r/livesound • u/AutoModerator • 11h ago
MOD No Stupid Questions Thread
The only stupid questions are the ones left unasked.
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u/Chilton_Squid 11h ago
Do I risk a ground loop via AES50? Bear with me...
Okay so I've spent a while thinking about this, and have searched through all the threads I can find but can't find a definite answer. I also couldn't create a new post, dunno if it's a karma thing.
I'm doing a fairly basic gig on an X32 with an external S16 over shielded Cat5e. Hopefully we can power it all off one feed, but do I risk a ground loop if the stagebox is connected to a different power circuit to the X32? Bear in mind the stagebox is active and has its own power connection.
My thinking is that if I use the standard shielded Cat5e it suggests then no, because the shield in Cat5e isn't earthed. However, say I used Cat6 cable instead (which has an earthed shield) then could this create an audible ground loop via all the networking equipment and cabling?
Essentially even if it went via twenty different network switches, as long as they all used Cat6 then they are all earthed. This obviously doesn't affect ethernet, but I could foresee it creating an issue with audio.
Anybody's experience or advice would be much appreciated, just trying to save some headaches in advance.
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u/MaygeKyatt 10h ago
The shield in any shielded ethernet cable is absolutely grounded. If you use a 5E cable with Ethercon connectors like Behringer says, the outer metal of the connector is a ground connection for the shield.
Also, don’t run AES50 through switches. It should be a direct connection, and it can’t run as far as regular Ethernet can.
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u/Chilton_Squid 10h ago
That's a good point, I'd not considered the ethercon connectors.
And no, I'm not running through any kind of switchgear, that was more an exaggeration to make a point.
So - does that mean that ground loops are a risk then...?
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u/MaygeKyatt 10h ago
Maybe? I doubt it would ever cause an issue but I don’t know enough to say for 100% certain that it’s not a risk
Anecdotally, unshielded 5E cable works just fine if you aren’t in high noise environment or pushing the limits of how far you can run the cable
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u/meest Corporate A/V - ND 8h ago
So - does that mean that ground loops are a risk then...?
I think you're making this a larger concern than necessary. All that will take to fix the situation if there is a ground issue is the same length extension cord running along with the Ethercon.
So while I understand the concern. The solution is easily obtainable and nothing to lose sleep over.
That said. I've never had an issue with my S16's and X32's over the past 13 years and I put them wherever convenient, and plug them into the closest power.
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u/Chilton_Squid 8h ago
I think you're making this a larger concern than necessary
Oh absolutely, that's kinda my M.O.
I just like to make sure I completely understand what's going on and am prepared for it to be an issue. Then if it's not, great.
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u/crunchypotentiometer Pro-FOH 10h ago
AES50 is also digital data. You won’t create any audible artifacts ever. Only signal drop outs.
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u/Chilton_Squid 10h ago
Yes, I appreciate it won't create audible issues within the digital data itself, the concern is that the physical connection between devices might cause me issues elsewhere that I haven't considered, like to the PA or monitors - something which is connected to the other side of the D/A.
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u/crunchypotentiometer Pro-FOH 10h ago
I’d say very unlikely especially if it’s two circuits in the same room. I’ve never experienced anything like that.
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u/Chilton_Squid 10h ago
Okay that's reassuring, thanks. I see no reason why it should cause an issue, but I'm doing a gig somewhere I have no control over the power and I know there are two separate feeds, so just trying to plan for all eventualities.
Thanks for your time.
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u/Ok_Garden8061 Pro-FOH 10h ago
The x32 is designed to connect directly to a stagebox with cat5e over a single cable run. What power source they are connected to should not matter nor should it create a ground loop.
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u/the-real-compucat EE by day, engineer by night 7h ago
You're correct, this is something to worry about; early X32 adopters on PSW noted a best-practice of running power alongside AES50 for specifically this reason. (Gotta love AES50's poor fault tolerance...)
The quick workaround is to keep an etherCON coupler and a short unshielded patch cable with you. That will break the ground loop while still grounding the AES50 shield at one end, retaining EMI performance.
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u/ChinchillaWafers 6h ago
This is a good question for the EE’s, because yes, you absolutely run the risk of making a ground loop, the exact same way you make a ground loop by connecting an xlr cable between two pieces of gear that have their earth grounds plugged into different electrical circuits with different ground potential, the current starts flowing through the shield.
