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NoCoPilot

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PostSubject: Re: Digital Audio 101   Fri Feb 02, 2018 4:38 pm

In 2014 I digitized the debut 1978 album from Flim & The BBs.  This album was the first non-classical album ever recorded digitally in the US.  It was recorded direct-to-digital (one pass, no edits) at Studio 80 in Minneapolis, using an experimental digital recorder that 3M there in town had prototyped.  The recorder was basically laid out in pieces on a table, held together by binder clips and scotch tape.  Within a year the recorder had been disassembled.  Because the prototype used an experimental sampling frequency (50.4MHz) and bit-depth (14 bits with emphasis, making it equivalent to 15.5 bits) the master tape could not be played ever again, so the rare digital LP dubbed from the session can never be released as a CD.  

I owned a copy.

It's decent-enough music.  In fact, pretty amazing considering it was all played live in the studio, each side of the LP played straight through.  I decided I wanted to make a CD-R of it, which took an awful lot of cleanup (ticks and pops).

I was never entirely happy with the results though.  The low end is kind of thin, and the upper midrange is a bit shrill.  This may be more due to my LP transfer, who knows.  The attack on the drums is phenomenal though.

So the past couple of weeks I've been digitizing the LPs of a Minneapolis guitarist named Wayne Johnson (never released on CD), who recorded in Studio 80 and used as his backup band, you guessed it, Flim and the BBs.  I've gotten better at making these CD transfers in the intervening 4 years, and the Wayne Johnson albums are coming out sounding as good as any CD (if I say so myself).

So I pulled out the old Flim debut, and listened to it again.

Yep, I can improve it.

It'll mean violating my cardinal rule in making that transfer -- no post-processing -- but today I feel listenability is paramount over accurately reproducing that original recording.  By using some judicious multi-band compression and EQ (and additional hiss cleanup) I can make this thing sound better than it ever did.

It's a hobby.  Probably nobody in the world will ever hear it but me, but it amuses me.
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PostSubject: Re: Digital Audio 101   Fri Feb 02, 2018 5:59 pm

Sounds like a fun project.
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PostSubject: Re: Digital Audio 101   Mon Feb 05, 2018 9:11 pm

NoCoPilot wrote:
I have a minor, real minor gripe with my digital editing software.  Tell me if it's petty.

When you're zoomed in on a sound wave, you use "page up" to go forward and "page down" to go backward.  That seems backward to me.
Okay, mark this in the books of "I never saw THAT coming."

Today I downloaded the new free version of Audacity (2.2.1) to replace my 2-year old 2.1.0. Everything is nearly identical, except for a few new menu options and colors and minor GUI tweaks.

EXCEPT the page-up and page-down now work like I said above they should. This'll take some new habits being formed!
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PostSubject: Re: Digital Audio 101   Tue Feb 06, 2018 12:57 pm

I finished Flim last night, and my goodness yes, it's MUCH better.  There's still ample tape hiss -- 1978 electronics -- but otherwise it now sounds a lot like their 1983 CD debut.

Regarding the hiss.  There are four possible ways of removing it:

