are you listening to the track I posted earlier in the thread? If so, that is quite significant, because there's no way you could miss the distortion on my unit with my er6is. It's possible Apple has simply swept the problem under the rug. Could you post the first six digits of your serial number and the model number from settings-->about?

 

[Vinnie R.]

Quote:

Originally Posted by Bob_McBob Are you listening to the track I posted earlier in the thread? If so, that is quite significant, because there's no way you could miss the distortion on my unit with my er6is. It's possible Apple has simply swept the problem under the rug. Could you post the first six digits of your serial number and the model number from settings-->about?

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

 

[Bob_McBob]

That result is extremely interesting.

 

[Vinnie R.]

Quote:

Originally Posted by Bob_McBob That result is extremely interesting.

Bob, now that I think about it, maybe Apple *did* fix the problem....with the opamps.

If you or someone else can find me photos of the 60Gb iPod Color mother board, I can compare them to mine to see if there is a change (specifically, the opamps...). Wouldn't that be something?

 

[Bob_McBob]

http://www.ipoding.com/modules.php?s...view_album.php

The photos aren't very large, and it is an older model, but it is a colour screen one (original Photo). I'll see what else I can find.

Edit: I'm not sure if these are useful, but they are quite detailed: http://ipodlinux.org/Photo_PCB_Images

 

[Vinnie R.]

Quote:

Originally Posted by Bob_McBob Edit: I'm not sure if these are useful, but they are quite detailed: http://ipodlinux.org/Photo_PCB_Images

I see the Analog Devices opamps in the photo. Of course, if they fixed the problem, it could have been as simple as changing the value of two resistors... The resistor values are not shown on the resistors, so it is impossible to tell when comparing to mine.

I cannot replicate the problem no matter what I play. Again, my headphones are 16-ohm and I have the volume maxed out and there is no distortion to speak of. I recently bought this iPod from Best Buy (last week).

Does anyone want to send me their distorting 60Gb iPod color to examine?

 

[chrisfromalbany]

Quote:

Originally Posted by Vinnie R. I see the Analog Devices opamps in the photo. Of course, if they fixed the problem, it could have been as simple as changing the value of two resistors... The resistor values are not shown on the resistors, so it is impossible to tell when comparing to mine. I cannot replicate the problem no matter what I play. Again, my headphones are 16-ohm and I have the volume maxed out and there is no distortion to speak of. I recently bought this iPod from Best Buy (last week). Does anyone want to send me their distorting 60Gb iPod color to examine?

Can you actually tell a difference between the lineout of the ipod and the jack out.

What would make the ishuffle sound better then the ipod color?

What is the difference between the sound quality from the ipod and 0404 EMU card. Do you think there is muc of a difference?

-Chris

info on the Nano...

Most of the other components are run of the mill as far as iPods go. The heart of the iPod, the PortalPlayer chip, was upgraded to a slightly newer model (the PP5021C-TDF), the audio codec is the same Wolfson Microprocessor (WM8975G) found in the current generation iPods, a new power management unit by Phillips (CF50607), a batch of 32MB of Samsung SDRAM (534-K9WAG08U1M) replaces the old Hynix chips, and the LCD is of unknown manufacturer but it's a 16-bit color, 176x132 1.5" model.

http://arstechnica.com/reviews/hardware/nano.ars/4