Dirt in the mic in Port (Maybe)
 

During a concert yesterday I tried to get clean sound from the Concert board xlr thru my 2 channel xlr rolls cam mixer to the 1/8 mic input on a sony 550v = noise 60 hz buzz. I think maybe the port is physically dirty. What to poke in there? to clean it up before a bit of deoxit
thaks

Re: Dirt in the mic in Port (Maybe)
 

If the connector was REALLY dirty there would be a possibility of an intermittent signal but 50/60 Hz hum usually indicates an issue with the power supply and/or grounding (ground loop to be more specific).

Re: Dirt in the mic in Port (Maybe)
 

thanks zoran
should I use batterys to supply power to the rolls cam mix rather than ac?

Re: Dirt in the mic in Port (Maybe)
 

A battery power supply may be best but it might be an idea to invest in a transformer Isolation box, I personally use the ART make but there re others from Rolls.

They also have the advantage of being able to ground lift the audio circuit but isolating via the transformer will be of great advantage.

Re: Dirt in the mic in Port (Maybe)
 

Agreed. RF noise can get in a bunch of ways, but the two biggies are the power cable (fix is to use batteries if you can), and the unbalanced mic line (fix is balanced XLR cables all the way to the camera, which is why they exist).

If your camera doesn't have XLR audio inputs, you can still run XLR cables right up to the camera. Then you have to convert from balanced to unbalanced audio, and from XLR to 3.5mm mini-plug. This requires a http://www.bhphotovideo.com/c/product/772496-REG/Sescom_SES_LZSLHZ_XF14_SES_LZSLHZ_XF14_Low_to_Low_High.html and an adapter. There are of course many ways to do this, and that link is just one example.

My point is that you can minimize the length of your unbalanced cable. IOW, minimize the size of the "antenna" that's picking up the stray RF noise.

Re: Dirt in the mic in Port (Maybe)
 

thanks
Never did understand why I always had obnoxious noise when plugging into professional mixing desks at theatres
looking thru ebay and other places for 2 - 9v rechargables and a charger, and noting that the usual suspects are not in the market place . Was hoping enerloop had a 9v setup but no luck

Re: Dirt in the mic in Port (Maybe)
 

If you are going from a mixing board's XLR, it iwas likely +4dB. (though the Mackie VLZ series mixers had a mic/line switch)
As was stated, you need the proper cables and interface box and/or attenuation to feed your unbalanced mic level input.
I can only imagine the distortion, EMI and other nastys that were present..

Re: Dirt in the mic in Port (Maybe)
 

If you are using the Rolls MX36 cam mixer, it has Mic/Line level switches on both the XLR inputs and the 1/8-inch output.

Make sure you don't have phantom power activated on the Rolls, and since you can't turn off the Plug-In Power on the Sony's mic jack, hopefully the Rolls is successfully handling this voltage since it's specifically made to mount under small video cameras (and has capacitors on the output shown in the schematic).

You may want to try another 1/8-inch TRS cable between the mixer and camera, making sure you clean the connectors and then avoid touching them. Also plugging, gently twisting and replugging to get a good connection.

Anything that is AC-powered in your system, including an external video monitor attached to the camera, can create hum when connecting to a house mixer that is AC-powered from a different location.

So your choices are to use the exact same power circuit as the house mixer, isolate your signal connections with transformers, or power everything with batteries.

Also use a cable tester that can latch onto intermittent wiring faults to check all your cables.

Re: Dirt in the mic in Port (Maybe)
 

As Jay stated, plug all video/audio gear should go into the same AC circuit. This should eliminate ground inconsistencies. (aka, loops) Obliviously, lighting should be distributed accordingly, as it draws lots of power.

Re: Dirt in the mic in Port (Maybe)
 

Try and see. If a ground loop between the main desk and cam mix causes the hum it should be eliminated by using batteries.

Re: Dirt in the mic in Port (Maybe)
 

Thank you everyone
I now have a much better understanding of the issues relating to the ingesting of clean audio to a camcorder from house sound.

