Audio Clip 48v Hiss / MIC input CLEAN

[zak forrest]

Camera 263, Build 13

http://zakforrest.com/redaudio

Two quicktimes, h.264 but the audio is uncompressed 24bit 48khz

First clip: Sennheiser 416 mounted on top of the camera, camera set to "48v." There is hiss. It is UNUSABLE AUDIO.

Second clip: Tram mike clipped on shirt with Lectrosonics 211 wireless system. Camera set to "MIC input." SOUNDS AWESOME.

I hope we get word from Red soon that the phantom power issues will improve, because I have had better results with every other camera I've used.

Only Channel 2 is working for me right now.

I exported the audio from the proxies with quicktime player as 24bit 48khz. and then pasted them into an HDV720P movie made with RedCine. Then exported with quicktime player as h.264, leaving the audio as 24bit 48khz. However, with the audio going through all these different steps in quicktime player, I get a bit worried, because quicktime has different settings. I put it on "best," but that still seems like its doing something. I wish there was a setting in quicktime player to just leave the audio alone, instead of "best" and "24 bit" (when i get info on the proxies, it says the audio is 32bit). anyone want to chime in on this one for me? maybe i'm doing extra steps, or theres a better way to do this.

[Nick Shaw]

If you use Compressor to encode the movie instead of Quicktime Player, it has a "pass-through" option for audio.

[BASSAM MSSALATIE]

thanks for this test .sorry i can not help you i don't have camera yet ?
BTW who are they ? your family . i like him .god bless them

[zak forrest]

thanks for this test .sorry i can not help you i don't have camera yet ?
BTW who are they ? your family . i like him .god bless them

aahh.. :biggrin:

my mom and dad

[Steve Sherrick]

Zak, I'm curious about this test. Reason being that you are trying to determine if a mic such as the 416 running through the Red's mic pre and phantom power system is generating some kind of unexpected hiss. By placing the mic on camera and hence several feet away from the subject it is hard to make a judgement. The gain is cranked a bit, no? Although I do agree that the hiss seems more than would be expected, I'd much rather see that mic put on a boom stand and get it within 2ft of the subject, as this would more represent a typical situation. Mic should never be left on the camera in the environment you are showing here. So easy to throw it on a boom or mic stand, even in a one man band scenario.

Perhaps the goal is to see what kind of audio you can get in a run and gun situation, hence leaving it on the camera. For my own purposes I'm very interested to hear it placed in a more normal location. Could you run that test for us. Get the 416 nice and tight on the subject. Get the audio to average -20db with peaks somewhere in the -10 range. I'd like to hear that audio scenario. If the audio is still bad, then there may be a problem.

Thanks for doing the testing!

Steve

[zak forrest]

hi steve. yeah the test was to see how the sennheiser was for run and gun. if you are using a sennheiser RIGHT UP on the subject, you could probably get the gain a little bit lower. but that hiss you are hearing on my sennheiser test is present no matter what the gain setting. the gain makes the hiss slightly louder or softer, but not really. and its definitely not any noise from the camera. the purpose of my test was to see if the hiss was present on both mic and phantom inputs, and i now know that it's not. i dont think i have time right now to do the test you want me to do, but perhaps tomorow or sometime in the next few days i could do it for you.

for your purposes, are you going right into the cam from the mike? would you use the phantom power from the cam or a seperate phantom power box or a mixer? the problem here is strictly related to the camera's phantom power..

oh also, the gain isnt really cranked at all. according to what the red manual says to rate your gain according to the mic's sensitivity rating, i might be 1 or 2 db higher than recommended, not really cranked at all...

[Peter Richardson]

hi steve. yeah the test was to see how the sennheiser was for run and gun. if you are using a sennheiser RIGHT UP on the subject, you could probably get the gain a little bit lower. but that hiss you are hearing on my sennheiser test is present no matter what the gain setting. the gain makes the hiss slightly louder or softer, but not really. and its definitely not any noise from the camera. the purpose of my test was to see if the hiss was present on both mic and phantom inputs, and i now know that it's not. i dont think i have time right now to do the test you want me to do, but perhaps tomorow or sometime in the next few days i could do it for you.

for your purposes, are you going right into the cam from the mike? would you use the phantom power from the cam or a seperate phantom power box or a mixer? the problem here is strictly related to the camera's phantom power..

oh also, the gain isnt really cranked at all. according to what the red manual says to rate your gain according to the mic's sensitivity rating, i might be 1 or 2 db higher than recommended, not really cranked at all...

Thanks for doing these tests Zak. I think it's time for you to do a doc about your parents ;) In all seriousness, for us EFP and doc folk these tests are invaluable.

In addition to the Phantom Power issue, I'm curious about fan noise. What's the longest take you've run on the camera so far, and did the fan kick on? Very curious to hear how the fan sounds with a camera-mounted mic.

