What is the simple external Mic solution?

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rick.lang

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What is the simple external Mic solution?

PostFri Mar 15, 2019 7:52 pm

That would be good, Iain. Certainly the Sennheiser MKE2 lavalier mic won’t need boosting on the AVX system. That’s really improved my audio capabilities recording theatrical performances. If I do purchase a Sound Devices MixPre-6/10T, would be wonderful to add a few more AVX mics.


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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 1:51 am

I just got this Neoteck HiFI Headphone Amplifier. I plugged the Polsen mini shotgun in to the auxiliary input, and the headphone out I put in to the bimpsy4k 3.5mm input. I turned the camera mic level up to 89. With the mini shotgun 3 feet away from my mouth with normal talking the meters were hitting -18. I plugged the mini shotgun in to the camera and I was barely hitting -36. I used Sony headphones to listen to sound quality and there was a little more floor noise, but not much. I will have to take it outside and record something real world. This unit is $30 and has a signal to noise ratio of 100db.
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Iain Bason

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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 2:02 am

I did a quick test with the 416 (no grading, and just available lighting, so you don't have to tell me how bad the video is!):

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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 2:07 am

Iain Bason wrote:I did a quick test with the 416 (no grading, and just available lighting, so you don't have to tell me how bad the video is!):


That sounds pretty good. What was the preamp you used? I could not quite make it out, but the sound was quite good compared to how far back you were.
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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 3:26 am

I did a similar test. I had the camera 3.5 mic input set to 89 and the headphone amplifier set as high as it would go. There was a fair amount of noise. Putting the camera internal mics up close to 100 would not have been as noisy but might have had better volume.
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Denny Smith

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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 4:46 am

Iain said he was using the Sound Devices MixPre mic preamp. This is a great little mic preamp, I have used for years.
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jponfilm

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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 6:04 am

Why don’t you guys just use the the mini XLR? That signal is super clean and great pre-amps.

And you can send it to both channels.






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Ric Murray

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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 1:04 pm

There is no 3.5mm unbalanced mic that is going to sound as good as a real professional phantom powered mic into the mini XLR input on the Pocket 4K. I know everyone would like to find an under $100 solution for that problem, but it's just not going to happen. I have used a Sennheiser 416 and MKH 50 into the XLR input and they both sound great, and levels are more than adequate. The 3.5mm input is there (in my opinion) for one reason only, for a scratch audio mic or a scratch audio feed from a second system recorder that only has mic output. There is no microphone other than something with a 24" parabolic reflector that is going to "reach out" to a sound source 15-20 ft away and make it sound "close". Physics just doesn't work that way, and there is no technical solution for bad mic technique. Get close or go home. Boosting signal just boosts noise, and the ratio of noise to signal increases as the distance from mic to source does.
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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 1:26 pm

Ric Murray wrote:There is no 3.5mm unbalanced mic that is going to sound as good as a real professional phantom powered mic into the mini XLR input on the Pocket 4K. I know everyone would like to find an under $100 solution for that problem, but it's just not going to happen. I have used a Sennheiser 416 and MKH 50 into the XLR input and they both sound great, and levels are more than adequate. The 3.5mm input is there (in my opinion) for one reason only, for a scratch audio mic or a scratch audio feed from a second system recorder that only has mic output. There is no microphone other than something with a 24" parabolic reflector that is going to "reach out" to a sound source 15-20 ft away and make it sound "close". Physics just doesn't work that way, and there is no technical solution for bad mic technique. Get close or go home. Boosting signal just boosts noise, and the ratio of noise to signal increases as the distance from mic to source does.

Thank you. I hear all you are saying. Can I say though, that it is not asking for much for the 3.5mm input to have a standard mic level sensitivity? I have a cheap "3 chip" consumer panasonic HD camcorder with 3.5 input that I mount a mini stereo shotgun on, and it sounds great for all sorts of shooting that is not cinema. The mic does a better job than the on board mic. I just thought it was not too much to ask to have a mic input that IS a mic input. What is sooo hard about that? If there were 2 xlr's... I would be silent.
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John Paines

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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 1:52 pm

It looks like the 3.5mm jack was designed for LTC timecode-in, rather than audio recording. Audio on the original BMPCC was pretty bad, but the levels were reasonably good, with both onboard and 3.5mm mics.

