XLR Hiss (Phantom Power and Helix)

[davidb7170]

Anybody experiencing audio clipping when running Stereo XLR out of Helix direct to FOH Snake?

I've run mostly mono out to FOH, without issues both with analog and digital snakes. I set my XLR output to mic level and only control the 1/4" outs to my stage monitor amp with the volume knob for stage level adjustments. Clipping may be due to too hot signal at line level to the FOH board. Always with the ground lift engaged. I play mostly smaller bar types of venues.

 

Dave

 

P.S. great work on your patches.

[brainbug]

Anybody experiencing audio clipping when running Stereo XLR out of Helix direct to FOH Snake?

 

No, no audio clipping in stereo either, just remember to set helix output for mic level though otherwise it will clip on the mic inputs of the board.

[phil_m]

Anybody experiencing audio clipping when running Stereo XLR out of Helix direct to FOH Snake?

 

No audio clipping here. In my home studio, I have the Helix hooked up to two mixer channels via XLR, and I just keep the gain of those channels down at zero so I'm effectively bypassing the mixer's preamps. I could see, though, that it is possible to clip a mixer channel pretty easily.

[GlennDeLaune]

No audio clipping here. In my home studio, I have the Helix hooked up to two mixer channels via XLR, and I just keep the gain of those channels down at zero so I'm effectively bypassing the mixer's preamps. I could see, though, that it is possible to clip a mixer channel pretty easily.

I didn't personally check the levels on the side monitor input board so I may have been clipping the input of that console. Thanks guys.

[kronda]

Just to conclude the Phantom Issue topic. I asked the support explicitly and finally after a longer wait have it confirmed that this cannot be fixed by firmware update, it's a design issue with Helix. I'm ordering two phantom blockers now.

 

I also got hit by this issue yesterday when recording a new album demo with my band in our rehearsal room. I was recording us myself and had the sessions in Cubase set up beforehand for each song with input channels assigned to tracks. But when we patched everything I realized I needed to switch on phantom power for drum overhead mics and on my audio interface (Fast Track Ultra 8R) it's only possible to do it for four channels at once (1-4 and 5-8). Bummer, as I had my sessions in Cubase set up so that overhead mics and helix channels (guitar + vox) were in the same group. Had to repatch cables and reassign track inputs in all 11 sessions in Cubase which added another time to the already quite long setup time. And I hope I haven't messed up some of the sessions as I haven't checked the results yet. Oh well.

[cletcher1]

Thanks for validating, although not really a surprise.  I find it interesting that more users aren't that upset about this.  I'm even more disappointed about  how Line 6 has handled this, or not in my opinion.  But not surprising given the expense to offer customer's a fix would be huge.  I'm sure we will see this fixed in future models or production runs if it hasn't already been addressed.  But they have left us first adopters out in the cold.  This will conclude my run as a early adopter for their products.  Has this been fixed in the floor model manual as a warning? Or is this thread I started handling that awareness for them.

 

Disappointed as the Helix is otherwise a great product. 

[kronda]

Thanks for validating, although not really a surprise.  I find it interesting that more users aren't that upset about this.  I'm even more disappointed about  how Line 6 has handled this, or not in my opinion.  But not surprising given the expense to offer customer's a fix would be huge.  I'm sure we will see this fixed in future models or production runs if it hasn't already been addressed.  But they have left us first adopters out in the cold.  This will conclude my run as a early adopter for their products.  Has this been fixed in the floor model manual as a warning? Or is this thread I started handling that awareness for them.

 

Disappointed as the Helix is otherwise a great product. 

 

Word.

[ozbadman]

Thanks for validating, although not really a surprise.  I find it interesting that more users aren't that upset about this.  I'm even more disappointed about  how Line 6 has handled this, or not in my opinion.  But not surprising given the expense to offer customer's a fix would be huge.  I'm sure we will see this fixed in future models or production runs if it hasn't already been addressed.  But they have left us first adopters out in the cold.  This will conclude my run as a early adopter for their products.  Has this been fixed in the floor model manual as a warning? Or is this thread I started handling that awareness for them.

