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What if the mixing desk has phantom power?


Mudloop
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Hi,

 

I recently played a gig with the Helix, but the PA was kinda crappy, and only had a global phantom power switch. I remember the Helix manual saying to never use the Helix out with phantom power, and since we needed power for the mics, we ended up connecting the Helix to a combo (in the return) and mic'ing that.

 

Good thing we had the spare combo (and mic), otherwise we would have been screwed.

 

How bad would it be if we actually used phantom power? Isn't this a bit of a shortcoming of the helix, because I would assume that there are plenty of smaller venues with crappy PA that only have a global phantom power switch.

 

Are there any little load boxes that could eat the phantom power, that could be used in situations like this? Or would a better solution be to turn off the board's phantom power, and get a dedicated mic preamp?

 

Or should I just ignore that warning in the Helix manual? (probably not).

 

Thanks!

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If you can't turn off the phantom power coming from the mixer, you'll need to use phantom power blockers in the XLR Lines going to the mixer. Or you could use a DI box that blocks phantom power. Or you could use the 1/4" outputs to the mixer. Or you could use the 1/4" outputs to a 1/4" to XLR DI box.

 

Phantom power coming to your Helix XLR outputs will make it sound bad.

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I don't really understand why you would consider ignoring the warning when it's self-evident that phantom power can affect the Helix's signal. The only question, really, is how much it will be affected. But at the very least, it will attenuate the signal from the Helix quite a bit. At worst, it will do that and make it very noisy.

 

Either pick up a blocker/isolator similar to this or use the 1/4" out(s) into a DI box.

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phil_m, can you clear something up for me?  I see discussions in FB about what people describe as "thin tone" or overly bright tone due to phantom power, but that doesn't sound right to me.  Phantom power can introduce noise, sure, but I don't see how it can gut your tone all on its own.  That sounds to me like impedance mismatching, which is something I originally experienced. 

 

For example: My homebrewed IRs were set too loud from my DAW, and my outgoing signal was too hot, going into a mic input from my DI.  I put a 20dB pad on it, and it sounded great.  I then went back and re-leveled my IRs, and now my maxed signal going into the DI with no pad sounds just fine.  

 

TL:DR- overly hot signal going into the wrong type of input can result in FOH dropping your gain to compensate, which results in a thin tone in IEMs or wedge monitors.  

 

I now set my patches to be generally equitable in volume to an empty patch, and now I have no issues with level or noise.

 

Edit: for reference, my output is set to instrument level, I have no pad on the Helix guitar input, and our console has phantom power going to all channels.  My DI is an ART cheapo DI.

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Thanks for the responses.

 

I don't really understand why you would consider ignoring the warning when it's self-evident that phantom power can affect the Helix's signal. The only question, really, is how much it will be affected. But at the very least, it will attenuate the signal from the Helix quite a bit. At worst, it will do that and make it very noisy.

 

Either pick up a blocker/isolator similar to this or use the 1/4" out(s) into a DI box.

 

Well, I would only consider ignoring it if I didn't have another option. I didn't know the warning was about the sound quality, I thought it had the potential to damage the unit, but that maybe it was very unlikely to happen, and just something they added in the manual to cover their asses. This is why I asked.

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phil_m, can you clear something up for me?  I see discussions in FB about what people describe as "thin tone" or overly bright tone due to phantom power, but that doesn't sound right to me.  Phantom power can introduce noise, sure, but I don't see how it can gut your tone all on its own.  That sounds to me like impedance mismatching, which is something I originally experienced. 

 

For example: My homebrewed IRs were set too loud from my DAW, and my outgoing signal was too hot, going into a mic input from my DI.  I put a 20dB pad on it, and it sounded great.  I then went back and re-leveled my IRs, and now my maxed signal going into the DI with no pad sounds just fine.  

 

TL:DR- overly hot signal going into the wrong type of input can result in FOH dropping your gain to compensate, which results in a thin tone in IEMs or wedge monitors.  

 

I now set my patches to be generally equitable in volume to an empty patch, and now I have no issues with level or noise.