It would be great to hear Red chime in on this thread regarding the Phantom Power hiss issue.

Peter

[Stuart English]

Thanks for doing these tests Zak. I think it's time for you to do a doc about your parents ;) In all seriousness, for us EFP and doc folk these tests are invaluable.

In addition to the Phantom Power issue, I'm curious about fan noise. What's the longest take you've run on the camera so far, and did the fan kick on? Very curious to hear how the fan sounds with a camera-mounted mic.

It would be great to hear Red chime in on this thread regarding the Phantom Power hiss issue.

Peter

No, it shouldn't have a hiss like that. Line and Mic input settings don't. Zak and I are discussing his issue at the moment.

As for length of a single take - I usually stop my recording tests after an hour, so at least that length anyway...

[Peter Richardson]

Thanks Stuart! Does the camera stay in "silent" mode on those 1 hour takes? Can you give us any info regarding temperature conditions when you rolled those takes? I'm guessing from your reply that the "hiss" is an isolated issue with this camera. Thanks!

Peter

[Steve Sherrick]

Zak,

In my situation I'd be running external mixers, hard disk recorders, etc that all have their own phantom power source. I'd be running line in to the camera. But, I'm sure others will want to run a mic directly into the camera at times, so I do have an interest in what is going on with the hiss. Perhaps it's an isolated problem. I'll have my camera soon enough, and rest assured audio tests will be on the list and posted promptly.

In the meantime, thanks again for running the tests and hopefully Stuart can help identify the problem and post back the solution.

Steve

[zak forrest]

Zak,

In my situation I'd be running external mixers, hard disk recorders, etc that all have their own phantom power source. I'd be running line in to the camera. But, I'm sure others will want to run a mic directly into the camera at times, so I do have an interest in what is going on with the hiss. Perhaps it's an isolated problem. I'll have my camera soon enough, and rest assured audio tests will be on the list and posted promptly.

In the meantime, thanks again for running the tests and hopefully Stuart can help identify the problem and post back the solution.

Steve


with your mixers and recorders and line/mic inputs you will be good to go right now. and im sure pretty soon this phantom power thing will be cleared up. so im sure we will all be good to go soon. i hope at least...

[zak forrest]

curious about fan noise. What's the longest take you've run on the camera so far, and did the fan kick on? Very curious to hear how the fan sounds with a camera-mounted mic.

It would be great to hear Red chime in on this thread regarding the Phantom Power hiss issue.

Peter

I don't think anyone is going to have a problem with fan noise no matter what.

On variable its pretty much fine all the time but it is SLIGHTLY audible. if that bothers me, i turn it onto SILENT. the only thing is then, when its on silent mode, when you arent recording, the fan rips into full steam ahead.

maybe the VARIABLE setting can be improved so that it goes dead quiet like it does in silent mode when you are recording?

[Steve Sherrick]

Cool. As long as it's not hardware related, I'm sure this will get cleared up right away. I will stay tuned to find out what you guys come up with.

Steve

[Kip Hewitt]

I have had trouble with this hiss sound as well. It seems to have nothing to do with mic or cables, etc. and more to do with firmware. I don't know what causes it. Suddenly, it appears like a switch has been turned on. The only thing that seems to correct it is a firmware reinstall.

I have experienced this problem with two different cameras (#99 & #99x) and two different builds (12 & 13).

Zac, please keep us posted with your findings.

[Stuart English]

Thanks Stuart! Does the camera stay in "silent" mode on those 1 hour takes?

Yes, fan will stay in SILENT mode.. I hour takes to RED-DRIVE in 75 degree ambient..

[Peter Richardson]

Yes, fan will stay in SILENT mode.. I hour takes to RED-DRIVE in 75 degree ambient..

Fantastic news Stewart! Do you feel that one could mount a shotgun mic (416) on the camera in silent mode and not pick up fan noise?

Peter

[Elizabeth Lowrey]

I have had trouble with this hiss sound as well. It seems to have nothing to do with mic or cables, etc. and more to do with firmware. I don't know what causes it. Suddenly, it appears like a switch has been turned on. The only thing that seems to correct it is a firmware reinstall.

I have experienced this problem with two different cameras (#99 & #99x) and two different builds (12 & 13).

Zac, please keep us posted with your findings.

That seems an interesting find, the flakiness of it and fact that it starts all of a sudden. Should be something they can fix with firmware.

[Fergus Meiklejohn]

Yes, fan will stay in SILENT mode.. I hour takes to RED-DRIVE in 75 degree ambient..