What I'm skeptical of is the claims here for XLR mics, without pre-amplication. But that testing will have to wait for another day.
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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 2:00 pm

John Paines wrote:It looks like the 3.5mm jack was designed for LTC timecode-in, rather than audio recording. Audio on the original BMPCC was pretty bad, but the levels were reasonably good, with both onboard and 3.5mm mics.

What I'm skeptical of is the claims here for XLR mics, without pre-amplication. But that testing will have to wait for another day.

Question: If 3.5 is for timecode, that is good. On a pro camera... why give an option if it is a joke? The electronics to digest an unbalanced mic input are not huge. It is quite small. Why can't they just deliver a standard unbalanced mic input like is standard on consumer camcorders? I would be happy with that. I know I am not in a league here only satisfied with balanced phantom powered sound. I'll use it when I need to, but for now, a standardized unbalanced mic input would be satisfactory. Come on Blackmagic!
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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 2:21 pm

John Paines wrote:It looks like the 3.5mm jack was designed for LTC timecode-in, rather than audio recording. Audio on the original BMPCC was pretty bad, but the levels were reasonably good, with both onboard and 3.5mm mics.

What I'm skeptical of is the claims here for XLR mics, without pre-amplication. But that testing will have to wait for another day.


Rode NTG3 in xlr is fine like I said earlier. It is a ‘hot’ mic though.
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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 4:07 pm

Iain Bason wrote:I did a quick test with the 416 (no grading, and just available lighting, so you don't have to tell me how bad the video is!):



Iain, seems decent levels are attainable with the Sennheiser 416 when subjects are not too far away. With the camera gain at 70% there is unnecessary gain added which is elevating the rumble. I don’t think that should be above 50% (no gain) for these tests. Or at least a test using gain should include the neutral setting as well as elevated levels. Maybe you can deal with the rumble in post, but better to keep it lower in capture.

Your test has me feeling confident the BMPCC4K and Sennheiser 416 are fine.


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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 4:13 pm

gwoiler wrote:I did a similar test. I had the camera 3.5 mic input set to 89 and the headphone amplifier set as high as it would go. There was a fair amount of noise. Putting the camera internal mics up close to 100 would not have been as noisy but might have had better volume.


Thanks for this test. At times I’ll need to use the BMPCC4K internal mic when shooting with the URSA Mini 4.6K at the same time. The Pocket4K will certainly provide a good scratch audio track fo syncing and depending upon the distance to the subject, the audio could be usable.

When I’m only using the BMPCC4K, I’ll use it with an external mic.


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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 6:15 pm

rick.lang wrote:
Iain Bason wrote:I did a quick test with the 416 (no grading, and just available lighting, so you don't have to tell me how bad the video is!):



Iain, seems decent levels are attainable with the Sennheiser 416 when subjects are not too far away. With the camera gain at 70% there is unnecessary gain added which is elevating the rumble. I don’t think that should be above 50% (no gain) for these tests. Or at least a test using gain should include the neutral setting as well as elevated levels. Maybe you can deal with the rumble in post, but better to keep it lower in capture.

Your test has me feeling confident the BMPCC4K and Sennheiser 416 are fine.


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Right, the gain was set too high for being reasonably close to the mic. There was also some room noise (a refrigerator in the kitchen near by; it was off axis, so probably not as loud as it might otherwise have been). And I was speaking very quietly; about the level of a quiet conversation with someone standing right next to you.

I was surprised that the mic picked up what I was saying even at the farthest distance, although of course it didn't exactly sound good.
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Re: What is the simple external Mic solution?

PostSun Mar 17, 2019 8:26 pm

Putting 30db of gain in during post will still leave you with more dynamic range than any feature film recorded up to 1990.
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What is the simple external Mic solution?

