For anyone considering purchasing a C5 portable amplifier from JDS Labs* for use with an iPod Classic or 5th generation iPod Touch, I decided to take a few comparison photographs to help give you an idea of how they fit together and how a few different connectors work with them as well.
In each case, you can see the BTG** cable is much nicer in every way. It has held up better so far (I've used it the longest without issue). It's more flexible for a better fit laying the devices together. It has a shorter 30-pin connector, and it's simply higher quality all around. The dock connector doesn't seem much different than the FIIO, however, it has held up so far and the rest of the adapter seems very nice. For what it's worth, I've been using the iPod Touch exclusively for a while.
Sorry for any bad lighting, etc. The photos were taken pretty quickly. I tried to get a few angles of each device and each adapter, as well as two styles of earphone connectors with the BTG adapter for a couple of overall "real life" examples. If you find this helpful or have any questions please leave a comment. :-)
5th gen ipod touch size comparison:
ipod classic size comparison:
FIIO L9 adapter:
You can see in both cases the adapter tension wants to lift the ipod up putting strain on the connectors. I tried a few things such as working the cable out physically, attaching bands and things to hold the cable in place, relieving the strain. This may have caused the downfall of the adapter, but it's better the adapter die than my C5. :-P The classic is heavier, so it looks better, but it's probably actually worse putting more strain on the connectors.
FIIO L3 adapter:
This is better in terms of strain "if" you let it sit crooked. Otherwise, it wants to pull the ipod to the side. Forcing it to sit straight puts more strain on the connectors. I couldn't get this to work itself out either and ended up using bands and things to hold the cable at the right angle. No vertical lift really with this adapter.
Much more flexible. Allows device to sit perfectly with room for movement. No tension on the connectors at all really (minus any inevitable "normal" strain). Shorter 30-pin connector allows a small footprint with both devices. Very nice with the classic. Much better with the touch.
Lightning Adapter and 30-pin connector size comparison:
Note that the L3 has the side buttons that you have to press to release the connector from the device. The BTG and L9 do not have these and simply pull free.
Real life example of two earphone connector types:
*C5 Portable Headphone Amplifier:
**BTG Audio iPod LOD:
Head-Fi in-depth discussion on the C5: