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1) Battery Upgrade: If I'm right, the battery in the iPod 5.5G is a 400 mAh Lithium Ion part. My idea here is to replace it with 3x 1000 mAh rechargable AAA batteries, which should take up about the same space as the stock batteries. If this works, then I might think about doing something to the iPod case to allow batteries to be swapped (imagine being able to just buy some new batteries if you are away from your charger!).
The only problems I see here are - 1) The batteries are NiMH type (will this cause any problems with charging? I'd also need to work out some kind of protection if non-rechargables are used), and 2) They are 1.2v each = 3.6v (iPod battery is 3.7) - will this cause any problems with Rockbox's measurements?
2) Output Stage (Headphone Driver) Capacitor Upgrade: I've heard that the iPod has a poor bass response with low impedance headphones (mine are 16 ohm). Apparently this is because the capacitors on the headphone driver are 220 uF. This creates a low-pass filter higher than the iPod's lowest frequency response (something around 25 Hz), if I remember the Wolfson document. That document also had a formula to work out the low-pass filter cutoff, so why not use 440 uF capacitors? These would create a sutiably low cutoff. If anyone has any suggestions here, it would be helpful (I don't want to mess up a new iPod!).
3) Replace the DAC: This crazy idea probably won't work, but if it can - why not replace the Wolfson DAC in the iPod with a higher-specced Wolfson model? I know there's no point - but still. I don't know too much about DACs - whether they can be programmed or if they just accept an input and give an output, but if it's possible you could even use a Burr Brown (TI) DAC, and get the best audio quality possible (FLAC files with an upgraded DAC and output stage would sound sublime).
4) Internal Headphone Amp: Even crazier idea! Instead of replacing the capactior on the headphone driver, it would great if it was possible to put a bespoke headphone amp (like the external ones you can buy...but internal) in the iPod. This could completely replace the existing output stage if possible, and a power supply that matches the battery life of the player would be needed inside. But if it can work - audio heaven! There would be no need for the line-out to connect to a headphone amp as this would completely replace the existing output stage.
AAA batteries are huge. You won't be able to fit even 1.
Where exactly are you going to put this amp?
QuoteAAA batteries are huge. You won't be able to fit even 1.Are you sure? I'm getting the iPod today (hopefully), so I'll get the case off and have a look. I'm sure there's enough room for 3, but I could be wrong.
Why not just build a battery box with a USB female socket in it? Four AAAs and you could have a 1AH external battery. Although if I'm going away I pack my car charger, I did contemplate doing this. If you were really going to build something like this you would want the largest capacity batteries avaliable.
Quote from: tychver on January 05, 2007, 08:39:29 PMWhy not just build a battery box with a USB female socket in it? Four AAAs and you could have a 1AH external battery. Although if I'm going away I pack my car charger, I did contemplate doing this. If you were really going to build something like this you would want the largest capacity batteries avaliable.wouldn't 4@800mAH be more that that?
If you do replace the wolfson codec (dac) how could one make it work. Could it be done now that an ipod has rockbox. Someone could come up with the proper settings for new dac?
I also thought about possibly ( and tell me if this is stupid) getting an outboard adac to dac using the line out. Is that a really stupid idea or using the best of the best chips you dont have to worry about messing with the internal codec.
Thats what i meant. use the analog line out and an analog to digital chip then digital to analog in an outboard setup. Using the best chips possible.
Taking the analog signal and trying to properly convert it.
So what could you use to make the signal better without touching the internals?
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