 

Disappointed as the Helix is otherwise a great product. 

 

And given L6 has given no response here and is in hiding, how will we know what model of the hardware it has been fixed in???? C'mon Yamaha, you can do better than this.

[phil_m]

And given L6 has given no response here and is in hiding, how will we know what model of the hardware it has been fixed in???? C'mon Yamaha, you can do better than this.

 

I doubt they'll be making any hardware changes. Line 6 has responded. Their response is "don't use the XLR outs on channels with phantom power".

 

Also, I think that one reason there might not be more outcry is that for some people, using the ground lift does seem to make the hiss go away. So some users might not even have a problem with it.

[PeterHamm]

And Yamaha may own them. It doesn't mean they RUN them. In the past, Yamaha has owned companies (like Korg) but not "taken over" and run them.

[kronda]

I doubt they'll be making any hardware changes. Line 6 has responded. Their response is "don't use the XLR outs on channels with phantom power".

 

I don't consider that a response, it's like if they were crappy shoemakers saying "don't walk in our shoes to prevent damaging them" and you'd take that as a satisfying response and would be happy with your crappy shoes.

 

Put simply: As proudly as Digital Igloo responds on the forums when he has a positive answer explaining that Helix can do that and that and takes credit for it, should Line 6 step up and humbly admit: we screwed up, it's not possible to solve this by firmware update. And suggest solutions...

 

Of course they won't fix it, of course I won't return my Helix because of this, of course I don't expect them to distribute phantom blockers for free. Just don't try to act like "this is normal" by just stating "don't do this with Helix". Otherwise they're bunch of hypocrites... Well, there's no such thing in business, only successful and unsuccessful businesses but here in the forums we can still judge :D

[djy8131]

Do we know if the phantom power will harm the Helix or is it just a matter of dealing with the hiss?

[PeterHamm]

Do we know if the phantom power will harm the Helix or is it just a matter of dealing with the hiss?

The warning in the Helix Rack manual makes me not want to mess around to find out.

[kronda]

I asked the support explicitly and should be fine, no harm to Helix or connected Variax should result from incoming phantom power.

[Joepeggio]

Just a quick question/thought. Is there an audio quality / dynamics difference when the circuit that blocks phantom power is in the path. Maybe not in a live situation, but for recording quality?

 

I've seen some of the solutions. Some say there may be a signal drop due to required resistor / capacitor combos, or the coloring a 1:1 transformer may inject. ??????

 

Just a layman wondering.

[brainbug]

Just a quick question/thought. Is there an audio quality / dynamics difference when the circuit that blocks phantom power is in the path. Maybe not in a live situation, but for recording quality?

 

I've seen some of the solutions. Some say there may be a signal drop due to required resistor / capacitor combos, or the coloring a 1:1 transformer may inject. ??????

 

Just a layman wondering.

I have 2 Triton Audio Phantom Blockers and there's no difference in signal when I use them and when I don't. As far as I know, they have inside as protection a circuit that stops DC current coming in, that is normally used by all XLR outputs and somehow L6 "forgot" to fit inside Helix..

[brainbug]

I doubt they'll be making any hardware changes. Line 6 has responded. Their response is "don't use the XLR outs on channels with phantom power".

 

Also, I think that one reason there might not be more outcry is that for some people, using the ground lift does seem to make the hiss go away. So some users might not even have a problem with it.

 

As far as I know, the hiss would stop using the ground lift Only in the situation where you phisically disconnect the ground from helix power cord at the same time.. otherwise the 48 V phantom power would find his way in anyway.. At least this is what happens. BUT manual  (like every manual) safety warning rightly says : This apparatus shall be connected to a MAINS socket outlet with a protective earthing connection.. So unless you are using totally different earths in helix and mixer, or unless you unsafely cut the mains ground from mixer or helix, ground lift won't make hiss go away.