PostMon Mar 18, 2019 4:26 am

Iain, that fridge may help explain the rumble!

Some day, some year, I may actually be able to update my out-dated audio tests when the BMPCC4K arrives and I have the kit assembled. I’m beginning to feel like I really am on that slow boat to Singapore.


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Re: What is the simple external Mic solution?

PostMon Mar 18, 2019 8:43 pm

I have done some tests too:
I used an Ohrwurm Lavaliere and an Octava MK12 (about 60cm distance)
I plugged both directly into the BMPCC4k (one into the 3,5 in, the other into the xlr), set levels as I would in real live (about -12 dB) ending up with 90% gain for the Lav and 100% for the Octava.
Then I plugged both into my Mixpre6, set levels as above and sent the output to the BMPCC4k (and recorded both at the same time).
Finally I plugged both back to the camera and set levels to 50%. The Lav showed barely up on the Meters the Octava not at all.

I brought all files into fairlight adjusted the levels to the same perceived loudness. The resulting 8 mono files (A1-4 and B1-4) can be download here (15MB):
https://www.net-artworks.de/download/Au ... MPCC4k.zip

Listen and try to figure out which track is which recording?
Which is BMPCC4K 90%/100% in camera gain?
Which is MixPre6?
Which is BMPCC4k with MixPre6 as preamp?
And which is BMPCC4K 50% in camera gain?

The game is on :-)
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Re: What is the simple external Mic solution?

PostMon Mar 18, 2019 8:59 pm

Johannes Hoffmann wrote:I have done some tests too:

Listen and try to figure out which track is which recording?
Which is BMPCC4K 90%/100% in camera gain?
Which is MixPre6?
Which is BMPCC4k with MixPre6 as preamp?
And which is BMPCC4K 50% in camera gain?

The game is on :-)
Johannes

Did you do any noise reduction? If not.... woW. There is very little noise amplification. I would like to have the files before you went in to Fairlight.
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Re: What is the simple external Mic solution?

PostTue Mar 19, 2019 2:31 pm

Li Chenghan wrote:I recently decided to purchase this microphone that will be used for bmpcc4k,

which has the same function as Rode Video Mic Pro, but it is much cheaper and lighter.



Been thinking of getting this Mic. My Gen 1 Rode Video Mic Pro’s cable is degrading, with its skin peeling off. I’m no cable repair man, nor own a kit to do the job. But even if that wasn’t an issue, when testing, the XLR port still gives better results when using my NTG3. It’s night and day better. But the problem with using that one is that it’s too big to be an on-board Mic. I can see the mic popping into frame with most lenses.

Now the Deity uses 3.5mm, and has an adapter for an XLR connection. I’m curious to know if the XLR adapter gives the same results as the 3.5mm, or if the sound is better. Probably not as good as an XLR to XLR Mic. But if it’s better then what I’m getting with the 3.5mm port, I’ll probably pick up that mic.
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Re: What is the simple external Mic solution?

PostTue Mar 19, 2019 3:41 pm

michaeldhead wrote:Does the inverse square law apply to sound?


Yes. Each time you double the distance from a sound source, its sound pressure drops by 6 decibels.
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rick.lang

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Re: What is the simple external Mic solution?

PostTue Mar 19, 2019 7:57 pm

Brad, the inverse square law applies to area, so at twice the distance, you would have one-quarter the strength or a loss of 12 dB.


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Re: What is the simple external Mic solution?

PostWed Mar 20, 2019 12:57 am

rick.lang wrote:Brad, the inverse square law applies to area, so at twice the distance, you would have one-quarter the strength or a loss of 12 dB.
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This is right! oi... I wrote it backwards previously somewhere.... :|
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Re: What is the simple external Mic solution?

PostWed Mar 20, 2019 7:24 am

gwoiler wrote:Did you do any noise reduction? If not.... woW. There is very little noise amplification. I would like to have the files before you went in to Fairlight.

