Here is a nano 1G disassembly tutorial.iPod Nano 1st Gen. Disassembly: Installing Battery & Logic Board - Removing Rear Panel (page 1/6)
I'm sure if Vinnie could have fit caps into the iMod nano, he would have done it. The nano 1G measures 3.5" x 1.6" x 0.27", or 88.9mm by 40.6mm by 6.89mm. The iMod's BG NX Hi-Q measures as small as 4mm x 7mm. It will be very hard to get that kind of clearance inside the super tiny casing. I'd try squeezing it underneath the battery. That would be my first guess, but I still doubt you could fit it there. Maybe you could drill two holes that will let the caps stick out of the casing. Just spitballing here, try at your own risk.
As for sonic impressions, I'll try my best. My setup is the 4G click wheel (with WM8975 CODEC) to 220uF Nichicon UPWs from Mouser to a Kobiconn 3.5mm stereo jack also from Mouser. The amp I listened most intently with was my Millett Hybrid MAX. The MAX's settings are a supply voltage of 27.0VDC with 12FK6 biased to 13.5VDC, Toshiba 2SC3422/2SA1359 BJT diamond buffers biased to 110mV. My boutique caps are 1000uF Panasonic FC at CA2 and CA7 with 5.1uF Solen bypass caps at CA8 and CA9. Mini-mini cable is generic. Headphones are Grado SR60s with rescreening, sticky tack driver mod, GS1K pads with glue mod. Indeed a very personal setup, nothing any of you might have, even within MHM builders and SR60 owners. My files are encoded to MP3 320kbps VBR.
Plugging straight into the WM8975 (the datasheet says headphones can be plugged straight into the DAC if 220uF caps are put in series first), I listened to the very first time, as Nigel Kennedy played Sibelius' Violin Concerto in D minor, the performer's breathing. I had heard this sound before and I suspected it was hard breathing, but the clarity and intensity of his breath was very evident. I assure you I'm not exaggerating, as I've heard people exclaim that x piece of equipment allowed them to hear performer y breath and they could tell which nostril they were breathing from and performer y had a cold for the past two weeks. It's impossible to ignore this breathing. Switching over to some Hillsong's Savior King for some Marty Sampson singing In Your Freedom, I heard a portion of a drum beat I'd never heard before. It's just the snare going away on a regular system, but with the diyMod + MHM + SR60s, I could hear the hi hats going off in the distance. It was fairly not but overly subtle on this setup, but it's unnoticeable even in the car where we listen to this track plenty of times. The instrument separation was very precise, as I could switch from focusing on the drums and go to the acoustic guitar in one ear and then to the electric in the other ear to the piano in the back very smoothly. Loads of detail were available to me as though I were at a detail buffet and I could choose to listen to anything I wanted. On this setup, the highs sparkle quite nicely, balancing out the Toshiba BJTs' punchy bass. The corner frequency for this setup is ridiculously low, so bass rolloff isn't a concern (much lower than 1Hz). In fact, I think I've struck a nice balance between punchiness and extension. I prefer a fun, impactful bass, and this setup delivers it almost as well as I had heard with the Ayre Evolution CD player + Stax SR404 + SRM006tII
listening to the same track. The noise floor is very quiet. Plugging in the iPod charger and pausing the music and turning the volume knob all the way up makes the AC noise only barely audible, so at listening volumes it's not a problem at all.
Overall, the take home message here is the separation. I really felt like I was onstage, walking between the performers to hear what they had to offer, although I'm sure volumes onstage are orders of magnitude larger than what I was experiencing. I like how everything meshes together right now, which is why I'm hesitant to even try the Black Gates. Even within the MHM builders, my setup is pretty far from what they recommend. My SR60s are one-of-a-kind, and I'm using Nichicons (220uF no less) as my diyMod caps. In other words, your mileage will vary greatly from mine as I'm sure no one will ever have this setup. That should be the caveat for a lot of reviews.