Pod X3 live - phantom power causing shocks - anyone else?

[exoteric]

I am getting nasty electric shocks from guitar to microphone with my X3 Live.

 

I have a much loved Pod X3 Live - and I have recently discovered (in our new practice room setup) that I get shocks when holding guitar and a properly grounded microphone. I have troubleshooted the system and mains supply thoroughly, and traced this to the way the X3 Live processes incoming phantom power. I have excluded bad grounds on all devices, except the Line 6 POD X3 which has no independent ground via its (original) Line 6 power supply - (ie the ground is 'floating' as it should). The negative power supply connection is not ground.

 

I bought a new digital multi-meter to troubleshoot this. 

I though it was a mic signal path problem at first but have now ruled that out.

 

I've measured 48-50V between the guitar and any good ground, eg the vocal mike in our studio /rehearsal setup - and other guitars, rack kit chassis etc.

 

Though just 50V, it's still a noticeable shock, a lip on the microphone was the first experience and is quite a 'belt' very much felt with fingers too.

 

The voltage drops to zero when I turn off the (global) phantom power on mixer 

My signal path is:

Guitar > Pod X3 > XLR out L to Desk (for monitoring) and XLR out R straigh into to a Firewire 8/8 Recording interface. 

If I have phantom on on either of those, there is 48-50V potential between the guitar ground and a microphone.

Turn both off, no voltage present.

 

The conclusion I have come to is that there is a problem in the Line 6 Pod X3 Live unit that's causing the phantom potential to raise the guitar input's ground wire to become 50V above ground 'proper'.

 

As our desk is Phantom Power 'global' (and other devices like active DI boxes and condensers need the phantom), it's not something I can turn off except perhaps by buying a decoupling transformer as a phantom blocker.

 

I've tested  adding a ground wire from my guitar to another guitar (other ground) - to check that the mixer phantom power supply does not object to that by just sending the unwanted 50V to ground - and remaining phantom-powered items connected to the board are still operating OK. They do.

 

So I'm thinking to jury-rig a 'proper' ground to the Pod X3 Live unit somehow to defeat this issue.

 

I'm minded to make a cable that connects one end to a good ground- the mains socket - and then using only the green earth wire of course, and connect this ground to the X3 Live to an used connection (XLR Microphone input Pin 1 ) which my meter tells me is on the same ground buss as the guitar input (as it should be).

 

I am well out of warranty with Line 6 on this unit, while Line 6 have been very helpful to me with an issue I had once before (on my Variax 300) - I'm not expecting their help on this or for this to become a 'send back for repair issue', and am not sure if it's a problem that has always been present and I have just noticed it...

 

My question to the forum community is: has anyone else experienced anything like this?

 

Perhaps in the X3 schematics there is something that shows the circuit schematic of how phantom power coming into the X3 Live through the Direct Outs as is in my case, on pins 2&3 is raising the ground voltage of the guitar input to 50V above 'good' ground. Perhaps there is an internal component that has failed. If so, what would it be? Is there an internal decouplng transformer to disregard any incoming phantom voltage that has failed?

 

Thanks for your time reading this.

 

 

 

 

 

 

 

[exoteric]

Received from Line 6 Support:

Dear customer,

If your Line 6 product needs repair, we strongly suggest you contact the nearest authorized service center in your region. Line 6 does not offer repair assistance via email or telephone. Also, Line 6 does not provide circuit diagrams, blueprints or schematics for consumer use at this time. Keep in mind that should you choose to modify or repair your unit at any time during your warranty period, the warranty will no longer be valid.

http://line6.com/find/service_center/

Best regards,
Technical Support

Line 6 Support Europe

Thank you. I was hoping you would help determine if the unit has a fault or if it is normal behaviour before electing a repair send-away. There is a potential of 50V between guitar ground and 'real ground' when phantom power is applied to the Line 6 Pod X3 Live Direct Outs. Can you please ask a colleague to review my post and reply advising whether this is normal for the unit, or not. I will then contact service centre. I am not proposing any user-modification of the unit. If I were to ground the X3 unit by connecting any other in/out that is connected to another device with a 'good ground' that would achieve the same result (taking the guitar ground back to 0V) as a jury-rigged lead.

 

Hello Line 6 - I have now spoken to the authorised service centre in my region. Before I proceed with a repair investigation and incur the associated costs with that, I need you, the manufacturer, to review my question and advise me whether this is normal behaviour for the unit (ie a design issue) or a component failure. The unit is fully working otherwise. It seems to be a vanishingly remote possibility that a internal decoupling transformer (if part of the X3 Live design) would fail to short circuit on both the direct outs, raising the potential of the line 6 ground buss to be 50V above ground. I have tested the equipment in two different studio setups and have ruled out all external equipment and cables. If it is a design issue, fine, I will avoid the XLR outs and/or purchase an external stereo XLR decoupling/isolating transformer to remedy at a lower cost equivalent to an initial assessment of the service centre. I look forward to your reply. 

[exoteric]

An update on this is that I have now used an XLR splitter box (one in two out) where one output is isolated (ie passes through a transformer). This clears the problem by not passing any phantom power into the X3 live through the direct outs. I was able to find a stereo one of these for $30 and that (plus a couple of short xlr leads) both solves the issue and is cheaper than an inspection by the line 6 repair centre that could well be fruitless. They did not have another X3 device on-site to compare to. I'm still awaiting contact from Line 6 support to confirm or otherwise that the X3 should not have this problem by design, which may yet arrive, but it's now a 6 years old device and understandably not their priority.  

