Hello members,
 
First of all, hi. I'm new on this forums as of today. I'm a 19 y/o student from the Netherlands. I study medicine and I'm really interested in Hi-Fi. I hope to have a great time on this forums. 
 
So, now to the point of this thread. I currently own mostly speaker-based Hi-Fi;
 
Denon AVR-2113 receiver
Boston Acoustics A25 speakers x2
Boston Acoustics ASW650 subwoofer
Sennheiser HD280 Pro headphone
Sansa Clip+ 8gb + 32gb sdhc
Asus Xonar DGX soundcard in my pc
 
Recently I've started to use my headphones more and more. They're not that great, but they work. Since my PC stopped auto-switching to my headphones whenever I plug them in, I started using my receiver headphone jack. Also, I thought my HDMI receiver would have better SQ than my headphone jack directly from my PC.  Now here's the problem: the HP output from my receiver leaks a humm: its not loud but audible when listening to music on a low volume. It's not a groundloop and it doesn't come from any of my sources. It also does this on all electrical outlets in my house. So it's defenitely a receiver problem. Also, the humm is monotome and the volume is constant; changing output volume does not influence the humm.
 
Is this normal with speaker receivers? Does this happen because my headphones are only 64Ω? Is there anything I can do about it? And if it's normal, should I upgrade to a headphone amplifier? 
I'm into head-fi since some time and i'm planning to upgrade my headphones soon. Also, I really love headphone amplifiers. But if there is a workaround for this, it'd be great. I could wait some time and make a better decision on what to buy.
 
I'm still wondering whether I should buy a portable or desktop headphone amp, because I might buy a laptop soon. Using a portable AMP at home doesn't seem ideal, but buying both kind of exceeds my budget. 
 
But first, I'd like your opinions/knowledge on the questions stated above.
 
-ai

No, that's not normal. I don't know what could be causing that issue - it sounds like you have already eliminated all the things I would have suspected.

There's nothing wrong with using a portable amp at your desk - you just want to make sure it has a overcharge protection so that you don't damage the rechargeable battery from being plugged-in all the time. Most amps do have that - but not all.

Let me ask you this: Do you hear a difference, at the same perceived volume level, between listening to music through your receiver vs through your PC sound card?

billybob_jcv said:

No, that's not normal. I don't know what could be causing that issue - it sounds like you have already eliminated all the things I would have suspected.

There's nothing wrong with using a portable amp at your desk - you just want to make sure it has a overcharge protection so that you don't damage the rechargeable battery from being plugged-in all the time. Most amps do have that - but not all.

Let me ask you this: Do you hear a difference, at the same perceived volume level, between listening to music through your receiver vs through your PC sound card?

Click to expand...

It seemed not normal to me aswell. I've contacted my dealer and they told me its normal, but I didn't trust this.
 
The difference I hear is kind of hard to tell since there is a disturbing humm when using the receiver. Nevertheless the receiver sounds more pleasent to my ears. At the same sound level, the PC has no disturbing sounds. There is no humm or whatsoever. On the other hand, the receiver does has this humm.

If you buy something like this, it *may* reduce the hum on your receiver. If you are hearing the noise floor of the amp, increased impedance will attenuate it. 
 
http://www.ebay.com/itm/Etymotic-ER4P-to-ER4S-6-35-to-3-5mm-resistor-adaptor/281224427556?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D19839%26meid%3D4069148601728015096%26pid%3D100005%26prg%3D8934%26rk%3D3%26rkt%3D5%26sd%3D290372905689%26

manbear said:

  If you buy something like this, it *may* reduce the hum on your receiver. If you are hearing the noise floor of the amp, increased impedance will attenuate it. 
 
http://www.ebay.com/itm/Etymotic-ER4P-to-ER4S-6-35-to-3-5mm-resistor-adaptor/281224427556?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D19839%26meid%3D4069148601728015096%26pid%3D100005%26prg%3D8934%26rk%3D3%26rkt%3D5%26sd%3D290372905689%26

Click to expand...

