KeithL
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Post by KeithL on May 23, 2014 10:57:23 GMT -5
First, to answer your question, there are no special settings for using the DC-1 with IEMs. The short answer is that some IEMs are VERY sensitive, and the sensitivity between various headphones and IEMs varies wildly. As with all electronics, the DC-1 has an inherent "background noise level"... and, while this noise in inaudible with normal headphones, and on the main outputs, it may be audible with IEMs that are ten or twenty dB more efficient. A bit here about noise..... Signal-to-noise Ratio (S/N) describes the ratio between a signal at a specified output level and the minimum "background noise" that is there (and so it's measured at one or more specific signal levels). Typically, in most equipment with gain and a Volume control, there is a fixed minimum "noise plateau". As you turn down the Volume, the noise gets quieter until it reaches this plateau; at which point the noise stays the same when you continue to turn the Volume down. Starting from Off, turning the Volume up doesn't change the noise until you reach this plateau, at which point turning the Volume up further increases the noise. (You're hearing the fact that the actual noise is a combination of a fixed minimum "noise floor" PLUS the noise that results from gain being applied to noise coming from the input circuitry and the source itself. Below some gain setting the unmoving noise floor dominates; above that setting the variable noise controlled by the Volume control dominates. If you end up listening with the Volume turned way down, the fixed noise floor will be the same, but the signal will be lower - and so the RATIO between them - the S/N - will be lower. Of course, this plateau point will be different, depending on the noise level present in your source material and, for an analog source, the noise level at the output of your source component itself.) The headphone amps in the DC-1, while very good quality "general purpose" headphone amplifiers designed to work very well with the vast majority of headphones, aren't specifically optimized for best performance with VERY high efficiency IEMs. So, while they are very flat, very low distortion, and very quiet with regular headphones - you may find other headphone amps that are slightly quieter with efficient IEMs. (Also, as some folks have noticed, while the headphone amps in the DC-1 are very good, they aren't quite as good as the main outputs - which are really REALLY quiet.  ) Now, all that said, it never hurts to minimize noise coming in from elsewhere... If you disconnect all the inputs from the DC-1 (physically unplug the wires), then you are probably hearing the inherent noise of the circuitry in the DC-1 itself. You could try a line filter (just in case you have a noisy line), or try plugging the DC-1 into a different outlet or physically moving it (in case you have something sending noise through the air - like a wireless phone base station or WiFi router). If the noise drops when nothing is connected, but gets worse when you connect a certain source, then you could have a grounding issue with that source. Specifically, computers are notorious for having noisy grounds, which can"inject" noise through the ground connection to the DC-1. (If the noise is entirely gone when the computer is disconnected or unplugged, then a USB ground isolator will almost certainly eliminate the problem.) KeithL are there options for listening to IEMs with the DC-1 |
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KeithL
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Post by KeithL on May 23, 2014 11:09:31 GMT -5
The ground and power connections on computers are notoriously noisy... In general, this is a problem with many USB-powered DACs (ones that don't plug into AC power anywhere). AC powered DACs, like the DC-1 and the XDA-2, are usually mostly immune to this sort of noise (although some can get through with especially noisy computers). Likewise, when using a USB powered DAC, but using headphones (which aren't grounded anywhere), it usually isn't much of a problem. However, it is often a serious issue when using a USB powered DAC to connect a computer to a stereo system (you're basically trying to ground the computer to the stereo THROUGH the DAC and audio and USB connecting cables). If that's the case, the noise will go away when you disconnect the USB cable. If you're using a laptop, it may also go away if you try running on batteries. And, if that is the case, a USB isolator will usually entirely solve it.) I've used this one "USB 2.0 Isolator" from www.electronics-shop.dk with good results; there are a whole bunch of others out there. (Do remember that, unless the noise goes away when you disconnect the USB cable, this isn't going to help - so save your money.) I would avoid fancy USB cables (ones that are just expensive wires) claiming to eliminate noise - since most of them don't help at all. 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? |
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KeithL
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Post by KeithL on May 23, 2014 11:15:46 GMT -5
That should actually work well - and, being passive, won't add any noise or distortion of its own. However, with one kudo.... Adding an in-line passive volume control WILL raise the source impedance of the amplifier (as seen by the IEMs or headphones). As such, you will lose the super-low output impedance that is one of the benefits of the headphone amps on the DC-1. Depending on your headphones, this may result in a slightly less flat frequency response (and the frequency response may vary slightly depending on where you set the volume control itself on your little passive volume control gadget). Overall, though, I think you'll be pleased with the results. |
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KeithL
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Post by KeithL on May 23, 2014 11:19:51 GMT -5
It's possible, but a static charge should (if anything) cause a bit of hiss or crackling - and not hum. It seems more likely that there are some sources of magnetic interference (hum) in some parts of your house and not others. These would be things like any device with a power transformer, or a fluorescent light, or even power lines running in nearby walls. (I've even heard of one case where a power line running several feet away OUTSIDE the house produced audible hum in a corner room.) 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. |
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Post by GreenKiwi on May 23, 2014 12:11:53 GMT -5
Just reading through Keith's responses now... figured I'd comment on the cheater plug. I'll try that out tonight or tomorrow. See if it's a noisy ground plane. I realized why I didn't try this before... the DC-1 already doesn't connect to the 3rd pin.  |
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Post by GreenKiwi on May 23, 2014 12:25:58 GMT -5
Hi Keith,
I totally understand S2N and noise floor issues. It sounds like my issue is probably that the inherent noise floor of the DC-1 is too high for IEMs. I'm contacting Cardas to find out the sensitivity for those IEMs. Online it says that they are 104db 1mw, which isn't actually that much more sensitive than many other headphones... and a far cry from the first ones that were 116db. I was hoping that this drop in sensitivity would decrease the noise.
