[ardour-users] It is not loud enough

Don Fredricks ardour at handsfull.net
Wed Oct 26 09:25:21 PDT 2005

----- Original Message ----- 
From: "Kevin Cosgrove" <kevinc at doink.com>
Sent: Wednesday, October 26, 2005 8:08 AM
Subject: Re: [ardour-users] It is not loud enough

> I'm trying to increase the signal as much as possible during the
> recording phase.

This is misguided in a 24-bit world, IMO. In the 16-bit days you had to hit close to zero or risk losing signal in the quantization noise. If you're using 24-bit converters, your signal (at the converter) should average somewhere around minus 12 to minus 14 dBFS during tracking, and peaks should hit around minus 6 dBFS. This leaves you 6 dB of "insurance" headroom.

> The maximum peak indicators in the mixer window
> are really great for this.  But, what decibel level corresponds
> to clipping?

0 dBFS at the A/D or D/A converters.

> I notice that the mixer peak meters go quite a
> bit above 0dB.

This is because internally, Ardour uses a 32-bit floating point format to represent digital samples. This gives you 700+ dB of headroom *internally*. The signal must be reduced to 0 dBFS before it hits the D/A converter, though, or clipping will occur.

> Also, waveforms are shown in the editor window.
> What scale is the magnitude of those waveforms?  Would 0dB be
> the top/bottom of the editor stripe? Is it linearly scaled or
> logarithmicly scaled?  Knowing this will help me to achieve a
> maximum input level before clipping.

A larger waveform represents a louder signal. A sine wave at 0 dBFS would fill the stripe completely. At minus 3 dBFS it would occupy half of the stripe. The scale is linear according to the voltage that the decibel level represents, if that makes any sense to you. So it's both linear and logarithmic, depending on how you look at it.

> If it matters, I'm recording drums and have a soft limiter on
> each channel which I've set to just start activating at what I
> think the maximum recording level before clipping would be.

Limiting past the A/D conversion stage won't stop clipping, as I believe someone else has pointed out.

Hope this helps,

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