Importance of Recording Levels for 16-Bit?

[steve]

That all sounds fine.

I have been led to believe that in digital land (Audacity/WAV/mp3), level settings are not nearly as critical.

Correct - not as critical, but while in the land of 16 bit a degree of care must still be taken.
Once it's into a 32 bit (float) Audacity track, then the levels become extremely non critical - you can safely amplify down to -30 dB and back up again with no noticeable affect - you can't do that on analogue tape
Note: Only later Beta versions 1.3.x can store values above 0 dB - the 1.2 series cannot.

I have been just setting levels roughly by eyeballing the wave form peaks against the 0 to1 scale on the left--getting peaks above .5, but clearly, I say never, above 1.

In practical terms that should be close enough. "Never above 1" is the golden rule. Around about 0.5 (-6 dB) is a good guideline.

[ignatz]

I have been led to believe that in digital land (Audacity/WAV/mp3), level settings are not nearly as critical.

Correct - not as critical, but while in the land of 16 bit a degree of care must still be taken.
Once it's into a 32 bit (float) Audacity track, then the levels become extremely non critical - you can safely amplify down to -30 dB and back up again with no noticeable affect - you can't do that on analogue tape

Am I "in the land of 16 bit" and must take "a degree of care"?

Or am I "into a 32 bit (float)" where...."the levels become extremely non critical"?

32 bit float is shown in my edit/preferences/quality/default sample format window, but I don't pretend to understand that, other than since 32 is a larger number than 16, it must be better.

So I really don't know which numerical land I am in.

[steve]

You are in the land of 16 bit while you are recording (and when exporting - assuming that you are using a 16 bit file format as the destination)
If you have the default "Quality" setting to 32 bit float (Edit menu > Preferences > Quality), then once the audio has been recorded you will have arrived in the land of 32 bit float, and will remain there until you Export your completed project.

other than since 32 is a larger number than 16, it must be better.

Very much better - when processing audio, the computer can calculate with fantastic precision.

Most consumer level sound cards and audio devices work at 16 bit.
Most high level audio devices are also capable of working at 24 bit, but unfortunately Audacity on Windows is not currently able to access 24 bit data from the audio device due to limitations in the current version of Portaudio (which Audacity uses to access the sound card). I believe this issue is being addressed by the Portaudio developers, so hopefully 24 bit sound cards will be fully supported in the future. I think that 24 bit audio is already supported on Linux and Mac, but I've not been able to test that.

[waxcylinder]

Question for you vinyl guys - does it matter if the click from a scratch is digitally clipped at 0 dB in your recording?

It doesn't seem to. Brian Davies' ClickRepair seems to clean them up nicely even when they clip like that.

What I do is:
record one side of an LP (I usual mark big clicks or click section with temporary labels)
Export to WAV file for CR processing (leaving the original track in place for later comparison)
Process the WAV through CR
Import the CRed WAV into the open Audacity project
Check that the repaired track has been fixed properly by CR (mute the original track - use the clipped points in that track and the temp. labels to identify the places to audition)
Mandraullically repair any that are not fixed ok by CR (an extemely rare occurrence - usually longish time duration noise events)
Delete the original track

WC

[waxcylinder]

How do you read "-6 DB" from a scale extending from 0 to 1?

ignatz,

you can reset your track waveforms to be calibrated in either linear or dB (or you can choose a couple of spectrum views - but I would not use thoise for recording mode as they are too slow to draw). Jist click on the "little-black-downward-pointing-triangle" at the top of the track control box - the third block lets you choose the track display format.

For the meters: either right-click in the meter or click on the meter's "little-black-downward-pointing-triangle" (next to the mic and speaker icons).

Personally I prefer to work with my track display set to linear waveform - but with my meters set to dB display. It is the meters that I use to monitor the levels rather than the graphic waveform display.

============================================

One of the biggest differences in moving from analog-tape-land to digital-land is that with good tape it was possible to temporarily go into the red on the meters to get a good fat signal - in fact one was encouraged to do this. The physics of the tape and its recording technology meant that this could be done without damaging (clipping) the signal. However in digital land clipping is always bad, so getting to 0 dB is to be avoided at all costs beacuase it always damages the signal and usually sounds horrible. And as Steve says working in 32-bit float gives you plenty of headroom for later amplification.
WC

[ignatz]

WC:

Can you comment on Davies ClickRepair declick and decrackle workflow.