  • Filtering. The easiest method and the one most commonly used in commercial LP transfers is to simply roll off most or all of the high end above 6-8,000 Hz.  Tape hiss is a broadband noise, running all the way from about 1,000Hz to well above 20,000Hz.  That's why notch filters are ineffective.  The only way to kill it with filters is to take out all the cymbal transients and flute overtones with it.
  • Subtractive noise reduction. The second most-common technique, particularly early in the digital revolution, was to take a sample of the pure hiss and subtract that from the whole file.  The problem is hiss is not a constant waveform, it's a myriad of tiny fast fluctuations in the waveform.  By subtracting random hiss what you're actually doing is subtracting a low-level high-frequency random waveform, which leaves audible artifacts known as "underwater bacon frying" on everything else.  The hiss is still there -- just changed into a different more-objectionable noise.
  • Noise gating. Noise gating is filtering based on amplitude, so when nothing but noise is present the hiss is filtered out.  However when an instrument plays, the increase in amplitude of the signal opens up the "gate" and lets the instrument through, along with the hiss which is largely masked by the louder music.  Very few commercial LP transfers have ever attempted noise gating, although it is common in studios for single instrument masking.  The reason is, it is very tricky to apply.  To be done inaudibly one would have to adjust the cutoff frequencies and gate attack and decay times to match each instrument you're masking around.  It would also be an advantage to have a variable-frequency gating (like my old software did) where you can trigger different profiles depending on whether you're gating around a kick drum, a cymbal or a clarinet.  I've heard it done, and if done well it can be amazing.  But my software has only non-variable gating, and everything I tried sounded like shit.
  • Manually. Lastly and most tediously, one can manually smooth out the ripples in the waveform that reproduce as hiss.  This works for a few milliseconds of audio, but to do an entire album would take several lifetimes.  I did a lot of this, smoothing out the larger noise events and thus reducing the hiss from a roar to a trickle, but to take it farther would drive one crazy.
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PostSubject: Re: Digital Audio 101   Thu Feb 15, 2018 6:15 pm

Finished the two Wayne Johnson LPs, they both came out sounding as good as any commercial CD.

So good in fact that I offered them to the man himself, who maintains a website, in case he'd like to dupe 'em off for anybody who inquires. Wayne told me he'd gotten LP dubs of the albums a few years ago but they weren't very good. He's anxious to hear mine, which I mailed yesterday (with a surprise copy of Flim's debut) . He's quite approachable.

So I started in on my next project, an obscure jazz fusion album I'm doing for a friend in Chicago. I'm working away on the first track when I notice a glitch. The music jumps, the beat hiccups, and the next bit is in a different key. It almost sounds like a record skip, except I know my turntable didn't skip and even if it did it wouldn't skip ahead a whole measure to a key change. Must've been a sloppy tape splice on the master tape, by somebody who failed to notice that his splice didn't maintain continuity.

So I searched the whole tune, found another section that starts the same way as the measure that's spliced. Cut and pasted it into the glitch, smoothed out the edges, and now you can never tell the mastering engineer fucked up.

Damn I'm good.
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PostSubject: Re: Digital Audio 101   Sat Feb 17, 2018 10:26 pm

Oh goodness. My Chicago friend also sent some classical LPs to digitize, I started in on the first one today. It was still sealed so I figured it would be in pretty good shape.

Wrong.

It must be pressed on wheatpaste because there's a constant loud grinding sound. There are ticks and pops like a Goodwill find. The piano is out of phase but the French horn is not -- if I invert the right channel the piano sounds normal but then the horn is out of phase.

Yikes. I'm not going to bust my balls on this turd of a recording.
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PostSubject: Re: Digital Audio 101   Sat Feb 24, 2018 8:37 pm

All THREE of the classical LPs Bob sent me were crap pressings.  Two were still sealed so I know it's not wear & tear.  Geesus, we forget in the digital era what we used to put up with in the way of rotten pressings back in the day. ESPECIALLY classical and jazz.

I vowed to myself that I wouldn't clean these up to the same standard as some of the stuff I've done recently, like Wayne Johnson.  I said I'd only hit the loud pops, and leave all the smaller ticks and clicks and scratchy noises as they are.... But man, that's harder to do than to say!  I see all those peaks in the waveform and I want to zoom in and correct them...  But with ~10 of them per second, a 26-minute Concerto would take a month of Sundays to complete.

I HATE doing a less-than-perfect job.
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PostSubject: Re: Digital Audio 101   Sat Feb 24, 2018 8:49 pm

NoCoPilot wrote:
Finished the two Wayne Johnson LPs, they both came out sounding as good as any commercial CD.

