DSLR Mic Input

[mcp6453[_2_]]

A friend wants to record video on a Nikon D800E DSLR while using an external audio mixer. He's going to get a
line-to-mic-level cable, which solves the level problem, but I wonder what he's supposed to do about the bias voltage on
the mic input. A lot of people just ignore it, but I blew the element out of a 635A once by doing that. What's the best
solution?

[Mike Rivers[_2_]]

On 2/15/2017 9:28 PM, mcp6453 wrote:
> A friend wants to record video on a Nikon D800E DSLR while using an external audio mixer. He's going to get a
> line-to-mic-level cable, which solves the level problem, but I wonder what he's supposed to do about the bias voltage on
> the mic input. A lot of people just ignore it, but I blew the element out of a 635A once by doing that. What's the best
> solution?

If the mixer has a transformerless output there will be a capacitor
between the guts and the output connector that will block the DC. Any
unbalanced output will have a blocking capacitor, so see if it has a
"Tape Output." And if it has an output transformer, the transformer is
robust enough to not burn out from the feeble external microphone
powering voltage. Purists will warn you that this will put a magnetic
bias on the transformer and and may cause distortion, practical
engineers will poo-poo this.

You could make a box with a blocking capacitor just in case. 50 uF
should do it. Or as small as electrolytic capacitors are these days, you
could even build one into a cable connector.

Or you could send your friend to a Nikon DSLR forum and ask if there's a
button on there somewhere that will turn the external mic power off.

I'm surprised that there was enough current to blow up a dynamic mic.
You just have just been unlucky. But given that the camera input is
single-ended (not balanced), the powering voltage is applied directly
across the microphone output rather than it being cancelled out by the
standard phantom powering scheme.




--

For a good time, call http://mikeriversaudio.wordpress.com

[[email protected]]

On Thursday, February 16, 2017 at 7:15:14 AM UTC-5, Mike Rivers wrote:
> On 2/15/2017 9:28 PM, mcp6453 wrote:
> > A friend wants to record video on a Nikon D800E DSLR while using an external audio mixer.




the other option is to record "B roll" audio on the DSLR with a small or built in mic and record the "real audio" on a separate dedicated audio recorder.

The hard part is then syncing the two together during editing.

If you can "slate" at the start of the take, it makes it pretty easy to sync.

Also the DSLR audio track will help in syncing the real audio to the video

m

[mcp6453[_2_]]

All true. I just wonder how many people destroy cameras or microphones by not addressing the bias voltage on the mic
input issue. Apparently it's not a big problem. Maybe I just got unlucky.



On 2/16/2017 9:33 AM, wrote:
> On Thursday, February 16, 2017 at 7:15:14 AM UTC-5, Mike Rivers wrote:
>> On 2/15/2017 9:28 PM, mcp6453 wrote:
>>> A friend wants to record video on a Nikon D800E DSLR while using an external audio mixer.
>
>
>
>
> the other option is to record "B roll" audio on the DSLR with a small or built in mic and record the "real audio" on a separate dedicated audio recorder.
>
> The hard part is then syncing the two together during editing.
>
> If you can "slate" at the start of the take, it makes it pretty easy to sync.
>
> Also the DSLR audio track will help in syncing the real audio to the video
>
> m
>
>
>
>

[Scott Dorsey]

mcp6453 > wrote:
>A friend wants to record video on a Nikon D800E DSLR while using an external audio mixer. He's going to get a
>line-to-mic-level cable, which solves the level problem, but I wonder what he's supposed to do about the bias voltage on
>the mic input. A lot of people just ignore it, but I blew the element out of a 635A once by doing that. What's the best
>solution?

The line-to-mike cable is a 40dB pad... and it will pad that DC offset down
40dB along with padding the signal in the other direction down. If it worries
you, stick a DC blocking cap in there (I keep a bag of the Shure low pass
filters in barrel connectors for that kind of thing).

