Switchers - How to properly connect multiple amps to one DAC output

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by rhythmdevils, Nov 7, 2020.

  1. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    TL;DR
    If you need to hook up more than one amp to a DAC the best/right way to do it is to buy a switcher. I will list the best units below for balanced XLR and se RCA.

    It is not safe for DACs to daisy chain amps via “PASS” jacks on the amps from one output in the DAC. Read this thread to find out why.

    Balanced XLR:

    custom number ins/outs

    custom high quality from Mapletree Audio available with any number of ins/outs. This is probably the best most transparent option. But not confirmed.

    LR-1 Pro

    [​IMG]

    “LR 1 Pro Line Router - This is a balanced signal version of the LR 1. The standard model can switch up to 3 inputs and 3 outputs. Additional I/O can be accommodated using special multi-deck rotary switches. XLR connectors are Neutrik gold-plated type with locking tabs on the female version. switches are Lorlin or C&K enclosed rotary types with silver-plated contacts, and wiring is silver-plated stranded copper with Teflon insulation.”​

    Goldpoint 1 in/out 2 in/out
    (this is the next best option)

    Nobsound 1 in 3 out

    Nobsound 3 in 1 out


    SE RCA:

    Custom number of ins/outs

    custom high quality from Mapletree Audio
    available with any number of ins/outs

    LR-1

    [​IMG]

    “LR 1 Line Router - The standard version is designed to switch one of up to three input stereo signals to one of up to three outputs. Other configurations are available to handle up to 6 inputs and/or outputs. Chassis sizes are chosen to accommodate the required I/O connections. As with all the Mapletree switching components, RCA jacks are high quality gold plated with inside and outside hex nuts, switches are Lorlin or C&K enclosed rotary types with silver-plated contacts, and wiring is silver-plated stranded copper with Teflon insulation.”​

    The AliExpress and Goldpoint units are probably the next best. But not confirmed.

    1 in/out 3 in/out

    (it’s passive so you can you can use these either direction)

    these 2 are the best, available on AliExpress in wooden or metal enclosures. The metal is probably better for SQ and cheaper.

    Wooden version

    Metal version

    1 in/out 4 in/out

    Goldpoint SW4


    2 in/out 4 in/out

    Beharesford clone on Amazon

    —————————————————-

    4 in 1 out switcher and passive preamp

    Goldpoint SA4

    —————————————————-

    I posted this question in the general advice thread but got little feedback and I decided that since so many amps especially the popular drop amps have “PASS” jacks, I figured it would be helpful for more people than just me because if those pass jacks are there, a lot of people are going to be using them and given the prices of the drop amps a lot of those people will use them and not have a lot of technical knowledge.

    I am borrowing a Schiit Gungnir A2 MB usb5 from a kind local SBAFer running it via usb and SE until I get XLR cables and a pi2aes.

    I had 3 amps daisy chained to one RCA output on the Gungnir. Which a few people here said was ok to do or use an RCA splitter like this one.

    but after a week or so of turning on the amp. It suddenly started distorting badly. I contacted SCHIIT and they said it was because of daisy chaining amps to one output and I should instead use one amp per output.

    here’s my email to them and their response.

    ———————

    Schiit,
    I’m borrowing a friend’s Gungnir A2 gen5 usb (not sure if you recognize A1 and A2 so if not then it’s a “more recent model”). It’s still under warranty.

    I’m using the RCA se output until I get some XLR cables in. I have it running 3 amps but no splitter cables or switch boxes. The first two amps are the massdrop 789 and Liquid Carbon X which both have SE PASS RCA outputs so I’m stringing the 3 together. I never use 2 headphones at once but I do have 2-3 amps on at the same time occasionally.

    I’m using an iPod 7 with cck adapter as source via usb.

    So it sounded fine for about a week. Then I unplugged my iem’s and plugged in an ortho into my SOHA1 (3rd amp at the end of the daisy chain) and it was super distorted. I thought the tube finally went bonkers in my SOHA1 but when I checked the other amps they all sounded distorted as well. Heavily distorted like blown headphone drivers. I then switched to my massdrop Airist R-2R DAC and there was no distortion.

    I turned off the gungnir for a few minutes and turned it back on and the LED on the furthest to the right was blinking for about 30 seconds which it didn’t do when I first turned it on. I don’t know what this means.

    It has been running pretty hot the whole time, as hot as my SOHA1, and I think I remember reading other people say that their Gungnir’s and Yggdrasil’s ran cool or luke warm.

    I’m writing you for my friend since it happened on my watch. But I haven’t touched the Gungnir since setting it up and first turning it on. It went from sounding fine to super distorted without anything changing except me switching headphones which I had previously done with no problem.

    Any ideas? Is it overheating? Does it just need to be sent in to you?

    Thank you!


    ————————————

    Reply from Schiit:

    “You shouldn't really daisy chain amps to it. The Gungnir has 3 outputs - 2 RCA and 1 XLR. You should really be using them like that, otherwise it will cause distortion and draw power from the DAC. “

    ————————-

    These are passive connections and work even when the amps are off. Does an amp simply being on really draw power from the DAC? I have my RDAC setup the same way and no distortion.

    if I ever own a gugnir I’m planing on using the XLR output with a Passive switch box but I don’t have the XLR cables yet.

    So does anyone know whether Schiit’s response is accurate about daisy chaining amps via the PASS jacks? If so I think a lot of people are making this same mistake.