No noise reduction at all. I was surprised myself. I can provide the original camera files later ...
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Re: What is the simple external Mic solution?

PostWed Mar 20, 2019 10:15 am

rick.lang wrote:Brad, the inverse square law applies to area, so at twice the distance, you would have one-quarter the strength or a loss of 12 dB.


That makes sense, but the intensity of sound is inversely proportional to the square of the distance from the source and decibels are measured on a logarithmic scale. See http://www.animations.physics.unsw.edu.au/jw/dB.htm for example, or http://hyperphysics.phy-astr.gsu.edu/hb ... prob2.html for the equations and a calculator.

The correct answer is you lose 6 dB each time you double the distance from the source.
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Re: What is the simple external Mic solution?

PostWed Mar 20, 2019 7:50 pm

Your first link discusses intensity and sound pressure. The intensity is one quarter, but the link was helpful showing I was wrong about the sound pressure in decibels, 6dB is correct. The second link comes up with the same answer mathematically but uses the term intensity referring to the sound pressure. Thanks for the correction!


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Re: What is the simple external Mic solution?

PostFri Mar 22, 2019 8:13 pm

Johannes Hoffmann wrote:I have done some tests too:
I used an Ohrwurm Lavaliere and an Octava MK12 (about 60cm distance)
I plugged both directly into the BMPCC4k (one into the 3,5 in, the other into the xlr), set levels as I would in real live (about -12 dB) ending up with 90% gain for the Lav and 100% for the Octava.
Then I plugged both into my Mixpre6, set levels as above and sent the output to the BMPCC4k (and recorded both at the same time).
Finally I plugged both back to the camera and set levels to 50%. The Lav showed barely up on the Meters the Octava not at all.

I brought all files into fairlight adjusted the levels to the same perceived loudness. The resulting 8 mono files (A1-4 and B1-4) can be download here (15MB):
https://www.net-artworks.de/download/Au ... MPCC4k.zip

Listen and try to figure out which track is which recording?
Which is BMPCC4K 90%/100% in camera gain?
Which is MixPre6?
Which is BMPCC4k with MixPre6 as preamp?
And which is BMPCC4K 50% in camera gain?

The game is on :-)
Johannes


It seems a cinematographer's forum is more the place for pixelpeeping than for soundpeeping ;-)

Anyway here are the answers and my conclusions:

A is the Ohrwurm Lavaliere (obvious from the bass response of the omni pattern)
B is the Octava MK12 (that could have been placed better as there is quite some interference from the desk and the floor that I could have avoided by angling it differently)
1 is from the MiPre 6 (clearly the best sounding tracks)
So far so expectable.

And now to the surprises:
2 is BMPCC4k direct (90%/100% gain)
3 is BMPCC4k direct (50% gain)
4 is BMPCC4k fed by the MixPre 6

Sound and noise wise they are almost identical. Biggest surprise is #3. I pushed the gain almost 22 dB for A and 30dB for B in Fairlight to match the levels of the other tracks – the noise floor is still low.

Conclusion:
Unless something in my test setup is wrong or I miss something, the noise floor of the BMPCC4k is very low on both inputs. The pre amp seems to be week, but it is no problem to raise the levels in post and get good signal to noise ratios.

So for me the simple solution is: Plug whatever mic you have into the BMPCC4k, don't worry about the low levels and 100% gain and adjust it in post. (And place your mics correctly.)

These findings seem to be different to some other reports. My Question: Are your tracks really unusable after raising the levels in post? Or are you just concerned that the meters are low and the in camera gain has to be set to 100%? (I have cameras and recorders, where this would indeed lead to very bad signal to noise ratio).

And for those how would try the original files from BMPCC4k/Mixpre 6:
https://www.net-artworks.de/download/Au ... iginal.zip

Johannes
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Re: What is the simple external Mic solution?