Re: Dirt in the mic in Port (Maybe)
 

Any idea how long a continuously powered up mx36 would run on 2 - 9v alkalines?
I've ordered Soshine 500mAh 9V Lithium ion Rechargeable Battery X2 Battery Charger | eBay
which should perform for at least as long

Re: Dirt in the mic in Port (Maybe)
 

When you have a balanced output provided, it's always worth using an XLR M/F barrel with no connection on pins 1 - lifting the ground completely. If the levels match and the connectors are correct it often cures it. you can also use this technique to convert to unbalanced, using just pins 2 and 3.

Re: Dirt in the mic in Port (Maybe)
 

That's a cool notion
Do I doctor a barrel myself by removing pin 1 or can I get one storebot?

edit I see a hosa
http://www.markertek.com/Audio-Equip.../GLT-255.xhtml
ordered one on ebay

Re: Dirt in the mic in Port (Maybe)
 

"Do I doctor a barrel myself by removing pin 1 ?"
- You would NOT physically remove the pin, just disconnect the shield / wire going to it. Make sure the XLR's shell is not tied to it as well.
Normally when going from balanced to unbalanced, Pin-3 is tied to shield/ground. This will not attenuate the signal though.
The Hosa connector should work also. But a DI would be better, and most have a ground lift switch built in.
The Rolls DB25b is a transformer balanced, passive direct box is affordable and has a variable pad build in. You would still need an XLR to 1/8" adapter however.

http://www.markertek.com/Audio-Equip...on/DB25B.xhtml

Re: Dirt in the mic in Port (Maybe)
 

True. But to clarify, we are not talking here about RF. We are talking about 60Hz (or 50Hz in those "slower" countries) hum from the AC power mains. It, too, can get in many ways, but in this case folks are suspecting a ground loop.

The correct spelling is "ENELOOP" a contraction of "energy" and "loop" according to the manufacturer, Sanyo.

Strangely, there does not seem to be a 9V version. Perhaps they feel such a battery would be very difficult to make reliable, because you'd end up charging seven or eight cells in series, and series charging requires the cells to be nearly perfectly matched, or else they do not charge evenly and you end up with greatly diminished capacity. (That's why a charger that charges each cell individually, like the LaCrosse models, is preferable... even compared to one that charges cells in pairs.)

Re: Dirt in the mic in Port (Maybe)
 

We can be. I've picked up 60 Hz trash from HMI electronic ballasts. No doubt about the source. The trash wasn't a sine wave, but it was definitely 60 Hz.

There are many ways to contaminate a signal. Hum from ground loops is just one, and the OP said it was "buzz" which leaves the origin open to question.

Re: Dirt in the mic in Port (Maybe)
 

A 'buzz' is usually 'EMI' (Electromagnetic interference), which can enter a system in a few ways. Usually cables and/or electronics in close proximity to A/C lines or transformers. In this case, 'lifting' the ground would likely not do much. High quality and 'Star Quad' type mic cables do a better rejecting this interference.. which is certainly not specific to wireless systems.
Audio 101: Mic cables should not be ran alongside power cables and crossed at right-angles. secondly, not be in close proximity to gear with large transformers like power amps. I have even experienced EMI from wall-wart and line-lump power supplies, which are normally not shielded by a metal case.

Re: Dirt in the mic in Port (Maybe)
 

Buzz, by definition, is not a 60 Hz sine wave. (Or, of course, 50 Hz in those countries.) It includes some amount of harmonic content. For example, it can be as little as the fundamental plus third harmonic (60 Hz + 180 Hz). Or it can include harmonics up into the thousands of Hz. Be that as it may, if the buzz is coupled into the audio signal (by way of poor shielding, ground loops, electromagnetic coupling, and/or electrostatic coupling) it's still audio.

"RF" implies electromagnetic and electrostatic waves being propagated through space, using some sort of antenna structures. The frequency range from 30 Hz to 30 kHz is defined as Super Low, Ultra Low, and Extremely Low Frequency (SLF, ULF, ELF) at the lower end of the RF range. So indeed harmonics of the power line frequency might be considered within the range of frequencies that encompasses RF.

