Subject:question about clipping

Posted by: wynton

Date:2/27/2007 6:30:54 AM

For months, I was digitizing my vinyl, using a USB turntable and Acid Music Studio 6. While doing that, I was making a basic attempt to avoid too much clipping. (In other words, I would lower the input level until the clipping only happened a handful of times during the entire album.)

Recently, though, I upgraded the cartridge on the turntable. It is my impression now that the signal strength from the turntable is noticeably stronger. And as an experiment, I made one recording. Despite a fair amount of clipping being indicated, the recording sounds pretty good to my ears.

So, here is what I am wondering: if I am using a somewhat better cartridge, can I allow for more "clipping" without the risk of distortion? Or should I still be equally diligent about avoiding excessive clipping? If this one recording is a good test, it appears that I can get away with more clipping now, but I don't know whether that was just an unusual album.

Subject:RE: question about clipping

Reply by: Vocalpoint

Date:2/27/2007 7:50:28 AM

"Clipping" is only a word to make reference to this occurance. It should NEVER actually occur in your recordings. If you are in fact witnessing any clipping of any sort - you are losing data that can never be retrieved - not to mention that you have severe gain setting problems with your gear.

Clipping (in digital) indicates your material has gone past the "line" and is now in a world where it cannot be represented by anything but nasty, ugly noise.

Remember in the digital world "0" is not the same "0" as in the analog world. When you are transferring your vinyl - if you are peaking (on ACID meters - I am assuming you using ACID since you are posting in this forum) any higher than -10dbFS - it''s too hot. Back it off.

For standard reference: -18dbFS (digital) = 0db (analog).

And as a suggestion - I would be using something like Soundforge or Wavelab to transfer vinyl. Acid is not a good choice for this kind of work.

Cheers!

VP

Subject:RE: question about clipping

Reply by: wynton

Date:2/27/2007 11:09:34 AM

Well, I didn't really mean to open that particular debate about clipping, but I'm always interested in what others think.

Frankly, I have read and spoken to people who say that the recording level should be set so that clipping never occurs. Just as many have the opinion that one need not be strict when it comes to diigitizing vinyl and suggest that it is better to set the recording level as high as possible, for maximum saturation, even if it means an occasional clip.

I have tried both approaches and now generally take an in-between view.

Subject:RE: question about clipping

Reply by: Vocalpoint

Date:2/27/2007 1:58:25 PM

"Frankly, I have read and spoken to people who say that the recording level should be set so that clipping never occurs. Just as many have the opinion that one need not be strict when it comes to diigitizing vinyl and suggest that it is better to set the recording level as high as possible, for maximum saturation, even if it means an occasional clip."

Saturation? This is not tape we are talking about here. In digital - there is no concept of "saturation" as much as there is NO concept of going "over". If that red light ever appears - your source material has now been destroyed - since it cannot be represented in little 1's and 0's when you fly past 0dbFS.

Whoever told you that "clipping" is okay anywhere within the digital realm needs to stop giving advice - because they simply cannot be more wrong.

However - if you are okay with destroying your source material during your transfers - then clip away. Remember too - if you are already hitting the red - you have added as much as 18 extra db to the source - which certainly way beyond what was intended.

VP

Subject:RE: question about clipping

Reply by: wynton

Date:2/27/2007 4:49:03 PM

I'm sure I'm getting bad advice from a few people, but it's hard to know who to trust so I have to rely on my ear.

And one thing I know is that if I have the input level down too low then the recording simply sounds too soft. Also, it makes sense to me that an occasional clip should be tolerated if that still leaves 95% of the recording at the ideal level. By "occasional" I mean a handful of times for the whole recording.

I keep going back and forth about this. My first set of recordings was done without even realizing I was clipping. Then I obsessively made sure my recordings had ZERO clipping. And I think that resulted in some being too soft. So, more recently, I've been somewhat less strict. I aim to get the level around -5 for most of the recording.