PostFri Mar 22, 2019 8:22 pm

Johannes Hoffmann wrote:A is the Ohrwurm Lavaliere (obvious from the bass response of the omni pattern)


Speaking of Ohrwurm, I see he (the maker) has come out with a new generation of mics, including an update of his popular binaural mic. The original Ohrwurm binaural did quite well on the original BMPCC as it was a high-output mic. Now that the new generation is available I'm considering buying one to try on my original BMPCC as a way to capture ambient sound.
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Re: What is the simple external Mic solution?

PostFri Mar 22, 2019 8:23 pm

Johannes Hoffmann wrote:Conclusion:
Unless something in my test setup is wrong or I miss something, the noise floor of the BMPCC4k is very low on both inputs. The pre amp seems to be week, but it is no problem to raise the levels in post and get good signal to noise ratios.

So for me the simple solution is: Plug whatever mic you have into the BMPCC4k, don't worry about the low levels and 100% gain and adjust it in post. (And place your mics correctly.)

These findings seem to be different to some other reports. My Question: Are your tracks really unusable after raising the levels in post? Or are you just concerned that the meters are low and the in camera gain has to be set to 100%? (I have cameras and recorders, where this would indeed lead to very bad signal to noise ratio).

And for those how would try the original files from BMPCC4k/Mixpre 6:
https://www.net-artworks.de/download/Au ... iginal.zip

Johannes
[/quote]
Thank you Johannes! I will test your suggestions.
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Re: What is the simple external Mic solution?

PostFri Mar 22, 2019 8:41 pm

Johannes Hoffmann wrote:My Question: Are your tracks really unusable after raising the levels in post?


Most of those claims pertained, as far as I know, to the 3.5mm input. And I can confirm that the 3.5mm sound really is unusable without heavy noise reduction. The noise levels were higher than anything you recorded.

Sorry if I missed it, but which input were you using? I tried your files just now, without reading your later account. Watching the meters during the room tone at the end of each clip, it's easy to say that 1A was the quietest, followed by 4A&B. I believe 2A and 3A were the noisiest.
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Re: What is the simple external Mic solution?

PostFri Mar 22, 2019 9:18 pm

John Paines wrote:Most of those claims pertained, as far as I know, to the 3.5mm input. And I can confirm that the 3.5mm sound really is unusable without heavy noise reduction. The noise levels were higher than anything you recorded.

The question is: Why? Perhaps different firmware? Faulty camera?
Where did the higher noise levels came from? Did they originate from the camera's audio circuits or from the recording scenario (noise ambience combined with mic placement and mic pattern)?

Sorry if I missed it, but which input were you using?

A was the Ohrwurm into 3.5mm input, B was the Octava into XLR.

I tried your files just now, without reading your later account. Watching the meters during the room tone at the end of each clip, it's easy to say that 1A was the quietest, followed by 4A&B. I believe 2A and 3A were the noisiest.

The Mixpre helps ;-) (1 is direct, 4 is into camera), 2&3 are without the Mixpre.
But they are not to fare apart, are they?

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Re: What is the simple external Mic solution?

PostFri Mar 22, 2019 9:42 pm

Johannes Hoffmann wrote:The question is: Why? Perhaps different firmware? Faulty camera?
Where did the higher noise levels came from? Did they originate from the camera's audio circuits or from the recording scenario (noise ambience combined with mic placement and mic pattern)?


I tested using a battery operated Sony condenser mic which delivers perfectly adequate signal strength to a consumer Panny camera, and the BMPCC. But to get a decent level on the BMPCC 4K, I have to place it within a few inches and yell. Two or three feet away, and it's hopeless, I'd have to wake the dead to get a usable level. The 6.1 firmware did add some gain, but not enough.

Maybe the mic you're using is much "hotter"?
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Re: What is the simple external Mic solution?

PostSat Mar 23, 2019 2:44 am

After reading several threads about these issues and accounts from people with different results I'm inclined to believe that this is only showing up for a few people, a subset of people who use the 3.5mm jack (of which I am one), which is already pretty low. Someone needs to do a direct comparison between 2 discrete BMPCC4Ks to provide proof. A friend of mine is getting one in April and at that time I will perform tests and upload them here.