So this noise floor you speak of, is it considered normal for AV receivers?
 
I'll look into those resistor adapters/cables.

Manbear is right - that could be the issue. Some receivers simply put resistors between the main output and the headphone jack to reduce the voltage to a reasonable range for headphones. I'm not really clear on how adding even more resistance between the amp and the headphone drivers helps the amp, but it very well might - I really don't know.

The idea is just that the noise floor corresponds to some constant number of millivolts, Adding an impedance adapter will form a voltage divider and reduce that noise floor to hopefully inaudible levels.

But that is only if this is a noise floor issue.

I just now remember that I've fergot telling you about my Sony EX300AP headphones that came with my Xperia Z dont have this issue, or at least not audible for me.
According to some site I've found, they are 16ohms.
 
Following your theory and my basic understanding of physics, I came to the following conclusion. There could be some resistors between the main board and the headphone out.
Say those are 16Ohms aswell. When using my 32 Ohms sennheisers, they will receive 32/48=2/3rd of the ground noise. When using the IEMs, they will receive 16/32=1/2nd of the ground noise. Thus, the noise floor is less audible when using this lower impedance IEMs.
 
Adding this impedance adapter will increase the impedance between the receiver main board and my headphones, resulting in this being 75+16=91ohms. My sennheisers will then receive 32/123 of the voltage, say 1/4th of the ground noise, resulting in it being less audible. 
 
Please correct me if i'm wrong because I only have a very basic understanding of how this works and i'm mostly speculating.

Yep, that's the idea. 

idsardi said:

  First of all, hi. I'm new on this forums as of today. I'm a 19 y/o student from the Netherlands. I study medicine and I'm really interested in Hi-Fi. I hope to have a great time on this forums. 
So, now to the point of this thread. I currently own mostly speaker-based Hi-Fi;
Denon AVR-2113 receiver
Boston Acoustics A25 speakers x2
Boston Acoustics ASW650 subwoofer
Sennheiser HD280 Pro headphone
Sansa Clip+ 8gb + 32gb sdhc
Asus Xonar DGX sound card in my pc
Is this normal with speaker receivers? Does this happen because my headphones are only 64Ω? Is there anything I can do about it? And if it's normal, should I upgrade to a headphone amplifier? 
I'm into Head-fi since some time and i'm planning to upgrade my headphones soon. Also, I really love headphone amplifiers. But if there is a workaround for this, it'd be great. I could wait some time and make a better decision on what to buy.

Click to expand...

How is the PC connected to the Denon, HDMI only?
I think the DG/DGX offer great value for the price, but the DG/DGX sometimes can have some weird issues, you might think of replacing it with an Sound Blaster Z
 
I'm going to guess their is an "issue" with the Denon receiver and Denon does not want to spend the money for warranty repairs for what is really a minor issue.
 
Chances are the Denon receiver's headphone output has a high impedance, which is normal for receivers, if you were looking for upgrading headphones for use with the receiver, you might try getting headphones that are around 120-Ohm to 300-Ohm range.

manbear said:

  Yep, that's the idea. 

Click to expand...

Okay, thanks. I will try this out.
 
Then, if I make this work, will it be worth to invest in an headphone amp still? I probably won't be spending more than 200$ for now, but will it be noticable better than a H/P out of a receiver? If so, do you have any tips for a nice little amp for a starter?

purpleangel said:

  How is the PC connected to the Denon, HDMI only?
I think the DG/DGX offer great value for the price, but the DG/DGX sometimes can have some weird issues, you might think of replacing it with an Sound Blaster Z
 
I'm going to guess their is an "issue" with the Denon receiver and Denon does not want to spend the money for warranty repairs for what is really a minor issue.
 
Chances are the Denon receiver's headphone output has a high impedance, which is normal for receivers, if you were looking for upgrading headphones for use with the receiver, you might try getting headphones that are around 120-Ohm to 300-Ohm range.

