The Apple diyMod: My Take on the Famous iMod [56k killer] Featuring 3G, 4G, 5G and nano 1G!

[dumbears]

Perhaps, I've missed this in the past. I wonder if the decoupling caps is recommended to be 220uF. The original ones are 100uF.

Moreover, I wonder if the bass becomes more solid if swapping in 220uF. I know some actually swapped in a pair of BG NX 100uF caps.

[joneeboi]

The 220uF recommendation comes into play when headphones are connected directly to the DAC. I wonder what the amplification stage looks like between the DAC and the headphones, as Wolfson's papers all talk about hooking headphones straight into the DAC. Again, we refer to that corner frequency equation, and 22uF seems to work for my 4G with my Millett MAX. IIRC, the input impedance is something around 50K, so the corner frequency is pretty much obliterated at 0.144Hz. The surprising thing was how the 47uF BGs gave me so much more bass. If you want to work straight into the headphone jack, 220uF goes great with 32ohms, and the BG version sizes up at 8mm x 11mm. What were you thinking of doing?

[no_eye_dear]

I'm having a play with that sort of configuration at the moment. I wanted to use a remote for the volume into my amp so I'm taking the signal from the headphone out instead of the line-out and using one of those clip-on remote units for my 4G.
The EQ will also give me some scope on DSP for my room/speakers... not much but it will be interesting to compare the line-out quality with the heaphone-out quality after all that internal DSP.
Obviously the output caps can be as usual (no low impedance HPhones) but I may not have any at all with this solution .......dependant on matching the DC bias input of my DC coupled amp that is.. Should be interesting

[ruZZ.il]

I believe there is some space in the mini up around the headphone jack area to stuff 2x47uf 6.3v BG NX caps.. a little round about for the signal cable, but I doubt it'll effect anything.
I should be getting some cf cards soon so I'll be able to play again.. when I get some time too.. hmpf.
been a bit busy, but it should even out soon

[dumbears]

Originally Posted by joneeboi

The 220uF recommendation comes into play when headphones are connected directly to the DAC. I wonder what the amplification stage looks like between the DAC and the headphones, as Wolfson's papers all talk about hooking headphones straight into the DAC. Again, we refer to that corner frequency equation, and 22uF seems to work for my 4G with my Millett MAX. IIRC, the input impedance is something around 50K, so the corner frequency is pretty much obliterated at 0.144Hz. The surprising thing was how the 47uF BGs gave me so much more bass. If you want to work straight into the headphone jack, 220uF goes great with 32ohms, and the BG version sizes up at 8mm x 11mm. What were you thinking of doing?

I was thinking of swapping out the 100uF decoupling caps in my iPod Photo 60G with 220uF. When I opened out the case, I think it may be possible to go for BG NX 220uF, though I heard sb commented it's already much improvement in using BG NX 100uF.

[Lil' Knight]

Is there any significant sonic difference between the 22uf and 47uf in gen5?
Which one do RWA and ALO use in their iMod?
And, has anyone tried bypass the 22uf with 0.1uf NX-hiQ?

[joneeboi]

Originally Posted by dumbears

I was thinking of swapping out the 100uF decoupling caps in my iPod Photo 60G with 220uF. When I opened out the case, I think it may be possible to go for BG NX 220uF, though I heard sb commented it's already much improvement in using BG NX 100uF.

I tried placing my 47uF caps like RWA did up near the HP jack, but they ended up getting crushed. Maybe if you have a 60GB back panel, it might be easier than in my 20GB. If you do, let us know how it goes, and take some pics along the way.

Originally Posted by Lil' Knight

Is there any significant sonic difference between the 22uf and 47uf in gen5?
Which one do RWA and ALO use in their iMod?
And, has anyone tried bypass the 22uf with 0.1uf NX-hiQ?

From the little I do understand about BGs, bypassing should only be with NXs that have 10% the capacitance of the original cap. Over in the Millett MAX thread, TomB reported that Sprague Vitamin Qs bypassed the BG NXs to good effect, and the Millett Hybrid MAX Boutique page (Can't Miss Build #1) will reflect that recommendation. I didn't hear much of a difference bypassing 22uF with my 1.0uF VitQs, but I did hear quite a bit of difference replacing the BGs with the Spragues. Nevertheless, the latter pair was far too large for practical use (for me anyway), as I prefer keeping the caps inside the iPod. This situation will have to change as I patiently wait for my iPod prying tools to come in so that I can diyMod my iPod touch. Then I will probably have to send the caps into the docking station. Maybe I didn't give the caps a good enough chance, but I don't foresee bypassing taking place in any of my diyMods soon.

Where are you planning on fitting those bypass caps? Seems like it'd be quite a tight fit in the LOD.

[wgr73]

Originally Posted by joneeboi

... so that I can diyMod my iPod touch.

I would not recommend this to anyone!! Lol, Jon is a master though, so it's ok . This is risky business on such an expensive piece of hardware! I hope the best Jon!

[joneeboi]

Thanks for that vote of confidence, wgr. I won't let you down.

[wgr73]

cool!