BavariaBarbarian
100+ Head-Fier
- Joined
- Nov 26, 2004
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As described in this thread: http://www6.head-fi.org/forums/showthread.php?t=161993
my Ipod developed massive DC-offset on the lineout.
So I started poking around inside the Ipod.
At first I intended to replace the obviously broken output caps, but then, some four weeks ago, I rather bought another Ipod mainboard on ebay to replace the whole thing.
With a new working mainboard on hand and the old one to spare I thought to myself: "Why not have some fun?"
- I suppose you're thinking along the same lines, so here it goes:
Lacking the datasheet dor the WM8975 I studied the publically available datasheets of the WM8971 and WM8973.
Playing a test tone and looking for the characteristic DC-offsets of my faulty DAC, I found that all three seem to use the same pins for the lineout:
Larger picture here: http://i1.tinypic.com/v66989.jpg
Those pins are a mere 0.5mm apart and I've got nowhere near the soldering skills to attach anything to them.
But conveniently, after only a very short while the signal passes through what I strongly suspect to be the output caps, and those pads are a diferent matter:
Larger picture here:
http://i1.tinypic.com/v669o9.jpg
I simply tacked two small wires (AWG 26 OFC) to the capacitor"leads" and fed the signal into a DIY switchbox along with the original linout (using the lineout GND for both signals).
So now for the interesting part: How does it sound?
- Nice. Very nice.
I don't have trained ears or very fancy gear, I used my Pimeta, modded Sennheiser HD25-1 and ALAC / lame -ape files for this test.
The difference in soundquality between the two signals was very subtle to my ears. Subtle, but noticeable and very likeable.
When I first switched from the lineout I thought "Wow, this is better!".
Then I asked myself "Why?" and started listening critically for differences until I was sure that, in fact, there were none and I had only imagined it.
But after tidying up and relaxing a bit I picked up the phones again - and there it was again: "This sounds better!" And this time I was able to picture the difference and could pick it out reliably when switching back and forth:
The soundstage was a bit broader and deeper, and there was slightly more bass. But what really impressed me, was an increased sense of clarity, especially in the highs: It was as if everything stood out against a deep black background where on the regular lineout it was only a dark grey... if that makes any sense at all.
Now, for all that, I'm not planning to make this mod more permanent.
Why? Two reasons:
1) I don't want to lose the headphone out, because I don't always want to lug around an amp when listening on the go.
While there IS some free space inside the Ipod case, there is barely enough to install another output jack. Let alone something fancy or that AND output caps of any size.
2) Rather more importantly: The modded logicboard is now toast.
The mod worked alright for several days, then I wanted to take the Ipod along for the weekend and simply removed the wires.
Several days later I wanted to experiment some more and soldered the wires back on. After listening for about half an hour the left channel cut out. I suspected a cold or broken soldering joint, but no. Both on the regularlineout, and directly at the dac-pins, there is no signal.
I don't know whether I shorted something, overheated the dac or whatever.
Perhaps omitting the output capacitors (The Pimeta has input caps for dc protection) has damaged the dac or maybe it was due to fail anyway. After all there was the issue of tremendous DC-offset, so there was some damage to begin with.
Still, I'm not planning to poke the soldering iron at the second mainboard.
But for these reasons, it might be simple enough to remove the output caps of the hp-out (to get rid of the regular hp-signal), install output caps (would have to be small - about 4*10 mm) and tack some wires to the now free l/r pins of the hp-jack, leaving GND alone.
Now mind you: I'm not calling this the iMod.
I've no way to know, how the Redwine Audio iMod works.
And I'm not saying, that I can perform this mod successfully, so don't ask me to...
But all this got me thinking about the iMod:
Before I was skeptic if the iMod was just snakeoil.
I now think it very plausible that it makes a difference. After all it's done by someone who knows what he's doing. - So it's bound to sound at least as good as my inexperienced tinkering, likely much better.
And I think the difference will be noticeable with less-than-top-level gear and even on compressed materials.
- Too bad that I'm only a poor student, no way I'm spending 200$ on this.
