That hum, what do do on site?

[Kimchoc]

I shoot depositions and often get zero time for setup. Just finished one today and I knew as soon as I put my headphones on, it was a bad one. No real time to trace it down. So I figured I'd just use the equalizer in Pinnacle14 to take most of it out.
I was using an ATR lapel mic, the cheap one, and a Realistic 1070B, plugged into my mixer and then out into the HMC40.

No, I cannot afford 1000.00 mics at this time. I just sprung for the HMC40 for the time/date stamp and that is my large purchase for probably the rest of the year.

So, I was wondering would there be an equalizer that I might put inline that would be reasonably priced? Sort of massage the sound a bit until more depos provide more money this year?
The end sound doesn't have to be perfect. Its not music and its not a movie. The customer is not really interested in perfect sound, just IF they can hear the witness and their questions. Frankly, I dont think it is ever seen as litigation usually settles out of court.

Be all that as it may, my large purchase is done for this year. If you pros could see your way to suggesting a future purchase, fine, and if you can suggest anything in the gorilla budget arena, please tell me.

As you can tell by my purchase of the HMC I don't mind spending a decent amount and I would buy the 1000 lapel mic if that is the end all fix. But, I cant at this moment.
BTW, this is just a hobby at the moment. Learning now so that video can provide enough money for obamacare when I retire in 3 years.


Suggestions?

Thanks,
Gary B.

 

[Alex H.]

Protect your ground. First, make sure that all wiring in your mics and signal chain is solid (no fraying or cold-soldered connections).

If you have anything plugged into the wall, there's potential of hum from dirty power. Ebtech makes this incredible little device called a HumX that cleans up dirty power and maintains a safe ground. I keep a handful of them in my kit, especially for live sound (our convention center has terribly dirty power).

Ebtech also has a ground-loop eliminator for audio signals.

Also, and this can degrade quality just slightly, you can try the DI box conversion from mixer to camera. Take an unbalanced, 1/4" out from the board. Connect it to a DI box in, then use the DI box's XLR connection to go mic-level in to your camera. That will give you a ground lift switch in your signal chain. Not the best solution, but it's reliable in a pinch. And it may not do much (if anything) to your signal, really.

 

[Richard Crowley]

You don't need a $1000 microphone to avoid hum. Indeed, a $1000 microphone is not really any more immune to hum than a $25 mic.

So when you bring the exact same equipment back home and set it up the same way, does it still hum? Is it intermittent? Wiggle all the connectors, fondle the cables along the whole length to see if there is a fault somewhere. Move the microphone around the room to see it if pickups up ambient acoustic or magnetic field hum from things like CRT monitors, appliances, etc. etc.

You can use software to remove a large part (perhaps even most) of the hum. If you don't want to spend any money, you could try the freeware Audacity. I believe there are special preset notch filters to handle mains hum (50Hz or 60Hz depending on where you live, you didn't reveal your location).

Had you used this combination and configuration of equipment successfully before? Was there anything in the room that might have been a source of a magnetic field?

IMHO there is no future in trying to filter out hum while recording. The only real solution is to eliminate the hum at the source. Perhaps that means having a backup audio cable and microphone (or whatever). For high-reliability applications (like network TV news) you will note that they use TWO microphones clipped onto the newsreader, and they have completely redundant audio.

 

[Chadfish]

Run on all battery power. You'll have no hum.


There are plugins to help with hum removal for the jobs you need to fix. Google around. "Hum removal plug-in" It's probably not necessary. I've done depos, and as long as the voices are intelligible that's all they care about.

 

[Richard Crowley]

Run on all battery power. You'll have no hum.

I would try to run all-battery in those kinds of situations. But it is not a guarantee against hum. A broken ground can still allow electrostatic hum, and nothing but a mu-metal "cone of slience" will be effective against a magnetic field.

There are plugins to help with hum removal for the jobs you need to fix. Google around. "Hum removal plug-in" It's probably not necessary. I've done depos, and as long as the voices are intelligible that's all they care about.

Indeed, I have found the hum-removal notch filter presets in Adobe Audition to save the day when I had an equipment failure.

OTOH, do they allow you to mess with the recording after the fact? Doesn't that destroy the chain of evidence?

 

[Kimchoc]

If I've learned anything from you guys it is to to what you can do in the field to eliminate what you have to do in post. In the deposition situation yesterday I was thrown into an examination room at a medical facility. And i had no time to try turning off and on lights, checking outlets etc.
I'm ashamed to tell you exactly what mic setup I had but I think after working in post today I can narrow it down to the ATR wired lapel mic. I noticed that when the subject got up for a break, the hum went away. When I put the mic back on, there was the hum. The ATR is the small 1/8" maybe 13' wire with the little button battery. I plugged that into a 1/8 to 1/4 adapter in order to plug into the line on the mixer. Then, I'm really ashamed to say that the mixer out was another 1/4" to stereo rca out adapter. Then from those rca's by cable to the 1/8" input on the HMC40.
Yes, i know, I am about throw up too. Buts that what i have to work with right now. I believe I need to get a XLR lapel mic. I have an Beachtek that would workk a bit better dont you think? Less adapters.

No, I never had this hum with the same setup before but that was an entire another location. I think I just have a cheapo setup.


@Chad, I believe you are correct, they dont really care as long as they are legible.
@Richard, yes I use a boundary mic into a small digital recorder as a backup. No hum of course. I have Sony Acid and it is pretty good but I'm trying to NOT do too much in post.
And no chain of custody issues as its just a filter and not a break in the clip. IMO. I wouldn't have a problem telling any jury that I just reduced a hum so it was legible.
@C2V, nice link. I'd pop for that in a second as my first line of defense.

