Ripping vinyl

Here are some random notes about my vinyl ripping process.

Input levels
My DJ mixer's "rec" line out is going into my on-board Realtek soundcard's line in. This output is not affected by the mixer's internal amp. There's also an "amp" line out which is going to my home stereo system; this output is affected by the mixer's internal amp.

In Windows, in the Sound control panel, Recording tab, (Realtek High Definition Audio) Line In Properties, Levels tab, the Line In slider can set the input gain from 0 to 100. What do these numbers mean? Some experimentation reveals that has the effect of amplifying the input to the ADC, so unless you are dealing with abnormally quiet signals, you want to keep it set very low.

With no incoming signal (DJ mixer powered off) and this slider at 0, the background noise is extremely low: sample values ranging only from -1 to +1, with the average RMS of my line noise coming out to -99.3 dB (my soundcard only records at 16-bit). As the slider goes up from zero, the level jumps, but the higher it goes, the smaller the jump. Here are the average RMS levels for various slider settings, and the sample value min/max. The last two columns are for when the mixer and turntable are powered on, but nothing is playing. These values will vary slightly depending on line noise conditions.

0 -99.3  -1/+1    -94.4   -2/+2   1 -94.2   -2/+2    -90.5   -3/+3   2 -91.4   -3/+3    -88.5   -4/+4   3 -89.9   -4/+4    -87.5   -5/+5   4 -87.5   -5/+5    -83.1   -8/+8   5 -85.8   -7/+7    -85.2   -8/+9   6 -84.1   -7/+9    -81.7  -10/+10   7 -83.6   -8/+10   -79.9  -11/+12  50 -68.2  -50/+64   -64.4  -69/+75 100 -62.4 -102/+127  -57.3 -139/+165

The input gain control does seem to introduce some positive skew, but even when it is set to 100, the DC offset is reported as 0.00%, so I wouldn't worry about it. I suspect it is just the nature of my electrical line noise.

I have to keep the DJ mixer's phono input level at about 7 out of 10, or the bass hits on a fairly loud drum & bass 12" will start to clip, regardless of the input gain level. If the master volume knob for the mixer's internal amp (which doesn't affect the line out volume) is at the halfway point, these bass hits peak at 0 dB on the mixer's VU meters (crude analog metering system showing averages, not instantaneous peaks). With the input gain at 0, Audition shows the loudest instantaneous peaks are about -14 dBFS, although most of them are down around -18 to -22. I think this is about what is to be expected, but accurate calibration is beyond my capability.

Conclusion: If I set my mixer's master volume at the midpoint, I can use 0 dB on the mixer's VU meter as an ideal peak for what's going out of the mixer. On the input side, I should set the Line In volume to make the actual peaks be about -3 or -4 dBFS in Audition. This will probably be between 3 and 6, depending on the loudness of the record. It's OK if you record it quieter; vinyl's noise floor is so high, you can

Why -3 dBFS? If peaks are going over -3 dBFS, they might be getting compressed. Soundcards have built-in dynamic range limiters to protect their circuitry from high input voltages. You can see them in action if you crank up the volume coming into the soundcard, and it just squashes everything into the 0 to -3 dBFS range and never clips.

Normalization
I used to normalize each track on a single or EP to have 0 dBFS peaks, thinking it didn't make much difference, and before I learned about ReplayGain.

Around 2004, I realized that it's normal for different sides of a single or EP to be mastered at different overall volume levels. So now I try to preserve the relative volume levels of the tracks, never adjusting the volume of one track without adjusting all the other tracks on the same side by the same amount. Basically it means treating each side as a separate "album", and that goes for ReplayGain scanning, too.

As for overall volume, I generally aim for whatever will produce a ReplayGain value within a couple of dB of zero.