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What the heck happened ! (Bad bad gig)

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What the heck happened ! (Bad bad gig)

Postby MarkyC » Mon Oct 28, 2019 1:06 pm

So just had a horrible gig experience and wanted feedback so I can make sure it does not happen again.

Just played a gig where unfortunately there was no sound check (this is the norm for these types of event so no getting away from it).

I have tried to build a built proof setup with much help from everyone hear. Basically TR8, Bass Station 2, Peak and PC all going into a Radial Keylargo mixer. The audio is taken directly from each unit and then directly out via a stereo balanced xlrs. The cabling is female xlr to ¼ jack.

In the past I have plugged directly into a mixing desk and had no issue (please tell me this is OK!)

BUT on Saturday I played a gig at a great venue which has great sound – much better than the usual.

Everyone else’s sound was top notch and spot on. However, when I came to play the sound was truly awful! There was no bottom end, and no mids just a truly horrible top end. It was so bad I should have abandoned it. I did stop but the engineer, said it was my gear as everyone else’s was fine. The guys had plugged me in via a DI box, but surly this should not have been an issue.

Went home dejected, plugged everything in as normal, into my little Soundcraft mixer, everything spot on.

What could have gone wrong? If it was my fault really happy to hold my hands up and apologies!

Would really appreciate any feedback as this has seriously dented my desire to do this again and the whole point in the rig is so I don’t get these issues.

On a PS The sound guy talked to me after and at one point seemed to think I was just coming out of an IPad

Cheers,

Mark
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Re: What the heck happened ! (Bad bad gig)

Postby Wonks » Mon Oct 28, 2019 1:20 pm

Sounds rather like a faulty lead somewhere. If you were running in stereo into a stereo DI, then it almost sounds like there was a polarity issue, so you were only hearing the difference between the two channels.
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Re: What the heck happened ! (Bad bad gig)

Postby Martin Walker » Mon Oct 28, 2019 1:25 pm

I'm glad wonks mentioned that as a possibility, as previously the only thing I could think of was deliberate sabotage for some unknown reason :shock:


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Re: What the heck happened ! (Bad bad gig)

Postby Wonks » Mon Oct 28, 2019 1:32 pm

Or the stereo was being fed into two separate channels (rather than a stereo channel) and one of them had the polarity invert switch turned on.
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Re: What the heck happened ! (Bad bad gig)

Postby MarkyC » Mon Oct 28, 2019 1:34 pm

Thanks Wonks,

But what I don't understand is, I use the same leads all the time (just so they can't be faulty) and when I got home and tested them they were fine. When other people played theirs sounded fine :headbang:
Honestly the rig is as solid is I can make it.
Could it be they plugged me into the wrong type of di? Sorry I'm not up on di's and what could have gone wrong, it had lots of different inputs......
The polarity thing had me thinking and somewhere else someone said that most places sum to mono for live or is that just a rabbit hole....
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Re: What the heck happened ! (Bad bad gig)

Postby MarkyC » Mon Oct 28, 2019 1:36 pm

Yep it was being fed into two seperate channels.....
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Re: What the heck happened ! (Bad bad gig)

Postby MarkyC » Mon Oct 28, 2019 1:38 pm

why would they "polarity invert switch turned on"

Sorry but it was such a bad night and I don't want it to happen again!
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Re: What the heck happened ! (Bad bad gig)

Postby Dave B » Mon Oct 28, 2019 1:40 pm

Wot Wonks said. +1

MarkyC wrote:Went home dejected, plugged everything in as normal, into my little Soundcraft mixer, everything spot on.

Silly question : did you plug your KeyLargo into the soundcraft? Or the individual items? I'm guessing that the former, as that way you are proving you entire chain is good. If that is the case, then the issue was downstream of your gear.

For future reference, the Key Largo provides an isolated output which is what we mainly use a stereo DI for in your described setup. So you should be able to safely provide (your own, tested and correctly wired) two xlr cables to the FOH with no worries. If it then happens again, given that you know all the gear and cabling to be good, I'd be checking the desk to see if one of the channels has the polarity inverted. These things can happen..
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Re: What the heck happened ! (Bad bad gig)

Postby CS70 » Mon Oct 28, 2019 1:43 pm

MarkyC wrote: The cabling is female xlr to ¼ jack.

