DC-1 and IEMs... and a high noise floor

[GreenKiwi]

I'm wondering whether or not anyone else has experienced any "hum"/background noise when using their DC-1s with In Ear Monitors (IEMs).

I got a pair of Logitech UE 600vis, while not out of this world IEMs, they are quite reasonable. When plugged into my DC-1, there is a very noticeable hum/noise. It's like white noise with a little vibrating signal on top of it that would seem to be close to the 60hz.

• This happens with no inputs selected and only power and my headphones connected to it.
  
• The noise level doesn't change with volume or input
• My Beyer T70s are dead silent

Some other notes, it is noticeably louder than the background noise on my MacBook Pro's headphone output, which is in turn noticeably louder than my iPhone's headphone output.

I'm going to try these headphones with my DC-1 at home... and also with the O2 headphone amp, both connected to the DC-1 and w/o any connections.

Just figured I'd see if others had noticed anything like this.

[GreenKiwi]

My O2 has the lowest noise floor of all of them.

[paintedklown]

I get hum with earbuds in, but it does go up and down with the volume level (no noise unless at a high volume and music paused). I assumed it was just the usual "amp noise" (sounds like white noise) that you get with amps that aren't dead silent.

[GreenKiwi]

Interesting that the noise you hear changes... while mine is constant. If i have the volume all the way turned down, I still get the same amount of noise.

I'll be trying it tonight to see whether my home one has a similar noise floor.

Also, my listening level is -40db or so with these, at least as one measure of efficiency.

[lsdeep]

don't get anything like it with my akg's, in ear i wouldn't know. i guess i could plug the iphone in ears in to check - but that would be as much reference as plugging in a telephone LOL

[GreenKiwi]

Yeah my senn hd650s are dead silent too.

[klinemj]

I don't have any headphones or IEM's, but your symptoms make it sound like you inserted the IEM's and trapped a fruit fly between the IEM's and your ear.



Mark

[GreenKiwi]

LoL

That must be it... I don't know why I swallowed that fly...

[GreenKiwi]

So some more points of reference.

I plugged them into my DC-1 at home and had the same results.

I tested further and found

• It was pretty much the same for all inputs
• the level is the same for volume levels -100 to -10
• The sound tapers down to nothing from -10 to 0
• At 0 there is almost no noise floor at all (I'd also blow my ears out)
• the sound returns when you go above 0 but changes to a slightly warmer white noise

These are the IEMs

ue.logitech.com/en-us/product/ue600#tab-specs

EARPHONE TYPE:In-ear
DRIVER TYPE:Single, top-firing armature
IMPEDANCE:13 ohms, 1 kHz
SENSITIVITY:115 dB SPL/mW, 1 kHz
FREQUENCY RESPONSE:20 Hz - 20 kHz
NOISE ISOLATION:26 dB
INPUT:3.5 mm (1/8 inch), angled
CABLE LENGTH:48 inch (121.9 cm)

At home I tried my O2+ODAC and it was slightly different than the one at work. It had a noise floor that went up as the volume was turned up, but the noise floor is completely quite at volume points well past reasonable listening levels.

[garbulky]

Are you using USB input? Try this.

- Remove the USB connection completely.
- Then....physically disconnect the DAC entirely from the AC power. Do not standby or anything. Pull out the power plug from the wall.
- Put the plug back in and start it up.
- Use a different input other than USB temporarily like a blu ray player or game console.
See what happens now.

[GreenKiwi]

I disconnected everything but the AC for my tests, and did turn them off (no background noise when turned off =D )

I tried all the inputs too.

The most interesting thing for me is the noise floor going away between -10 & 0.

I'm guessing it's an issue with these being very efficient IEMs, but I do still hope there is a good solution. I like listening to IEMs at work at times, and I was really hoping to sell my O2.

[GreenKiwi]

Also, to show the different between these and big cans, the HD650s specs

FR: 16 – 30,000 Hz (– 3 dB)
Impedance: 300Ω
Characteristic sound pressure level (at 1 kHz): 101dB (1Vrms)
Max Power: 500mW

[GreenKiwi]

KeithL are there options for listening to IEMs with the DC-1

[Leif]

I've experienced the same thing -- low noise -- like electrical hum. Mine does not change as the volume on the DC-1 changes but is constant. I've tried isolating it away from my monitor, using both the power cord supplied with the unit and a shielded cord (1 m) bought from Emotiva. I've tried with different USB ports from my Mac Mini (late 2013). Tried plugging into different outlets in the room. Finally I've tried it with nothing at all plugged into any of the inputs to the DC-1 and the hum is still present. I'm using Bose over the ear noise canceling phones (the hum from these is more at a low level hiss) and also use Apple stock earbuds (the hum from these is more like a true electrical hum). With music playing at -100 to -20 db into the Bose the hum is still noticeable but the music overcomes it from -20 db and up. The impedance is different for the apple buds so the volume range in which the hum is noticeable is different but still there.

The interesting thing with my situation is, that after I would play music (either from iTunes or streaming directly from Audirvana) the hum would go away and there would be silence in the background when the music was stopped. To check, I power cycled (on to standby and back to on -- or a soft power cycle) and still silence and no hum. So to test a theory I disconnected the DC-1 entirely and took it to a part of my home where there are no carpets but wood and porcelain floors only. I made sure there was no static build up on me, the DC-1 or in the earbuds -- set the DC-1 on top of a granite counter, discharged myself once more by touching a steel object -- turned on the DC-1 and there was nothing but silence -- dead silence. My previous test whereby there was nothing connected to the DC-1 but the power cord (as was the case for this step just described) was done in my static-y room above the garage. It is winter-time here and quite dry. In my case at least, I believe the hum is a result of built up static. I could test the theory fully by yanking my mac mini, monitor and DC-1 out of here to a static free (or nearly so) area of the home -- but that's a lot of work.

[GreenKiwi]

Well, just to provide some more feedback. I'm now listening to it with some IEMs that have 104db/mW sensitivity and I sill very much hear the background electrical hum.

No amount of power cycles, disconnecting cables etc addresses the problem.

It's very frustrating.

Is my DC-1 defective or do all DC-1s have this background electrical hum with IEMs?

[tiframelock]

Have you already tried using a cheater plug on the power cable of the DC-1? This can work at times if its power line noise. I'm very interested to see if this problem gets solved as the DC-1 is one of about 3 DAC's I'm currently looking at and I will be using Westone W40's with it sometimes.

Best of luck!

[GreenKiwi]

I'll try that out tonight or tomorrow. See if it's a noisy ground plane.

[rcohen]

Very high sensitivity headphones will often reveal noise. Many IEMs are high sensitivity. The solution is to use an inline volume control to dial the sensitivity down.

Something like this:
www.amazon.com/Koss-155954-VC20-Volume-Control/dp/B00001P4XH/ref=sr_1_1?ie=UTF8&qid=1400818141&sr=8-1&keywords=Headphone+volume+adapter

[d1sturb3d]

I have a Fischer Audio DBA mkII..I don't get any audible noise when listening to the headphone out..I get some audible noise when I try an Fiio e10 and I have found out it has something to do with the USB cable..are you using USB?

[GreenKiwi]

I get the noise with only power and headphones connected, no other inputs.

My O2 amp has almost no noise, coming from the RCA outputs on the DC-1 with the same headphones.