The Apple diyMod: My Take on the Famous iMod [56k killer] Featuring 3G, 4G, 5G and nano 1G! - Page 104

not sure if the drive would work, but if I were you i'd install a CF card adapter in there and buy a 32GB or 64GB CF card for it. Much better battery life, quieter and starts up in like half a second

Not sure about the resisters; i've never had to use them. but then I've never done a mini

where are you going to put the second set of caps? the bypass caps?? Its a good idea and does produce SLIGHTLY better results, but the 47uf will do just fine by itself. if you are going to try and get much better results you are better off using a separate enclosure and getting some really nice caps. Such as the VCAP dock i'm building. using 3.3uf OIMP vcap and bypassed with .047 teflon Vcaps. but there\s no way thats fitting an a cable or the ipod. only just fitting in the hammond case

I've got a separate Apple dock I hope to fit everything in. There's no room inside the mini for any quality caps, like BG or any film for that matter. I also found the source of the 100K ohms, something I doubt anyone else found and it was driving me crazy. Believe it or not a 5.5G iMod picture clued me in to my discovery. I got it running now, with no output caps and it sounds amazing. Now I just need to wait for a 16GB CF card and whatever caps I'm going to choose.

"I also found the source of the 100K ohms"
Care to share your findings?

no output caps :concerned: what are you using it with? are you prepared to replace it??? and yes; do share about the 100k/ohms after all thats what this thread is about

Caps, impedance, and you...

To put a few misconceptions to rest, it should be noted that the schematic diagram above has a coupling capacitor, a bypass resistor and a current limiting resistor. In the diagram, R1 is 47K ohms (not needed), that resistor is meant for impedance mismatching with the next amplification stage. Impedance matching is not desirable in audio (with few exceptions) because it can degrade signal quality. C1 is the coupling capacitor, and as many of you have noticed it's capacitance and construction greatly affect the musical quality of the program material. Which capacitor works best with this mod is more subjective than objective. Since there are some probable differences in each generation iPod outputs having different impedances between DAC chip numbers, being coupled with multiple input impedances from the different headphone amplifiers, and even different headphone impedances, not to mention that everyones ears has slightly different frequency responses from ~10Hz to ~22.7kHz.
You don't actually hear 10Hz nor much above 21kHz, some people can "perceive" or detect these frequencies. Barometric pressure (also altitude changes), temperature and humidity all affect sonic performance to some degree. You can see that with all these variables, it would be hard to be definitive as to which type and capacity value will work best with a given system. Given one persons iPod setup and several listeners, you will get multiple impressions of that one setup simply because of the human hearing abilities of each listener. One says it's a warm, smooth sound, and another may say its clean and crisp sounding. So musical nirvana comes in the form of experimentation with your particular setup and to what you perceive as what music should ultimately sound like. As far as capacitors go, a general rule is that physically larger caps which often cost more than the garden variety, will usually pass more musical nuances then their cheaper cousins. I would start with a high quality encoding (lossless) of a classical score you prefer and only changing out different coupling capacitors from different makers and of a few different capacitances. 10uF/25V is a good starting point, and working up from there. Looking at which capacitors "audiophile applications" use can be a good source for high quality grade manufacturers of capacitors.

well that screwed with my day for nothing then I was just about to make a final order for supplies when I spotted your post and it threw all my prep out the window. so R1=not necessary if you have impedance matched your set up; R2 not necessary if you take care to follow the right turn on, turn off procedure and make sure the caps are charged before plugging an amp or any load in. glad I didn't change my order I was looking at some very expensive resistors

R1 shouldn't be needed at all, as far as I can tell, impedance matching in audio is undesirable because it's said to degrade audio signal quality. R2 is there just to limit peak current going into your amp. C1 & R2 can be high quality, R2 can be lesser quality and higher resistance (47K min). As there is ALOT of calculations and R&D to go over from others, I'm investigating the confusion behind "to impedance match or not to impedance match" further, more for my own knowledge but I will pass what i have learned onto you guys as well. Far as i can gather, it's not desirable for audio applications with the exception of transformer uses.

well I ordered a 330k caddock ultra precision film resistor to try out with the VCAP dock when i'm using it with the bantam; but will only leave them in if it doesn't audibly effect the SQ in both DIYMOD and bantam coupling duties mainly DIYMOD, since thats why I started this project. i'm not willing to trade-off performance in the ipod rig so I can use it with the bantam. ideally I can leave it out for both applications and it will be fine. Its not a difficult thing to put into and take out of the path in the hammond case anyway; plenty of room to jerry rig it (R1) to test it out. R2 is as you said for the 'ham fisted ' users who dont know how to treat audio equipment; or at least aren't in the habit of following a turn on/turn off procedure

Got my iMod Mini 1G running

Here's the board, pre-soldering of wires:



Squares:
RED (C53) - Right Line-Out from DAC (~1.7Ω)
BLUE (C54) - Left Line-Out from DAC (~1.7Ω)

YELLOW (C69) - Dock Connector Pin 3
MAGENTA (C70) - Dock Connector Pin 4

Basically I soldered a jumper wire from C53 to C69 and C54 to C70. Having removed the inductors and capacitors, from the line-out signal now leaves a perfectly "virgin" signal, except for one more thing...

After my initial attempt at the mod, when I measured between C53 and GRD (same with C54 and GRD) I was reading ~100k ohms. I couldn't figure out where is was coming from and I almost gave up.

When I was looking back at the original iMods (5G or so) something hit me, there was one photo that had every cap and inductor label needed for removal, including the caps, 100Ω resistors, and the 100kΩ resistors. The one thing they all had in common was they were tied to this "Zener Diode Array", labeled ZP1 on the board. The original mod effectively cut off all "signals" to it, except its ground.



I found this same diode, ZP1, and I Ω'd it out to the other free pads (C69 & C70) and what do you know, I have a connection (100k) and there is a TINY trace from those pads to the diode.

YELLOW (C69) - CONNECTED TO - WHITE
MAGENTA (C70) - CONNECTED TO - ORANGE



Since I could see these tiny traces from the cap pads (C69 & C70), I just took a exacto knife and cut the trace. You can kinda see the nicks in the board from cutting the traces. Bingo! NO more 100kΩ to ground

That's it, I also installed an A-DATA 16GB CF card and Rockbox.

that 100k resistance would be for input impedance matching IMO something myself and rink customs have been investigating. It does seem however that they are not really needed, so why have them there.

Not sure what you're getting at? I removed those resistances since they were part of the original 'high-pass filter' / Coupling section. Now I can run my own caps and resistors.

ah ok sorry forgot you were adding the resistors in the large capped dock. my bad

I've just done my first mod on a mini (while adding a 32gb compact flash card) and was wondering where is a good place to check ground to on a 2nd gen mini? I'd like to remove the 100Ω as bmwpowere36m3 did on his 1st gen (if it is present)


Kinda off topic but while doing the mod I noticed that all the links I clicked on the first post say the correct post number, but link to a page with posts at about half that number. The amount of people I've told to "read the first post" instead of duplicating the info I just hope they had the sense to find the post number not click the link! Did I change a setting to mess the numbering up or are the links or is it like this for everyone?