[phil_m]

As far as I know, the hiss would stop using the ground lift Only in the situation where you phisically disconnect the ground from helix power cord at the same time.. otherwise the 48 V phantom power would find his way in anyway.. At least this is what happens. BUT manual  (like every manual) safety warning rightly says : This apparatus shall be connected to a MAINS socket outlet with a protective earthing connection.. So unless you are using totally different earths in helix and mixer, or unless you unsafely cut the mains ground from mixer or helix, ground lift won't make hiss go away.

 

Nope... With my mixer, the hiss goes away as soon I hit the ground lift on the Helix, and the ground plug on my Helix is most definitely connected. The Helix and my mixer are plugged into the same power strip - so same ground.

[brainbug]

I give up.. <_< :rolleyes:

[DoeWoe]

I had an issue with the hiss the first time I brought it to practice.  I thought to myself "not again" as I've had issues with my HD500x being somewhat more noisy than the other guitarists X3 and I was hoping the Helix would be above all of that.  Luckily the soundperson is very good and figured out it was the phantom power.  The hiss came back for that weekends services unfortunately.  I switched channels and it seemed fine so we thought it was the XLR cable.  The question I have is should I set the level to Mic level like others are saying to do?  I thought it was recommended to use Line level, but all of this stuff is outside of my expertise.  I was also noticing some audio clipping on a specific patch.  Oddly enough Glenn asked that question and I happened to be switching back and forth between his patch and a different one...the clipping was not on his patch.

[ge31]

Hi all,

 

Just received my Phantom Blockers from TRITON and It works perfectly :-).

 

Have fun with Helix.

[ozbadman]

I doubt they'll be making any hardware changes. Line 6 has responded. Their response is "don't use the XLR outs on channels with phantom power".

It wasn't really a proper response. So that leads me to believe they L6 knows this is a mistake on somebody's part. Even a reply saying they will note it in the manual would have been something. But it also suggests that the next hardware revision may have this fixed.

 

I'm sure there will be another hardware release, there always is after initial manufacturing finds minor problems, but whether they will just slip it quietly into the next minor board revision, or whether it will be fixed in HELIX-2, or not at all, only Line 6 can tell us.

 

If they didn't see it as a problem, they would have given us a reply, but they are visibly absent from this thread. Indeed, the only good information we have received was from the call to support, which filled in some of the concerns.

[jeremyn]

It is never a good idea to connect line level powered gear to a phantom powered input without first considering a number of things:

 

1) If the gear has a transformer isolated output, then it is generally safe.

 

2) If the gear is DC isolated, and has phantom inrush limiting and diode protection on the output, it is also generally safe.

 

3) If the gear has line drivers that are unprotected or marginally protected, then make sure all gear is plugged in before turning on the phantom power. Plugging in while phantom is already powered on will cause the coupling capacitors to discharge into the output device's drive transistors/protection diodes, possibly damaging the device's output stage and/or the desk's input stage. This damage can be cumulative, eventually causing failure only after a large (or small) number of 'plugins', and then just fail completely when you least expect it.

 

4) Phantom power is usually available on microphone preamplifiers inputs, and not line inputs. So line devices should be connected to the correct line inputs, other use a DI or level transformer to connect to the mic input. Transformers and DIs will block phantom power and properly match the levels (and line impedance for longer runs) to achieve the best result.

 

5) 'Good enough' results can be had by playing with gain staging, phantom blockers and using pads, but care must be taken that the DC path is being blocked and inrush current is limited (eg. Use isolators that are designed for this). Again, gradual/cumulative damage occurs if components are over-stressed.

 

6) In regards to the question above about adversely affecting the signal by adding these outboard protection devices; you are already compromising the chain by not using the right inputs/connections, and it is unlikely you'll notice the SNR reductions compared to having them built into the unit.

 

7) If possible, always connect line level outputs of powered gear to the TRS 1/4" jack input on the desk when a channel has both XLR and 1/4" inputs (many desks have this and the phantom is only supposed to be on the XLR). Yes, this requires a proper cable or an adapter, but it's better to be safe than have your gear fail when you least expect it.

 

So, yeah, the Helix could (or maybe should, knowing their user base) have had protected and/or transformer isolated XLR outs. But, I'd never have that expectation for any piece of gear where the XLR is marked as a line output.