I just don't believe they would deliberately make the audio levels lower than the original bmpcc. It makes zero sense
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Re: What is the simple external Mic solution?

PostSat Mar 23, 2019 1:49 pm

Johannes Hoffmann wrote:But they are not to fare apart, are they?


I had a look at your original files, and can't account for how quiet they are.

The two with the lowest recorded levels are braw.056 and the .wav file. What were these? I normalized "56" to -3 in Resolve, which added nearly 26 units of gain in the Inspector, and yet it's still very quiet (though for some reason the left channel is much stronger on this clip than the right).

It's puzzling.... I wonder if there are lots of defective cameras out there, mine included, or if something about the process isn't being accounted for here.
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Re: What is the simple external Mic solution?

PostSat Mar 23, 2019 5:06 pm

John Paines wrote:I had a look at your original files, and can't account for how quiet they are.

The two with the lowest recorded levels are braw.056 and the .wav file. What were these? I normalized "56" to -3 in Resolve, which added nearly 26 units of gain in the Inspector, and yet it's still very quiet (though for some reason the left channel is much stronger on this clip than the right).

the .wav is the MixPre 6 and the 56 is "3" (BMPCC4k direct (50% gain)).
The left channel is the Ohrwurm that has a bit more "power" than the Octava.

It's puzzling.... I wonder if there are lots of defective cameras out there, mine included, or if something about the process isn't being accounted for here.

Let's have a look at the whole process from a s/n ratio perspective:
1) location: how noisy is the location and how loud is the signal I want to record?
2) mic placement: How close can I get the mic to have more signal and less room tone?
3) mic pattern: A hyper cardioid would pick up less room tone than an omni capsule
4) mic noise: every mic introduces some noice of its own. Some more, some less
5) analog amplification: every stage will raise signal and noise collected so far in the chain. And it will introduce some noice of its own – depending on the number of analog stages, their quality and how good the inputs and outputs match.
6) AD conversion and recording: as we are dealing with 24bit and wav, I would not worry to much about added noise here.
7) Gain in Post: no further change in s/n ratio (I skip noise reduction for now)

Unfortunately stages 1-4 are very different in all those audio tests online. But perhaps we can try to get them at least similar. What mics do you have?

I did one more test: I plugged the Ohrwurm into the old Pocket, gain set to 50%. The meters are reading a healthy level (about -18) but the resulting file is almost as low as the BMPCC4k with 50% gain (about -30 dB). And noise floor is much higher.
In short: the old pocket looks better on its meters but has a far worse s/n ration than the BMPCC4k.
(here is the wav from the old Pocket:
https://www.net-artworks.de/download/Po ... 17.wav.zip)

Can you try the same mic on the old and the new pocket and compare the files?

Johannes
Apple M1 Max, 32GB, 32 GB GPU – macOS Monterey
almost retired: MacPro 5.1, 48GB, RX 580 – macOS Mojave
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John Paines

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Re: What is the simple external Mic solution?

PostSat Mar 23, 2019 9:34 pm

There is one reasonably well controlled experiment I could manage: comparing the external mic to the camera mics.

The difference must range between 6-10db, in favor of the camera mics, with the camera mics producing a reasonably quiet signal, after normalization. The difference between that and the hiss of the external mic recordings is immediately apparent.
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Johannes Hoffmann

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Re: What is the simple external Mic solution?

PostMon Mar 25, 2019 7:20 am

John Paines wrote:There is one reasonably well controlled experiment I could manage: comparing the external mic to the camera mics.

The difference must range between 6-10db, in favor of the camera mics, with the camera mics producing a reasonably quiet signal, after normalization. The difference between that and the hiss of the external mic recordings is immediately apparent.


Please do 50% and 100% gain for both both scenarios.

Johannes
Apple M1 Max, 32GB, 32 GB GPU – macOS Monterey
almost retired: MacPro 5.1, 48GB, RX 580 – macOS Mojave
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