[makasin]

hey, so I have been using the E11 with L9 LOD to my ipod nano 6G and koss KSC35, ksc75 and it sounds great. Also sounds good with Grado SR225i and Apple IEMs, awaiting my TDK BA200s. However when I switch to my iphone 4s, I get some RF interference. I am wondering. Has anyone actually opened up the other side of the the E11 and inspected it? I know it's "better than a Mini3 but with mini3 parts but the DC-DC converter incurs some RF coupling into the audio path" 
 
I was wondering if using aluminum foil surrounded in theelectrical tape would help the RF issue. I notice that the USB port has a metal pin exposed and goes to nothing. Ground? Could I solder a wire to it and the aluminum so the energy sinks to ground or is that a bad idea.
I was also thinking about using a ferrite bead (the ones that go around a cable like ones found in USB cables and stuff) at the end of the L9 LOD and at the jack of my ksc35s.

 
 
Would that help? I really want to open the other panel and poke around, possibly mod it and improve it. Any takers? Right now all I have is foil covered in elec tape on the battery panel and over the area where the pot and inputs are, but they aren't connected to anything so they dont really do anything. Im trying to find a place to connect them to. perhaps the USB floating pin:

Note: The pin is at the top leftish, above and left of the battery contacts
 
Anyone know what the best way to remove the non-battery panel and wonder if it shows any parts of the PCB?
 
2 mods could work well:
1) for virtual ground channel, use same opamp as the music channels? (or something that sinks twice as much power)
2) filter the DC-DC converter's output somehow.
I am an Electrical Engineer (getting diploma in 5 days so dont have too much time to waste on it ATM but will soon), so I know a bit out electronics and have a bunch of tools/parts at my disposal.
 
 
Off topic a bit:
I just got my Koss KSC35s (had several pairs of the 75s) and I really like them. They sound great. Do they ever exhibit the buzzing issues like the 75s or other "titanium" drivers where a crinkle happens as a result of a harmonic and makes bass create buzzing or a hair getting caught in there. Also, does Kramer modding/recabling these do anything much? My 75s are Kramered and I think it helped a good bit. I am looking to find some bare wire to recable several headphones and make interconnects, but am having trouble sourcing parts, if someone could PM me about the off topic discussion that would be grand. I'm basically looking for SPC, pure silver, pure oxygen free copper, preferably single conductor (if itll be flexible enough for the koss at 26guage)for everything for the most part. Also, Teflon or HDPE insulation for the conductors. Dont care too much about outer jacket. Would like to get it in either single wire spool so I can make my own entire shindig or 4xconductor pairs similar to the canare star quads. Just getting into sourcing parts for cables so I dont know wherethe best palces are. Since I work in the RF industry, I was kinda fascinated about using some flexible SMA cables for my Koss 75s to test it.
 
 
Anyways, back to original discussion, for those who have the E11, let's try to improve them to sound even better! Just like we did with the Asus Xonar ST/X (I have one, but havent modded it, gonna get the vanguard clock and maybe also linear regulated power supplies for the opamps/clock.

 

[makasin]

So i just connected the iphone 4s to the e11 and its unacceptable. On my nano 6G it is amazing. It bring detail, clarity and really amazing impact (especially with bass combined with a high frequency hit). When I launch Audiogalaxy, I hear all the blipping and blopping like you would when you would have your phone next to an unshielded alarm clock, its pretty bad. The music drowns it out but the fact that it's there makes the SQ not as good. How could they have overlooked something so fundamental. Did Fiio assume that we live in an RF-free environment?
Anyways, when I get home I am going to measure the "ground" pin of the usb charging jack and the (-) battery voltage differential when the thing is plugged in to charge and a battery is out. Would this voltage test and see if that ground is the same ground as the battery? Ideally, I want the aliuminum foil "RF cage" to ground in one place to the battery (-) rails and not the rails created by the DC-DC and rail splitter, right? Coz that would then couple it to the signal channels. Also, I am thinking of having the output of the DC-DC pass through a low-pass filter that couples to battery ground. Would these two things null out the problem?

 

[ClieOS]

I think you are mistaking the noise referred by NwAvGuy to the RF noise coming from your cellphone. Like NwAvGuy has said, 'There’s some RF leakage of the DC-DC converter into the audio output (but it’s much better than the E5 and E7)." and "it has a frequency of 96 Mhz and it’s likely the DC-DC converter which is probably designed to run somewhere around a nominal 100 Mhz."

96Mhz is well beyond anyone's hearing, so whatever you are hearing isn't those 96Mhz wave and the only logical conclusion is EMI from your cellphone. Switch it to airplane mode and those EMI should go away.

You might think EMI is a big issue for E11, but the true is it is much more common than you think. Of the 20+ portable amps I have, most of them suffer from EMI issue simple because they are not designed to be used with a cellphone source. Do note that portable amp are usually an audiophiles' thing and a good number of us don't consider cellphone as our main source, even though it is gaining popularity. Also, designing a portable amp will full EMI shield will likely to compromise SQ and definitely increase cost .

 

[makasin]

How would it decrease sound quality? And would just simply having some aluminum foil on both sides connected to battery ground (or the little pin sticking out of the USB port which I assume is "chassis ground") help a little? Also, what about the ferrite beads or winding magnetic wire 5 or 7 turns around the 1/8inch connector side of the LOD and input of the headphone have any effect?

 

[ClieOS]

Actually the housing (the aluminum panels) of E11 are already grounded, so adding foil won't solve the problem either and the EMI issue is definitely not because of the lack of grounding. To really fully take care of the problem, the best way is to add an RF filter circuit, which adds cost as well as having a negative impact in SQ sine it must be in the signal chain.

 

[makasin]

what about the inductor around the input and output idea? 5 or 7 turns of wire wrapped around the signal wires. So the silver part around theamp is aluminum? I just thought it was just more plastic.
 

 

[ClieOS]

No really sure what you are talking about, but the main body is indeed plastic.

 

[Bas Horneman]

Old thread. But since I only got one recently...does anyone have a schematic?