Anyway, I definitely don't understand the technology of it all. I thought that one problem with clipping was that it created distortion. If the clip merely eliminates the source material, though, why would that manifest itself in distortion?

And are you really saying that I should try to keep the level so it reads -18?

Subject:RE: question about clipping

Reply by: Vocalpoint

Date:2/27/2007 6:41:49 PM

"And one thing I know is that if I have the input level down too low then the recording simply sounds too soft. "

Too soft does not compute. If it's too soft - turn it up with the volume control. Even your vinyl - when played back on a properly calibrated input - will "seem" too low at first go. How do you handle it when the record is playing? You turn it up.

"Also, it makes sense to me that an occasional clip should be tolerated if that still leaves 95% of the recording at the ideal level. By "occasional" I mean a handful of times for the whole recording."

In digital - one "occasional clip" is too many in my book.

"I keep going back and forth about this. My first set of recordings was done without even realizing I was clipping. Then I obsessively made sure my recordings had ZERO clipping. And I think that resulted in some being too soft. So, more recently, I've been somewhat less strict. I aim to get the level around -5 for most of the recording."

-6 is nice round spot to be peaking at. Again - turn up the volume on playback. What the hell is the obsession with being loud? Are you comparing your transfers with the latest top 40 crap that has had the life compressed out of it by volume enhancing limiting? Don't get caught by using a 2007 hypercompressed piece of crap to compare against a decent sounding album recorded in 1975. The 1975 album (while perhaps a little dated in sound) is right on the mark for levels.

"Anyway, I definitely don't understand the technology of it all. I thought that one problem with clipping was that it created distortion. If the clip merely eliminates the source material, though, why would that manifest itself in distortion?"

That's okay. Many folks don't understand it. The most important thing to know is that ANYTHING over 0dbFS (the top of the Acid Meters) is no mans land. That's the only reason for a clip light. If you see red - you have gone wayyy too far.

To answer the "what happens beyond 0dbFS question"...in it's simplest terms - a digital audio signal is regulated by a mathematical pair of bookends...one is around -90dbfs (super silent) and the other is at 0dbFS (really freaking loud)...if your signal falls within this range - it can be properly represented and reproduced digitally.

However if a digital signal goes beyond 0dbFS - it cannot be represented digitally. It IS represented - but by a nasty grainy ungodly distortion that - if it was possible to string it out for 4 minutes at moderate volume - would drive you insane with it's annoying grating bite.

But in digital - when you get the odd clip light - it's usually a sample or two going "over". Too short a span to actually hear anything nasty...but why bother? Stay at a safe distance like -6 and enjoy.

This is the complete opposite of the "old days" where we could drive an analog signal (usually to tape) well into the "red" and most likely get a somewhat pleasing "warm" overdriven signal that could work well. Tape has that "built in compression" to handle such analog "overs".

WIth regards to -18...no - that's a reasonable tracking level for a multitrack session. For transferring vinyl - I would recommend level constant around -10 and occasional transient peaks (like cymbals etc) up to -4 as being your optimum range. Due to the nature of digital - you don't need to go any higher. If you need it a touch louder on playback - be normal and use the volume knob.

Cheers!

VP

Subject:RE: question about clipping

Reply by: Chienworks

Date:2/27/2007 7:10:49 PM

I'd also say that 95% undistorted is WAY too low a figure for most people's tastes. I'd have to have at least 99.999% undistorted or i throw the recording out and start over. 0.001% of a 4 minute song is still 106 samples being clipped, and that's more than most people would want to listen to, especially if they come grouped together in small areas.

Subject:RE: question about clipping

Reply by: wynton

Date:2/28/2007 1:06:15 PM

Vocalworks,

Thanks very much for the patient responses. You are persuading me to try to go back to avoiding all clipping whatsoever.

Allow me to "amplify" (pun intended) my thoughts about the volume. The endgame for all of this is to listen to my albums on my ipod. With a handful of albums that were recorded at low levels, I noticed the sound was pretty low unless I turned it up higher than usual. This is not really a big deal in itself, except I was wondering in the back of my head whether this actually meant that the recording level was too low in terms of getting the best quality. Certainly, I have no particular need for extra volume. (And most of my music is accoustic jazz.)