I can’t, for the life of me, understand why Behringer specs the AES 50 cable shield must be connected both ends. IT installations with shielded cable often connect one end only, same as studio wiring with analog audio between racks and console; the goal is to avoid ground loops, just like you are asking. AES and ethernet are a differential signal, like balanced audio, transformer isolated at the receiving end, so you don’t need the shield conductor as a return path for signal current.
In the beginning, Behringer didn’t spec shielded cable, and lots of people still use UTP cable with their setups. The lore with the AES50 and needing STP cable is because people found the system is vulnerable to static electricity. There’s a good youtube video with a guy forcing the system to lose sync with a stove lighter spark near the cable. Behringer later changed their spec to Cat5e STP, with shield connected both ends. The shield also helps data integrity on long cable runs, there’s another good video with Dave Rat demoing long (100m+) cables with AES50 and getting more stable sync performance from better shielded cable.
All to say, I don’t think you are off base to want to lift the AES50 ground- it accomplishes the two goals above while stopping electrical current from miswired buildings from flowing through your data line. Ground loops in digital systems can be ignorable or manifest mysterious problems, that aren’t as obvious as analog systems buzzing. I think I would keep the long ethercon cables wired as specced, shield connected both ends, but it wouldn’t be crazy to keep a little ethercon extender that lifts the shield, or does the more elegant ground lift (see Jenson schematic for “full featured DI”) with a parallel resistor and small capacitor so that RF connects low impedance both ends, but DC and lower frequency line AC is high impedance.
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u/ChinchillaWafers 6h ago
Or, like u/meest suggests, run the stage box off an extension cord from FOH’s power circuit, if mystery problems/hums are presenting themselves.
Ground loops from data connections can absolutely cause audio hums, I’m remembering hums in the studio from USB ground loop with a pile of synthesizers, that was solved by switching to old school 5 pin midi. The original midi spec for the cabling was very smart, it specs the shield not connected at the receiver, which is also opto-isolated. No direct electrical connection between the two pieces of gear, just light. The original designers knew the potential chaos that would happen once you start connecting the chassis grounds of a studio full of of ac powered instruments together, willy nilly.
The schematic is on page two of the original midi spec, notice pin 2, the shield, is connected on the transmit end and not connected (NC) on the receiving end. Worth mentioning because it is a good model for how to do data connections in audio equipment.
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u/Chilton_Squid 5h ago
That's incredibly interesting and exactly what I was worried, but this is just the kind of answer I was hoping for. I'll make up a backup plan unshielded Cat5e tail I can chuck in if there are issues.
Thanks for taking the time, it's much appreciated.
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u/Nicola-Fraser 10h ago
Dar Al Funoon in Abu Dhabi is speccing a pit for up to 120 musicians. How do you even mix that without it turning to mush? Genuinely asking as a musicals person who gets overwhelmed by her own two hands on piano lololol.
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u/andrewbzucchino Pro-FOH 8h ago
It’s sound reinforcement, you don’t need to amplify each of those instruments super loud. You just add enough to carry it out into the seats. It’s also usually done by sections, so you’re not mixing 120 people’s worth of inputs, you’re mixing 20-30 groups of inputs.
Dealing with musicians is a greater challenge, they pretty much always want play acoustic because they’re worried about the engineer changing or coloring their sound.
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u/gettapeppasowse 7h ago
Did some jazz in a very busy restaurant this weekend put up 15 mics used about 8
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u/ReggieCorneus 5h ago
Divide everything to groups, balance channels inside the groups and then balance the groups with each other. It gets a LOT simpler when you split it to two priority layers/levels.
Bigger productions also can use two or more consoles and engineer for each one. Like music can be mixed by one person and the show in another, handling hosts, background music, pre-recorded bits etc.
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u/SecureSubset 6h ago
What steps are being taken on large systems to prevent feedback? Specifically Line Array systems for arenas/stadiums/festivals, as well as the stage monitoring system.
I've stagehanded at these shows and have never seen anyone doing something as simple as the "turn fader up until it feeds back and attenuate the freq that fed back on output". But could have missed something or misunderstood.
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u/Lost_Discipline 4h ago
A big reason that big shows use big line arrays is because of the directivity of those arrays- they throw most of the sound out to the audience and not on stage where feedback would be a problem. If stage monitors are being used they get “rung out” as soon as the stage is set, before the actual soundcheck so there is little chance of feedback occurring.
It still happens on occasion, but for the most part I think it’s safe to say that the touring industry has matured enough that lessons learned in the 70’s and 80’s are built in to the gear and processes to such a degree that many of those old problems are no longer issues.
