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Monty
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Question for you recording guys

I have a few recordings on disc that seem to be ever so slightly out of synch and I was wondering what causes this and if it is intentional or a product of poor reproduction.

What is going on when I can hear the track begin just a split second before it actually comes in? I'm talking about an extremely low in level jump the gun kinda thing? Is this some sort of ambience enhancement attempt or what? This has me curious and I have always wanted to ask somebody what was going on. Thanks in advance.

Editor
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Re: Question for you recording guys


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What is going on when I can hear the track begin just a split second before it actually comes in? I'm talking about an extremely low in level jump the gun kinda thing?

When you master a CD, you have to decide where to place each Track Start marker in the PQ subcode. If you place it exactly at the start of the first note of music, only a few CD players will start here; most will trim the transient off the note, due to the time it takes their output circuit to unmute. If you place the marker significantly before the music, there will be an annoying wait with all but the laziest players.

As a rule of thumb, it is safe to place the Track Start Marker 10 video frames, ie, 1/3s, ahead of the actual music start. However, if there is ambient noise during this period and the track doesn't fade in from digital black (individual movements of a symphony, for example) and your CD player is quick to unmute, you will hear exactly what you're describing.

John Atkinson
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Monty
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Re: Question for you recording guys

Years of bewilderment cleared up in a few minutes. Thanks, JA.

Buddha
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Re: Question for you recording guys

I can remember LP's that used to do that, too.

As I recall, wasn't it due to the master tape having a little bleed through during the quiet part before a song began? You'd hear what was on it's way because the signal leaked through from the tape layer below the quiet part.

So, we end up with similar artifacts in both CD and LP?

I hadn't noticed the digital version of this phenomenon. Interesting synchronicity!

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Cliff Clavin flashback moment: I had a friend who used to try and judge low level system detail when auditioning equipment by playing the LP version of Squeeze's "Tempted" because it had a relatively faint "I bought a toothbrush" vocal you could hear before the cut began.

That cut lead him to buy the old Apt Holman preamp back in the day.

jazzfan
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Re: Question for you recording guys

I always thought that what you heard was bleed over from the magnetic signal on the master tapes from the recorded part to the unrecorded part, i.e. the silence before the start of a track, which is why it always pre-echoes the music one is about to hear. Of course this would only happen with analog and not with "perfect" digital sound.

Edited:

I see that Buddha also seems to remember the same thing. Urban myth or something we smoked?

Buddha
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Re: Question for you recording guys

I also remember being told that both pre-echo and post-echo could be the result of too closely spaced grooves on the LP. Thinner walls between grooves, I guess?

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Re: Question for you recording guys


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I see that Buddha also seems to remember the same thing. Urban myth or something we smoked?

There's another explanation, which is that lacquers are actually somewhat unstable and that loud passages tend to "creep" to the other side of the groove if they aren't plated within a couple of hours or kept cool -- preferably both. When I worked at a high-end plating facility, we'd have Ted Jensen at Sterling and Bob Ludwig at Masterdisk call us to make sure we had plating tanks ready before they would cut really important projects. Special messengers would arrive from the cutting rooms with insulated bags (that looked suspiciously like the ones that pizza delivery guys use now) and we'd have to time-stamp their receipts and guarantee that the lacquers were pre-plated and in tanks ASAP. When A&M was ordering mothers and stampers for <I>Synchronicity</I> and Donald Fagen's first solo disc to be shipped all over the world, we were kept busy for double-shifts just cranking those babies out.

You don't hear that kind of groove-deformation pre-echo on DMM stampers or half-speed cuts, but each has its own trade-offs.

Also, as Mikey (and Jeff Wong) will attest, there can be differences between stampers pulled from the same mothers.

Making an LP is really hard to do, which is why so many record labels were prepared to walk away from it at the first opportunity. And doing it well didn't come cheap -- still doesn't, just ask the guys at AcousTech, who do it really well today.

stereophillips
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Re: Question for you recording guys

Oh yeah, I forgot to say that the tape explanation probably isn't correct, when you consider that pro recording is done on large reels and at high speeds, so hearing a passage a few seconds early doesn't work out mathematically.

jazzfan
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Re: Question for you recording guys


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Oh yeah, I forgot to say that the tape explanation probably isn't correct, when you consider that pro recording is done on large reels and at high speeds, so hearing a passage a few seconds early doesn't work out mathematically.

Okay Wes, I'll buy that. So that leaves urban myth or something we smoked, now which one is it?

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Re: Question for you recording guys


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So that leaves urban myth or something we smoked, now which one is it?

I used to hear cross-talk between adjacent tracks on LP's routinely (before I turned 100% digital). It was real without a doubt.

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Re: Question for you recording guys


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I forgot to say that the tape explanation probably isn't correct, when you consider that pro recording is done on large reels and at high speeds, so hearing a passage a few seconds early doesn't work out mathematically.

Two other factors:

1) analog tape reels tend be stored "tails out" so that magnetic bleedthrough _follows_ the musical event so sounds like reverb, which is innocuous, rather than pre-echo, which is not.

2) On rock album master tapes, there should be leader tape spliced right up to the actual start of the track so that even if the tape is stored "heads out," there won't be any pre-echo.

Both of these are recommended practices, of course, not inviolable rules, which means that there are probably many LPs where audible pre-echo has been faithfully preserved in the grooves :-)

John Atkinson
Editor, Stereophile

Jeff Wong
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Re: Question for you recording guys

On Brian Eno's album, Before and After Science there's what seems like pre-echo right before the tune, 'Energy Fools the Magician' on the LP as well as the recently remastered CD. I always figured it must be some bleed through on the master tape, or some subtle sound Eno used to foreshadow what was to come shortly (which always seemed possible, with Eno.)

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