[a_recording]

Hi guys, I have a bit of a mystery that I am hoping someone with a bit more electronics know how can solve for me.
 
I have a HRT Music Streamer II+ with its RCA outs split, so that one pair of L/R RCA's goes to a pair of active desktop monitors and another pair of RCA's goes to my O2 headphone amp.
 
I've had this set up for some time, but recently after some really critical listening I started to feel that there was some distortion coming from the active desktop monitors that I could hear in the form of warbling in the bass notes and a 'bluntness' to the treble.
 
After connecting the monitors directly to the DAC without using split cables, I felt that the distortion went away. However I couldn't really confirm whether or not it was just a placebo to my ears, until I tried this test file with split cables and without: http://www.audiocheck.net/testtones_imd.php There was a clearly audible warbling in the high frequency tone when using split cables which was not present when just using a direct RCA connection from DAC to the monitors' input.
 
There is no audible distortion on the O2 when using the split cables and at 1x gain. I do know that the HRT Music Streamer II+ outputs a signal slightly above line level (around 2.25v if I recall correctly).
 
Can anyone tell me why I am hearing this distortion when using the split cables? It sounds almost like splitting the cables is causing some part of the amp stage on the active desktop to overload. I am not necessarily looking for a solution, I'd just like to understand why the problem is there in the first place. Thanks!

 

[NA Blur]

The first thing to try is to lower the input voltage to your amp to 75% and use the amp to control the volume from then on.  This will reduce or eliminate clipping as a source of the distortion.
 
The cables also may have some impedance that is causing transmission line issues.  These issues are reflections, attenuations, or complete inversions of the original signal.  Try another set of cables.
 
I bet if you take the splitter, disconnect one of the splits, the monitors sound fine?  This would indicate that there is a reflection from the other split coming back into the other split.
 
Smart money is on clipping.

 

[a_recording]

Thanks for the suggestion! 
 
I do feel that its a clipping issue. I'm just wondering, why would splitting the cable cause the signal from the DAC to increase in voltage, causing the amp stage on the monitors to clip? I cannot change the volume before it gets to the monitors.

 

[Roseval]

[size=10pt]As you are using a splitter the DAC is facing 2 inputs with 2 impedances in parallel.[/size]
[size=10pt]If you have a resistance of 10 and you add another source also with a impedance of 10 in parallel the total impedance will be 5.[/size]
 
http://www.1728.org/resistrs.htm

 

[a_recording]

Quote:

[size=10pt]As you are using a splitter the DAC is facing 2 inputs with 2 impedances in parallel.[/size]
[size=10pt]If you have a resistance of 10 and you add another source also with a impedance of 10 in parallel the total impedance will be 5.[/size]
 
http://www.1728.org/resistrs.htm

 
So is this changing the level of voltage that the speaker is receiving from the DAC, or the amount of current?
 
 

 

[headfinoob]

I suggest getting an RCA switch. There are good quality switches out there. When you have multiple loads connected to HRT, the voltage is the same, but the impedance it sees is less, so you will have a larger current draw.
The HRT is a fixed voltage, so it is possible you are overloading its current output with too little ok impedance. It is also possible that that there is some feedback from the other device since it would be partially an inductive load.
My advice is to only hook up one device at a time.

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