How would you suggest I get 3-4 mics into the HMC40? Even the $300.00 XLR adapter would only give me two. Same boat as the Beachtek. I'm sort of forced to use some type of mixer. 2 lawyers, 1 witness and me/court reporter.

When you say run on battery that's not quite possible if you want to record for more than an hour or so with the HMC40. I dont make the lawyers take breaks to change battery's or tapes. One deposition lasted over 3 hours. I have to use AC power.

Thanks for you guys input. I'll work on less adapters and the hum eliminator gizmo.

Gary B.

 

[j1clark@ucsd.edu]

If I've learned anything from you guys it is to to what you can do in the field to eliminate what you have to do in post. In the deposition situation yesterday I was thrown into an examination room at a medical facility. And i had no time to try turning off and on lights, checking outlets etc.
Gary B.

Don't know if you want to analyze it further, but hospitals are notoriously bad RF environments. Don't know what the device you were using is succeptable to, but any number of hospital devices could be throwing crud out, and because of your wiring setup, could have had any number of places where noise could 'get in'.

 

[Alex H.]

Then, I'm really ashamed to say that the mixer out was another 1/4" to stereo rca out adapter. Then from those rca's by cable to the 1/8" input on the HMC40.
Yes, i know, I am about throw up too. Buts that what i have to work with right now. I believe I need to get a XLR lapel mic. I have an Beachtek that would workk a bit better dont you think? Less adapters.

Your Peavey mixer, while not ideal (I'm not a fan of Peavey at all), has 1/4" balanced line outputs and those can be connected to the Beachtek with a couple of 1/4" TRS - to - XLR adapter cables. Your Beachtek should have Mic/Line selectors for the inputs, and those should be set to Line.

As for lapel mics, or lavalier mics, look at something like THIS for deposition work. You don't need $1000 mics.

How would you suggest I get 3-4 mics into the HMC40? Even the $300.00 XLR adapter would only give me two. Same boat as the Beachtek. I'm sort of forced to use some type of mixer. 2 lawyers, 1 witness and me/court reporter.

Doesn't matter if you use the Beachtek or buy Panasonic's XLR adapter for the HMC40. You still only have two record channels. Your Peavey mixer has 4 XLR inputs, which you mix into the two main outputs. There's your answer.

 

[Richard Crowley]

1) Your Peavy mixer is more than adequate for deposition work. You have nothing to apologize for or to be ashamed of.

2) You identified that the hum went away when the mic was separated from the subject. That should give you a clue exactly where to start looking for the problem. Furthermore, it exhonerates the all the cables, adapters, etc.

3) I don't think the inexpensive ATR mic is inherently inferior for this (or any) kind of application. Any mic (even one that costs $1000) can break, especially if subjects get up and try to leave without unclipping them, etc. That puts a great strain on the cable where it ataches to the mic head, and no mic is immune from that kind of abuse. The ATR might be not quite as rugged as a more expensive mic, but at that price, you can afford to carry a hot standby replacement in the bag.

 

[Kimchoc]

Copy.
@Richard, yes, the hum changed as the subject took off the mic and then put it back on. But not like a broken wire or any cracking. Feels/sounds more like when you hold something and it grounds? Like an antennae?
@C2V, I copy your entire suggestions and wiring scheme. Not afraid to spend that on a good mic. I've read you guys talk about the Countryman. I'll have one before the next depo.
@j1, you not kidding. I kind of figure that almost anywhere I go. Usually like to scout out my locations in advance but sometimes it is not possible.

Thank you all for your help and your advice will be will taken.

Gary B.

 

[Noiz2]

I suspect like others have been hinting at that the mic was picking up on some electrical device the doctor was wearing. They are carrying pagers and cel phones and god knows what else. You might try sticking some other devices around the mic and see if it picks up hum. I have a $1000 mic that is very susceptible to strange RF, part of the reason I don't use it any much. So $$$ is no lock against hums. I would get some power cleaners (or go all battery) because that may have set up a ground loop that made the mic more problematic.

 

[Chadfish]

It's possible that the guy who took off the mic had a cell phone in his pocket. I get odd noises if my iphone is too close to my audio interface.

The guy I do depos for has a simple Rolls mixer - I know low-end, but cheap. He has 4-6 wired lavs, and the rolls. http://www.bhphotovideo.com/c/product/422588-REG/Rolls_MX44S_MX44s_Mini_Mix_IV_.html#features

And you can always buy a larger battery for your camera - we all do that. People are used to stopping in depos for tape changes, so battery changes are understandable. It's really worth it if you can get your gear simple, sonically clean and battery powered. You can get Giant Squid lavs for 25.00 and they aren't too shabby. If you get your set-up right you can do your post quickly which is money in your pocket. The more post you do the less money you've made IMP.

 

[j1clark@ucsd.edu]

It's possible that the guy who took off the mic had a cell phone in his pocket. I get odd noises if my iphone is too close to my audio interface.

GSM is incredibily 'noise', not because it operates at 850 MHz and above... but because it chops up its signalling in to nice littly packet bursts, which are in the 'audible' range, if the device is sensitive, and 'demodulates' the packet envelopes...

The iPhone, at least mine... are some of the quietest GSM phones around.

I don't know what set rules are, but were I a director, cell phones would be out for anyone who would be likely to be near the set, if it was a sound shoot.

CDMA phones use a different method of simultaneously using the spectrum, and so, don't produce the same sort of problem.

But in any case, the GSM noise that I've heard is most 'chirp' and sequences of pulses, not continuous 'hum'.

Without a spectrum analyzer, and creating a map of the place, there could be any number of 'sources', other than the obvious, such as x-ray, nmr, sterilizer, or similar equipment.