Even the 45$ for another Ipod mainboard off ebay is serious money for me to spend on experiments. But perhaps someone else is daring/crazy enough and can use what I found out.
my Ipod developed massive DC-offset on the lineout.
So I started poking around inside the Ipod.
At first I intended to replace the obviously broken output caps, but then, some four weeks ago, I rather bought another Ipod mainboard on ebay to replace the whole thing.
With a new working mainboard on hand and the old one to spare I thought to myself: "Why not have some fun?"
- I suppose you're thinking along the same lines, so here it goes:
Lacking the datasheet dor the WM8975 I studied the publically available datasheets of the WM8971 and WM8973.
Playing a test tone and looking for the characteristic DC-offsets of my faulty DAC, I found that all three seem to use the same pins for the lineout:
Larger picture here: http://i1.tinypic.com/v66989.jpg
Those pins are a mere 0.5mm apart and I've got nowhere near the soldering skills to attach anything to them.
But conveniently, after only a very short while the signal passes through what I strongly suspect to be the output caps, and those pads are a diferent matter:
Larger picture here:
http://i1.tinypic.com/v669o9.jpg
I simply tacked two small wires (AWG 26 OFC) to the capacitor"leads" and fed the signal into a DIY switchbox along with the original linout (using the lineout GND for both signals).
So now for the interesting part: How does it sound?
- Nice. Very nice.
I don't have trained ears or very fancy gear, I used my Pimeta, modded Sennheiser HD25-1 and ALAC / lame -ape files for this test.
The difference in soundquality between the two signals was very subtle to my ears. Subtle, but noticeable and very likeable.
When I first switched from the lineout I thought "Wow, this is better!".
Then I asked myself "Why?" and started listening critically for differences until I was sure that, in fact, there were none and I had only imagined it.
But after tidying up and relaxing a bit I picked up the phones again - and there it was again: "This sounds better!" And this time I was able to picture the difference and could pick it out reliably when switching back and forth:
The soundstage was a bit broader and deeper, and there was slightly more bass. But what really impressed me, was an increased sense of clarity, especially in the highs: It was as if everything stood out against a deep black background where on the regular lineout it was only a dark grey... if that makes any sense at all.
Now, for all that, I'm not planning to make this mod more permanent.
Why? Two reasons:
1) I don't want to lose the headphone out, because I don't always want to lug around an amp when listening on the go.
While there IS some free space inside the Ipod case, there is barely enough to install another output jack. Let alone something fancy or that AND output caps of any size.
2) Rather more importantly: The modded logicboard is now toast.
The mod worked alright for several days, then I wanted to take the Ipod along for the weekend and simply removed the wires.
Several days later I wanted to experiment some more and soldered the wires back on. After listening for about half an hour the left channel cut out. I suspected a cold or broken soldering joint, but no. Both on the regularlineout, and directly at the dac-pins, there is no signal.
I don't know whether I shorted something, overheated the dac or whatever.
Perhaps omitting the output capacitors (The Pimeta has input caps for dc protection) has damaged the dac or maybe it was due to fail anyway. After all there was the issue of tremendous DC-offset, so there was some damage to begin with.
Still, I'm not planning to poke the soldering iron at the second mainboard.
But for these reasons, it might be simple enough to remove the output caps of the hp-out (to get rid of the regular hp-signal), install output caps (would have to be small - about 4*10 mm) and tack some wires to the now free l/r pins of the hp-jack, leaving GND alone.
Now mind you: I'm not calling this the iMod.
I've no way to know, how the Redwine Audio iMod works.
And I'm not saying, that I can perform this mod successfully, so don't ask me to...
But all this got me thinking about the iMod:
Before I was skeptic if the iMod was just snakeoil.
I now think it very plausible that it makes a difference. After all it's done by someone who knows what he's doing. - So it's bound to sound at least as good as my inexperienced tinkering, likely much better.
And I think the difference will be noticeable with less-than-top-level gear and even on compressed materials.
- Too bad that I'm only a poor student, no way I'm spending 200$ on this.
Even the 45$ for another Ipod mainboard off ebay is serious money for me to spend on experiments. But perhaps someone else is daring/crazy enough and can use what I found out.