Let me ask about going in the other direction. The only distortion or noise that I am getting that bothers me is a kind of "fuzzy" sound accompanying instruments at higher registers occasionally (like trumpets or alto saxes). I thought this might be caused by the input level being too high, but I was also told once that it could mean I need a better cartridge.

So my question is the following: if the input level is set so that clipping never occurs - and I still get that particular sound - is there any additional benefit to reducing the input level even more? In other words, could I be getting distortion even without clipping?

I guess I'm just restating my earlier question whether clipping actually indicates distortion, or merely indicates lost data (which presumably does not involve distortion).

Subject:RE: question about clipping

Reply by: Illogical

Date:2/28/2007 4:23:06 PM

Wynton, I'd take what these guys say with a grain of salt. If you have extended clipping or extreme clipping, it sounds horrible and you'll know it right away. But a big drum hit clipping for an instant isn't the end of the world, and despite what some people say, it can even sound good.

Trust your ears. The point you made about saturation is valid, even if saturation isn't the best word. Imagine recording at -18db or whatever vocalpoint suggested...there is simply less data defining the sound at this lower level, with all sorts of silent zeroes floating by unused that could be carrying a bigger signal.

Ideally you'd be getting very close to zero but never going over...good luck. In the real world, I'd say your in-between approach is pretty wise.

Subject:RE: question about clipping

Reply by: Vocalpoint

Date:2/28/2007 6:23:16 PM

"The point you made about saturation is valid, even if saturation isn't the best word. Imagine recording at -18db or whatever vocalpoint suggested...there is simply less data defining the sound at this lower level, with all sorts of silent zeroes floating by unused that could be carrying a bigger signal."

Well - I didn't make the rules but -18dbFS (digital) = 0db (analog). This formula is present in every analog recording made since before digital became the new standard.

Example: When I put on my copy of Machine Head (on vinyl) by Deep Purple and transfer it digitally - it averages around -16dbFS for the entire album. That seemingly "missing" 16 db never seemed to bother me or the million of others who have enjoyed this album. Or any other classic album recorded in the analog era - I have never heard anyone say "Wow - does Dark Side of the Moon ever suck - it's so low in volume"....

What's with this complete BS about using "all" the "silent" ones and zeros up to 0dbFS. In a 24bit transfer - this is totally irrelevant and if you studied the basics of digital recording, you would see that as being clear. There is no "bigger" signal - simply a louder one. Loud does not mean better. Loud means no headroom and no dynamics.

Finally - 18dbFS is standard when ensuring your digital material plays back in the analog world at around 0db (right where that VU meter needle should be) assuming that most analog gear is calibrated (and engineered) to that standard. -18dbFS ensures that the signal is output with optimum efficiency, little to no distortion and does not overload any other points in the chain.

For what it's worth - this standard varies from region to region...the US standard is actually -20dbFS.

Wynton - Finally - I believe where you are getting the wool pulled over your ears is by placing your vinyl transfers on your iPod and then listening to them right next to today's latest hypercompressed crap that most certainly has had 20 or 30db of hard limiting applied to it.

This is a record company gimmick that every moron at every studio does today to try and give their mix the "edge" against the competition. Except it sounds like complete shit. And it seems to get louder with every new CD that comes out. Today's tracks have no dynamics, no life, no nothing. Just a hard wall of volume that induces a headache by track 3.

Today's releases (and their overbearing crushing volume) bear absolutely NO resemblance to how records were released (and balanced) in the days of vinyl. Like I mentioned - a 1975 album mix was done on an analog board with standard VU meters that most likely were peaking somewhere just over 0db - like +2db or so (-16dbFS in the digital world).

