[mrdon]

I have had my Icon now for about two weeks. I listen to it at my desk while I am working. 90% of the time I use the USB input for Pandora, iTunes, and BBC World Service streaming from my MacBook Pro. On Friday I did some long term listening through one of the two analog inputs and I noticed two things:

1. Gain is a little hotter on the Analog inputs; that is, for an identical listening level, I would have it at 2O'clock for USB and 12 O'ClocK for the analog input.
2. There appears to be more air and detail on the analog inputs.

This is not a criticism but an observation which has made me curious as to why this is? Could this be a results of the "1.83 nanoseconds (1830ps) of word-clock jitter" John Atkinson reported in his Stereophile review of the Icon? Let's face it. That is high and I can imagine it could be the culprit here. If so, this is the weak link in this rather exquisite device.

[srb]

Are you listening to the same sources - Pandora, iTunes and BBC - from the MacBook analog (headphone) out versus the MacBook USB?
 
Steve

[mrdon]

No. I was listening to identical songs (file) but through a different device - which is my whole house audio system with many more variables in the signal chain and in theory a lesser quality source.

I was not expecting much difference but it was different and the analog inputs sounded better to my ears.

[Katronix]

I have also noticed this phenomena.  Both Icon amps are now using the RCA's.  Played around with many different sources and setups (I wanted to like the usb solution for simplicity sake) but kept coming back to the RCA's not believing my ears at first.

I would like to share that the source is so incredibly critical for these amps.  On-board sound from a motherboard sounded horrid.  Dedicated PCI high-end card not much better.  Even high-def pcie-x cards were introducing noise.  The magic key for me was a sound dac that was Outside the system that routed the front and rear channels independently to the amps.

[rustydoglim]

Those computer designers don't pay much attention to optimize for audio performance so not surprising that even onboard sound card doesn't sound good due to system's noise.

Try using ASIO driver (asio4all.com) to replace Windows Audio device driver. That should help to improve the USB sound quality.

[mrdon]

Jason,

Thank you for your response and suggestion.

However, I would only use Windows if I was on a desert island with no other choice.

Therefore, any suggestions for Mac OS X?

Thanks!

[rustydoglim]

I am not familiar with Mac but there is a lot of discussion on head-fi.org forum about uDAC and Mac. I think on Mac you don't have to do anything to optimize the USB output.

[mrdon]

Thank you for the link. I will check it out.

However, this still doesn't answer my original issue. Why does the USB input have a lower gain than the analog inputs?

[rustydoglim]

We have to balance the gain between the two input sources so that's just a design compromise for Icon.