Hiss

[zak forrest]

Hiss that I can't get rid of. I have a Sennheiser 416 plugged in with phantom power selected, no matter what gain settings i use the hiss is there. It's not the fan, and its not the LCD by the way.

[Cail Young]

It's not an old T-power 416 is it?

[Elizabeth Lowrey]

zak, been hoping someone would post some audio clips. The only one I've heard so far is the quickie Evin Grant put up, and I noted in that thread that there was a disturbing amount of hissy noise in the recording (which had not been compressed). But his was admitedly not a very careful audio test, so I've been hoping there was an explanation like very low gain setting or mic setup.

Could you post a sample of what you're getting (just audio), each with details about the gain settings?

[zak forrest]

It's not an old T-power 416 is it?

no. ive phantom powered it for a long time now with all sorts of things..

[zak forrest]

zak, been hoping someone would post some audio clips. The only one I've heard so far is the quickie Evin Grant put up, and I noted in that thread that there was a disturbing amount of hissy noise in the recording (which had not been compressed). But his was admitedly not a very careful audio test, so I've been hoping there was an explanation like very low gain setting or mic setup.

Could you post a sample of what you're getting (just audio), each with details about the gain settings?

http://zakforrest.com/red/audio


sennheiser 416 mounted on cam (its not fan or lcd noise though). dont remember the gain settings but they were pretty good. the hiss is there no matter what the gain...

you can hear the hiss nice and clean on the left, i think there is no audio on the left and only hiss.. on the right is some electric guitar and hiss..

ALSO- have only tried one pair of headphones so far, but my LEFT headphone is playing the RIGHT channel.. when i mute the left channel in the settings i dont hear anything in my right ear, etc... is this a bug with the red cam audio settings, or my headphones being mislabeled

[10s]

I suggest you need to conduct some tests.

Go plug in a few other mics and see if the hiss continues. This will determine if your mic is somehow faulty.

Check these mics in another system (dosen't need to be a camera) and check for hiss. Your mic will continue to be noisy in any system if it's at fault. This should determine that the mics are good. If they are good then the camera settings, camera output, or internal system isn't functioning correctly.

Check your audio output for hiss. Some output amps, i.e., headphones amps can be noisy. Make sure your speakers, headphones are clean and not a source of trouble. Cords often cause problems caused by poor connections, RF, shielding, and other mysteries.

Bottom line, you need to do a bunch of various tests to isolate where the hiss is coming from.

If others are not having this problem, it could be your mic, cords, settings...

[zak forrest]

ive also tried my audio technica at 2020 and the problem is identical. in that sound clip i posted, you can hear th ehiss in the channel that the mike wasnt going into. it seems like any channel thats activated gets a hiss. its not the headphone outs cuz its hissing on my computer when i play a proxy...

[Greg M]

Zac,
This is a being addressed. Should be fixed in new firmware update.

[Elizabeth Lowrey]

The hiss I hear in your sample is very similar to what I recall from Evin's clip.

Nice to hear this is being addressed in a firmware update. Digitalfx, did you get that info from a private communication with someone at RED? I don't recall reading anything here regarding this issue.

[Greg M]

The hiss I hear in your sample is very similar to what I recall from Evin's clip.

Nice to hear this is being addressed in a firmware update. Digitalfx, did you get that info from a private communication with someone at RED? I don't recall reading anything here regarding this issue.

I emailed support when I noticed the issue and they immediately responded.

[philper]

Can you confirm that only one mic channel was open when you did this, that this isn't the sum of all 4 inputs all open @ mic level? Could you try recording nothing--nothing plugged in at all and see how hissy that is? Do you have a mixer you could plug in, take the camera down to line level and record that way? Thanks for the posting. This noise is another reason that I'd like to know what the Red's real phantom voltage is.

Philip Perkins CAS

[Stuart English]

I emailed support when I noticed the issue and they immediately responded.

Yes, we are aware of it and working on it.... I think we have all the data we need for now.

[Cail Young]

no. ive phantom powered it for a long time now with all sorts of things..

I ask because I had a strange hissy problem with a T-power (with converter) 416 on a Sony V1P a couple months ago... Good to know it's a resolvable problem!