So good in fact that I offered them to the man himself, who maintains a website, in case he'd like to dupe 'em off for anybody who inquires.  Wayne told me he'd gotten LP dubs of the albums a few years ago but they weren't very good.  He's anxious to hear mine, which I mailed yesterday (with a surprise copy of Flim's debut) .  He's quite approachable.
..
Wayne Johnson wrote:
Hey Robert.
I finally got time to compare multiple tracks on your new versions and my old versions. I listen with great headphones to both on my computer and then burned discs of my old versions to compare to your new copies in my wife’s car… she wasn’t even sure if she had a cd player in her relatively new BMW... she did! Then I was able to play them on my Blu Ray 4K player through the surround sound system in our family room. When thinking about not having a cd player, that last option didn’t cross my mind at first. At any rate… comparison complete and your discs are hands down better than mine. My original has a thinness in the high end that is hard to describe. As well, sometimes the reverb on the drum kit seems to be in mono… only really audible with headphones. Your discs are simply fatter/fuller in tone and takes care of these issues along with a few others. So… I want to thank you again and also a big thanks again for the WeTransfer files… very helpful.
All the best… probably chat around the corner. You being in Seattle, you’ve probably noticed or read somewhere that I’m from Spokane. Great city, Seattle.
All the best,
Wayne
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PostSubject: Re: Digital Audio 101   Sun Feb 25, 2018 11:26 am

NoCoPilot wrote:
I vowed to myself that I wouldn't clean these up to the same standard as some of the stuff I've done recently
Sometimes I hate myself.

I finished the last classical LP last night and set it to burning when I went to bed. Got up this morning and listened to it.

It is not acceptable. Too many audible pops & clicks! Even though my friend probably wouldn't care, and I'll never listen to this piece again, I just can't abide doing a job this incompletely.

It is not in my nature.
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PostSubject: Re: Digital Audio 101   Sun Feb 25, 2018 12:31 pm

NoCoPilot wrote:
I finished the last classical LP last night and set it to burning when I went to bed.  Got up this morning and listened to it.

Really? How long does it take for you to burn a CD?
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PostSubject: Re: Digital Audio 101   Sun Feb 25, 2018 12:36 pm

About 5-6 minutes, depending on length. It was just a convenient stopping place to go to bed.
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PostSubject: Re: Digital Audio 101   Sun Feb 25, 2018 9:06 pm

Okay I finished going through the 26-minute Concerto again, removing another 1000+ clicks. When I was listening this morning I noted that SMALL ticks -- the kind that compete with / can pass for hiss were not audible on a reasonable listening level play-through on speakers. Only the MEDIUM ticks, which rise above the level of the music (and are thus mostly visible when examining the waveform) were audible. And it bugged me.

I'd already removed all the BIG ticks.

So I have reburned the CD and this time I'm packaging it up and not listening back to the finished product.
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PostSubject: Re: Digital Audio 101   Fri Mar 23, 2018 3:24 pm

My customer said he thought even the LP I claimed "was pressed on oatmeal" sounded pretty good to him after I finished it.

I'm telling you, nobody appreciates me.  

Well nobody else.  There are two albums by Art Lande's Rubisa Patrol, one self-titled (1976) which was released on CD in 1991, and the second "Desert Marauders" (1978) which has never been re-issued on CD.  I think the second one is far superior.

Of course I no longer had a copy.  So I spent most of yesterday looking for files online, found a very good dub on a German website.  Downloaded and started cleaning up the files.  It was coming out sounding GOOD.  The dubber used an excellent turntable -- not a lot of rumble or surface noise.

But for some reason, track 4 was posted in monaural.  Went looking for a stereo version, found a YouTube video of it, downloaded & converted to audio.  But the sonic balance was different than the other tracks -- high end rolled off, dynamics squashed.  I re-equalized the track, pumped up the D/R, did a lot of spot corrections where somebody had killed hiss by hamfistedly imposing a lowpass filter on sections.  When I was done the track sounded consistent, and fits in pretty well with the other tracks.

Burned a CD.  Playing back now.  Sounds like a commercial release!

Nobody will EVER appreciate the work I put into this, except me.

So I'm telling you. Smile
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PostSubject: Re: Digital Audio 101   Fri Mar 23, 2018 4:00 pm

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