ALC/AGC Disable... Where are we?

A

alexsalmona

Member
Hi all. Just curious on where the Auto Gain is at? Has a disable been found or is it close at hand? How can we help? (without taking the camera apart) Is it even possible. I apologize in advance if someone has already answered this somewhere else. I just bought a Juicedlink DT454 which by the way is hands down the BEST of all the adapters I have tried. (I mix audio for a living for CBS Television). The problem is I want to use both channels and not use the AGC disable built into it (you can only use 1 channel if you use the AGC disable). Just curious as to where the hack is at. I am happy to test stuff if a way to disable can be found. The seperate record is NOT an option for the things I am shooting. Sound must be IN CAMERA. No time to resync stuff in post.

Alex
 
Yeah I read the thread but it seems to go back and forth. If I have time this weekend I will try and do some testing to see if I can get a good setup going and report. The nice thing about the DT454 is that it has small level meters that can be calibrated! So if we can find a nice level and calibrate the meters so 0 is that level then we can shoot more confidently. The DT454 also gives you an input for your playback in camera so you can hear that you got the audio you needed. If we can nail this down it could be a very workable solution.
 
+1 for AGC gettin disabled. It would be nice to know exactly what would be needed (for Vitaliy & testers) in order to get some progress on this... Every time a great breakthrough happens with the hack I feel the need to donate a little. I'm sure if AGC got disabled (or ext. monitoring enabled) many people would feel the same way.

I have used Juicedlink products a number of times and they are a pretty good work around (if not wanting to sync in post). The obvious issues are the added weight & size, only recording to one channel and of course $$$.

Hope all that can be eliminated with a hack!
 
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This problem is already solved by using readily available external attenuator adapters or cables. The mic input of the GH1 is way too sensitive so you simply need to lower the mic-level audio signal being sent into the GH1. I'm sure the Canon DSLR's have the same type of problem and could be fixed in the same way.

Not sure why JuicedLink came up with that AGC Disable thing since it eats up one audio channel when they simply could have integrated an adjustable attenuator into all the mic-level outputs on their audio mixer and kept both audio channels active.

The few people that have tried using attenuators with the GH1 have been happy with the results. Since it looks like the JuicedLink DT454 mixer has a mic-level 3.5mm stereo output, I would recommend getting a 3.5mm attenuation cable from Markertek, there are 3 different ones available.

Of course, if all it takes is an attenuator to fix this audio problem then you have to conclude that there wasn't a purposely built AGC in the GH1 to begin with and maybe that's why most people can't grasp the concept that such a simple fix is available and working.

Randy
 
Cavemandude, would you say that it is possible to achieve similar results recording direct into the camera vs recording to a zoom H4n if the proper attenuation was used?
 
Doesn't the Juicedlink have two separate modes for disabling AGC, including one that gives you access to both channels? Tone[FONT=&quot][/FONT] and Safety Mode where Tone uses a 20khz tone to disable the AGC but gives you access to both channels. Granted it doesn't work on all cameras, but have you tried it with the GH1?
 
mojo43 said:
Cavemandude, would you say that it is possible to achieve similar results recording direct into the camera vs recording to a zoom H4n if the proper attenuation was used?
Click to expand...

Well the GH1 (without the firmware hack) has a bitrate of 192 Kbps (2 channels) in AVCHD mode which is pretty good but not at the quality level of an uncompressed WAV file (1536 Kbps) that the Zoom H4n can record. It's just a little thinner sounding but I think usable in most all situations unless you're really picky about your audio. Most people wouldn't be able to hear the difference.

Now you can increase the bitrate with the firmware hack up to 448 Kbps and that should be comparable to the WAV file but I still don't think you can play those files in camera on the GH1 yet if that is needed in the field. Just doubling the rate to 384 Kbps should be enough and be comparable to the WAV file of the Zoom.

Randy
 
Cavemandude said:
Well the GH1 (without the firmware hack) has a bitrate of 192 Kbps (2 channels) in AVCHD mode which is pretty good but not at the quality level of an uncompressed WAV file (1536 Kbps) that the Zoom H4n can record. It's just a little thinner sounding but I think usable in most all situations unless you're really picky about your audio. Most people wouldn't be able to hear the difference.

Now you can increase the bitrate with the firmware hack up to 448 Kbps and that should be comparable to the WAV file but I still don't think you can play those files in camera on the GH1 yet if that is needed in the field. Just doubling the rate to 384 Kbps should be enough and be comparable to the WAV file of the Zoom.

Randy
Click to expand...

but don't you have to have the attenuators run through a separate audio recorder?
 
Car3o said:
but don't you have to have the attenuators run through a separate audio recorder?
Click to expand...

Nope, attenuators are used directly to the GH1's mic input only. External audio recorders don't need attenuators.

Now if you want to send the Line-level out of the external audio recorder to the GH1 you have to do a double attenuation. First you need to get the audio level down from Line-level to Mic-level which is typically 40-50dB. Then you need to get it down from that Mic-level to the GH1's ultra sensitive Mic-level which is another 20-30dB.

Problem with that method is that the Line out on some external audio recorders is dual purpose. It is used as a Line-out and a Headphone jack and it also has a volume control on that output. I guess you could use a 3.5mm stereo Y-splitter to send the audio signal to the GH1 and your headphones you just have to remember to not raise and lower the volume level for your headphones in that setup as it will raise and lower the audio level going to your GH1. You could get a separate volume control switch for the headphones.

Randy
 
Car3o said:
i suppose if that's the case you can skip the audio recorder get one of these

http://juicedlink.com/index_files/CX_camcorder_XLR_microphone_adapter_audio_mixers.htm

and hook up the attenuators to it like this guy did.

http://vimeo.com/7616987
Click to expand...

I already have a decent portable audio mixer so I don't want to spend over $400 for a JuicedLink mixer. I'm working on a wireless solution to send the audio from my existing mixer's Mic level output using a wireless plug-in transmitter (or my regular transmitter since I have an XLR cable for it) and then using an attenuator out of the wireless receiver into the GH1. Since the wireless receiver has an adjustable output of -10, 20 and 30dB I can adjust it along with the -35dB attenuation 3.5mm cable to get it low enough to not hit the GH1 limiter.

The main reason to use the wireless is that it has a Mic-level output and my audio recorder (Sony PCM-M10) only has a Line-level output that I will be using with my headphones. Other nice thing is that there is a headphone jack on the wireless receiver that is connected to the GH1 so I can check that also if needed.

My Sony PCM-M10 audio recorder and wireless transmitter will be Velcroed to the audio mixer and connected using the Line-level (PCM-M10) and Mic-level (wireless transmitter) output of the mixer so I won't have any cables connected from the audio mixer/audio recorder/wireless transmiiter to the GH1 which will make it mobile and less cluttered.

One problem with the second link you posted with the Zoom H4n. That guy didn't do the double attenuation, he only converted the Line-level out of the Zoom to Mic-level and that's not low enough for the GH1's mic input so he's still going to have an "AGC" problem. The only thing he fixed is that his audio is not distorted.

Randy
 
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Note to Moderators: Can this thread be made a sticky so the same question is not asked over and over again?
 
Car3o said:
that's just how forums work. if that was the case, this forum would have 122 stickies with new questions that are asked everyday.
Click to expand...
You are right, wait, we do have an FAQ sticky though. Can you add this under "Can I disable AGC" question?
 
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