You've sort of got a bit mangled in the understanding.

¼", RCA (UK phono) and sometimes even XLR have two properties - impedance and level. Microphones and a few XLR outputs on professional gear are low impedance (250-600 Ohms typically) and usually balanced - so a ground plus a hot and cold, or +/- or pin 2 or 3 - the signal, being AC has a two wire connection. grounds are separate.

RCA/phono and ¼" jacks are mostly high impedance - BUT - they are working at a lot higher a level. A tape deck, CD player, VCR and other line level gear sit at around .7V when loud - some equipment is at a 'pro' level of double that.

Mics, at the other end produce very little voltage. 100ths of a Volt or even lower. Line level can be balanced (on XLRs or 3 circuit jack plugs) or it can be unbalanced with a hot audio line but sharing the other audio line with the ground. Phono/RCAs are two circuits, so unbalanced.

Keyboards, guitars and organs are usually at a higher level than mics, but not all are even .7V - guitars and some synths designed to be connected to guitar amps are a bit lower. Above mics, but below say, a CD player.

Plug an organ into a mic input and two things are wrong. The impedance is wrong, and the level is too high. It means a mic gain knob might need to be set to 1 on scale of 1-10, so might distort. Impedance comes in three typical varieties - mic impedance, so 150-600 or so, electronic equipment high impedance 50 thousand Ohms or so. Some guitars use piezo pickups and their impedance can be up to a million Ohms!

Matching is important for noise and distortion free recordings. DI boxes allow you to stuff a high level, higher impedance source into a mic socket designed for low level, low impedance mics.

Synths go to line inputs, and will be unbalanced, mics go to balanced XLRs normally.

It's considered bad practice to put synths and line level stuff on a patchbay and also put your mic level things there too. You can do it, but mic inputs with 48V phantom power could easily be patched back to your synths by accident. will it like having 48V stuffed up it? probably not. Don't forget that patch bays are also normally - the idea being that you design the wiring so that everyday stuff does not need patch cables - the unusual connections are when you slap in the patch cables. If your synth always comes gets patched to inputs 1 and 2, then you arrange the normalising of the patch bay to connect top row 1 and 2 to bottom row 1 and 2 - UNLESS you want something different.

Thank you.

Thats a lot to digest. I'm going to print it out, and read..and re-read.

So far so good. My sound is much cleaner than my last studio set up. Iv'e got nearly no noise right now.

From what I gather, if I do plug in something wrong, there will be tell tale signs; like clipping with the gain barely turned up,

or an audible noise floor ( if I even used that term correctly) .

A few more questions, if you would be so kind.

1.I assume the red clipping lights at my mixer channels fire up when there is too much voltage? or is it something else...like current?

2.Is the best practices for patchbays simply to protect against accidents? Because I really need patch points... Except for the mics. I dont see me needing to move those signals around. So keep the mics out of the patchbays, and i'm good?

3. Uh...my interface...  XLR/multi's in, and TRS out.  That makes me think the output is intended for a mixer line input?

I have always been able to plug in a ton of stuff and make it work. People seemed to be amazed. I guess a lot of equipment is made to accommodate non-professionals. Doing it correctly really takes a lot of knowledge and understanding . Thank you for the info.

-Brian

In general, red lights are warnings. Over level, so it’s too much Voltage. The thing is that when you are close to red light level, that’s also the best signal to noise, as in most level for least distortion. Accidentally, a few red flickers mights go through without audible distortion. I have a sneaky suspicion that most digital gear, where distortion is horrible sounding actually make those lights come on a tiny bit before distortion point. In general, though reed light is danger.

if you shove in a jack into your patch bay and the input channel has the gain cranked up from the feeble sound source you last used, then your loud synth will slam the meter to the stop. It happens often, and if it damaged anything, nowadays that would be a seriously poor design. Certainly plugging a loudspeaker level source into the line level mixer would be permanent bad news. Just too much. That said, when I’ve been pushed, I’ve connected a headphone level signal to a line input. It’s bad practice, but if you set the headphone low to start with and set the input gain fully down, you can usually get away with it in an emergency. Same with mic inputs on XLRs, with the correct cable you can feed a line level into the mic preamp if you manage it. So start with the gain right down. Sometimes you just don’t have a DI box, laying around, so don’t be afraid to try these things, just carefully. Before I knew better, I just soldered a jack cable to my guitar speaker and plugged it into my Ferrograph line in. As long as the gain was very low it worked fine. Wrong, of course, but I didn’t know at 16. If you have a patch bay designed properly, everything will just work.  Keep your mics separate, so XLR is low level stuff, jack sockets are higher. Guitar and line can usually be swapped around with little difficulty. Often, even if you get it wrong, it’s just reflected in the sound. Too trebly or no treble, that seems the common result of mismatches. 
 

train your ears to assess sound. The tone and the purity. You can learn to detect distortion even at very low levels. As in, somethings a bit odd here, and then you can turn knobs and fix it.