So then it's just a question of whether my noise floor is potentially higher than it should be... and/or there are any ways to decrease the noise floor.
I'm guessing that given that I have two separate DC-1s in two locations, that when not connected to anything, exhibit this noise floor issue... and that the noise changes based on the gain being applied, in both cases, that it is working "as designed"/"as specified". The weirdest part for me was the noise getting much quieter from -10db to its quietest at 0db and then getting louder again by +5db.
But I guess I was wondering whether or not others were having the same issue.
Do you have any ratings as to what the most sensitive headphone that can be used w/o having this background noise be an issue? i.e. find for all headphones with sensitivities lower than XXX db.
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Post by GreenKiwi on May 27, 2014 16:52:06 GMT -5
I contacted Cardas and they confirmed that their ear speakers are only 104 db efficient, not crazy like 116 or 118 db. So it looks like one is likely to have noise floor issues connecting IEMs that have efficiency at or greater than 104db @ 1mW.
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KeithL
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Post by KeithL on May 28, 2014 9:18:41 GMT -5
IEMs have a few issues when it comes to noise sensitivity. First off, 104 dB is on the high side of average for headphone and earphone efficiency. Second, because they are sealed, using IEMs is sort of like listening in an anechoic (or, at least, very quiet) room - since you don't hear any background or environmental noise, your ears become very sensitive to whatever noise is there. Some people are also simply more sensitive to noise than others, and some phones exaggerate certain types of noise. You should also note that this "effect" also works for the background noise that is present on the recording itself (you hear it more on a dead silent background). At this moment, I'm listening to a pair of AKG 55 ohm K240 MKII semi-open headphones.... which are middling quality phones (and "semi-open").... and are rated at 104 dB efficiency. I'm sitting in a relatively quiet office, with them plugged into my DC-1, and I do NOT hear any hiss or hum unless I pause the music and pin the volume control on the DC-1. Even then, all I usually get is a barely perceptible hiss. (Except on one or two recordings where the noise clearly jumps up when the music starts playing - which obviously means that it is background noise on the recording itself.) Obviously, if I was sitting in a dead quiet room, in the middle of the night, I would probably hear some background noise.... The DC-1 is on the quiet side of average for a headphone amp... but it is not the quietest headphone amp in the world. If you have super-sensitive IEMs (or cans) and you happen to be very fussy about noise, then you might have to consider a more specialized headphone amp. (Since most of the headphone amps I've heard that can top the ones in the DC-1 cost more than the entire DC-1 - just for the headphone amp - we can live with the embarrassment....  ) Incidentally, while they are very good, the headphone amps in the DC-1 aren't as quiet as the line outputs (the DC-1 is a really excellent DAC, but only a very good headphone amplifier)- so connecting a really high end headphone amp to the main outputs of the DC-1 will give you slightly better performance if you choose to go that way. I contacted Cardas and they confirmed that their ear speakers are only 104 db efficient, not crazy like 116 or 118 db. So it looks like one is likely to have noise floor issues connecting IEMs that have efficiency at or greater than 104db @ 1mW. |
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KeithL
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Post by KeithL on May 28, 2014 9:24:56 GMT -5
Just one more note on noise....
While the low level hiss you're hearing is almost certainly the normal noise floor on the DC-1's headphone amps, and so isn't something you're going to change, hum is more "negotiable" - and so things like reversing the power cord, or even simply repositioning the DC -1 a few inches, may well help reduce that a tiny bit. Likewise, experimenting with where each device is plugged in (same power conditioner, different one, same circuit, etc) may well help - although, since every situation is different, I can't give you any specific advice there.
Things like light dimmers are also prone to creating a sort of buzzing interference - which can find its way into lots of stuff - either via the air or the power lines. About the only to confirm or troubleshoot those is to start, in the middle of the night, with everything you can find turned off - and see if the noise goes away.
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KeithL are there options for listening to IEMs with the DC-1
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