 

Edit: for reference, my output is set to instrument level, I have no pad on the Helix guitar input, and our console has phantom power going to all channels.  My DI is an ART cheapo DI.

 

I honestly don't know the answer, really... Speaking from personal experience, when I left phantom power on my mixer, I didn't really notice the tone changing so much, it was just that signal was really quiet. I started cranking up the gain on the mixer channels, and then I remembered the phantom power thing. I guess, though, I wouldn't rule it out that the signal might not be attenuated at the same level across the whole spectrum. It's hard to say with people on Facebook. Many people have no clue about gain staging in the first place, so there's any number of things that can be affecting their tone.

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Well, I would only consider ignoring it if I didn't have another option. I didn't know the warning was about the sound quality, I thought it had the potential to damage the unit, but that maybe it was very unlikely to happen, and just something they added in the manual to cover their asses. This is why I asked.

 

There's no risk of damage... Just sound quality. And the issues with sound quality seem more likely to happen than not.

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There are times when phantom power will be stuck on, turned on by mistake, or you simply don’t know.

 

So... I ALWAYS use my 1/4†to a Whirlwind IMP2.

 

It sounds just as good as the XLR to the board would.

 

It eliminates any phantom power issues.

 

It eliminates any impedance mismatch issues.

 

It even mitigates or eliminates any level issues in my experience.

 

So what I do is this. XLR out to my onstage monitor FRFR. I control the volume with the big volume on Helix. I use my 1/4†at full output to a DI to the board (or two identical DI when I go stereo).

 

It’s a no-brained for me. If you are positive about the desk you plug into, then go ahead and use XLR, but in eliminating all those potential pitfalls, I give the sound guy more time to make me and the band sound great.

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It's a simple and easy fix.  Just use an isolator box like the one phil_m noted or a phantom power blocker like the following link on your XLR out to the board.  It plugs into the Helix XLR out and then into the XLR cable to the board.  I use it every time whether there's phantom power or not and it allows me to completely ignore the phantom power issue.

 

https://www.amazon.com/Sescom-Inline-Phantom-Blocker-Sescom/dp/B00A6ZE7A8

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It's a simple and easy fix.  Just use an isolator box like the one phil_m noted or a phantom power blocker like the following link on your XLR out to the board.  It plugs into the Helix XLR out and then into the XLR cable to the board.  I use it every time whether there's phantom power or not and it allows me to completely ignore the phantom power issue.

 

https://www.amazon.com/Sescom-Inline-Phantom-Blocker-Sescom/dp/B00A6ZE7A8

This is what I use... But correct me if I'm wrong...

 

   the 1/4" out to the board would NOT suffer from the problem, correct?  Many mixing boards can take either an XLR OR a 1/4" input, so if you just use the 1/4 out from Helix to the 1/4" input on the board, it should not have the issue?   I'm not stating, I'm asking because I haven't tried that yet (I use the power blocker when I do (rarely) plug into FOH). 

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This is what I use... But correct me if I'm wrong...

 

   the 1/4" out to the board would NOT suffer from the problem, correct?  Many mixing boards can take either an XLR OR a 1/4" input, so if you just use the 1/4 out from Helix to the 1/4" input on the board, it should not have the issue?   I'm not stating, I'm asking because I haven't tried that yet (I use the power blocker when I do (rarely) plug into FOH). 

 

RIGHT. Phantom Power can NOT affect anything on Helix's 1/4" TS (there are no TRS connectors on Helix) connectors.

But if your mixer is more than 20 feet away, you really should be sending a balanced XLR line.

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This is what I use... But correct me if I'm wrong...

 

   the 1/4" out to the board would NOT suffer from the problem, correct?  Many mixing boards can take either an XLR OR a 1/4" input, so if you just use the 1/4 out from Helix to the 1/4" input on the board, it should not have the issue?   I'm not stating, I'm asking because I haven't tried that yet (I use the power blocker when I do (rarely) plug into FOH). 