[PeterHamm]

I have to say, I never turn on phantom power for a device that doesn't absolutely need it. That's kind of audio engineering 101 stuff.

 

And Helix isn't the only device out there that has a problem with phantom power.

 

Sorry, fellas, I think it got left out of the manual by accident, and I don't think there's  story here.

[cletcher1]

Peter,

 

With all due respect, there is absolutely a story here.  A lot of us are aware of audio engineering 101. I studied it at college level.  No one intentionally wants to run phantom power to a device that doesn't need it.  You seem to not understand what many have explained as not an option in some cases.  Your mixer(s) might be fine, however many do not allow for individual power switching.  Again, citing Line 6's own M20, of which we have 2.  Yes there are work-arounds, but they include multiple direct boxes or phantom blockers....additional investments.  And why the hell would they have put protection on the now inferior HD500, but not the flagship Helix?  Why are they so silent on the issue?  Why was it missing from the manual?  Scooby-Doo could put these clues together. For them to say something would possibly have legal implications, even though no one here is probably interested in a class action law suit.  I'm done with this thread, although I hope it has educated some of this issue so they don't freak out when it happens.  It has probably saved a bunch of returns also.  We can revisit this post in a year and discuss if the current production model does this then.  That will tell it all.

 

Other than this and the El Capitan issues, I'm enjoying my Helix.

[Joepeggio]

As a sample, I have a Sony laptop with WIFI issues.  Sony immediately sent out a USB mico wifi "card" to temporarily solve the issue until internal wifi card issue was resolved or replace.   Laptop costs about 1/3 that of the Helix.

 

My point - Line 6 fixes the issue in newer units (Helix 1.1), and issues blockers for all pre-protected units.  Cost would be very cheap for them.  A few bucks each, with the kind of resources Line 6 / Yamaha has.  It costs us about $70, either for the blockers or a "cheap" ART DTi 2 channel iso box (transformer - $60 plus 2 cables).

[PeterHamm]

...And why the hell would they have put protection on the now inferior HD500, but not the flagship Helix?...

 

The HD 500 was mic level, basically two built in D.I. boxes. the Helix is line level. Different.

[brainbug]

The HD 500 was mic level, basically two built in D.I. boxes. the Helix is line level. Different.

 

I do not agree. The helix is mic level switchable line level

[brainbug]

I have to say, I never turn on phantom power for a device that doesn't absolutely need it. That's kind of audio engineering 101 stuff.

 

And Helix isn't the only device out there that has a problem with phantom power.

 

Sorry, fellas, I think it got left out of the manual by accident, and I don't think there's  story here.

 

Out of all RECENT products I bought, and as having a studio and playing guitar live I bought quite a lot of stuff, I only found 2 products having big problems with phantom power: One was YAMAHA piano CP4, the other is YAMAHA - L6 Helix.

Now that this problem with L6 products only comes out after they've been bought by YAMAHA, might or might not be a coincidence.

This issue does not bother me a lot, i bought two blockers for small gigs where only small mixers are available, I keep them in my bag and bring them out when needed. It bothers me a lot instead the answer I had from YAMAHA for the piano: it's a professional keyboard so is supposed to go with a professional mixer, meaning i presume that lots of their own mixers, that cost even more than the so called professional piano, are unprofessional. And it bothers me a lot the silence from YAMAHA - L6. At least i learned something, next time I want to buy a piece of gear when I try it out I will definately try its behaviour with phantom power, then I'll decide if it bothers me or not, and if to buy it or not. Expecially if it's a YAMAHA product

[gunpointmetal]

If I hand a sound guy two XLR cables and tell him they're line-level, I'm gonna get a lot of funny looks. 9/10 times people are expecting a microphone level signal with an XLR (mic) cable. The whole reason people would need a DI box would be to turn the Line Level to microphone level, which the Helix already does, optionally, via the XLR outs which should, theoretically, eliminate the need for an external DI box. Having less crap to lug around and plug is kind of one of the the big draws of a MFX set-up like Helix, so adding in another DI box to get the functionality of a $500 unit doesn't really make sense. When have you ever seen, outside of special use, a DI box that even has XLR inputs on it. If I'm gonna have to run a DI in between me and the FOH, I'm just gonna patch off the 1/4" outputs and use the "through" outputs of the DI to send back to my on-stage monitoring, effectively rendering the XLR outputs pointless. 

