Schiit SYS Passive Preamp

Discussion in 'Headphone Amps (full-size)' started by barry s, Mar 25, 2014.
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  1. Alcophone
    Technically you could use a second SYS in reverse to do the output selection, but of course that's an extra box, extra cables, extra money, etc.
     
  2. gvl2016
    That would connect 2 pots in parallel to the ground - half the resistance. I'd prefer just a 2x2 matrix switch in the same form factor if I were to add a new box, or just an A/B switch but would be nice to have all in one box.

    2 switchable outputs one fixed w/no volume pot in the path and one variable, no volume bypass switch, should be safer and satisfy my initial goal. Variable for active speakers/fixed for a headphone amp with its own volume control.
     
    Last edited: Dec 19, 2017
  3. Alcophone
  4. gvl2016
    It can definitely be done, but I don't have room for even one extra box on my desk. I have a plan, should be an easy SYS mod no metal drilling required, I will sacrifice one input and make it into a fixed output as I don't typically use the 2nd input anyway. Need to open it up and see how messy it will be to rewire the switch to instead of switching the inputs it will hard-wire one input to another and disconnect the volume pot at the same time, looking at the PCB picture on Schiit web-site it shouldn't be too bad.
     
    Last edited: Dec 19, 2017
  5. gvl2016
    For those who refuse to use Schiit SYS in reverse introducing SOS - Switch Outputs with SYS,

    Skill level: basic soldering and screw-driving skills
    Tools needed: Philips screwdriver, X-ACTO Knife, soldering iron, solder, flux, single-strand copper wire AWG 28-30
    Time required: 1-2 hours

    1. Cut the 2 printed conductors connecting the pot with the switch on the top side of the board:

    DSC_3157.JPG

    2. Cut the 2 printed conductors on the bottom side of the board connecting Input 1 with the switch. Install jumpers as shown:

    DSC_3158.JPG

    3. Finished product:

    DSC_3160.JPG


    Code:
    ---------------------------------------------------------------------
    PUSH BUTTON : FIXED OUTPUT     : VARIABLE OUTPUT
    ---------------------------------------------------------------------
    Out         : Disconnected     : Connected to IN1 via pot (no change)
    ---------------------------------------------------------------------
    In          : Hardwired to IN1 : Disconnected
    ---------------------------------------------------------------------
    
     
    riffrafff and KewlMunky like this.
  6. KewlMunky
    Very interesting. Something like this would be nice to switch between a pair of active monitors and a headphone amp running off the same DAC.

    Have you tested sound from the variable output to check for signal degradation?
     
  7. gvl2016
    That's exactly why I did it, I have a power amp w/no volume driving passive speakers and a headphone amp with volume control. There is no more signal degradation on the variable output than originally as that circuit is technically unchanged.
     
  8. Naugrim
    I just ordered one of these bad boys. My system will go Computer - Gumby - Mjolnir 2 (to headphones) - Sys - Vidar - KEFLS50. I'm using the Sys with no other device - basically it give me the ability to switch off of the channel with the speakers and Vidar on it so that I can listen to headphones only at times. Does this make sense? Is there a better solution?
     
  9. redrich2000
    While we're on wish lists... would it be possible to have the Loki and Sys in the same enclosure?
     
  10. gvl2016
    Did you check if Mjonir already cuts pre-outs when the headphones are connected? If not and you want to keep the Vidar ON, you're adding a passive pre-amp where you don't need one. I'd use something like this instead: https://www.amazon.com/Three-Way-Ta...itch+Box+Metal+Case+With+Non-Skid+Rubber+Feet
     
  11. KewlMunky
    +1

    Why the need for the switch at all, though? If the user just wants a headphone output and a pre out to Vidar, Mjolnir cutting the pre out when headphones are plugged in is already providing all the switching they should need.
     
  12. gvl2016
    Does it actually cut the pre-out? I don't know, I looked at the manual it doesn't specify.
     
  13. Naugrim
    It doesn’t. Sucks.
     
  14. KewlMunky
    Well that's no fun. Do you intend to leave Vidar on at all times? I have both my headphone amp and powered monitors connected to my DAC/preamp and just leave the headphone amp off when using the monitors, and leave the monitors off when using my headphones and headphone amp.
     
  15. Naugrim
    I’ll leave the Vidar on all the time because it won’t be in a convenient location to power on/off all the time. I’ll also leave the Gumby in all the time. The headphone amp I’ll turn on and off.
     
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