The question then is how the noise is introduced into the audio system. I suppose if you have an unshielded power cable at any distance from an audio input cable, you could consider those two cables to be antennas. You might even make that argument if the two cables are touching each other, because the electrical conductors are separated by some finite distance. But if we're talking about a ground loop problem, then RF propagation isn't involved, (I'd think that in theory it's more of a voltage divider issue) so in that case the term "RF" might not be correct.

When I'm thinking of "RF interference" I more likely am thinking of a high powered radio transmitter, with a frequency significantly about the range of audio frequencies (i.e. much higher than 20 kHz) getting into the audio system, and then being demodulated by some non-linearity in the electronics, which creates an unwanted component within the audio signal. That's entirely different from having a signal within the audio frequency range induced into the system, and being directly audible without any sort of demodulation taking place. But again, that isn't defined with "stone tablet" authority anywhere.

All fine points which probably don't affect the solution to this particular problem.

Re: Dirt in the mic in Port (Maybe)
 

We sometimes use two terms her in the UK:

BUZZ is the description for the RF type of noise that is peaky or can also be a connection fault.

HUMM is the low frequency mains inducted 50/60hz sine wave or can be caused by earth loops.

Re: Dirt in the mic in Port (Maybe)
 

That's pretty much the same set of terminology I'd use.

HUM is usually just the fundamental power line frequency, or perhaps fundamental plus third harmonic (introduced commonly by 3-phase power wiring systems).

BUZZ contains a lot of higher harmonics. If you look at it on a scope, you no longer see rounded sinusoidal waveforms... it starts to look jagged, perhaps a variant of sawtooth or square wave.

The difference is that I wouldn't describe "Buzz" as "RF type of noise" because in my mind, RF implies a signal that is intended to be transmitted via a radio system (e.g. a wireless mic or a nearby broadcast transmitter) which is accidentally received by some part of the audio system. And "Buzz" can be introduced by a bad or open ground, or by a ground loop (typically at a site where lighting dimmers are in use) rather than being "received" at a distance from the electrostatic field produced intentionally by a radio or TV transmitter.

But, going strictly "by the book" the frequencies in "Buzz" do fall within the lowest end of the "RF" range.

[And in my experience, hum is much more easily removed from a track than is buzz, because you need to filter only a few frequencies with mostly sinusoidal waveforms.]

Re: Dirt in the mic in Port (Maybe)
 

What a great re-read of the technical reasons for unwanted audio noise
Well it's a year later and the only method to achieve in-camera noise free audio to my new cam, an ax100 is to either use the onboard mics or a wireless mic designed with a 3.5 out to the camcorder a samson al1, am1
However I still need to ingest house audio via xlr.
I've gone battery everything, the rolls mx36 mixer and the camera 100% battery, bought a ground lifted xlr adapter, all to no avail.. Still have very hummy buzzing going on.
Is there a black box or other device which filters out the noise or other simple solution
tks

Re: Dirt in the mic in Port (Maybe)
 

It seems like the only item that hasn't changed in your setup is the MX36 mixer.
Do you still get hum if the MX36 is attached to the camera input but there is nothing yet connected to the MX36 from the house mixer?

Re: Dirt in the mic in Port (Maybe)
 

I never leave home without a few IL19s.. if I will need to interface with other systems.. especially A/C powered gear. Sescom IL-19 Inline Pro Audio Hum Eliminator THE INDUSTRY STANDARD
I've used them for years.. long before Tower Products (Markertek) acquisition of Sescom . One of the few pieces of useful gear that actually went down in price

Re: Dirt in the mic in Port (Maybe)
 

no noise what-so-ever when the mixer is turned on and the stereo output from the mixer is plugged into the Mic in on the cameras via a 16" cable.
ditto on the noise level when the samson wireless and a sony 44b lav with its own battery are attached and functioning.
It's finding a way to quietly ingest the audio from the house system (I have 4 venues tested and all are similarly fraught with buzzhumm
I have been attempting to input via an xlr on the mx36 and acccording to the rolls docs "2 xlr balanced inputs for connection to any standard dynamic or condenser mic. The input circutry has a very wide input range and can accommodate almost any (mic ti line) level signal"

will order up a sescom today (fingers crossed)

Re: Dirt in the mic in Port (Maybe)
 