 

I don't personally see how this could be anything OTHER than a design flaw. 

 

Everyone knows you're not supposed to connect non-phantom-powered gear to powered inputs, but most mixers under 20 channels either have it off or on, or they might have two sets of on/off switches. Hey, no big deal if I'm running my own sound, but I'm not going to expect the sound-guy at a club to rewire his whole rack to accommodate my input needs, so I'm going to have to invest in some phantom blockers, or another DI box to avoid it ever being an issue, which brings us back to full circle in that the Helix, like the HD500X, is supposed to be an AIO unit that doesn't need external anything for a complete guitar rig....

 

 

So yeah, its a design flaw. 

[brainbug]

Gunpointmetal I agree

[cletcher1]

well said....

[phil_m]

If I hand a sound guy two XLR cables and tell him they're line-level, I'm gonna get a lot of funny looks. 9/10 times people are expecting a microphone level signal with an XLR (mic) cable. The whole reason people would need a DI box would be to turn the Line Level to microphone level, which the Helix already does, optionally, via the XLR outs which should, theoretically, eliminate the need for an external DI box. Having less crap to lug around and plug is kind of one of the the big draws of a MFX set-up like Helix, so adding in another DI box to get the functionality of a $500 unit doesn't really make sense. When have you ever seen, outside of special use, a DI box that even has XLR inputs on it. If I'm gonna have to run a DI in between me and the FOH, I'm just gonna patch off the 1/4" outputs and use the "through" outputs of the DI to send back to my on-stage monitoring, effectively rendering the XLR outputs pointless. 

 

I don't personally see how this could be anything OTHER than a design flaw. 

 

Everyone knows you're not supposed to connect non-phantom-powered gear to powered inputs, but most mixers under 20 channels either have it off or on, or they might have two sets of on/off switches. Hey, no big deal if I'm running my own sound, but I'm not going to expect the sound-guy at a club to rewire his whole rack to accommodate my input needs, so I'm going to have to invest in some phantom blockers, or another DI box to avoid it ever being an issue, which brings us back to full circle in that the Helix, like the HD500X, is supposed to be an AIO unit that doesn't need external anything for a complete guitar rig....

 

 

So yeah, its a design flaw. 

 

Not trying to be too picky, but a DI box doesn't convert a line level signal to mic level - it converts a high impedance signal to low impedance. The level of the signal should remain at whatever it was before going through the box (assuming you don't attenuate it).

 

As I've stated before, I personally think that the reason this is an issue is the auto-summing feature on the XLR outs. This is relatively unique. No other Line 6 products have it, as far as I know. So I don't think it's a design flaw as much as one design limitation being chosen over another one.

 

Being in the design field myself, I'm always hesitant to throw out the word "flaw". It's all in the eye of the beholder, and you need to start from a place where you assume best intentions with things.

[gunpointmetal]

Not trying to be too picky, but a DI box doesn't convert a line level signal to mic level - it converts a high impedance signal to low impedance. The level of the signal should remain at whatever it was before going through the box (assuming you don't attenuate it).

 

As I've stated before, I personally think that the reason this is an issue is the auto-summing feature on the XLR outs. This is relatively unique. No other Line 6 products have it, as far as I know. So I don't think it's a design flaw as much as one design limitation being chosen over another one.

 

Being in the design field myself, I'm always hesitant to throw out the word "flaw". It's all in the eye of the beholder, and you need to start from a place where you assume best intentions with things.

 

That is too picky, the point of changing the impedance of the signal is to send it to a microphone input instead of a line input, so you can call the levels whatever you want.