Really!? That is fantastic news Stuart. You should be shouting that bit louder..:biggrin: The prevailing impression in these discussions is that the fans will kick in after 20 minutes. Which for some of us would compromise certain common filming scenarios. I've never expected miracles! But I've got to be realistic about RED's strengths and weaknesses..
I couldn't ask for more than 1 hour straight at 75 degree ambient, (well I could but.. :).. ) .. My Macbook Pro sounds like it's about to explode if have to render on it for an hour..
And if this mic level hiss problem is Firmware fixable then...:love:

I may even eat my hat.

[donatello b]

"fan will stay in SILENT mode.. I hour takes to RED-DRIVE in 75 degree ambient"

i just don't get "silent "
could you define "SILENT "
to me silent is - i stand 1ft from the camera and i don't hear it ...
today RED 103 back from RED where FAN has been checked and is to spec - in my 70 degree liv room ... camera on 1 min
i have RED with fan in "silent mode" - i hit record and fan goes to a lower setting AND i can hear fan 15ft away from the camera ( could be more ft but i'm at end of liv room) ...
if i switch FAN to "vari" mode - now the FAN speed is approx the same as silent (when it's recording) when camera is on/standby .. i hit RECORD and now i do NOT hear the camera at 1ft = it is silent.. i take it out of record and fan is at a low speed - which you can hear 15ft away ....
today within 10 min of being ON ( in vari mode) - when i hit record -the fan stays the same = i hear it 15ft away ...
so i just do not get what is SILENT to RED spec's ...

[Stuart English]

"fan will stay in SILENT mode.. I hour takes to RED-DRIVE in 75 degree ambient"

i just don't get "silent "
could you define "SILENT "


The technical difference is this - VARIABLE runs the fans at a variable rate, in both record and when not, SILENT runs the fans at full speed when not in record and a fixed speed of about 10% when in record. And it will stay at that same speed throughout a recording.

If its cold, shoot VARIABLE mode. Else consider SILENT mode.

[Mike Prevette]

The 416 likes to be close to it's subjects. I have the older "t" power version. It would be interested to see if you powered it via an external mixer for the phantom power, and then passed a line in into the cam. Just trying to narrow down if it's indeed the phantom power circiut causeing the hiss.

[jbeale]

The technical difference is this - VARIABLE runs the fans at a variable rate, in both record and when not, SILENT runs the fans at full speed when not in record and a fixed speed of about 10% when in record. And it will stay at that same speed throughout a recording.
If its cold, shoot VARIABLE mode. Else consider SILENT mode.

If I'm understanding this right, it sounds like the (only?) way to get "truly inaudible" operation, as I would understand that term, is to set the fan in VARIABLE mode, AND prevent the camera body from getting any warmer than about 72 F by whatever external means may be necessary. So in normal room-temperatures, that might mean a large slow-turning external fan, a large external heatsink clamped to the camera, a tripod plate with chilled water supply, freeze spray, ice packs, frozen peas, whatever.

[Greg M]

The 416 likes to be close to it's subjects. I have the older "t" power version. It would be interested to see if you powered it via an external mixer for the phantom power, and then passed a line in into the cam. Just trying to narrow down if it's indeed the phantom power circiut causeing the hiss.

Yes, the bulk of the problem w/ usability of Zacs clip is related to the distance from the subject. But I can confirm w/ Build 13 Phantom Power does introduce hiss. The biggest issue though is the DC offset.

[Elizabeth Lowrey]

Yes, the bulk of the problem w/ usability of Zacs clip is related to the distance from the subject. But I can confirm w/ Build 13 Phantom Power does introduce hiss. The biggest issue though is the DC offset.

I magnified a waveform in Vegas to where I could see the offset. I understand that it restricts normalization range, but what are the other audible consequences of DC offset?

[zak forrest]

Yes, the bulk of the problem w/ usability of Zacs clip is related to the distance from the subject. But I can confirm w/ Build 13 Phantom Power does introduce hiss. The biggest issue though is the DC offset.

i dunno man, i have gotten some pretty damn nice results with that distance and that mike before..

and yeah, the gain could have been higher, but i didnt bother doing another test with higher gain because i already saw that the problem was that hiss and the hiss would just get louder with the gain change so i stopped..

[Steve Sherrick]

DC offset can affect headroom(can reduce in direction of the offset). If excessive enough it could affect gaining up (clipping). Interesting, have to see if this is an issue during my tests.

Zak, If you like the 416 from several feet away, then no one can hold that against you. You are entitled to get the "sound" you want. Personally, for medium and closeup shots I wouldn't want that mic that far away. But f a wide angle, it might be an okay perspective. Also, the 416 is not the ideal indoor dialogue mic but that's yet another subjective area. And besides, Schoeps just raised their prices so....

Steve

[Brian Ferguson]

I don't know what the problem is but when i downloaded the 416 audio on my iBook at home with the volume full up I could barely hear the dialog let alone the hiss. It seems to be output at a very low level. I held the computer to my ear and heard the hiss but if your levels are that low to start with you only amplify your signal to noise issues maybe the mic was set at way to low a db setting?