However, my suspicion is that he will find that the sound quality is not so
hot and that being tethered to the console is a problem, and that he will
be much happier using a cheap digital recorder on the console and slating
everything.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Nate Najar]

On Wednesday, February 15, 2017 at 9:28:27 PM UTC-5, mcp6453 wrote:
> A friend wants to record video on a Nikon D800E DSLR while using an external audio mixer. He's going to get a
> line-to-mic-level cable, which solves the level problem, but I wonder what he's supposed to do about the bias voltage on
> the mic input. A lot of people just ignore it, but I blew the element out of a 635A once by doing that. What's the best
> solution?

you must record audio separately and slate it. While I have not used that particular DSLR, every DSLR I Have come into contact with has non defeatable AGC on the external inputs, which will trash your audio.

[geoff]

On 17/02/2017 3:33 AM, wrote:
> On Thursday, February 16, 2017 at 7:15:14 AM UTC-5, Mike Rivers
> wrote:
>> On 2/15/2017 9:28 PM, mcp6453 wrote:
>>> A friend wants to record video on a Nikon D800E DSLR while using
>>> an external audio mixer.
>
>
>
>
> the other option is to record "B roll" audio on the DSLR with a small
> or built in mic and record the "real audio" on a separate dedicated
> audio recorder.
>
> The hard part is then syncing the two together during editing.
>
> If you can "slate" at the start of the take, it makes it pretty easy
> to sync.
>
> Also the DSLR audio track will help in syncing the real audio to the
> video

Naa. Just line the two up in your editor, with a significant peak
nearthe start.

The move towards the end, find another significant peak, and stretch one
so that the peaks like up.

With good clock stability these days that shouldn't be a big stretch.
Hopefully.

geoff

[geoff]

> I'm surprised that there was enough current to blow up a dynamic mic.
> You just have just been unlucky. But given that the camera input is
> single-ended (not balanced), the powering voltage is applied directly
> across the microphone output rather than it being cancelled out by the
> standard phantom powering scheme.

Pretty sure that there is a menu somewhere to do this on the 800E. They
don't force you to use an electret.

I'll check mine.

geoff

[geoff]

On 17/02/2017 8:23 a.m., geoff wrote:
>
>> I'm surprised that there was enough current to blow up a dynamic mic.
>> You just have just been unlucky. But given that the camera input is
>> single-ended (not balanced), the powering voltage is applied directly
>> across the microphone output rather than it being cancelled out by the
>> standard phantom powering scheme.
>
> Pretty sure that there is a menu somewhere to do this on the 800E.
> They don't force you to use an electret.
>
> I'll check mine.
>
> geoff
>

My D800 (not 'E'} has a system menu option to have Mic Sensitivity
either Automatic or Manual. I assume this is AGC versus fixed.

Can't find anything to turn off Mic power though. Mine measures 2.7V .

geoff

[Trevor]

On 17/02/2017 1:33 AM, wrote:
> On Thursday, February 16, 2017 at 7:15:14 AM UTC-5, Mike Rivers
> wrote:
>> On 2/15/2017 9:28 PM, mcp6453 wrote:
>>> A friend wants to record video on a Nikon D800E DSLR while using
>>> an external audio mixer.
>
> the other option is to record "B roll" audio on the DSLR with a small
> or built in mic and record the "real audio" on a separate dedicated
> audio recorder.
>
> The hard part is then syncing the two together during editing.
>
> If you can "slate" at the start of the take, it makes it pretty easy
> to sync.
>
> Also the DSLR audio track will help in syncing the real audio to the
> video

That's what I always do, and find audience applause "spikes" are often
enough to line up the two audio streams for concert recordings, adequate
for lip sync.

Trevor.

[Trevor]

On 17/02/2017 5:03 AM, Nate Najar wrote:
> On Wednesday, February 15, 2017 at 9:28:27 PM UTC-5, mcp6453 wrote:
>> A friend wants to record video on a Nikon D800E DSLR while using an
>> external audio mixer. He's going to get a line-to-mic-level cable,
>> which solves the level problem, but I wonder what he's supposed to
>> do about the bias voltage on the mic input. A lot of people just
>> ignore it, but I blew the element out of a 635A once by doing that.
>> What's the best solution?
>
> you must record audio separately and slate it. While I have not used
> that particular DSLR, every DSLR I Have come into contact with has
> non defeatable AGC on the external inputs, which will trash your
> audio.

Not to mention throwing away a huge chunk of S/N by attenuating the line
signal to mic level, and amplifying it back again in the camera even if
you can defeat the AGC. :-(

Trevor.