[headphonatic]

  If your Dac is self powered, cut the red / red + black wire in the Usb cable, this got rid of noise for me.  Of course make sure it's a cheap usb cable.  Since I have upgraded my motherboard to one with a usb power disable feature (Gigabyte Z87 G1 Sniper) has worked wonders and I no longer hear noise.   

I've tried that, now I'm getting a single frequency from my comp, it plays music, but the external sound is extremely annoying.
 
It stops after a while when I'm not playing music, but starts once I play something. 

 

[StanD]

  I've tried that, now I'm getting a single frequency from my comp, it plays music, but the external sound is extremely annoying.
 
It stops after a while when I'm not playing music, but starts once I play something. 

Shaolin monk? We know where David Carradine ended up.

That last part of "It stops after a while when I'm not playing music, but starts once I play something" is an interesting clue. Did you cut the ground wire in the USB cable? That can't be good. Roughtly which spurious frequency are you hearing?
You might want to try another computer in the loop, perhaps visit a friend and give it a go.

 

[headphonatic]

  Shaolin monk? We know where David Carradine ended up.

That last part of "It stops after a while when I'm not playing music, but starts once I play something" is an interesting clue. Did you cut the ground wire in the USB cable? That can't be good. Roughtly which spurious frequency are you hearing?
You might want to try another computer in the loop, perhaps visit a friend and give it a go.

Yes, I cut the ground and the vcc, and the original sound disappeared. The frequency is roughly around 1000-2500 Hz, a mix of tones around that range. I tried the same setup on my laptop and there was no sound, but the device didn't work either.
Using it on a seperate desktop has the same effect.

 

[fluidz]

  I've tried that, now I'm getting a single frequency from my comp, it plays music, but the external sound is extremely annoying.
 
It stops after a while when I'm not playing music, but starts once I play something. 
 

 
Hi,
 
I had the same issue when cutting both the ground and power wires, a sine wave sound that appears whilst the dac is active, hence why I mentioned both methods in my post.  Did you try cutting the power (red) alone first? 

 

[StanD]

   
Hi,
 
I had the same issue when cutting both the ground and power wires, a sine wave sound that appears whilst the dac is active, hence why I mentioned both methods in my post.  Did you try cutting the power (red) alone first? 

That might be worth trying but if it's ground related cutting wires may not be the answer.
 
Another possibility is using a USB to optical SPDIF adapter, assuming one's DAC has an optical SPDIF input. That is assuming the problem lies in having a ground between the PC and DAC/Amp.

 

[headphonatic]

   
Hi,
 
I had the same issue when cutting both the ground and power wires, a sine wave sound that appears whilst the dac is active, hence why I mentioned both methods in my post.  Did you try cutting the power (red) alone first? 

Yes, I tried cutting red first and nothing changed. Only after cutting the black did the noise stop, but the sine wave came up shortly afterwards.

  That might be worth trying but if it's ground related cutting wires may not be the answer.
 
Another possibility is using a USB to optical SPDIF adapter, assuming one's DAC has an optical SPDIF input. That is assuming the problem lies in having a ground between the PC and DAC/Amp.

I'll take anything right now. I checked and my DAC does have an optical SPDIF input.

 

[StanD]

  Yes, I tried cutting red first and nothing changed. Only after cutting the black did the noise stop, but the sine wave came up shortly afterwards.
I'll take anything right now. I checked and my DAC does have an optical SPDIF input.

I bought a "NuForce U192S is a High-Performance Asynchronous USB to SPDIF Converter" on impulse a few weeks ago. I tried it once between my sources and Bifrost DAC and it worked, I can't attest to its SQ as I didn't listen extensively but it seemed OK. It draws power so if you connect to an Android Device or iPod you will need a Hub to power it. A USB port from a PC should power it fine, my laptop worked fine with it. So if your PC is the source of the problem, then that breaks any electrical connection between your PC and DAC->Amp. I would still try to resolve the problem at the source and hopefully not lose my mind in the process. We're all rooting for you.
http://www.amazon.com/NuForce-U192S-High-Performance-Asynchronous-Converter/dp/B007XIK39A

 

[Nevod]

Does anybody own at once a good voltage-out amp and a current-out amp? I'm wondering about possible differences in external noise isolation between these kinds of amps.

