AT875R mic phantom powered directly by the GH2

balazer

Here is a small secret: some microphones that require phantom power with a minimum of 9-12 V will operate happily using the 2.5-v "plug-in" power provided by the GH2's mic port. I have my GH2 set up with the Audio-Technica AT875R, and I am very pleased with the results.

More details: http://personal-view.com/talks/discussion/3197/at875r-mic-phantom-powered-directly-by-the-gh2#Item_7

Audio samples: http://personal-view.com/talks/discussion/3197/at875r-mic-phantom-powered-directly-by-the-gh2#Item_11

Which phantom powered mics will operate on such a low voltage? Electret condenser mics (i.e. permanently charged) are good candidates. You'll also want a mic with high sensitivity, to give a high SNR given the noise of the GH2's pre-amps and the quantization noise of 16-bit samples. I speculate that mics that can operate on a low-voltage battery are good candidates. But ultimately you'll have to test the mic to see how well it works. Here's more info: http://recording.org/pro-audio-gear/30016-phantom-power-is-a-mystery.html

How do you wire the mic cable? From my testing, the AT875R can be wired with XLR pin 3 unconnected, or shorted to pin 1, which apparently means it is impedance balanced. Here are wiring references:
http://www.audio-technica.com/cms/site/4ffc7039c199613a/index.html/index.html#unbalancedinput http://www.benchmarkmedia.com/discuss/feedback/newsletter/2008/05/2/helpful-how-tos-how-properly-connect-balanced-outputs-unbalanced-input

You must lose something by operating the mic under spec, right? Generally speaking, the max sound pressure level before distortion will be reduced somewhat, and the sensitivity will be reduced a tiny bit. Judging by the specs of other Audio-Technica shotgun mics that can operate on phantom power or from a 1.5-V battery, the max SPL is reduced by about 10 dB. Even with that reduction, the max SPL is still quite high - so high that if you are in that environment, you better be wearing earplugs. I tested some loud sounds, and I was getting distortion inside the GH2 with the mic level setting set to 1 (the lowest gain setting) before I got any distortion from the mic.

Of course the weak point in any GH2 mic connection is the 2.5-mm jack. I got the highest quality cable with a right-angle connector that I could find, and made my cable just the right length to keep it secure and out of the way. The link is unbalanced, so to minimize interference, use a shielded cable and keep it short.

The GH2's lack of real-time audio monitoring prevents the use of the mic port for any application in which the audio is critical. But you can work around the lack of monitoring to a certain extent. Plug the mic into something that does allow monitoring (e.g. the Zoom H1), and do some walk-around tests to identify problems. I found and eliminated noise coming from my shock mount, cable, and XLR connector. You can also record a short test video and play it back and listen through the GH2's terrible, tiny speaker before shooting.

The shock mount configuration in my photos is intended to have a very low profile. A more standard configuration would put the shock mount higher and allow for the use of wide-angle lenses. But in my configuration the mic is out of the view of all of my lenses, including the Lumix 20-mm. I swapped and reconfigured the elastic bands to improve the isolation and give a slight upward tilt that keeps the mic out of the lens's view.

With the GH2 mic level set to 4 (the highest gain setting), speaking in a normal voice from about 3 feet in front of the mic puts the meter at 7 bars, just into the red.

Compared to the MKE-400, the AT875R has better rejection of off-axis sounds, and the shock mount I'm using performs much, much better than the one built into the MKE-400. I might have been satisfied with the MKE-400, except for its shock mount. Every time my finger touched the camera, you could hear it in the recording.

Where to get mike:

MikeLinn

balazer

It's an old thread, I realize. I did finally determine that the AT875R sounds a lot better when powered to spec instead of with 2.5 V. Of course some external pre-amplification also helps to overcome the noise of the GH2's preamps (or whichever camera. These days I use the Sony a7S).

The inexpensive iRig Pre provides phantom power and pre-amplification. It needs to be adapted or rewired to plug into a camera's mic input. I haven't tried it myself , but if my math is right:

The AT875R's self noise is 20 dB. With the mic's high sensitivity, that makes -102 dBu on the mic's output.
The iRig Pre's equivalent input noise is -113 dBu.

So the iRig Pre's noise is well below the AT875R's noise. They should be a good match for each other. A mic that's much less sensitive or much less noisy than the AT875R wouldn't be as well matched to the iRig Pre.

I still like the AT875R a lot for dialog. (it's not very good for music) It has particularly good wind resistance. I wish there were some on-camera mic solution that was smaller, lighter, and simpler that sounds just as good, but I have yet to find it.

gameb

AT875R also works really good on G6

LucasAdamson

I also use a Tascam DR100 Mk2 but I do think that having a good directional mic on the camera is a great backup for pro work, or else a greatly convenient way of improving the sound for non pro shooting, when you just want to grab the camera and shoot something. Perhaps you're right that a Juicedlink is the proper way to go.

balazer

For as big and heavy and expensive as that phantom power supply is, I'd get a preamp instead.

balazer

@LucasAdamson, you clicked an ad instead of the 4shared download link.

Powering the microphone with a higher voltage will improve its sensitivity just a little. I think most of your problem is that the preamps in the GH2 just aren't very good. If you're not using an external preamp, you'll only get good SNR if the signal is strong, i.e. when the sound is loud or very close to the mic.

