Some Audio Testing Results

[Ed Watkins]

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....

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.

[BASSAM MSSALATIE]

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.

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:

[JFirestone]

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:

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.

[Cail Young]

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?

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...

[Kevin Halverson]

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.

[Fergus Meiklejohn]

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.

It's not right though.. 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

[JFirestone]

It's not right though.. 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

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.

[Fergus Meiklejohn]

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

thanks,

fergus

[JFirestone]

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

thanks,

fergus

Here is the audio test file. This is build 13. now you can hear it for yourselves.

http://www.perennialmedia.com/redrel...0Tests_1-2.aif

[Kevin Halverson]

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