Quote: Sorry, whenever I found the compressed file was not good, I simply replace it with higher rate (use 320k as my standard recently) or use lossless. Never paid too much attention to this, thus I can't point you the the song. Some recordings are pretty bad, so I just learned to live...

Doesn't sound like ground loop. It seems to me that your i-Qube has very high impedance internally but has insufficient shielding. Therefore, it picks up very weak noise/interference and amplifies it. The buzzing sound is the 50 or 60 Hz AC frequency.   Is your DAC's chassis grounded...

If you have poorly recorded/compressed music, go with HD555. HD555 will smooth the music out and make it more pleasant to hear. Otherwise, AD700.

While HD650 gives you more bass, the "emotion" comes in Grado headphones.   I know a lot of people dislike this, but can't you use equalizer to adjust the sound to your like? Theoretically you can get similar sound signature as most of the headphones.

Maybe it's the music you listen to? Signal quality loss is related to the source signal, sometimes the loss is not that high at all, while the same bit rate can have intolerable distortion/loss for other signals. This is why VBR is more efficient than CBR compression.   As my conclusion, I...

Quote: Exactly! If you like it, just enjoy it and forget about those other things. The key is that you have fun.

  Quote:   Depends. Power supply decoupling capacitors have so much margin in capacitance (well, if the design is done correctly), the change really doesn't matter to the performance. DC blocking capacitors are also selected in similar ways, only the very low end in frequency might be...

Most modern designs using solid state components should not change. Especially with Op-Amps, where passive components (resistors and capacitors) determine the response. Those passives don't change.

That's a surprise. I tested his Predator side by side with my design using HD650, which is 300ohm impedance, both drove the HD650 to unpleasantly loud level. It's hard to believe with 600ohm it will be too weak (only 3dB lower power). Maybe he meant the gain was not high enough in the design...

I don't know ipad's design, but this sounds like it's using some current output type driver, which doesn't like to see high impedance loads. As a simple experiment, use a splitter and connect a pair of headphones in parallel with the amp input, so ipad sees some lower impedance loads. If you...

Can you try with higher volume setting on ipad and lower volume on the amp? I guess that lowers the noise level.

Thanks. It seems to be a decent place to buy. Don't know why HD650 is much more expensive now comparing to a couple of months ago. I guess I purchased at a bad time.

Hi, I just bought a pair of HD650 from Amazon market place (from Sarjo Wholesale Group and Fulfillment by Amazon). I'm a little bit concerned whether this is counterfeit because I hear a lot about those counterfeit these days. Does anyone have experience with this seller? Is there anyway to...