...

The guys had plugged me in via a DI box


Besides bad cabling as Wonks say, this is the only thing that got me thinking. Do you know how the cable XLR to jack cable is wired? Is there a single cable joining two XLR female to a single TRS jack?

EDIT: while I was writing you answered already that they were two individual cables, right?
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Re: What the heck happened ! (Bad bad gig)

Postby Hugh Robjohns » Mon Oct 28, 2019 1:47 pm

MarkyC wrote:I have tried to build a bullet-proof setup with much help from everyone hear. Basically TR8, Bass Station 2, Peak and PC all going into a Radial Keylargo mixer. The audio is taken directly from each unit and then directly out via a stereo balanced xlrs. The cabling is female xlr to ¼ jack.

I suspect this is the start of your problem ... I presume this cable terminates in a TRS? In other words, you are providing a balanced line-level feed? I think you (or actually the PA guy) has fallen foul of not recognising the requirements of a good old-fashioned output transformer!

Radial use high quality output transformers in the Key Largo's main outputs for lots of good, old-school, engineering reasons... but they're not as idiot-proof to use in all circumstances... as your idiot PA chap as proved! :lol:

In the past I have plugged directly into a mixing desk and had no issue (please tell me this is OK!)

Absolutely fine. The Radial Key Largo is a very solid bit of kit with floating transformer-coupled line-level outputs, so no problems with isolation or ground loops.

There was no bottom end, and no mids just a truly horrible top end.

Obviously a connection issue... I suspect the DI box was wired to pickup only the tip and sleeve connections of its jack input socket, leaving the ring contact unterminated. That would mean only the hot side of the Largo's output transformer was connected to anything (the cold side went nowhere), so there was no actual audio circuit path and thus what you would have got was just stray capacitive coupling. That has a very distinctive sound character which is very low level, all top end, and nothing else.

Transformer to DI box.png


The muppetry was entirely on the part of the sound guy, not recognising and understanding the implications of connecting a balanced source to an unbalanced DI Box.

The guys had plugged me in via a DI box, but surly this should not have been an issue.

Well, I'd say it was a completely predictable issue... but then I know about the transformer output format of the Key Largo and understand how most DI boxes are wired!

There are two reasons for using a DI box in this situation: either because it's necessary to connect a line-level source to a mic-level input; or to provide galvanic isolation between source and FOH to guard against potential electrical fault damage.

In your case, the latter is not required because the Key Largo's transformer outputs provide galvanic isolation anyway.

If the former was required -- ie, it was necessary to feed a mic input -- then some system would be required to pad the signal level down, and a DI box is the obvious way.... BUT when the source is balanced some intelligence is required to ensure a valid connection.

With electronically balanced outputs you can almost always get away with not connecting the cold side... the active hot side will still deliver a usable (unbalanced) signal. But with a transformer output it is absolutely essential to tie the cold side to the destination ground. Without that there is no audio circuit path.

There are two simple solutions in case this problem arises again. The first would be for you to make or purchase a couple of XLR(f) to TS cables (or adaptors, but adaptors have a habit of going missing!). These are wired with the cold connection (pin 3 in the XLR) tied to the screen (pin 1) -- which would maintain the circuit path for your transformer output.

The other option would be to invest in a couple of 30dB inline XLR attenuators so you can pad the Largo's output down to mic-level and the PA guys can just plug their mic cables into them.

Hope that helps.
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Re: What the heck happened ! (Bad bad gig)

Postby MarkyC » Mon Oct 28, 2019 1:50 pm

Thanks as always guys.

Hay Dave - yep wanted to check the rig so changed absolutely nothing.

All the cables are fixed, usb fixed, everything is velcrosed down the only thing that changes is that the power cables are plugged in. And yo to test I took the output from the Keylargo and checked that - exactly the same setup.
But you are correct in that I use a stereo input on my desk..
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Re: What the heck happened ! (Bad bad gig)

Postby CS70 » Mon Oct 28, 2019 1:52 pm

Ahah Hugh you got there first, I was thinking as well of a mismatch on how the signal was presented on the cable and what the DI was expecting.
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Re: What the heck happened ! (Bad bad gig)

Postby shufflebeat » Mon Oct 28, 2019 1:58 pm

MarkyC wrote:...I use the same leads all the time (just so they can't be faulty)...