BriFerg

[zak forrest]

DC offset can affect headroom(can reduce in direction of the offset). If excessive enough it could affect gaining up (clipping). Interesting, have to see if this is an issue during my tests.

Zak, If you like the 416 from several feet away, then no one can hold that against you. You are entitled to get the "sound" you want. Personally, for medium and closeup shots I wouldn't want that mic that far away. But f a wide angle, it might be an okay perspective. Also, the 416 is not the ideal indoor dialogue mic but that's yet another subjective area. And besides, Schoeps just raised their prices so....

Steve

well when the camera isnt hissing etc, it really sounds pretty good for me if i'm doing run and gun type stuff. not feature stuff. does that make my decision seem more sane to you?

what do you recommend over the 416 for an on camera documentary mike, where you are alone and have only the camera mounted mike? and you are filming things that arent staged (no lavaliers allowed)

[zak forrest]

I don't know what the problem is but when i downloaded the 416 audio on my iBook at home with the volume full up I could barely hear the dialog let alone the hiss. It seems to be output at a very low level. I held the computer to my ear and heard the hiss but if your levels are that low to start with you only amplify your signal to noise issues maybe the mic was set at way to low a db setting?

BriFerg

ill try and do another test with it at several gain levels. it just seemed obvious to me that it wasnt a low level trick, that hiss would only get louder as i boosted the gain so i cancelled the test and decided to wait for red to fix this. ill try another test though but i think its just bogus right now to begin with..

ive recorded stuff from the same distance, in fact kept the mike on the camera and kept talent in the same place, and just plugged the mike into my MBOX and recorded some dialogue onto the computer and the results were really amazing. my first reaction was "oh my god are the preamps on the red complete garbage????" but now i'm hoping they are just fine and the problem can be fixed with software. and if it can't, i would say they should do a recall...

[Fergus Meiklejohn]

ill try and do another test with it at several gain levels. it just seemed obvious to me that it wasnt a low level trick, that hiss would only get louder as i boosted the gain so i cancelled the test and decided to wait for red to fix this. ill try another test though but i think its just bogus right now to begin with..

ive recorded stuff from the same distance, in fact kept the mike on the camera and kept talent in the same place, and just plugged the mike into my MBOX and recorded some dialogue onto the computer and the results were really amazing. my first reaction was "oh my god are the preamps on the red complete garbage????" but now i'm hoping they are just fine and the problem can be fixed with software. and if it can't, i would say they should do a recall...


I don't doubt it Zak. I've also recorded plenty of stuff with an on-camera shotgun at that distance and it didn't sound anything like your test. There is clearly something wrong with RED audio, and I don't think RED should get distracted by the nuances of your test. But thanks for doing it again anyway.. just to ram the point home :-)

Incidentally some users seemed to suggest that by reinstalling the Firmware they were able to make the hiss go away (for a while). Has that been your experience?

[Stuart English]

I've also recorded plenty of stuff with an on-camera shotgun at that distance and it didn't sound anything like your test.

Incidentally some users seemed to suggest that by reinstalling the Firmware they were able to make the hiss go away. Has that been your experience?

There is obviously a MAJOR difference in quality between these two clips, and the hiss evident in the +48V case should not be taken as de-facto evidence of a poor A/D conversion - the Mic input passes through the same section and it is clean. I don't know why only the +48V input is exhibiting this behavior, but I do know we are on it.

For the majority of cameras that I am aware of, on Build 13 the Mic and Line inputs are hiss free. Please PM me or Brent if you have a camera that isn't.

[Fergus Meiklejohn]

the hiss evident in the +48V case should not be taken as de-facto evidence of a poor A/D conversion - the Mic input passes through the same section and it is clean.

I agree with you Stuart. Good luck solving the problem.

[donatello b]

"on Build 13 the Mic and Line inputs are hiss free"

on monday when Red 103 was returned - i shot a few clips .. i had a low volume tone/noise in all clips ( not a hiss ) when played in FCP . i didn't have a mic connected ... looking into it more ( as in hrs).... the camera was returned with all audio channels enabled. the tone was coming from 3 & 4 in Mic mode changing it to LINE or un-checking 3 & 4 ( un-enable) got rid of the low volume tone ( which you can hear thru headphones ) ...

if i plug a mic into 3 and disable 4 the tone goes away ... and if i plug mic into 4 and disable 3 tone goes away ...
there is no tone in 1 & 2 when they are enabled with no mic connected ..
so why the tone in 3 & 4 ?

2:00pm ... correction - i am finding the low tone in channel 1 if 2 is enabled ...
also one of my mic's is very low - so i have to set RED channel 1 volume to 41 - which now i hear the low tone .. if i reset the volume to 26 i do not hear it but then i can't get any volume out of my mic ...