Click to expand...

The problem is with my receiver, not the PC. The DGX works fine, except for the fact that my pc doesnt automaticly switch to my front audio ports when I plug in my headphones. The receiver is connected through HDMI from my HD6950 graphics card. Also, I run an SP/DIF coaxial cable form my Asus Xonar DGX to my receiver, but i'm not using it at the moment.
 
So I thought running the sound from the DGX to the receiver, and then to the headphones would leave me with the highest possible SQ in this situation. Also, it would eliminate the automatic switching problem, as my receiver does automaticly switch to H/P-output whenever I connect them.

idsardi said:

Okay, thanks. I will try this out.
 
Then, if I make this work, will it be worth to invest in an headphone amp still? I probably won't be spending more than 200$ for now, but will it be noticable better than a H/P out of a receiver? If so, do you have any tips for a nice little amp for a starter?

Click to expand...

If you are happy with the sound, then I'd just hold off on a headphone amp. The only significant issue is damping factor. Dynamic headphones like the HD-280 have different impedances at different frequencies. Thus, the voltage divider value will be slightly different at different frequencies, changing the frequency balance of the headphones. If the HD-280 impedance doesn't change very much, this effect might not be noticeable. Even if it is noticeable, you might find it pleasant. No headphone has perfectly flat frequency response to begin with, so it's not necessarily a problem. 

However, a headphone amp with a low output impedance will minimize this voltage divider effect and give you a frequency balance closest to the "native" balance of the headphones. 

If you want to get an amp anyway just to experiment with a different sound, some popular choices are:

Schiit Magni
Schiit Vali (though this amp has some noise floor issues of its own)
Little Dot 1+
Bravo Ocean
one of the Garage1217 amps

That said, I think the money would be better spent on upgraded headphones before you start getting into amps. 

idsardi said:

 
The problem is with my receiver, not the PC. The DGX works fine, except for the fact that my pc doesnt automaticly switch to my front audio ports when I plug in my headphones. The receiver is connected through HDMI from my HD6950 graphics card. Also, I run an SP/DIF coaxial cable form my Asus Xonar DGX to my receiver, but i'm not using it at the moment.
 
So I thought running the sound from the DGX to the receiver, and then to the headphones would leave me with the highest possible SQ in this situation. Also, it would eliminate the automatic switching problem, as my receiver does automaticly switch to H/P-output whenever I connect them.

Click to expand...

As the Xonar DGX only has a S/PDIF optical output, not sure how you are able to use a coaxial cable?
Have you tried running an analog audio cable (3.5mm to RCA) from the DGX's green 3.5mm jack to the RCA inputs on the Denon receiver, see if you still get the hiss problem.
 
Might try asking about the hiss issue on this thread, someone might know an easy fix.
http://www.avforums.com/threads/denon-avr-2113-official-owners-thread.1719371/

purpleangel said:

  As the Xonar DGX only has a S/PDIF optical output, not sure how you are able to use a coaxial cable?
Have you tried running an analog audio cable (3.5mm to RCA) from the DGX's green 3.5mm jack to the RCA inputs on the Denon receiver, see if you still get the hiss problem.
 
Might try asking about the hiss issue on this thread, someone might know an easy fix.
http://www.avforums.com/threads/denon-avr-2113-official-owners-thread.1719371/

Click to expand...

I'm sorry, I meant to say optical but my brainfart made me write coaxial.
> Yeah, the cable running from my DGX is S/PDIF optical.
 
The hiss also is always there, whether I'm using HDMI, S/PDIF, RCA, Internet Radio, USB device or whatever. Also when I remove them all, the hiss is there. It's also no ground loop, I've checked.
 
I've tried the mini>double rca cable, the hiss is still there. I'll ask the AV-forums. Somebody posted the same question on there and didn't get a reply, but it might be worth a try.