Blackmagic Forum

In a word it's awful, peaking around -30db. I've attached a file recorded in a quiet room at 50% level both channels.

The XLRs are much better at around -55db. However the headphone amp is also very noisy so it's not ideal for monitoring.

I should be getting my camera pretty soon. This is the first post I've seen about the sound from the URSA Mini Pro. It sounds like the XLRs are better, but one of my biggest gripes about the URSA Mini 4.6k is that I can't properly monitor the sound. I need to be able to hear what is being recorded.

Adam

It could be I have one that's worse than what you may get. That's why I posted the sample. So us new owners can compare. I suspect a low impedance headphone may make monitoring the XLRs more palatable. I used Zennheiser phones @ 60ohms.

Will do some test on ours and get back to you...

I use the Bose Quiet Comfort at 25% volume successfully. Or less.


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Rick, those are active phones, I gather. So you use them in high sensitivity mode?

Has BM published the output impedance of the headphone jack?

Yes, they're external noise cancelling headphones. Sorry I don't know if they have a high sensitivity mode. I just plug them in and activate the noise canceling feature via a switch.


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What about the lag, that occurs when monitoring sound. Is there a chance, it will be fixed in firmware update?

Back to OP:

This new article at Pro Video Coalition https://www.provideocoalition.com/ursa-mini-pro-blackmagic-reveals-new-audio-specs/ quotes Blackmagic as saying

"XLR MIC Preamp has E.I.N. (Equivalent Input Noise) = -128 dBV(A) or better."

When I recorded the XLR inputs with no mic attached (but the phantom power on) the residual noise was peaking somewhere around -55dB. How would that reconcile with -128dBV(A). Is the BM figure RMS?

A question which wasn't asked in the article is about the camera mic residual noise. So, Blackmagic or anyone else:
Does the camera mic use the same preamp as the XLRs? (Probably). But if so, why is it so noisy (peaking at -30dB)? Is mine defective? Or is it a shielding from the electronics issue?

Built in Mic's are always worse than using good quality external balanced (XLR) Mic's. End of story, you are comparing apples to oranges here.

David Cherniack wrote:XLR MIC Preamp has E.I.N. (Equivalent Input Noise) = -128 dBV(A) or better.

Correct

David Cherniack wrote:When I recorded the XLR inputs with no mic attached (but the phantom power on) the residual noise was peaking somewhere around -55dB. How would that reconcile with -128dBV(A). Is the BM figure RMS?

This is not how you measure the noise floor and why would you switch phantom power on when nothing is plugged in?

David Cherniack wrote:Does the camera mic use the same preamp as the XLRs? (Probably). But if so, why is it so noisy (peaking at -30dB)? Is mine defective?

No the inbuilt Microphone preamps have 100dB(A) audio ADC’s. Our inbuilt headphone preamps are also 100dB(A).

It looks as though one of your inbuilt camera microphones is noisier than it should be and may need to be looked at by one of our support centres.

David, just for your reference:
This is what my URSA Mini 4.6k sounds on internal mic at 50%:


The room had a measured 32dB (C weighted). Total RMS level -56,54dB

EDIT:
Did also a XLR test without an external mic attached:
Phantom power ON/OFF did not make a difference.

Channel 1 Gain 33% High ... Total RMS level -93,72dB
Channel 2 Gain 50% Low ... Total RMS level -103,24dB

Robert: Thanks for the file. It's helpful.

Tim: I'd like to get to the bottom of this and determine whether it should go in to a service centre. So here's what I did this morning:

1) I used a sound pressure meter to measure my environment at 40dB (A) at the camera.

2) I recorded using the camera mics at 50%

3) I recorded using the XLRs (no mic, no phantom) at 50%

4)Using Adobe Audition I measured the Amplitude Statistics of files:

a) Camera mics


b) XLR Inputs


c) Robert's Camera mics (For Comparison)


Robert's camera mics appear much quieter than mine (in a similar quiet environment) by about 10dB.

So would the advice be to send it in through my dealer?

Yes, or request a RMA directly with your BM support center, they will sort the issue and give you a quick turn-around time.

Is this available in Perpignan?