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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Some Audio Testing Results

Stuart English said:
No Finner, its a direct 1 to 1 patch of each mini-XLR into its A/D converter. But an alternative is to create a Y cable with a full size 3 pin XLR at one end and two 3 pin mini-XLR's at the other. I'm making one up today....
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Stuart I'm making a Y-cable, but I had a wiring question.

I was going to use two lengths of mogami mic cable and wire them both to a single XLR-F (1,2,3) pins then each to the corresponding TA3M's (1,2,3) pins.

Will that work correctly? Or should I wire them XLR-F pin 1 to right TA3M pin 2, XLR-F pin 2 to left TA3M pin 2, and XLR-F pin 3 to both TA3M's?

I can't test this myself as I don't have my REDs yet.
 
JFirestone said:
The microphone requires phantom power, so when we ran it through the mixers, it was powered by the mixers. When using the mixers the camera was set to Line Level. When the mic was connected directly to the camera without a mixer, the camera provided the phantom power and was set to Mic level with +48V.
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i think when you powered it (mic)form mixer no sound buzzing problems
addresed from other users audio test. is that right ? .did you notice difference between 2 methods of lining up mic with the camera.:excl:
 
BASSAM MSSALATIE said:
i think when you powered it (mic)form mixer no sound buzzing problems
addresed from other users audio test. is that right ? .did you notice difference between 2 methods of lining up mic with the camera.:excl:
Click to expand...

Correct, when powering the mic from the mixer, there is no buzzing or hiss, it is nice and clean sounding.

Hiss is only heard when the camera is let to mic level, it is not there when set to line level. My audio guy thinks the hiss we are hearing has to do with the pre-amps on the red camera, which are only used when we are running mic level. The pre amps on both of the mixers are very clean and produce very little noise. Therefore audio on the camera sounds great when using a mixer, and has some hiss when not using a mixer.

This is not a huge deal to me, because rarely am I going to be shooting with the red camera and not using a mixer for my audio.
 
Ed Watkins said:
Will that work correctly? Or should I wire them XLR-F pin 1 to right TA3M pin 2, XLR-F pin 2 to left TA3M pin 2, and XLR-F pin 3 to both TA3M's?
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That will give you 180° out of phase audio on one of your channels. On the flip side, if you make a true Y cable, you risk seriously messing up your phantom power...
 
Normal 3 pin XLR audio connections for any audio device (that are compliant with the current AES standard) are as follows:

Pin Function
1 Ground (may or may not be common to the shell)
2 Non-inverting (sometimes called "hot")
3 Inverting

Some devices take liberties with the pin 2 & 3 designation, but never with pin 1, its always ground or common.

If phantom power is applied, it is +48 elevated in reference to ground (pin 1) and is applied to both pins 2 & 3 each via a 6k8 resistor.

One can turn a balanced input (only) to an unbalanced one by connecting the inverting input to ground and applying signal across the resulting signal pairs as follows:

Pin Function
1&3 Ground
2 Non-inverting input

The same should not be used for an output as it would have one (inverting output) connected directly to common, which is typically not recommended.
 
JFirestone said:
Correct, when powering the mic from the mixer, there is no buzzing or hiss, it is nice and clean sounding.

Hiss is only heard when the camera is let to mic level, it is not there when set to line level. My audio guy thinks the hiss we are hearing has to do with the pre-amps on the red camera, which are only used when we are running mic level. The pre amps on both of the mixers are very clean and produce very little noise. Therefore audio on the camera sounds great when using a mixer, and has some hiss when not using a mixer.

This is not a huge deal to me, because rarely am I going to be shooting with the red camera and not using a mixer for my audio.
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It's not right though.. :huh: RED's whole sound philosophy seems to be built on the idea that with 24bit we can set the levels low to avoid peaking and bring them up in post. But if there is hiss then that is not really possible huh.. Are you on Build 13? Have you told RED? I'm sure they'd want to fix this asap.
How much hiss are we talking about here? Could you post a quick sample please ? 10 secs with and without hiss would be plenty, just to get an idea..

thanks
 
fergus said:
It's not right though.. :huh: RED's whole sound philosophy seems to be built on the idea that with 24bit we can set the levels low to avoid peaking and bring them up in post. But if there is hiss then that is not really possible huh.. Are you on Build 13? Have you told RED? I'm sure they'd want to fix this asap.
How much hiss are we talking about here? Could you post a quick sample please ? 10 secs with and without hiss would be plenty, just to get an idea..

thanks
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It's all subjective, on how much hiss is acceptable, so it's best to give you an example so you can decide. I am just working out where to host the file from. I have not talked directly to RED. It seems the forums are a good place to get feedback, and confirmation of these things before consulting RED directly. This is nothing mission critical for me right now, just observations. I am using Build 13. The audio section on the camera is still pretty early in its release, so I expect that there will be further improvements.
 