I've also read that description in the manual about the wide range of input signal. However on the web page (but not in the manual) it says there are mic/line switches on the inputs as well as the output.
I don't see any switches on the inputs in the photos, but they don't show all the sides or the phantom power switches.
Other than the hum and buzz, does the level of the signal seem ok or is it extremely hot when getting a signal from the house mixer?
Are you certain the phantom power is switched off for the input you're connecting to the house mixer?
Have you tried using the Aux Input jack with a correctly wired cable for a line level signal test?
The illustrations also show a headset mic input, but it's not on the block diagram.
Maybe their claims about the XLR inputs being able to handle line level signals just arent correct.
Good luck with the IL-19. I don't have one of those but I use other transformer isolation boxes.

Re: Dirt in the mic in Port (Maybe)
 

mic/line switches on the inputs: None that I can find. The only switches on the side are Phantom and they are both in the off position.
The last venue I tried it a couple of weekends ago the signal was so hot from the house system that I could not attenuate it at all. Just blasted in and If I had vu meters they would have been hard over, bending the needles
The headset mic input on the front works fine with the wireless receiver but I have not yet attempted to ingest house sound thu that 3.5

I sent a message to Rolls asking about the slr mic/line switches (you have a good eye as well as a good ear)

Apart from the rolls which has a handy under the camera mount to the tripod, I have a new tascam dp 004 purchased a few years ago but never figured out how to use it however I might soon if the sescom inline hum elimenator fails to quiet things down. or try that passive beachtec under the cam which seems to work in similar situations for those reviewing it on the bh site

Re: Dirt in the mic in Port (Maybe)
 

Unfortunately the manual is vague. But I agree with Jay and also suspect the MX36 'Auxiliary' input is for line level input sources. I don't recall seeing an XLR mic/line input w/o some kind of switching.. (I don't see any switch on schematic input stage either)
The manual does however state under the 'CONNECTION'' header on page 6: " Stereo auxiliary sources such as the output from another mixer ...... ... ... be connected to the AUX IN via a stereo 1/8” (3.5mm) Tip-Ring-Sleeve plug."
The specs state it has a maximum input level of +20dB, which is typical for nominal +4dB op level that one would find on a console mixer.

Re: Dirt in the mic in Port (Maybe)
 

so If I were to use the 3.5 aux in to the mx36 from the house desk what sort of xlr to 3.5 would you suggest ? the Il19 will be here Monday so whatever should have it in line too I presume.
Also wondering about attenuating or adjusting the level of the signal at the aux in jack

Re: Dirt in the mic in Port (Maybe)
 

The aux. input on the MX36 mixer appears to be a 'stereo' L/R input and uses a 1/8" TRS connection.
So if a single line output from a PA mixer is balanced, (typically a 1/4" TRS or XLR connector) a custom cable (or plug) would be needed.
The 'hot' terminal, (XLR pin-2 or 1/4" tip) would be connected to both the 1/8" plug's tip and ring. XLR pin-3 or 1/4" ring terminal are tied together and connected to shield/ground. If the cable run is long, put the IL-19 iso transformer at your end of the cable, so the cable run would remain balanced most of the distance.
If the PA mixer's output is unbalanced (typically a 1/4" TS), the tip connection would feed the 1/8" plug's tip and ring. (There's a diagram in the MX36 manual)
The other option is to get a 'line to mic' level attenuation/pad and use an XLR mic input on your MX36 mixer. In this or the unbalanced case the IL19 should not be necessary unless there's a ground loop or other issue.
In all of the scenarios, Phantom Power should be OFF.

Re: Dirt in the mic in Port (Maybe)
 

Thank you sirs for the detailed explanations
I've ordered a hosa ATT448 to try
Hopefully the audio quality will now compliment the video much better than it has in the past.

Re: Dirt in the mic in Port (Maybe)
 

I wish to thank the contributors to this topic
Just tapped into the sound system at the university auditorium which was giving me so much trouble previously and with the aid of the devices recommended in this thread was able to record clean audio for the fist time at this venue

Re: Dirt in the mic in Port (Maybe)
 

That's good to hear about your greatly improved results!