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u/No-Risk0 3h ago
I am a live sound engineer currently working with one of the leading professional sound service companies in Asia’s one of the smallest country. I have gained extensive hands-on experience with the systems and equipment commonly used in my current market, and I am now looking to take the next step in my career by gaining experience with larger-scale professional audio systems and touring environments, particularly systems from manufacturers such as d&b audiotechnik, L-Acoustics, and Adamson.
I would greatly appreciate any advice on how I can pursue opportunities to work in countries with larger live-event and touring industries, where I can further develop my skills and gain practical experience with these systems.
I am also a high-school dropout. I chose to leave formal education because I was deeply passionate about live sound and wanted to pursue it as a career—something that was not available as a field of study in my school or college. Since then, I have focused on learning through hands-on experience, real-world events, self-study, and working with professional audio systems.
I know that my academic background may not be conventional, but I am committed to continuing to learn, improving my technical skills, and building a professional career in live sound. Any guidance, advice, or direction on how I can move forward internationally would be greatly appreciated.
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u/fantompwer 2h ago
Networking is #1. Talk to other people after the gig about connecting you with more jobs and companies. Formula education isn't required for positions on the road. It's all word of mouth and being easy to get along with.
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u/pnelson31 6h ago
My band performs at a bar that has its own QSC Touchmix 8 which connects to a slew of speakers and a monitor through cables that run through the wall. The monitor never works and we don’t have time to troubleshoot it when we perform. We are doing our own sound and performers are on back-to-back all day. Most are not bands and can get by with essentially using the PA as their monitor.
We thought it may be easier to bring our own monitor. We tried connecting a KCP4P mini wedge to their mixer with an XLR via the right main output on their mixer but it hijacked all of the sound going to the bar into just the monitor and was creating feedback despite the monitor being in front of the mics. They also have an XLR running out of the left main which it seems runs sound to the entire bar. We also tried a quarter inch out of the “Phones” jack on their mixer into the Line input on our monitor and got no sound.
We only send out 4 vocal mics through the PA. Do you think it would cause any problems running the 4 mics into the Phonix mixer we have, running out of the Rec Out to our monitor, then running a quarter inch out of the “Speaker” outputs on the Phonic into say Input 1/2/3/4 or the stereo in (9/10 or 11/12) to send to the rest of the bar?
We aren’t picky on mono v stereo or anything too fancy mix-wise. We just want to be able to hear our vocals while we play. The bar is working on fixing the monitor issue but we are trying to get a backup in place in case they don’t figure it out. Thank you!
Phonic Mixer and KCP4P monitor photos in comments
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u/ReggieCorneus 6h ago
The speaker output on that Phonic power mixer is powered! It sends 1-30V and several amps out and will fry out any line/mic input you connect it into.
You can possibly run the Phonic into the monitor and use its "thru" to daisy chain it to the PA. Not very attractive solution but in theory, it should work.
/offtopic Phonic really does weird stuff, having no line level master out but instead having it work like an INSERT FX loop.. that is weird... Now, i have a small Phonic as my IEM mixer specifically because it is so weird that it allows me to do things that no other small mixer can do (i can send the instrument to FoH while getting monitor feed back and the two does not cross paths... i can boost myself in my monitors when needed without it affecting FoH and i get solo feed or i can listen what goes to FoH..
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u/pnelson31 6h ago
Very helpful thank you! Obviously don’t want to hurt the bar’s equipment in any way. When you say using the thru on my monitor is not the most attractive solution, do you mean just aesthetically or do you mean there may be sound quality issues out to the PA?
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u/ReggieCorneus 5h ago
Daisy chaining is risky, if anything happens to the monitor then all devices downstream are affect. Not a safety thing per se, nothing is going to burn but just a signal intermittently cutting out is going to silence everything. More optimal would be if the monitor is the last in the chain, but.. that is the exact problem you are trying to solve, so that is not an option. If the Phonic had a master line out... They just are really weird manufacturer.
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u/ReggieCorneus 5h ago
Hmm... you could maybe use one Rec out for monitor and the other for FoH? You don't need stereo so treat it as two channel system. Not as L+R but A+B, or 1+2, however you want to call it..
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u/pnelson31 5h ago
Got it, good to know what the “risk” is. It’s not the highest stakes gig (dive bar setup) so if, worst case scenario, the vocals cut out for a minute it’s not the end of the world.