[Dan Hudgins]

Try making a WAV file of the hiss and bost the gain, then look for any periodicity in the wave form that is close to the frame rate the camera is running at. It is hard to filter all the digital noise out of the power and bias in the audio circuits to get 120db S/N. The circuit baords can have capacitive and inductive coupling, that goes for the mic cables as well since the power drain is in the AMPS going into the camera... you would not want the mic cable near the monitor and such (the backlight makes a 20KHz magnetic field)...

If the hiss is not linked to the frame rate (shoot a frame that is top half white and bottom half black then left white and right black) it may be from the voltage regulator feeding the audio section since there can be issues with noise in the power. Or they may just need to add a stage of desecreate JFET with the bias set to high current to lower the Z on the source lead. Also if the input capacitor is too small it can give low Hz noise, to fix that use 10mf or more on the input, even if the JFET input is in the Meg ohm.

Try making a mic input plug with a 600 ohm metal film to see what the base noise is, shorting may give a false level...

[Shawn Nelson]

I wonder if this could be partially the quality of the preamps. Sound Devices makes excellent preamps.

[Dan Hudgins]

If the problem is just some noise in the preamps, and they have enough head room then using a good external pre-amp to get the signal 40db or more higher should help. But if the internal preamps or A2D's are making noise and the noise does not fall when the gain is turned down in the camera, then you cannot "yell" over all the hiss...

I have build low noise preamps, when you get the noise very low and you flex the mic cables you can hear a "tinkling" sound like small bells, normally the pre-amp hiss is way over that.

It may be best anyway to have a external preamp within 3 feet of the mic, and run a stronger signal on the long cable to the camera since the camera will be making EMF and RFI with all of its power and other cables going to the monitor and memory packs...

With double system sound the audio is far from the camera and its EMF/RFI...

[Anders Holck]

Hmm...not just white noise (on the silent channel), it does seem to be modulated by the capture rate.
The Aiff posted was sample rate converted into 44.100, and a rough mesurement of the modulation lenght was 1850 samples, so thats very close to 24p.

http://andersholck.com/red/redmodul.jpg

There is also some crosstalk audible across the channels, dont know how much this signal is boosted through the chain though. Eliminating it totally is close to impossible in a portable device.

[Dan Hudgins]

If they put the audio external in a solid block of metal with MU metal shields, and have a digital input for the Audio that should help get the noise down to studio levels.

I built a digital bias oscillator once for recording on Mag film, and had a divide down to get 1000Hz output. When it was used there was a 1000Hz whine in the audio from small -100db+ load on the power supply, so I unpluged the divide down chips and the whine went away.

It is probably a fixable problem, but it is never good to have anything digital close to analog since even a few pf can cause crosstalk...

Great illustration! I see that all the time, I live in the direct beem of a TV xmiter so I can tell 60Hz from TV by the fact that if I sync my 'Scope to the power line Hz the TV ripple moves slowly like a worm....

P.S. That is a great way to check the camera frame rate! Just count the distance between 100 ripples, but it will be off a little since computer sound boards are off about one frame per four minutes of recording...

[Tony Lorentzen]

Hmm...not just white noise (on the silent channel), it does seem to be modulated by the capture rate.
The Aiff posted was sample rate converted into 44.100, and a rough mesurement of the modulation lenght was 1850 samples, so thats very close to 24p.

http://andersholck.com/red/redmodul.jpg

There is also some crosstalk audible across the channels, dont know how much this signal is boosted through the chain though. Eliminating it totally is close to impossible in a portable device.

Great find, Anders. Always the analyst :-)

[zak forrest]

Zac,
This is a being addressed. Should be fixed in new firmware update.

awesome. is it too much to ask for an ETA on the audio firmware update?

If it's more than two weeks away, can a brother get a beta version? In the middle of a shoot right now.

[zak forrest]

Can you confirm that only one mic channel was open when you did this, that this isn't the sum of all 4 inputs all open @ mic level? Could you try recording nothing--nothing plugged in at all and see how hissy that is? Do you have a mixer you could plug in, take the camera down to line level and record that way? Thanks for the posting. This noise is another reason that I'd like to know what the Red's real phantom voltage is.