 

The picked the wrong functionality to accommodate. It would've been, to me, more logical to skip the summing, because its not hard to to make all your stereo patches mono in a different setlist should that be required for your gig. Or save different bundles of for mono environments, costing the user nothing but extra time. And saying that its a trade off would make sense if, when used summed to mono, the single XLR out was not affected by phantom power, but otherwise, its just poor implementation.

 

I get it Phil, you really, really, really like Line 6. So do I. I really dig the sounds coming out of my Helix. I planned on using it in the same capacity as I had been doing my HD500(X, now) for years, but I will need to invest in outboard gear to make sure that I am able to do so no matter where I play, which is kinda silly considering this is advertised as, and I would imagine intended to be, and an all-in-one guitar rig solution.

[jeremyn]

You'd never plug the output of your mixing desk, your wireless mic receivers, outboard compressors or other rack gear into the phantom input of a desk.

 

The problem here is that people are assuming the Helix is an instrument, not a piece of pro-audio 'rack' gear. Whereas the designers seemed to assume it was going to be used like rack gear. Rack gear is probably DC coupled on the output side with drivers that maximise the SNR for ultra high fidelity studio recordings, and allows the user to choose the level of protection required versus any compromises to signal quality (and increased cost) that they entail.

 

A manufacturer may add cost and compromise the output slightly with high quality coupling capacitors to block any DC, but this doesn't block inrush. Another manufacturer may choose to go to even greater expense and put in a high quality line output transformer (which would allow maximum flexibility for live use).

 

If a device does not explicitly state that it is safe to apply 48V phantom power to the output, I would NEVER directly connect it to a phantom powered (or otherwise unknown) input. Even a device that 'seems ok' might be stressed and be damaged over time.

 

One aforementioned example is the inrush currents when plugging in to an active phantom input (even if you use a non-transformer based phantom blocker) - a known problem with all line level outputs. This causes stress on the output drivers / protection diodes, and possibly the device's internal rail for a short burst while various coupling capacitors charge/discharge at high current through protection diodes. A carefully designed output would have appropriate protection and limiting, but there are no guarantees without examine the circuit in detail.

 

A DC coupled output stage will have it's bias point changed by the phantom voltage causing it to behave asymmetrically, therefore increasing distortion and/or noise. This will probably not cause any damage (as long as the phantom power was turned on AFTER connecting the gear).

 

Another problem is applying excess voltage to an AC coupled output stage where the coupling capacitors are rated below 48V. This puts stress on the capacitors and may cause them to fail prematurely. This may eventually manifest as reduced signal quality or complete loss of signal (and further damage to other internal components). This applies even if you take the precaution of turning phantom power on after all devices have been plugged in - as it is the continual presence of the 48V DC bias, not the inrush, that degrades the underrated coupling capacitors.

 

Most devices will likely survive both of the above scenarios (depending on circuitry at both ends) for limited exposures, and seem ok for a while or even indefinitely. But, why chance it.

 

A 'phantom blocker' that just uses a couple of inline capacitors to block the DC is an acceptable protection measure, but you MUST remember to make sure the phantom is off before plugging in, as it won't block the in-rush current. It might soften the 'blow', but again, why chance it.

 

The safest option when connecting line output gear to an unknown (or known phantom) input is to use a fully balanced isolation transformer which are designed for this and other voltage differential problems (like mains current leakages superimposed on the earth line). The transformer will both block the DC bias AND the discharge inrush - so you are still protected even if you happen to plug in while a phantom powered input is active (which can happen accidentally during a momentary lapse of concentration, or a 'helpful' sound guy that turns it on when you're not looking). It also protects the mic input stage on the desk, which is also stressed during the inrush event.

 

It is crazy to expect Line 6 to include free external protection devices, especially since most people will either not have a problem, or be already taking appropriate engineering 101 precautions with better quality gear than a 'free' inclusion would end up being. The kind of device that they include would likely not suit everyone anyway. I have a bag full of 'problem solvers' that include expensive Jensen transformer based isolators, DIs, ground lifters, pads, etc.

