Hey all -
Let me try and shed a little light on the whole USB micro A/B/AB/OTG thing...
The Glacer is a slave-only, non-OTG device. It has a USB micro-B connector.
The Glacier can be connected to anything that can act as a USB host. This includes (obviously) things like PCs, and also the iPad using the Apple CCK. In these cases a standard USB A to Micro USB B cable (like the one supplied with the amp) is used.
It can also be connected to an OTG device that can act as a host, like the newer Samsung phones. The correct cable to do this would be a micro A to micro B cable, with the A end plugged into the host and the B end plugged into the Glacier. You can also use a micro B to standard USB B female adapter (as was reported to work if plugged in the right way, with the adapter into the OTG device)
According to USB spec, such a cable should be labelled with A and B on the overmolds on the ends. Also, the A end should have a rectangular cross section, and the B end should be chamfered.
Now, I don't know if all the cable makers follow the spec or not.
I've tested with the iPad and CCK quite a lot. I also tried two different Samsung phones at RMAF and both just worked. To be honest I didn't even look at the cable orientation - maybe I just got lucky.
Apple devices (iPhone, iPod) don't work as OTG hosts. As was pointed out, as a developer, you have to pay Apple to play, as the interface that uses USB to send audio is proprietary. It requires additional hardware as well. So I didn't go there.
Not to mention I'm not a big Apple fan
As of now, the standard Android releases do not include USB host support. Samsung decided to add this feature on their own. The Android folks are working on a funky USB dock protocol that works over USB (sort of like what Apple does) that, frankly, most of us developers think is stupid. There is certainly a push to put USB host support for standard devices (like audio, keyboards, etc.) into the normal Android releases. (I was going to point you to the discussion on developer.android.com, but the server is down...)
Oh, one other point while I'm here: in its normal state, the USB DAC connector will ask for 500mA of power so it can charge the battery when it enumerates. In USB descriptor-speak, MaxPower = 5 and bmAttributes (self powered) = 0.
If you disable USB charging, no power is drawn from the USB port. The device will enumerate as self-powered (e.g. it does not use USB VBUS power). We're getting deep here, but technically the Glacier enumerates as a compound device containing an embededd hub - it has some HID functions that are unused - so it enumerates with a "1" in the MaxPower field, which indicates 100mA. But since the "self-powered" descriptor is set, the iPad has no problem with enumerating and connecting.
Oddly enough, it looked like the Samsung phone will try to charge the Glacier battery! That might kill your phone's charge pretty fast, so you should disable USB charging.
If anybody is masochistic enough to read them, USB specs are available to the public at
http://www.usb.org/developers/docs/
Hopefully that helps?
Pete