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Post Posted:: December 7th, 2017, 5:58 am 

Joined: December 5th, 2017, 7:13 am
Posts: 3
Hi everyone,

Just finished recording my first book, which was very amateurish but a great experience. I'm so excited about reading more audiobooks I invested in some equipment to get better sound quality, specifically a RODE NT1-A condenser microphone and a Focusrite Scarlett Solo audio interface.

I've been using ocenAudio to record in "punch and roll" mode. However the audio that is recorded gets clipped at -6 dB.

On the sound monitor, I can see the levels going all the way up to 0 dB, but the recorded waveform is always clipped. Here's a screenshot: http://i.imgur.com/mSlIXSY.png

This happens only with the new microphone. With my old USB microphone, it records the complete waveform with no clipping.

Any ideas why this might be happening, how I can stop this clipping?


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Post Posted:: December 7th, 2017, 7:46 am 
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Joined: July 14th, 2008, 4:54 pm
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The first thing that comes to mind is recording volume, the waveform you've posted looks too high.
A lot of folks here use Audacity, this is the advice we give regarding volume level...
You should aim for your wave forms to peak near the 0.5 mark, like this:
Image

You can check your volume using our Checker program - see info at http://wiki.librivox.org/index.php/Checker Make sure you download the experimental version - you will find the volume in decibels on the Information tab. For your information, we look for around 89 dB (87-91 is OK)

Please try our One minute Test to get feedback on your recording setup. :wink:

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Post Posted:: December 7th, 2017, 8:32 am 

Joined: November 10th, 2016, 3:54 am
Posts: 397
Location: LONDON UK
The Rode NT1A mic has quite a high output and very low noise. It requires 48 volt phantom power. I don't know anything about the interface you have. You will need to turn the gain control down - either on the interface or in software in the computer operating system - PC or Mac.

Your example linked was quite severely clipped and must sound quite distorted.

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Post Posted:: December 7th, 2017, 8:40 am 

Joined: February 24th, 2013, 7:14 am
Posts: 1602
Location: New Hampshire, USA
I have used two XLR-to-USB interfaces, and both pretty much never deliver the sample all the way to 0db. They scale their delivery to the computer at about -6 db. As lurcherlover says, make sure the gain is adjusted so that clipping does not happen - the interface may have a way to tell you (is there a red LED lighting up when you speak louder, on the interface itself?). You will likely need to amplify your track in post-processing, and that's normal for using audio interfaces with external audio sources.

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    reality prompts me to scale down my reading, sorry to say
    to PLers: do correct my pronunciation please


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Post Posted:: December 8th, 2017, 6:59 am 

Joined: December 5th, 2017, 7:13 am
Posts: 3
Hey everyone, thanks for the attempts to help. However I see I didn't explain the problem too well.

I realize the waveform I posted looks like the levels are set way too high because of the way it's clipped. But this is not the case.

Normally that kind of clipping occurs at 0 dB, and if you are seeing that then your levels are set too high. That's how the same setup behaves with my USB mic.

But in this case the waveform is getting clipped at -6 dB. That shouldn't happen.

Of course I could just set my recording level low enough to avoid the clipping, but that isn't how a mic like this is supposed to work. The sound should only get clipped above 0 dB, leaving the range below that for the actual recording, which normally never goes above -3 dB.

This seems to be either a software setting or an actual problem with the hardware, presumably the interface. I'm assuming it's a software setting but I can't find it for the life of me.


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Post Posted:: December 8th, 2017, 7:11 am 

Joined: October 6th, 2012, 3:27 pm
Posts: 381
I understand your problem, and I agree with you - it shouldn't behave like that.

My suggestion would be to try different recording software (maybe Audacity). If you can replicate the problem that would rule out the recording software. In which case I'd be inclined to take the problem to the technical support folks at Focusrite.

Best,
-Ian


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Post Posted:: December 8th, 2017, 8:35 am 

Joined: February 24th, 2013, 7:14 am
Posts: 1602
Location: New Hampshire, USA
It does not depend on the software that accepts audio input, I suspect. It depends on the driver that controls the device or maybe the internal circuitry of the device itself. The samples are limited on the device or in the driver, and the limited samples are sent from the driver to the software. Audacity gets them limited just as any other audio editor. At least that is so in my experience. :|

Of course, one should try other software to confirm, and, yes, speak to Focusrite folks... Be prepared that the result is going to be the same.

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Post Posted:: December 8th, 2017, 8:56 am 

Joined: October 6th, 2012, 3:27 pm
Posts: 381
Yes, I'd expect the result to be the same too. But ruling out any possibility of strange interraction between the software and driver would demonstrate to the Focusrite people that it's 'their' problem. It looks so odd that I don't think it's going to be a simple setting, so I suspect the Focusrite people will be interested in hearing about it.

Let us know what you find...

ETA: rogrossm, it would be interesting to know how far round your gain knob is set...


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Post Posted:: Today, 1:42 am 

Joined: November 10th, 2016, 3:54 am
Posts: 397
Location: LONDON UK
Can you try a different mic? Borrow one?

It may men you need an attenuator between the mic and the interface if another mic works fine. This could be a simple in circuit resistor.

Peter

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