Alert! Alert!

Nothing really specific to add except when I see the word "can't" I begin to imagine situations where it actually can.

Have you checked the polarity of your own leads? They may seem fine in isolation but problematic in combination.

Personally I'd carry a line level isolator (ART DTI) rather than a stereo DI.

Running in mono as suggested is often a safer option if your show doesn't depend on stereo.

[Edit] ...or all the more likely stuff mentioned since I started writing this post.
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Re: What the heck happened ! (Bad bad gig)

Postby MarkyC » Mon Oct 28, 2019 4:04 pm

Thanks everyone and especially Hugh for enlightening me on stuff I have no idea about :blush:

OK so get what the issues is, which is a relief in a kind of way (Yes the cabling does end in a TRS connection grr)

So moving forward should I always use XLR(f) to TS cables and use them for mixing consoles and DI boxes as default?

This sounds straightforward, but am I now creating other issues?
What do you think is the best default position?

Thanks everyone!

(and yep as someone that presents every day, believe me I know nothing is foolproof and you have to practice and plan in order not to fail!)
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Re: What the heck happened ! (Bad bad gig)

Postby Hugh Robjohns » Mon Oct 28, 2019 4:56 pm

MarkyC wrote:Yes the cabling does end in a TRS connection grr

Ah ha! That would explain it. DI box only picking up the tip and sleeve contacts. Classic! :D

So moving forward should I always use XLR(f) to TS cables and use them for mixing consoles and DI boxes as default?

No. It's always better to stick with balanced connections where you possibly can. So XLR-TRS is the perfect choice for the balanced line inputs of most mixing consoles.

The only potential problem is where the PA guys want to use a mic input. You can obviously use straight XLR-XLR cables for the physical connection -- and the Largo's main output transformers are protected against phantom, of course -- but you will potentially have a problem with the largo's line output level which may well overload the desk's mic preamp inputs.

The most elegant engineering solution would be a couple of inline XLR pads, as I mentioned -- 30dB is the standard value for such applications, but 20dB might well be enough for most cases. That would allow the balanced, padded-down Largo outputs to feed the balanced mic inputs without further problems.

However, the standard live-sound way of dealing with a line output feeding a mic input is a DI box. So if faced with that from your friendly local PA guy, your best bet is to whip a couple of XLR(f) to TS plug cables from your emergency kit bag and use those to connect your Largo to their DI boxes, thus ensuring that the cold sides of the Largo's output transformers are grounded to provide an unbalanced output suited to the DI box's input.

H
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Re: What the heck happened ! (Bad bad gig)

Postby MarkyC » Mon Oct 28, 2019 5:18 pm

Thanks Hugh, blimey that advice is so clear and easy to follow. :thumbup:
I'll get the 30bd pads and some of the XLR(f) to TS plug cables you mentioned.

Beginning to feel (slightly) less nervous about the whole thing again ish....

Cheers as always!
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Re: What the heck happened ! (Bad bad gig)

Postby Hugh Robjohns » Mon Oct 28, 2019 6:56 pm

:thumbup: :ugeek:
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Re: What the heck happened ! (Bad bad gig)

Postby The Elf » Mon Oct 28, 2019 10:55 pm

I had Orchid build me a couple of stereo line-in to line-out AND mic-out boxes. These have proved popular with the PA guys I've worked with - they have the choice and I can absolve myself from blame! :mrgreen:
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Re: What the heck happened ! (Bad bad gig)

Postby Dave Rowles » Wed Oct 30, 2019 10:00 pm

Depends on the DIs that he was using, but you a lot of the DIs I use are able to accept XLR inputs, and then you can apply the pad.

It sounds like you should connect XLR-XLR to the mixer and not XLR to TRS. The pads sound like a good idea to be safe, however, I connect line level stuff to Live mixer XLR ins and most of them either cope fine, or have Pads built in. If someone appears with something with an XLR out, I'd always just take it straight into the Mixer XLR.
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Re: What the heck happened ! (Bad bad gig)

Postby MarkyC » Thu Nov 21, 2019 12:34 pm

Quick update - made the purchases Hugh mentioned, giged last night using the XLR(f) to TS cables. All was good sonicaly, so thanks guys! Performance wise took me a bit to relax after the last show, but this one will help!

So thanks all!
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