Splitting a Line Out Signal to 2 Different Inputs

[shanethiede]

Hi all,

I'm pretty new to electronics design, but I'm working on a monitor controller/signal analyzer project and I have a question on splitting a line level signal.

So I want to take a line level signal output from my interface and simultaneously run it to both an ADC for a signal analyzer on and also to my monitors for playback. I'm vaguely aware that the issue with just splitting the output cables and connecting em to the inputs is that there'd probably be different impedances for both those paths, and that could degrade my signal quality in some way.

Am I on the right track with my thinking there? Or does that not really matter? If it does matter, then my next vague thought is to add an op amp circuit for both paths so each path will only have to deal with the impedance of its specific output. Does that thinking also make sense? Definitely feel like there's something I'm not understanding fully, but can't put my finger on it.

Appreciate your help!

 

[Newmarket]

What are the input impedances of the ADC and the monitors (presumably these are powered monitors) ?

 

[shanethiede]

I don't know the impedances and can't find any info in the documentation... the ADC is the HiFiBerry DAC + ADC, and the monitors are some Focal Alpha 50s going through a JBL SR310S subwoofer that handles the crossover. But I'd like to upgrade my monitoring in the near future so that's even subject to change.

 

[JohnRoberts]

There are multiple issues to consider. First you don't want to overload the output. Second if you use a hardwire mult (Y connection), if one of the loads is not balanced, it can imbalance both, compromising CM noise rejection.

Most line level inputs are high enough impedance that paralleling two should not cause catastrophic problems. Some consumer/prosumer gear have higher source impedance than pro gear.

Have tried it to see what happens?

JR

 

[scott2000]

https://www.focal.com/sites/www.focal.fr/files/shared/catalog/document/fp_alpha_50_evo_en_0.pdf
file:///C:/Users/user/Downloads/LSR_3Series_OwnersManual_Mar10_2014.pdf

https://www.hifiberry.com/docs/data-sheets/datasheet-dac-adc/

 

[Tubetec]

I never had an issue with splitting an out into 2x25k balanced loads ,
I did go to a small studio once , the guy thought because his monitors had both XLR and balanced Jacks he could feed in two inputs
Everything was loaded down and distorting , he was a little imbarressed when I plugged his shitty graphic EQ out and the levels jumped up and everything sounded much better .

 

[emrr]

Wow this just came up recently

https://groupdiy.com/threads/line-level-splitter.82684/#post-1069233

 

[shanethiede]

There are multiple issues to consider. First you don't want to overload the output. Second if you use a hardwire mult (Y connection), if one of the loads is not balanced, it can imbalance both, compromising CM noise rejection.

Most line level inputs are high enough impedance that paralleling two should not cause catastrophic problems. Some consumer/prosumer gear have higher source impedance than pro gear.

Have tried it to see what happens?

JR

Parts are still on their way to me so I haven't tested it out just yet. Just didn't want to test it out without a sanity check in case it'd destroy my apollo, but I guess if I can assume high general input impedance then I can just give it a whirl to see what happens.

Upon further inspection I bought the hifi berry board that doesn't accept 2 balanced inputs though... Just 2 unbalanced. shoot. I guess that's what I get for trying to get the cheaper option. Any advice on dealing with 1 balanced load and 1 unbalanced? Or should I just buy the other one and deal with the return?