More recently I've tested the AT875R on the Sony a7S, and though it works, I've come to the conclusion the mic sounds much much better when connected to a proper preamp with phantom power. The frequency response is flatter (fuller; more bass), and the hiss is much quieter. I'm not thrilled about the bulk of a preamp, but I don't know any way to get really good sound without one. There are some small and light ones, e.g. Juicedlink Riggy or Fostex AR501. The older Juicedlink CX series can be had cheaply on eBay. I use a Tascam DR-100 mkII.

LucasAdamson

Something like this might work well, for this mic/ camera combo, don't you think?

http://www.bhphotovideo.com/c/product/403002-REG/Denecke_PS_1A_PS_1A_Portable_Single.html

LucasAdamson

Hi Balazar,

I tried to access your new links to your tests, but was bombarded with requests to install a video app I'd never heard of, and don't need, so I declined.

I am using the AT875r with my GH2, using a cable I made as you've described. I am getting a hell of a lot of hiss on the recording, but it's otherwise really good quality at level 4 on the GH2.

Would supplying a higher voltage to the mic from an external source, such as a 9v battery be a good idea? I could then presumably lower the gain on the GH2 preamps to say, level 2, and get a really excellent onboard mic sound, similar to the AT875r on a real video camera with phantom power and XLRs.

balazer

I've re-uploaded my old GH2 mic tests: http://www.4shared.com/folder/gyOvzT6_/GH2_mic_tests.html

adamquesada

Just got a GH4. The ATR875 does not really work, mic levels are far too low just like with the reports of the GH3. I think this has to be an incorrectly wired cable, going to try a TRS to TRRS adapter.

Roy_Batty

@John_Farragut

The AT875R combined with the XVM-101F and a very inexpensive 2.5mm to 3.5mm adapter works like a charm.

Kudos to balazer for the original post.

Thank you.

Roy_Batty

@John_Farragut

Actually, I do have the XVM-101F. I typo'd that last post. Many thanks for your reply.

gameb

@HillTop1 ATR875 never really worked on the GH3, mic levels far too low, GH3 works perfectly with AKG C747

John_Farragut

@Roy_Batty You say you have the HVM-101F but it should be the XVM-101F, the mono to stereo version. Then use a regular 2.5mm to 3.5mm jack adapter, like Hama B000X1CDME, or even cheaper stuff.

Roy_Batty

@John_Farragut

I have the Hosa HVM-101F cable and the Audio Technica AT875 mic. What 2.5mm to 3.5mm adapter did you use to have this set-up work? Can you provide link or picture or simple description?

Thank you.

smoke23

@HillTop1 never did purchase the GH3 unfortunately .

HillTop1

@smoke23, thanks and good to know. I can get it know to use on the GH4 when I buy sometime next year. Did you ever tried it with the GH3 to compare the levels with the GH4?

adamquesada

That's good news it works with the GH4!

smoke23

Hi everyone. I have the Hosa XVM-101F cable and AT875R mic. Very good combo for the GH2. Just got my GH4 yesterday. This combo seems to be working, I'm getting good levels with Mic Level Limiter set to off. I'll do more testing but I have the Mic Level Adj set to +2dB.....so far so good!

adamquesada

Does anyone have any update with the AT875R on the GH3 or G6?

kankala

I dismounted my em320e some time ago :D

now I completely bypassed the original preamp. I removed the XLR connector and I soldered a 2.5mm stereo jack plus cable directly to the electret capsules. They are now supplied directly from the GH2, each separately.

What I get on recording is 2 separate channels, one for each capsule. Then in post I subtract a certain amount of the back capsule signal from the front capsule signal to get the shotgun effect. Nice that you can play with this to get different effects. It sounds reasonable on level 2, too noisy on level 4 (with thepalalias Pasadena settings) together with izotope noise reduction.

I plan to get better capsules because the originals are quite noisy. Now that Panasonic 61A are out of production, does anyone now of good replacements? I haven't looked much into this subject.

AfricaGH2

Ok guys looks like this is the one to get, it has a battery and it's about $250 on amazon - AT897 or At8035. See

- when I get my GH3 ;) perhaps I will amazon prime them both and see what works.

AfricaGH2

Anyone have an answer to the question of what mic works with the GH3? Seem like the AT mic mentioned is not sensitive enough for use with the GH3. What about a panasonic mic - Panasonic DMW-MS2 Stereo Shotgun Microphone for Panasonic DMC-GH3. If you're getting a hiss then this most lightly a sensitivity issue and not fixable with an amp of some sort. The ATR875 specs say OPEN CIRCUIT SENSITIVITY–30 dB (31.6 mV) re 1V at 1 Pa - and impedance is 100 ohms but I have a $700 mic that is a big brother to this and is slightly more sensitive but is 50 ohms.

HillTop1

@idealist, thanks for the update. Wow ok, is just that mic on the GH3 or all mics? Has any body else use a different mic on a GH3?

idealist

I received a XLR / jack 3,5 cable and plugged my AT875R on the GH3. The audio level was very low... even with GH3 audio setting at max. It "works", sure, but it's obviously unusable to well work.

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