Philip Perkins CAS

sure phil i will do that, but it looks like red is on the case =]

i can confirm though, that it was only one channel (channel 2) that was enabled when i made this recording. the proxy movie had sound in left and right channels and the left was silent with hiss and the right was the channel with my sennheiser and hiss...

[philper]

sure phil i will do that, but it looks like red is on the case =]

i can confirm though, that it was only one channel (channel 2) that was enabled when i made this recording. the proxy movie had sound in left and right channels and the left was silent with hiss and the right was the channel with my sennheiser and hiss...

Thanks--well that confirms that it is some sort of system noise, since your Left channel would be a recording made with nothing plugged in in that case, right?

Philip Perkins CAS

[Brian Ferguson]

sure phil i will do that, but it looks like red is on the case =]

i can confirm though, that it was only one channel (channel 2) that was enabled when i made this recording. the proxy movie had sound in left and right channels and the left was silent with hiss and the right was the channel with my sennheiser and hiss...

Zak have you tried any other mic inputs say 3 or 4? to see if the noise level was the same on those? Also in the Headphone menu are you listening to 1&2 or Quad. I suggest for the moment you monitor 1&2 or 3&4 whichever you have your mic plugged into. I have been doing a lot of tests on these issues and have not seen any difference between a Phantom powered mic and a self powered one. The suggestion to only enable the inputs you use is also a good one. We are working on the audio issues and are always trying to make the camera better.

briferg

[Jeremy Neish]

We have hiss on all four channels, even without anything plugged in. Patiently waiting for a firmware update...

[zak forrest]

Zak have you tried any other mic inputs say 3 or 4? to see if the noise level was the same on those? Also in the Headphone menu are you listening to 1&2 or Quad. I suggest for the moment you monitor 1&2 or 3&4 whichever you have your mic plugged into. I have been doing a lot of tests on these issues and have not seen any difference between a Phantom powered mic and a self powered one. The suggestion to only enable the inputs you use is also a good one. We are working on the audio issues and are always trying to make the camera better.

briferg

i have it to monitor 1&2, have not tried audio inputs 3&4 yet, i'll try that tomorow, but i have a feeling it will be the same, based on jeremyn's comment..

is there an estimate ETA on the audio upgrade

[Greg M]

Zak have you tried any other mic inputs say 3 or 4? to see if the noise level was the same on those? Also in the Headphone menu are you listening to 1&2 or Quad. I suggest for the moment you monitor 1&2 or 3&4 whichever you have your mic plugged into. I have been doing a lot of tests on these issues and have not seen any difference between a Phantom powered mic and a self powered one. The suggestion to only enable the inputs you use is also a good one. We are working on the audio issues and are always trying to make the camera better.

briferg

briferg,
The hiss is in all 4 channels. We have tried all types of mics and mixers, so it is there regardless of line or mic level. The noise is doubled when selecting "quad" monitoring.

One interesting note;
For a period of time the hiss would disappear occasionally on a reboot...but after rebooting again it would come back. This was prior to a camera repair that was done last week, since the repair the hiss is now there all the time.
We have #83 (pre updates)

[chuck colburn]

Sounds like, (no pun intended) a gain structure problem.

[Brian Ferguson]

What I hoped to get when I ordered my RED was the digital equivalent of an Arri IIc, so to speak (albeit three perf S35, of course). All additional perks would be icing on the cake.
Good luck!

regista - we applaud your spirit of adventure! And an Arri IIC wasn't even "Crystal Sync" so you had to add a crystal sync motor back in the day to do audio. Not to mention what a loud camera it was anyway...

We are aware of, and are monitoring audio issues with the latest RED ONE build - and have only had the audio firmware to go with our hardware for a few weeks. Hopefully everyone knows that Jim has always said you can take the camera now or wait until fully featured. Most of you know Jim has always gone way out of his way to make things right if you were an early adopter.

Welcome to all who accepted early to the new part of the adventure. Your ears and your eyes! The camera does take timecode jam sync for dual system recording for crucial audio projects.

Even a simple old style clapper on a slate will work as long as you are recording at the same frame rate. This is the first build with audio, it will be better soon, this camera always gets better.

briferg