I’ve got a modi/Magni 2 stack for headphones and I want to be able to output to powered speakers. Ideally use the Magni volume to control the speakers. So I need to switch the output after it leaves the Magni.
You don't switch the output "after" it leaves the Magni2, you need an amp that can internally switch where the signal goes - headphone amp output stage or goes from the preamp stage then straight back out. Like the preamp output on the Magni2 Uber, Magni3, Asgard2, Valhalla2, Lyr2...
But this does not seem like a great idea what with the single headphone jack output.
You're not supposed to run a signal through an active preamp and then run it through a headphone amp's output stage before feeding into the line input of a speaker that isn't a high level (ie amplified signal) input that can step down the voltage, something that is very rare. Off the top of my head only car audio amps and processors designed to work with stock receivers/CD players can do that.
What other options do I have?
Get a Magni3 or any other HPamp with a Preamp output.
What do I need to add to this setup?
Get a Magni3 or any other HPamp with a Preamp output.
Like can I switch when it leaves the dac? I’d need another volume control for the speakers but I can handle that. The Schiit Sys almost works but it’s backwards - two ins one out.
The Sys is a passive unit so it can be wired backwards. Just make sure that if you do then both sides are consistently running the other way around.
Still, why add a third box when all you need is to have a preamp output? The Sys is labelled that way because the main idea is to be able to integrate a TT with a primarily digital (ie only one input on the amps) ecosystem like Schiit's.
Magni3 is interesting but the line out doesn’t help me bc I want to use it to control the volume. Right?
Wrong. If the output is labeled a "Preamp Output" then the signal goes from the input stage, through the preamp stage (the most visible part of that is that you have a volume knob out in front, ie, the potentiometer being the key component), then back out bypassing the headphone amp output stage. The same potentiometer will control the output voltage.
Also I’d need to unplug the headphones to kill the sound to them, so at that point I should just plug the speakers in.
The input sensitivity of a powered monitor's inputs may not necessarily work their best with a high level amplified input signal. Also any amp output stage has a tendency to add noise, which will be part of the signal that will be amplified by the succeeding amplifier circuit. Amp's don't work like science fiction weapons such as the ZGMF-X20A Strike Freedom or GAT-X103 Buster connecting two beam rifles to increase range or two beam cannons for increased power output because noise is a thing (let alone the parallel beam cannons and rifles on the Gundam Virtue and Wing Zero), plus it doesn't actually even add power to the second output stage to prevent it from clipping.
Also, even for the reason cited, it doesn't work that well. If you think pulling a headphone plug out is too much work, now you have to do double the work - pull headphone plug out, plug in speaker cable (or vice versa).
If you really don't want to waste any calories for that then there's an alternate option: sell all your Schiit and get an AudioGD NFB-11, which has an output switch on the front panel. Just make sure you flip it to the center position for variable (ie preamp controlled) output.