Cool. You are quite right.. Mr Firestone :-)

I only need on-camera sound for some applications; if I was recording live music I'd use my 744T.. But I'd love to hear that clip when you have a minute to upload it :biggrin:

thanks,

fergus
 
Hey JFirestone,

Thanks for posting this clip. Can I ask what your camera gain setting was for the first part of your test (using in camera mic pre).

Thanks!

Kevin
 
One additional question. When you were using the 302 mixer, was there a high pass filter (low cut) engaged? There is a noticeable shift in LF portion of the noise spectrum compared to the NGSX2 mixer.
 
JFirestone, thanks so much for posting this clip. I'm hungry to hear any new audio sample from the camera since there've been so few up to now.

My observations are that, while the noise with RED preamping is improved over what it was in the sound clip that predated the hiss fix in Build 13, there is still an unacceptable level of noise, way more than I expect with a piece of pro gear. I didn't hear this level of noise in Tonaci's clips but then don't recall whether he was using an outboard mixer. If this is indeed the inherent noise floor of the camera's audio subsystem when providing preamplification and phantom power, it is, in my judgment, unuseable. Very, very disappointing, although I will certainly give the dedicated and brilliant folks at RED ample opportunity to address the cause of this noise and implement necessary improvements, be they firmware or hardware.

The good news is that the audio sounded fine in line mode with the outboard mixers handling the mic chores. I concur that there was a very different tonal fingerprint between the two mixer samples with the 302 giving a pronounced boost to higher frequencies (and a louder output overall). I presume that was due to differences in gain settings and in the mixers themselves?

A very low level of noise is evident at the beginning of each mixer clip but is so low as to be totally lost once the speaker started. Was that noise the noise from the camera fans or from something else in the environment?
 
I am checking with Jeff, my sound guy, and one of us will post more details shortly. I know when I did a test with my ME66 I had to crank the levels almost all the way up to get proper levels. We used a MKH416 in these tests though, and I know it is a much hotter mic than the ME66, and the levels were significantly lower than what they were with my ME66. Jeff will be able to answer more definitively. I just checked my camera, and I don't think the settings have been changed since the test. It is currently set at 37dB.
 
eclaire said:
A very low level of noise is evident at the beginning of each mixer clip but is so low as to be totally lost once the speaker started. Was that noise the noise from the camera fans or from something else in the environment?
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I do believe that the noise you are hearing on each of the mixer clips is the camera fan. Jeff was sitting less than 3 feet away from the camera when doing the recordings, and while the microphone is very directional, he was close enough to pick up the fan noise.
 
JFirestone said:
I do believe that the noise you are hearing on each of the mixer clips is the camera fan. Jeff was sitting less than 3 feet away from the camera when doing the recordings, and while the microphone is very directional, he was close enough to pick up the fan noise.
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I don't suppose you can remember what the fan setting was can you?
That noise isn't what I'd describe as "silent"..:pinch:

As far as the hiss goes, I'd agree with you all that this amount of hiss makes the RED mic level inputs pretty unusable.. I'm sure RED will sort it out as usual.. :biggrin:
 
JFirestone, thank you for posting the audio clip. I agree with the others here that the noise level from the Red preamps are unacceptable, especially from pro level gear. I'm surprised we haven't heard more complaints about this. Anyway, I hope Red is looking into this problem and can come up with a fix soon.
 
Wow. Just read this whole post today for the first time. I can't believe someone from RED has yet to respond.

One person I would be very interested in hearing from on this is Gibby. He seems like 'the man' when it comes to RED as an EFP solution. Gibby, you put it through it's paces with audio on an ENG type shoot yet? What are your thoughts?

And folks at RED, what are you saying about all this? I am assuming things are not as bad as this thread leads us to think. Although it is scary. I just know that REDs have been in many situations shooting sound, and as of yet (until this thread) I haven't heard any alarm bells going off.

Very interested to hear from Gibby AND RED on the topic though.
 
The preamps are unbelievably noisy. I have my preamps set at 20db and the hiss is still very much there. Audio is clean with the line inputs as eclaire has pointed out.

It'll be interesting to see if they can get rid of the hiss as another software fix instead of swapping out the hardware.

I'm a post audio mixer as well, and I'd call this amount of hiss disastrous on a mix stage.
 
kenn michael said:
ALSO, there is a huge DC offset in the recorded audio. I'll be calling RED tomorrow about the audio issues.
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I reported the DC offset to Red last week, the hiss is gone on my camera w/ Build 13 if I only enable CH1 and CH2.
Do you have all 4 channels enabled? Try enabling only the channels you are recording to and you should lose the hiss.

The DC off set is another issue, I was told they are working on it.
 
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