 

[Loquah]

Can you explain what you mean, Nevod?

 

[Xenophon]

  Does anybody own at once a good voltage-out amp and a current-out amp? I'm wondering about possible differences in external noise isolation between these kinds of amps.

Not sure if I understand, the vast majority of amps are voltage-driven.  The one exception that comes to mind is the FirstWatt F4, that's a pure current buffer with <1 voltage gain.  Relies on the gain provided by the preamp for functioning though.

 

[Nevod]

Can you explain what you mean, Nevod?

 
I've had an (unfounded) thought that perhaps, current-out (i.e. very high output impedance, current source) amps could increase isolation in open-back isodynamic headphones by "stabilising" the membrane, counteracting EMF created by external sound on the membrane. It's unfounded and I can't erally unwrap the idea to figure out how it should be in theory, so I wanted to hear from anyone who have tried an current-out amplifier.

  Not sure if I understand, the vast majority of amps are voltage-driven.  The one exception that comes to mind is the FirstWatt F4, that's a pure current buffer with <1 voltage gain.  Relies on the gain provided by the preamp for functioning though.

Yes, most amps are voltage amplifiers, with low output impedance. Some however, are voltage-controlled current sources, with output current proportional to input voltage and high output impedance. Current buffers are not these, as they have low output impedance. IIRC, the FirstWatt FW1 was/is a high output impedance design.

 

[nserra]

I have the HE-500 since January and I'm really happy with them. I use them with a Audio GD NFB-28 in balanced mode and I think It's a great combo for not a lot of money. In the past I had the Audeze LCD-2 which are really good also, but finally when I bought the Hifimans, I sold them, because they were quite uncomfortable for me, and the sound signature was not of my preferences.
 
I also tried the HE-6 and they are great, but they need sooooo much power that even my Audio GD which is really powerful can´t push them to the 100%.

 

[Utopia]

Great rig, nserra! That's probably one of the most cost-effective, close-to-summit-fi rigs one can get.

 

[Xenophon]

   
I've had an (unfounded) thought that perhaps, current-out (i.e. very high output impedance, current source) amps could increase isolation in open-back isodynamic headphones by "stabilising" the membrane, counteracting EMF created by external sound on the membrane. It's unfounded and I can't erally unwrap the idea to figure out how it should be in theory, so I wanted to hear from anyone who have tried an current-out amplifier.
Yes, most amps are voltage amplifiers, with low output impedance. Some however, are voltage-controlled current sources, with output current proportional to input voltage and high output impedance. Current buffers are not these, as they have low output impedance. IIRC, the FirstWatt FW1 was/is a high output impedance design.

You're right about the F1/F1-J, very unusual design that is.  And you might be onto something, at least theoretically a current source *could* give you most control as it allows you to put aside many of the elements at play that determine a voltage source interaction with the driver.
 
Have you read this?
 
http://www.firstwatt.com/pdf/art_cs_amps.pdf

 

[StanD]

  You're right about the F1/F1-J, very unusual design that is.  And you might be onto something, at least theoretically a current source *could* give you most control as it allows you to put aside many of the elements at play that determine a voltage source interaction with the driver.
 
Have you read this?
 
http://www.firstwatt.com/pdf/art_cs_amps.pdf

That paper is biased to their point of view. The part about overdamping produces less bass is manipulative as damping keeps the bass tight and accurate, underdamping results in what many call flabby bass. There is nothing bad about an amp having a very low output impedance. A current mode amp can have distortion and nonliearities, it is not magically cleaner than another design, that is up to the individual design. The part about tubes, SS amps and transistor radios is another weak attempt at manipuling the reader's opinion. Some of that paper is interesting.