PauloJosé Contributor - Level 2 2018-10-03

2018-10-03

XR18 Hi-Z Inputs: what they're really for?

Hi! I bought a XR18 mixer (haven't received it yet) and after searching a lot I couldn't get to a consensus about Hi-Z Inputs 1 & 2. I still have some doubts about it.

1) Hi-Z Impedance means that it is designed for high level signals, right? So, it means that signals that are higher than line level should be plugged into this input. If this is right, then what type of instruments should be connected to this input? The manual shows a Acoustic Guitar and a Bass. But a passive bass, electric guitar with no active pickups, shouldn't be connected to a line level? Do acoustic guitars have a high level signal? And what about keyboards, are they line level?

2) Why balanced signals have a higher impedance than unbalanced?

Basically, I know now exactly what type of instruments should I connect to Hi-Z input.

  • 0 Kudos
  • 16 Replies
  • Reply
Contributor - Level 2

Re: XR18 Hi-Z Inputs: what they're really for?

Thank you for explaining it! I've already tested my new mixer and I'm loving it, so far one of the best investment I did. Idk if I should post a new topic, but I have one last doubt not related to this post. While I was testing the inputs, I thought something that I never did with non-digital mixers. What is the correct way to unplug a mic or instrument if the console still needs to be on? The best practice would be to connect everything before turning the mixer on and unplug everything after turning the mixer off, but what if I need to plug the mic that was in a channel in another? I though this when I saw the gain level while plug/unpluging a mic. E.g: If mic gain is really high and I unplug it while mixer is on, is there a risk of damaging the channel (supposing an extreme situation)?
Contributor - Level 3

Re: XR18 Hi-Z Inputs: what they're really for?

No risk of physically damaging a channel, but you could clip something, and that would sound bad. You'd also get some nasty cracks and pops whereever that channel is routed (FOH, monitor wedges, and IEMs, which could damage downstream equipment\peoples' ears.

Mute the channel(s) (and\or the outputs) before you start moving cables around, don't un-mute them until everything's plugged in again. The meters will still be active even if a channel is mutes, so if you plug something in to a muted channel, the meter will tell you if the gain is too high, and you can adjust the gain down to a sensible level before un-muting the channel and letting it through the rest of the system.

My process would be:
Mute both channels (the one the cable is coming out of and the one the cable is going into.)
Re-patch the cable.
Check meters and adjust gain levels accordingly (and perhaps copy\paste\re-set processing if applicable.)
Un-mute channels.
Continue adjusting channel processing if applicable.

Also ensure you mute channels before playing with +48v. The last thing you want is a massive pop going through someone's IEMs straight to their eardrums.
Contributor - Level 2

Re: XR18 Hi-Z Inputs: what they're really for?

Thank you Craig, that was what I thought.

One last doubt (I swear this time, c'mon guys, u know it feels to have a new "kid" at your setup). Is it okay to put it in the case after using, even if XR18 is still hot?
Contributor - Level 3

Re: XR18 Hi-Z Inputs: what they're really for?

That'll be fine. It's not like it's going to get any hotter (unless you leave it in the sun for hours on end.) As long as you're not *using* it inside a case, it's all good.
Contributor - Level 2

Re: XR18 Hi-Z Inputs: what they're really for?

An old thread, but since I'm new...:

Can I damage anything by plugging an instrument into channels 3-16 instead of 1-2? If the guitar was Hi-Z when I thought it was Lo-Z for example. I haven't decided exactly how to mix our band, but if I know I don't have to (or rather, ABSOLUTELY have to) use 1-2 it's good to know.

Highlighted
Super Contributor - Level 2

Re: XR18 Hi-Z Inputs: what they're really for?


@Sverker wrote:

An old thread, but since I'm new...:

Can I damage anything by plugging an instrument into channels 3-16 instead of 1-2? If the guitar was Hi-Z when I thought it was Lo-Z for example. I haven't decided exactly how to mix our band, but if I know I don't have to use 1-2 it's good to know.


@Sverker 

Hi Sverker, you would not damage anything by plugging an instrument into non-Hi-Z inputs but it may sound strange if the instrument has a passive pickup.

 

Most passive pickups work best with an input impedance of around 1MOhm. If you want to use normal (Low-Z) inputs for these, connect through a DI box - like a Radial SB-1 or Radial Pro48. I also connect active pickups, pedal outputs and keyboards to the mixer through DI boxes. This reduces noise from long unbalanced cables and usually sounds better.

 

An unamplified piezo pickup works best with a 5-10MOhm input impedance. I often use a Radial SB-4 to connect these.  

Contributor - Level 2

Re: XR18 Hi-Z Inputs: what they're really for?

@RexBeckett Thanks a lot for your reply.