I am currently doing this:

Open track in ClickRepair.

Set decrackle to zero.

Set declick settings as desired

Process and save as WAV. This yields a WAV file with CR extension that has been declicked but not decrackled.

Open the new file with the CR extension.

Set declick to zero.

Set decrackle setting as desired.

Process again and resave.

This yields a new file with a CR-1 extension that has been both declicked and decrackled.

Use the CR-1 WAV for further processing in Audacity.

I know you CAN do both in a single pass, but does that do declick first and decrackle second, as if in separate passes? I'm guessing not.

I know the preferred order is declick, then decrackle, but does that necessarily mean one, save, then the other? I'm guessing yes.

[waxcylinder]

ignatz,

personally I never use the decrackle (most crackling on LPs comes from cold-pressings and I was always very fussy about taking those back to the shop - the record shop was very pleased when I moved to buying CDs ...).

But knowing Brian and his meticulous approach to this I suspect that it is quite safe to do both in a single pass. What I woul do is find a clicky and crackly record - and with a small noisy section experiment with single and double pass and then compare the results - you will need good speakers or studio quality headphones (but I suspect you have those ...).

Does Brian's manual have anything to say about preferred workflow?

The other approach would be to email Brian asking on his opinion on best use of the software - I usually found him helpful when I have had queries in the past.

If you do this I would be extremely interested in your conclusions.

WC

[ignatz]

WC:

I believe he states somewhere that the preferred workflow is:

Derumble, declick, decrackle, debuzz, and then dehiss.

Which in his world would mean Denoise LF, Click Repair, Click Repair, Denoise LF (I think, for Debuzz), Denoise. The only question is--how many passes of Click Repair--one or two? Can you DeNoise LF the rumble and buzz in a single pass--even though that would violate the above preferred order of operations?

But I did not see a single word implying that both can be done in a single pass--so I have chosen to do them separately.

I am from mono-land (pre 1960 recordings). When you get back to pre-1955, most original issues (back into the 1930s) were in fact on 78---which are quite prone to crackling--that semi-constant "frying bacon" sound not typically found on an LP.

So I am interested in decrackle to the extent it works.

Suppose you had a 1984 reissue of 1940s recordings. You would not consider decrackle?

I do know that some LP reissues were in fact mastered from actual 78 discs and these do contain the crackle--it's just a form of groove noise, even on a mint 78. I'll admit I'm not sure how that translates into a purpose for decrackle, considering that the reissue is on LP vinyl, not 78 shellac.

Tape was not typically used for original studio recordings until the late 40s. Ampex recorders I think. Anything earlier was recorded directly to disc of some type.

Considering your name, I imagine you know all of this.

I get quite a few mp3s that someone has personally made from their own 78 collection--and decrackle is useful.

I emailed Davies a couple of weeks back about lacking a "zoom into the waveform" capability. He did write back, confirming it did not exist, so I may write him on this issue.

My 21 day trials are about to expire. I think I will buy Click Repair and pass on Denoise. It seems Audacity is as good for denoising and it is certainly more user-friendly in that you CAN zoom into the waveform and make that 1/8 second of lead in groove an inch wide and therefore easily grabbable with the mouse.

[waxcylinder]

... Suppose you had a 1984 reissue of 1940s recordings. You would not consider decrackle?

I no longer have any 78s - my parents threw them all out when I left home to go to college

When I was doing my LP transfers I had a couple of blues compilation records that were taken from original 78s and long before the days of digital processing. so these sounded like 78s. I didnt use de-carckle on them - but I did experiment with Brian's De-Noise. It worked ok, not as easy to setup as ClickRepair. I didn't bother buying DeNoise as those were the only albums I had like that - but CR is an extremely valuable item in my e-toolbox.

I don't bother with low frequency filtering as frm looking at the spectrum analyses my TT dosn't seem to be prone to rumble. But if I did I would just use Audacity for this rather than Brian's De-NoiseLF

... Considering your name, I imagine you know all of this...

The grey hair and grey beard are a bit of a giveaway too - "all" is stretching it a bit far - but I have learnt a lot more from the last couple of years that I have spent on this board and helping out on the Audacity manual.

WC

[ignatz]

WC:

I have another question or two about Click Repair, but will add them to your thread devoted to that app rather than continue here.

Please take a look there shortly.