 

If I was designing the Helix main output stage circuits, I'd have a DC coupled fully balanced and protected line output on the 1/4" jacks that could also be connected to an unbalanced input. And I'd have but a transformer coupled and pad switched output stage on the XLRs, calling them DI outs. That'd add at least $50 extra to the end user price of the unit - probably not an issue in this price range, but the marketing department would probably disagree.

 

If cost wasn't an issue, then we could also put a set of level translating transformers on two of the send/returns to allow connection to old school tube amp loops that operate at high voltage (70V+). And don't forget a dual channel transmitter for driving wireless IEMs, and a dual channel receiver to allow wireless input of either two separate guitars (or a two voice guitar like the Crowdster). A couple of built in isolated 9V DC outputs for powering external pedals would be cool too.

[ozbadman]

Just to clarify terms, line level refers to voltage (amplitude), as does mic level.

 

Line level is in the 1V region, and Mic level is in the 0.001V region. Much, much lower voltage than line level.

 

So, SNR (signal to noise ratio) is a much bigger problem for mic levels. Balanced outputs (XLR) reject noise better than unbalanced outputs (1/4 inch), so it is much more important to use XLRs for mic level outputs. But, it is fine, and actually better, to use XLRs (balanced) for either mic or line level.

 

DI boxes are used to change the impedance for a variety of reasons. Usually to make it a low impedance output into a high impedance input.

[bjoecool]

jnysen,

 

I intend to send a signal from the Helix Left (mono) XLR output to the main mixer input. I'll have the master volume knob assigned only to the 1/4" outputs, which will connect to my monitors. Sounds like the phantom blocker is insufficient for my XLR output because I can't, in every situation, be sure the phantom is off before plugging in. Can you please recommend specific units that meet your stated criteria for a fully balanced isolation transformer? I would probably buy two units or a dual unit just so that I have a backup in case one fails at some point.

 

Thanks for your help!

 

 

A 'phantom blocker' that just uses a couple of inline capacitors to block the DC is an acceptable protection measure, but you MUST remember to make sure the phantom is off before plugging in, as it won't block the in-rush current. It might soften the 'blow', but again, why chance it.

 

The safest option when connecting line output gear to an unknown (or known phantom) input is to use a fully balanced isolation transformer which are designed for this and other voltage differential problems (like mains current leakages superimposed on the earth line). The transformer will both block the DC bias AND the discharge inrush - so you are still protected even if you happen to plug in while a phantom powered input is active (which can happen accidentally during a momentary lapse of concentration, or a 'helpful' sound guy that turns it on when you're not looking). It also protects the mic input stage on the desk, which is also stressed during the inrush event.

[jeremyn]

jnysen,

 

I intend to send a signal from the Helix Left (mono) XLR output to the main mixer input. I'll have the master volume knob assigned only to the 1/4" outputs, which will connect to my monitors. Sounds like the phantom blocker is insufficient for my XLR output because I can't, in every situation, be sure the phantom is off before plugging in. Can you please recommend specific units that meet your stated criteria for a fully balanced isolation transformer? I would probably buy two units or a dual unit just so that I have a backup in case one fails at some point.

 

Thanks for your help!

Anything like the Radial ProDI, JDI, Stagebug passive would do if using the 1/4" outputs. The Whirlwind ISOXL looks like an inexpensive compact transformer for line level XLR to XLR isolation. Basically anything that says it includes an isolation transformer. There are products from Art and Behringer that meet this criteria for multiple channels. Google shows heaps when doing a search for XLR isolation transformer.

[ach1983]

Anything like the Radial ProDI, JDI, Stagebug passive would do if using the 1/4" outputs. The Whirlwind ISOXL looks like an inexpensive compact transformer for line level XLR to XLR isolation. Basically anything that says it includes an isolation transformer. There are products from Art and Behringer that meet this criteria for multiple channels. Google shows heaps when doing a search for XLR isolation transformer.

The ISOXL will request to run the XLR output in the Helix in line level instead of mic?

[jeremyn]

The ISOXL will work with any Helix output level. Use mic if you want a lower level into the desk.