[rebelx]

I have a QC15 and now the Philips X2/27 Fidelio Premium Headphones. 

Initially, I used my QC15 with in-line mic connected to my PC's soundcard (ASUS XONAR DG Headphone Amp & PCI 5.1 Audio Card) but quickly realized that since the mic and sound are transmitted through the same cable on the QC15, I would need to get a sound and mic splitter cable (Y cable) to plug into my sound card. One side goes into the mic and the other into audio and the QC15 goes into the connector portion of the splitter. It is this item here ("Smartphone Headset to PC Adapter - Use a 3.5mm iPhone/Smartphone Headset With Your PC, Converts 3.5mm Plug to Dual Mic/Audio 3.5mm, for Skype/VOIP (01-PH35-PC35").
 
I no longer use the in-line microphone as I've purchased an external microphone connected via USB; I've disconnected that portion of the splitter. 
 
My question is whether I am losing audio quality by keeping the splitter in place. I treat it as an extension cord since I like to connect my desktop speakers when necessary. I could have the desktop speakers plugged into the PC's onboard audio, but I'd prefer them to connected to the sound card instead. 
 
If I am losing audio quality, is there some alternative method I could use to maintain quality? 

 

[Music Alchemist]

You could compare with and without to see if you can hear a difference. There most likely won't be.
 
By the way, I owned the QC15 for years and eventually discovered that using a normal headphone cable (such as the V-MODA Audio Only Cable) dramatically improved the sound quality of the headphones. This is because the stock cables have electronics that interfere with the signal. I had to wrap toilet paper around the connector shell to keep the cable in place, and the channels were switched due to the active circuitry of the headphones, but it was worth it. That cable costs less than a replacement stock cable, so you should try it (or another normal headphone cable) out sometime. I also found that the audio only stock cable sounded more smooth and less grainy than the remote stock cable.

 

[tinyman392]

Depends on who you ask around here...  The only thing I can see is that it increases the impedance of the cable "system".  Chances are it won't make that big of a difference though.  

 

[money4me247]

no, shouldn't have an audible effect