 

HELLO X3 LIVE USERS FORUM

I would be interested to learn if any other POD X3 Live users out there have had a similar problem - the test is to use only the direct out xlr connection, hook that to something that provides phantom power, such as mixer, connect guitar to guitar in, then measure with a multimeter (Amazon from $2 - solid investment) if there is now a 50V DC voltage between guitar ground (i.e. strings) and any other 'good ground'. That's my situation,

 

it could be a failed internal component in the X3 Live (typically an isolating transformer or a capacitors to kill off the not-needed phantom)  in which case I cannot believe I am the only one to experience it... or maybe I'm the first, so if you have one look out... or just a design issue (which is very unlike Line 6 who are of course fab product designers) ...

[jimbyatt]

Yep, I have this same problem with my X3 Live, when phantom power is turned on at the desk. The splitter option sounds like the sensible way to go. It hadn't happened for a while, but yesterday the phantom power got turned on by mistake, and nearly blew the tip of my nose off. The ground on the X3 was set to lift - I shifted this back to gnd and turned the phantom off and the problem went away. It definitely seems to be a problem with the unit itself - I've had it happen in the past using different desks, mics and cables, which narrows it down to the X3. Not good...

[exoteric]

[to JustStartin'] - having tested with a single channel 'XLR Mic Splitter - that typically has a 'direct out' and an 'isolated out' (via transformer), and seeing it would 'lose' the phantom power for me, I purchased a stereo isolator which works for me to remove the phantom power and I now have ground potential at guitar not 50V above ground... This is what I got (I am in the UK):  [ https://www.bax-shop.co.uk/miscellaneous-peripherals/art-dti-ground-loop-isolator] which was £35 - It would have cost me £50 plus carriage both ways to send to Line 6 repair just to look at it and is of course out of warranty, plus any repair work.  I do think this is something Line 6 should take more interest in - it's arguably a borderline product safety recall issue for Line 6 as this problem - now confirmed as not an isolated incident - could conceivably cause someone a serious injury - not only with guitarist with pacemakers - I am very disappointed that Line 6's response to me was limited to 'if it's broken, send for repair' with no interest in dialogue whatsoever. I love my X3 live and have been mithering about  buying an ebay replacement - there are a few there - but I'd like to know more about what this problem is exactly, what component has failed specifically or if it is just a design flaw I never noticed before. Good luck with yours.

[k1mcleod]

Thanks for being so thorough on this subject. You answered a problem I had that I should have sorted quickly myself....

I too was getting an electric 'tingle' from my mic and looked at everything else except the phantom power coming from the desk.

I'm (so far in life) fairly resistant to electric shocks, so didn't think the 'tingle' was anything like 48v.

In swapping my XLR's from the desk to my Firestudio interface and back again, I must have inadvertently pressed and latched the little phantom button on the desk for the left channel from the X3 Live.

I have to admit that I also had the ground lifted on the X3 Live and because of this process have now switched the ground permanently on.

I don't believe allowing the voltage to pass through to the user is a fault which has just appeared and therefore yes, Line 6 should be concerned enough to robustly inform users that passing live voltage down the XLR's into the unit will expose the user to high risk of electric shock.

[exoteric]

to k1mcleod: Thank you for you support on this topic. Yes I'm measuring precisely the same. My test rig is to hook up the Line 6 Pod X3 Live to a mixer with switchable phantom power, connect guitar - and then place a multimeter to measure Volts between the guitar strings and a 'good ground'. If I switch the 'Direct Out Ground Lift' switch to position: 'GRND' then there is 0V between guitar and ground. Hoorah.

 

If however the switch is in the 'LIFT' position, then the voltage between guitar strings and ground is 47.4 Volts. This is far from normal behavior of phantom power and something the original person replying on behalf of Line 6 support should now clearly see is a 'product design' issue and not a 'repair' issue and refer it to someone.

 

The risk of electric shock in this common situation is, I agree, high.

In my personal case, I elected to buy a device to isolate the Pod X3 from phantom power sources entirely, but the same effect can be achieved by keeping well away from setting 'Ground Lift' to 'Lift' when phantom power might be presented to the XLR Direct outs.  

 

Presenting phantom to XLR sources is more likely than not in modern situations - and the principle of phantom power is that it should be disregarded when not required by the device, by means of a capacitor or coil in the device.

 

Because phantom voltage is applied positive to the two signal connections equally (appx 48V), and returning on pin 1 (ground), it seemed to me that just isolating the ground (return) wasn't sufficient isolation to totally make the rig safe and solid - the phantom voltage was still being presented +48V to pin 2 and 3 could, perhaps, conceivably, find another way to ground.

 

For example, it is not only the 'Guitar In' connection that has its ground lifted to a shocking 50V - the same voltage is measured on: the mp3/headphone out; the ground pin of MIDI; - and on the 'microphone in' pins (1,2&3) are all 50V above ground. While all of these are 0V when ground lift switch is on the 'grounded nor lifted' setting as above, in my mind, the 48V is still knocking around somewhere in the Pod X3 and I'm just happier if it isn't.

 

Anyone reading this that thinks that phantom power is too low a voltage to be significant or worth bothering over can try playing guitar and allowing one's lips to touch a grounded microphone. It's a 'belt' indeed. It is a distraction when playing at the very least. I get slightly sweaty hands playing sometimes, and that naturally helps the circuit complete to maximum effect.

 

From what I can see this is something overlooked in the design of the otherwise brilliant X3 device and in its documentation.

 

It is now surely appropriate for some sort of a 'message to users' to alert them to an issue that can create an electric shock in normal use. They must have sold thousands and not everyone can afford to upgrade to a newer model.

 

If I were Line 6, I'd start with talking to their tech people then PR and legal, to put it in proportion but aiming to email all the warranty registrations details they hold of X3 owners and tell them to not use 'lift' where phantom may be present - at the very least; then I'd make sure the tech support people knew abut it and make sure the repair people knew about it.

 

 

Over to you, Line 6.