Asus Essense STX II 7.1 Line-Out question

Discussion in 'Computer Audio' started by RayTrace77, May 21, 2018.
  1. RayTrace77
    Hi Everyone,

    I got an Asus Essense STX II card and can't find any information regarding the RCA out, I want to connect it to a Little Dot MK II using Phono - Phono cables but I'm aware you shouldn't connect an already amplified source to another device than can amplify again.

    I've searched around the internet for the last few days but couldn't find anything regarding detailed specs about the card and weather or not the setup I want to have is ok:

    Asus Essense STX II > RCA(Left/Right) > Little Dot MK II > Fostex THX00

    Any help is greatly appreciated.
     
  2. PurpleAngel Contributor
    The line-output (RCA) jacks on the STX II are not considered amplified.
    They are designed to send an analog audio signal to a line-input jack, not headphones (but would technically drive headphones if needed).
    You just need a cable with dual RCA jacks on each end to connect the STX II to the LD MKII.
     
  3. RayTrace77
    Many thanks for the reply PurpleAngel, I tested that setup, and although the RCA output from the STX II is not amplified I am still able to control the volume from the Windows Asus Audio Center and it can get fairly loud, is this normal as I can then further amplify through the LD MKII ?
     
  4. PurpleAngel Contributor
    I'm not an expert, but i would guess when you up the volume controls in Windows, you could think of it more as a signal boost, to drive a stronger signal (from the RCA jacks of the STX II)?
    Where as the volume knob on the LD MKII is more about headphone amplification, amplification that is directly effecting the diaphragms in the cups of the headphones.
    I would say to up the volume controls (75%-100%) in Windows, to feed a strong signal from the STX II to the LD MKII.
    And just control the volume using the LD MKII volume knob.
    so make sure the volume on the LD MKII is turned way down, before upping the volume control in Windows,
     
  5. ProtegeManiac Contributor
    If you use the FL/FR output of the STX it should have a 2V line out. Even if OS volume control works that affects the digital signal, not an analogue potentiometer (even the headphone amp output stage just runs through an output driver op-amp but it's the digital signal being controlled on soundcards with no analogue volume pot), so just set that to 100%.
     
  6. RayTrace77
    Thanks guys for the responses, I'm starting to get the idea that volume on Windows should be left at 100% going through RCA to the LD MKII, then the LD MKII controls the final volume, I am finding though that there's a loss of volume when doing that, if I plug the Fostex's directly into the sound card's 6.3mm stereo jack it can get very loud, when going through the LD MKII it can't go as loud without muddying the audio in the lows (or that could just be the colouring of the LD MKII)

    For now I've just left the LD MKII out of the equation, the stock STX II comes with 1 x 8820 and 2x 8920's, I am thinking of getting a Muse02 to replace the 8820 to see if it helps.
     
  7. ProtegeManiac Contributor
    An OTL amp has lower output at low impedance. Even if it isn't clipping hard on the Fostex, THD and noise can be higher. Damping factor is also reduced, although not as much with planars compared to dynamic drivers.
     
  8. RayTrace77
    Ah ok yes I read elsewhere that that these types of headphone amps require high impedance headphones to work properly, low impedance headphones (Fostex's are 25 Ohms) while they work aren't best suited, better to use the 6.3mm out from the sound card directly ?
     
  9. ProtegeManiac Contributor
    Compared to the MkII, yes.
     
  10. PurpleAngel Contributor
    The STX II headphone jack has a 10-Ohm output impedance, it would be nice if it was lower, but it's should be considered a fair bit lower then an output impedance of an OTL headphone amplifier.
    25-Ohm headphones (like the Fostex) really should be connected to a solid state headphone amplifier with an output impedance of around 3-Ohms or less.
    With connecting 25-Ohm headphones to the STX II, I would guess you would get a slightly bloated (louder, less detailed) bass.
    I would suggest getting a solid state headphone amplifier, like the O2 (Objective 2) or a Schiit Magni and connect it to the STX II line-output (RCA) jacks.
    The STX's line-output bypasses the STX's Dolby Headphone surround sound feature, but you really have no need for that feature with music or movies or any video that only has stereo audio.
    I use PowerDVD for movies, which comes with it's own build in headphone surround sound.
     
    Last edited: May 22, 2018
  11. RayTrace77
    Thanks for the response PurpleAngel, where did you find out about the 10-Ohm spec for the STX II ?, I've been trying to find detailed specs but couldn't. In general terms the output impedance from whatever device your using should be as low as possible compared to the headphones of choice ?

    For the Schiit, is this the one your referencing ? : http://www.schiit.com/products/magni-3
     
  12. PurpleAngel Contributor
    My Essence STX's headphone jack has a 10-Ohm output impedance, a lot of the headphone amplifiers that use the same amplifier chip as the STX (& STX II), have a 10-Ohm output impedance.
    So call it a decent guess the STX II headphone amplifier has a 10-Ohm output impedance.

    The Schiit Magni 3 you listed is the Magni series i'm talking about.
     

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