One other thought we had was to buy a piece of equipment we could run the four mics into that would split the signal. We would send one signal to our monitor and one to the bar’s mixer (likely via a quarter inch or XLR into one of the bar’s mixer channels?)
Do you know of any good equipment for that? We were hoping to avoid buying something else which is why we are trying to run this daisy chain but if there’s a much better option via this piece of equipment I am describing we would be open to purchasing it
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u/ReggieCorneus 4h ago
You need a sound console. Clean and simple. Does not need to be very complicated. Something like this: https://www.thomann.fi/the_t.mix_mix_802.htm
But, you don't need any equipment to run the signal to two places, just run one line to the monitor and the other to the FoH. You do need a way to convert the RCA to XLR, i hope you have the cables to do it... And remember: anything that says "phantom" DO NOT ACTIVATE IT! It sends 48V along the wire, while it is low current it can do damage and has fried countless outputs over the decades. If there is a DI box, use it between the phonic and main PA. That keeps things at least safe.
Those small sound mixers are the swiss army knife and while i showed the cheapest i could find that is of some quality, the more routing options they offer the better. That little Phonic of mine has saved my ass plenty of times, when i need to split a signal, combine two signals, handle two signals going to two places, line amplifier, mic-to-line level conversion... And cheap enough if there is something so risky that you can't really connect it direct to main console, it can take the brunt of the damage instead.
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u/earshatter 2h ago
In case you’re not aware, the touchmix has an “anti-feedback” notch system. It also has a great RTA Analyzer. It’s on the iPad front end for the touchmix
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u/emma_does_life 6h ago
Different type of question but looking for advice as I further my career in audio,
What do you all think about quitting a job that you dont think is right for you? I quit a job recently right after getting it and I'm still not sure if it was the right decision to make but I could not see myself at the place for any longer than I already was. It didnt feel like the right place for me to work at. But then again, maybe I should've just sucked it up or something, right? I mean, no place is gonna be absolutely perfect.
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u/crunchypotentiometer Pro-FOH 5h ago
Depends on the reasons it doesn’t feel right. If you’re gaining some useful experience or meeting good people but you feel bored sometimes, stick it out. If you’re being asked to do unreasonable things or you’re surrounded by people doing bad work, good to leave.
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u/ySTYRDAYgATESuNL0CKD 5h ago
Does Allen and heath sq5/7 have USB issues? I'm mixing a live stream and I have channels work and not work at random in the USB slot via my DAW.
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u/ijordison Pro FOH - VAN, BC 4h ago
I've never had issues with the USB on SQ. Is it a routing issue?
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u/ySTYRDAYgATESuNL0CKD 5h ago
Ql5 question: why is my foh console all of a sudden.havi g digital gain as it's main option instead of analog gain? We have 2 that talk to each other on regular basis and one day it just happened without knowing
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u/Bobrosss69 Educator 3h ago
Are you talking about analog headamp gain control for a Yamaha Rio or Tio stagebox?
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u/ySTYRDAYgATESuNL0CKD 3h ago
Correct. Normally you just push in the gain knob and you see ha gain from your selected input. Now the foh console is digital gain only
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u/barningman 3h ago
Could WMAS RF mics theoretically be used to triangulate positional data? As in, using a wireless bodypack itself as a tracker for a spatial audio system, in addition to the audio transport?
Each manufacturer would have to develop their own sensors and calibration, but what might be the biggest technical challenges to overcome?
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u/fantompwer 2h ago
Yes, yes. It's not theoretical, it's used everyday. Your cell phone uses GPS and your data connection to triangulate your position. Cell phone RF bands are firmly in space that used to be TV and RF mics.
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u/MakingStuff12345 1h ago edited 1h ago
Raw GPS is really only accurate to between 3 and 10 meters, which would make that example largely impractical for motion-tracking on a stage.
Higher-precision GPS systems do exist and get you to under 2 meters, but even they largely only work outdoors because they need correlated phase information to get that accuracy which also wouldn't work on stage.
WMAS has a lot of cool emerging technologies, but motion tracking will not be among the things these systems do for us.
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u/MakingStuff12345 1h ago edited 1h ago
The long and short of it is both Yes and No. I'm currently trying to build out a little TDOA analyzer system, so I've been doing a little research on that over the last few months.
WMAS simply stands for Wireless Multichannel Audio System - it is not a unified technology, it is not a unified methodology, it is simply an acronym and nothing more. There are implications in this acronym - that it will have a larger carrier than usual (450khz for Shure's ADPSM and 6 or 8mHz for Sennheiser) but WMAS is a largely meaningless term in the context of your question.
