Is there a small external Pre-amp for camera's?

[Bram Corstjens]

Is there a (small) pre-amp that can be placed in between the camcorder and the mic's? The idea is to set the camcorder's XLR audio input to LINE mode (bypass internal amplifiers) and use a small external pre-amp and thus increasing audio quality.

All solutions I found where either very large mixers intended to be used by a seperate person or zoom's that record the audio by themselfs (not needed) and didn't have any XLR line outputs...

Any ideas?

[Chris Barcellos]

JuicedLink Cx231 Camcorder XLR Audio Adapter/Mixer/Preamp with Phant

[Bram Corstjens]

Ah yes, thanks for that quick suggestion. However this has 3.5mm stereo jack output where I would need dual XLR outputs...

My search continues :)

[Stephen Mick]

Check out the MixPre-D…

MixPre-D Compact Field Mixer | Sound Devices, LLC

[Bram Corstjens]

Thanks, that looks quite interesting! Especially the 'unclippable input limiters', 5-18vdc input and the small size.
Not the cheapest, but you get what you pay for.

Thanks again for the suggestion!

[Stephen Mick]

Buy once…cry once. :D

Seriously, Sound Devices gear is stuff you'll have for years if not decades. It's that tough and that good.

[Edward Carlson]

Also the MM-1 or MP-1 from Sound Devices. The Sound Devices price is definitely worth it.

MM-1 Line Driver / HP Monitor | Sound Devices, LLC

MP-1 Portable Microphone Preamp | Sound Devices, LLC

[Steve House]

Originally Posted by Bram Corstjens

Is there a (small) pre-amp that can be placed in between the camcorder and the mic's? The idea is to set the camcorder's XLR audio input to LINE mode (bypass internal amplifiers) and use a small external pre-amp and thus increasing audio quality.
...

Alas, most, if not all, prosumer cameras inputs don't bypass the mic preamps when you set them to line level. Switching the input to line level merely inserts a pad into the signal path in front of the preamp to lower the level down to mic level. There are good reasons for using a mixer in front of the camera but avoiding the camera's own preamps isn't one of them.

[Les Wilson]

@ Steve, Good point. Do you know which cameras that do or don't put a pad on the XLR inputs?

[Bram Corstjens]

I have had a very noticable improvement in signal to noise ratio when I got an audio feed at line level into my EX1R.

Even very low volume parts could be amplified in post without noticable noise, or at least at a vast improvement over the normal mic level inputs.

But better safe than sorry, so can anyone confirm about the EX1R?

[Bram Corstjens]

Hmm I can't seem to find an confirmation anywhere about the ex1r completely bypassing the internal mic pre-amps when in LINE mode... I'll do some tests and report back.

[Richard Crowley]

I would bet at least the $20 in my pocket that there are NO current-model, un-modified video camcorders which actually BYPASS the mic preamps for true line-level inputs.

NO camcorders are designed to have dcecent audio. At the low-end, it is a matter of economics. And at the high-end, it is assumed that you aren't seriously using the camcorder audio track for anything but a scratch sync source. And in the middle, there may be some cameras still left (???) which may reduce the gain of the mic preamp input stage for somewhat lower noise when used with line-level inputs. But still a kludge.

I would wager that the camera with the VERY BEST audio performance is no better than your average decent modern, portable digital recorder. Jay Rose used to test the audio performance of higher-end camcorders, but I don't believe we ever learned anything except that there wasn't anything much above average in any of them.

[Bram Corstjens]

Did some testing and as Richard above points out the EX1R probably doesn't bypass the internal mic preamps, but merely pads them. Here are my (non scientific!) findings:

The following yields exactly the same noise floor or signal to noise ratio. These two settings create about the same overal volume.

1)
Setting my Sennheiser G3 wireless set at maximum output and my EX1R to line mode with volume knob at 10

and

2)
Setting the Sennheiser G3 reciever to -12db, the transmitter to -6db and the EX1R to mic mode with volume knob at 5 and the trimmer to -53dBu ( I use this setting on a regular basis for interviews)


Next I plugged my Samsung Galaxy S into one of the XLR's from the EX1R (line mode) and played a piece of classical music. The nice thing is this piece of music has a long fade out which shows what noise the phone itself is creating (and the noise in the track itself, but that's pretty much non existent). After the song ends the amp from the phone shuts off, which only leaves the EX1's noise audible. And after that the clip ends and all we're hearing is the noise from my speaker/amplifier set.

-The Samsung Galaxy S is creating a little bit more noise compared to the Sennheiser G3. It's like a little humm (it was just battery powered btw)
-When the phone amp shuts down (end of song) the remaining noise is (as expected) again the same as with the sennheiser G3 (compared to either in line mode or mic mode with the according settings on the EX1R)


Next was the -20dBu setting on the EX1R. Volume knob at 5 on camera. I plugged in the Samsung Galaxy S once again and set the volume on it so it would give me the same overal loudness:

-The same humm coming from the Samsung phone itself was again audible
-However, near the end of the track I noticed the overal noise was just a bit lower
-When the track ended (phone's amp shut off) it became more obious the remaining noise was lower than the line input mode, lower than the sennheisers G3 line input mode and lower than the sennheiser mic mode with the EX1r at -53dBu.

Plugging in the Sennheiser G3 again (and setting outputs accordingly to match the -20dBu on the EX1R resulted also in a similar small but very noticable improvement. Will try some more!

/edit
It stays about the same till about 30dBu, after which the signal keeps getting louder but then relatively more noisy. So the best (or the least bad) solution would be to set both the inputs between 20 en 30 dBu and set Wireless mic's accordingly...

Ofcourse phantom powered mic's have fixed output (except from maybe a wind filter or a pad) and 20/30 dBu is WAY to low... so in that case one could add a Mixpre-D and set that to match the EX1R's 20/30 dBu input. It would give pretty good results although not what the MixPre-D theoretically could achieve. Probably not worth the money if it's only about getting one step lower noise...

[Les Wilson]

One of the pioneers of this issue:
greg j. winter :: modifications

[Steve House]

As previously mentioned, there are a lot of good reasons to use a proper mixer upstream from the camera - better high-pass filters, better limiters, more control over levels, etc - but avoiding the camera's mic preamps by using its line-level inputs isn't among them.