    BTW, after reading Schiit’s response I bought this RCA switcher. Any thoughts on whether this is a good unit?
     
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    Last edited: Nov 8, 2021
  2. Abhishek Chowdhary

    Abhishek Chowdhary Friend

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    IIRC, the blinking LED is the one that tells you the dac is trying to lock digital signal . My A2 was sometimes instantaneous, othertimes would take 10-15 seconds.
    While never had distortion issue but then I never daisy chained amps to it
    Next time it happens you may want to reconnect digital source (ipod in thia case) or see if the other set of RCA out distorts too. This one looks like a digital signal issue. My older dacs would sometimes do this with usb to spdif converters
    Schiit dacs don't run too hot unless the top plate is choked of ventilation
     
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  3. Armaegis

    Armaegis Friend

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    As mentioned in the general thread, I think you're overloading the output circuit. Those circuits can typically only put out a few mA because they're expecting a very high load impedance. In some rare cases an amp's input impedance may actually be too low for a source and then you wind up needing some kind of buffer. Passthroughs are basically just passive splitters, and going into three amps is likely too much.

    With that much heat being generated, I wonder if there's also possibly a ground offset somewhere causing a constant current draw. Just speculation on my part though.
     
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  4. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    I have drop RDAC 789 and LCX stacked over the ventilation holes on the top of the Gungnir, but the drop DACs/amps have tall feet and I figured that if Schiit stacks their own amp on top of the Gungnir (is it the Jottenheim that’s the same size?) that it was ok. If it’s ok to stack on top off the Gungnir, then It’s fine with the height of the feet of three drop DACs and amps. But I don’t know for sure if it’s ok to stack.

    the heat does worry me because it’s equal to my SOHA1 which seems wrong.

    Thanks. why are they included then? Because 2 is ok but 3 is too much?

    if pass through jacks shouldn’t be used it’s definitely something people should know about.
     
  5. edd

    edd Facebook Friend

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    I use them for hooking up powered monitors, not daisy chaining amps.
     
  6. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    Is that any different? Powered monitor = amp
     
  7. edd

    edd Facebook Friend

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    Yea. I suppose you’re right; though, I don’t go beyond the monitors. Perhaps, that’s pushing things overboard (by hooking up 3 amps)?
     
  8. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    I don’t know but it would be good to get to the bottom of this question.
     
  9. dBel84

    dBel84 Friend

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    Typically, with passive passthrough, the source is seeing the load impedance of both end points , the more you daisy chain, the more these electrical elements change on the load. The primary consideration is the impedance / resistance but capacitance could also become an entity. At some point there could be negative impact on the load or even a filter effect causing unanticipated rolloff.

    The advice you have for using a switcher is spot on. I try never to load any output with more that one load ( not always an option )

    ..dB
     
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  10. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    Great information as usual @dBel84 !

    so to clarify,

    1. is this still the case if only one amp in the chain is on at a time? If I only one amp is on, it’s no different than having a passive switcher in the path no?
    2. This is true even with only one headphone plugged into one amp and 2-3 amps daisy chained and powered on?
     
  11. dBel84

    dBel84 Friend

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    1. The input section is normally passive so the effect is there if on or off.

    2. Yep
     
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  12. loadexfa

    loadexfa Friend

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    Thanks @rhythmdevils , I really appreciate you following up on this while my hands are tied up with stuff. (Everyone else, the Gungnir is mine). I found that it runs pretty hot stacked with the Freya, perhaps I should stop stacking and ensure it has enough airflow. Fortunately I ordered a second audio rack.

    Thank you everyone for the useful into. I assume the same issue would apply to the XLR outputs and I would need a passive switch box like this one? Too bad the Freya doesn't have more than one XLR out. :p
     
  13. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    Sure thing. It’s the least I can do when an issue happens on my watch.

    I’d like to know why your Gungnir runs so hot. I turned it on again after Schiit’s response because it would now be their fault if something else was wrong and they blamed the daisy chaining. And it’s still as hot as my SOHA1 even with nothing connected to it. Maybe I’ll post in the gungnir thread.
     
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  14. rhythmdevils

    rhythmdevils Best SBAF member of all time

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  15. Erroneous

    Erroneous Friend

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    I use the TC 7240 rca switcher from Amazon in my system. Works great, no crosstalk, nice and solid. No complaints from me and I can't detect any audible nasties with it.
     
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  16. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    I guess it’s passive since it doesn’t use power but I’m curious how it’s wired. Too bad these devices don’t have internal pictures.
     
  17. Erroneous

    Erroneous Friend

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    I cracked it open to get some pics for you: https//imgur.com/a/qc9WSkK
     
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  18. Erroneous

    Erroneous Friend

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    Pics here, if it'll let me.
     

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  19. bilboda

    bilboda Florida boomer

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    I don't think anything is wrong with daisy chaining so long as only 1 amp is powered at a time.
     
  20. Armaegis

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    Eh, not necessarily true. Even turned off, it could still be passively loading what the source sees.

    Sometimes in rare cases, a source/preamp's output stage can't even handle the regular input stage of the connected amp. We saw this a couple years ago here, it was a Schiit source connected to an EC (I think) amp, and something with how the input transformers and tubes were all hooked it, it just didn't jive with the schiit. There was some minor hooplah here until they figured it all out.
     
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