TLDR part before hand.
Has anybody had any interference issues with this combination of phone/DAC, and any suggestions on how to fix a fluttering problem that I think is driver related.
And a little bit about a custom case that I am working on.
Hello. I just got an S4 a few weeks ago, partially because of the compatibility with my E17 for USB audio. I got it, hooked it up, and it works. YAY! But after a few days I start to notice that when the song is quiet there is a fluttering in the background every couple of seconds. My primary headphones that I use with this setup are the Shure SE215 (20ohm). Now that I have noticed it this is starting to bug me a little bit, but when the song gets going I can't hear it. Only when the song is quiet, or has a silent gap between songs.
I am using Neutron as my primary player, but I tried it with the stock Android player with the same fluttering. Hooked up through USB with my laptop there is no problem. Desktop with coaxial into the E17, through the E09k there is no problem, so it seems to be something specifically with the Android E17 combination. With my Vsonic GR04's (50ohm) the problem is much less noticeable. With my Beyerdynamics 880 Pro, and 990 Pro (both 250ohm) I can't hear it at all. I know that impedance and resistance aren't the same thing, but for a lot of things they can pretty much be considered the same thing because the capacitive reactance portion of it doesn't have a large effect in many cases. But it seems that the higher the impedance the lesser the problem which would make sense from the resistance standpoint as it takes more to drive the headphones so small imperfections wouldn't actually make it through. I just ordered some 1964 V6 stage customs, and they are only 22 ohm so hopefully they aren't any worse than the Shure's for this problem.
I have tried it with a USB cable that had a choke near the DAC, and no change, I also turned my phone on airplane mode to turn off the transmitters to see if it was possibly some other form of RF interference, and no change. I have tried using the generic driver setting in Neutron both on and off, with no change, and like I said it does it with the stock player also so I don't think it is a player issue. I tried USB Audio Recorder which has a custom built driver, and it seems to lessen it, but I'm not sure it it is the driver or something else with the program. Has anybody else had this issues, and if so what did they do to solve it, or hopefully someone very Android savvy will be on here, and have some suggestions.
Also I am working on a custom case for myself that would be specifically for the S4 E17 combo that would basically be a slide in dock for each with the OTG cable built into it, and was wondering if anyone else would be interested something like that. If you are, keep reading if not then thanks for reading my actual question for this long. I hate the rubber straps, and the thickness of velcro or other form of attachment in addition to the extra stress on the USB jack/cable from being bent up, and curled up in my pocket. It looks like it is going to be about 2mm thinck than the 2 devices put together, and about 12mm longer than the phone with use of the camera, and the phone effectively acting as a strain relif for the headphone cable coming out of the DAC. Right now it is in the hot glue, and soldering plastic together phase to get dimensions, and just starting on the CAD stuff to start on the CNC fun. But I figured if there was a need maybe I could make extras and sell them if there was any desire since the hard work will already be done at the point that I get one made for myself. I envision it looking kind of like an external battery case (picture below) with another channel for the E17 on the back. It is probably going to have a charging port on it as well so you can charge while using the DAC (this is the next thing that I am going to solder on because I don't now if it can be done, but since the DC, and Data are on separate line I don't see why not. But I don't know about how the jumpered sense/ground thing will work with that, so I promise nothing). Also it will have a duct for the speaker to project out of the bottom sense the speaker will be covered by the DAC (will probably not sound good, but considering the people on this site we already think that little speaker sounds pretty terrible right?). I'm guessing about $50 if it works how I want, but I don't guarantee that I won't be really annoyed by the time I get mine done, and never want to do it again. PM me if you would be interested at all, and I'll get you more info if you want. I can even send you the picture of the current iteration of my hot glued Frankensteined prototype if you want a good laugh.
If you made it this far thank you for listening to my mental shotgun blast.