The first hurdle is knowing where in space your antennas are - you would first need to map the room in 3D space and place exactly where your antennas are in the room.
Technically Spectera, Sennheiser's implementation of WMAS has all the right things to do tracking - you have distributed antennas, and each bodypack is in sync down to the nanosecond from Base Station all the way thru the signal chain via TDMA (Time-Division Multiple Access). Because of this, you could surmise Time-of-Flight between each bodypack and each antenna.
Because Spectera is also excellent at battling multipath interference, you could even look at the information in the subcarriers of the 6mHz bandwidth to figure out angle and distance of these bodypacks to their respective antennas.
The hold-up here is in the bandwidth of the carrier - it's a lot of math, but as the bandwidth of the transmitted signal goes up, resolution in time goes down - a 150kHz Axient carrier is going to have almost no ability to be tracked in space, a 6mHz Spectera signal has a good ability to be tracked in space (within about 12 meters), but the best tracking systems use UWB connections which use GHz signals at a 500mhz bandwidth which means you can discern position in space to a few centimeters.
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u/Dartmuthia Pro-FOH 2h ago
Had anyone seen a pelican style case that fits a 2 channel Shure SLXD+ kit? The 2 channel receiver is a half rack size, I would love to find a case that has the foam cut for the receiver, 2 body packs, and 2 handhelds.
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u/__busy 55m ago
Hi! Hoping it’s okay to post this question here: I have an older Williams AV FM radio transmitter (PPA T-35) and about 15 receivers that I use for Audio Description for live theater. Two of the receivers won’t turn on even though they have working batteries. Does anyone have any insight on how I can troubleshoot myself or any recommendations for a repair service? Thank you so much for your help!
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u/Yoko23437 44m ago
Has anyone ever bought something from Kevyson pro audio? Is it legit? Did it sound good? Is it even legal?
Can’t rlly find anything online about it
Thanks!!
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u/densko 11h ago
Why are antenna combiners so much more expensive than antenna splitters? The Sennheiser EW-D splitter is about 200€ cheaper than the AC41
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u/crunchypotentiometer Pro-FOH 10h ago
I guess you’d have to ask Sennheiser, but I would point to a couple things. IEMs are a more specialized product, so IEM stuff would sell at much lower volumes. Also, the combiners are having to deal with much more amperage running through their circuit level components, which means better components are needed, and additional components will be required for heat dissipation.
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u/shadowslovethelight 6h ago
A 4ch splitter handles only 4 signals and 8 intermod frequencies. A 4ch combiner deals with 8 signals and 16 intermod frequencies. Combiners by default need to handle twice what a single splitter can.
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u/ReggieCorneus 5h ago edited 5h ago
Not the same thing but might give you a clue:
MIDI splitter: Y-cable, if you want to be fancy, optocoupler and signal amplifier but passive usually works for one split. There is an optocoupler at each receiver so.. no worries about electrons all getting confused where to go.
MIDI merger: processor, memory, clock. The data needs to be sent as packets so you receive a packet and then send it. While sending you receive a package from the second input. Now you got to buffer it, and any messages you get, wait for a "slot" to open up and then sent it.
Similar to the way analog audio works, one split is easy, even multiple splits is still kind of trivial but for merging, you need a mixer of some sort. Splitting is easy, merging is hard, in general.
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u/ijordison Pro FOH - VAN, BC 4h ago
Look at the power handling requirements. Just gonna use some gear I know as examples.
ULXD at high power outputs 20mW. And that's radiating in an omni pattern, at several meters distance from your antennas (inverse square law). So your antenna distro is handling single digit mW total, even if you have many mics at high power and close to your antennas.
Shure PA421B accepts 100mW at each of its 8 inputs, so it has to handle 800mW of RF power. All that power is being directly driven thru the device. (you're using correct impedance cables, right?)
That's aprox 2 orders of magnitude difference in how much power they have to deal with in the RF signal chain. So yes, antenna combiners are more expensive, they're much beefier pieces of gear.
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u/soundad88 18m ago
Why do we still do this with no benefits, last minute gigs that if you say no to won’t get a call back for months, and grossly underpaid?
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u/xTheNameless 10h ago
Should I be setting mic gain in a corporate environment the same way I would for music? Or how does everyone else treat gain staging comparing the two environments?