 

No, you won't have any issues with phantom power if you use the 1/4" outs into a 1/4" input on the desk. The only thing is that the 1/4" outputs on the Helix are unbalanced, high impedance outputs, so wouldn't want to run them further than 20' or so because you can run into issues with noise and signal degradation past that. The best way to use the 1/4" outs, imo, is to take them into a DI and then use an XLR to run to the board.

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The only thing is that the 1/4" outputs on the Helix are unbalanced, high impedance outputs, so wouldn't want to run them further than 20' or so because you can run into issues with noise and signal degradation past that. 

 

 

While they don't appear to have published output impedance specs anywhere, I'd be very surprised if it was "high impedance".  I'd hazard a guess that it's probably around the 700Ω value that you once posted for the M13.  While that value might be higher than on the XLRs, it should've have an issue driving a cable run of any "reasonable" length.  Relative to running XLR, I think the greater concern would be noise rejection than signal degradation.  

 

But that's just my opinion: I could be wrong.

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While they don't appear to have published output impedance specs anywhere, I'd be very surprised if it was "high impedance".  I'd hazard a guess that it's probably around the 700Ω value that you once posted for the M13.  While that value might be higher than on the XLRs, it should've have an issue driving a cable run of any "reasonable" length.  Relative to running XLR, I think the greater concern would be noise rejection than signal degradation.  

 

But that's just my opinion: I could be wrong.

 

The 1/4" outs are 10 kOhm according to my meter, and they stay the same regardless of whether they're set to line or instrument. I mean, yeah, you'd still have to go a long while to actually hear signal degradation, but I wouldn't want to send a signal from the 1/4" outs through a 75 or 100' snake back to the mixer without using a DI.

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I ordered one of these puppies for my gig basket, in case I run into this situation again : https://www.thomann.de/gb/millenium_die_dibox_passiv.htm

 

It's cheap, and not sure if it is any good (reviews seem to say it is), but it's only for situations where the phantom power can't be turned off.

 

So I plug my Helix's line out into this DI, run a mic cable to the mixing desk, but if said mixing desk has phantom power enabled, wouldn't that reach my helix, and now on the line connection... Or would the DI box "eat" that phantom power? It's a passive box, FYI.

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I ordered one of these puppies for my gig basket, in case I run into this situation again : https://www.thomann.de/gb/millenium_die_dibox_passiv.htm

 

It's cheap, and not sure if it is any good (reviews seem to say it is), but it's only for situations where the phantom power can't be turned off.

 

So I plug my Helix's line out into this DI, run a mic cable to the mixing desk, but if said mixing desk has phantom power enabled, wouldn't that reach my helix, and now on the line connection... Or would the DI box "eat" that phantom power? It's a passive box, FYI.

 

It can't reach your Helix because your Helix is running out of the 1/4" out jack.  See the discussion above regarding phantom power and 1/4 out.

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The 1/4" outs are 10 kOhm according to my meter, and they stay the same regardless of whether they're set to line or instrument. I mean, yeah, you'd still have to go a long while to actually hear signal degradation, but I wouldn't want to send a signal from the 1/4" outs through a 75 or 100' snake back to the mixer without using a DI.

 

Hi!

Just a quick side question not all unrelated.

I use my helix plugged to my audio interface with 1/4" cables. The 1/4" outputs are set to line level.

If you say the 1/4" outputs on the helix are high impedance even when set to line level should I turn on the Hi-z pad on the audio interface?

I only notice a drop in the level when I turn the pad on. Am I losing frequencies coming out of the helix by not turning on the pad?

Thanks.

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Hi!

Just a quick side question not all unrelated.

I use my helix plugged to my audio interface with 1/4" cables. The 1/4" outputs are set to line level.

If you say the 1/4" outputs on the helix are high impedance even when set to line level should I turn on the Hi-z pad on the audio interface?

I only notice a drop in the level when I turn the pad on. Am I losing frequencies coming out of the helix by not turning on the pad?

Thanks.

 

Pads are (or should be) purely attenuators, It shouldn't affect any frequencies but if your input is clipping then you should turn it on.

Craig

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