To place that 1975 album in a 2007 mind crushing volume prospective - that analog board VU meter would be off scale - meaning it would be somewhere around +20db - well into solid red lights and major distortion meltdown to even approach the volume level of some of the stuff out there today. ( at or over 0dbFS in the digital world)

"So my question is the following: if the input level is set so that clipping never occurs - and I still get that particular sound - is there any additional benefit to reducing the input level even more? In other words, could I be getting distortion even without clipping?"

If you are getting distortion from surface noise/cartridge wear/vinyl wear - that has no bearing on transfer levels. You don't have to go real low and no amount of reduction will help that kind of distortion. But anywhere from -10 to -6 for a "home" vinyl transfer should be right in the pocket.

Just try your best to keep it out of the red. Clipping has NO benefits whatsoever - it's the immediate destruction of your music .

VP

Subject:RE: question about clipping

Reply by: Chienworks

Date:2/28/2007 6:49:37 PM

Clipping is always distortion. Distortion is when the sound waves are, well ... distorted, and clipping most definitely distorts the sound wave.

There are other kinds of distortion besides clipping. Intermodulation distortion occurs when two frequencies combine in a more complex wave than the recording system is capable of reproducing. This could be what is happening with the higher register problem you mention.

Subject:RE: question about clipping

Reply by: shredheadinstead

Date:3/1/2007 3:43:25 AM

I always always use soundforge. They got an awesome and accurate function called "Detect Clipping," and it works great. I still go through the entire song and double check for myself, and it always seems to pull through. An incredible asset to what this software can do for you.

Subject:RE: question about clipping

Reply by: Illogical

Date:3/1/2007 12:44:53 PM

lol, vocalpoint, you are wrong but that's okay.

Why not record at -100db if it makes no difference?

- If you've ever normalized a really quiet digital file, you will know that getting a decent signal on the first pass is important.

And why would turning the volume up reduce dynamics?

- Dynamics are reduced by compression, not by uniform volume increases.

Subject:RE: question about clipping

Reply by: Illogical

Date:3/1/2007 12:56:00 PM

"Clipping has NO benefits whatsoever - it's the immediate destruction of your music ."

Sounds dramatic (destruction!), but clipping is distortion. I'm not sure what era you join us from, however you should be aware that in some forms of modern music distortion is employed INTENTIONALLY.

Curious what distortion does to a signal? Find out here:

http://en.wikipedia.org/wiki/Distortion#Audio_distortion



I'm just here to help.

Subject:RE: question about clipping

Reply by: DKeenum

Date:3/1/2007 1:06:42 PM

Wynton, let me throw in my two cents! Get as close to zero as you can, but don't go over. Too soft causes you to loose information and too loud causes distortion. My view is that any digital distortion is something I want to avoid.

Subject:RE: question about clipping

Reply by: Vocalpoint

Date:3/1/2007 2:27:29 PM

"I'm just here to help."

Well - with the kind of advise you are throwing around - you are definitely not helping.

And I quote:

"Sounds dramatic (destruction!), but clipping is distortion. I'm not sure what era you join us from, however you should be aware that in some forms of modern music distortion is employed INTENTIONALLY."

Wow - what a stunning statement of knowledge - that's fantastic advice if it's analog tape you are peddling....in the digital realm - clipping = NOTHING. A flat squared off waveform with no shape. As in - data that used to be data - but because it cannot be represented past 0dbFS - it has been "destroyed".

Since you seem to be so in the dark about what we are talking about here - I am gonna help ya out - firstly go here:

http://www.digido.com/modules.php?name=News&file=article&sid=8

Then read. Absorb. When you are done - read it again - and don't stop with this page...explore his whole site.

Then at the very bottom of this very informative page - with the heading of:

"Dubbing and Copying - Translating between analog and digital points in the system"

Notice Bob's recommendation for working in digital...you will see a lot of -14's, -18s and -20s thrown around in his text. This guy knows what he is talking about.

Maybe after a read or two - you will too.

VP

Subject:RE: question about clipping

Reply by: Illogical

Date:3/2/2007 10:27:12 AM

Ha, dude you are just being silly now. I'm not advocating clipping for the sake of clipping, but clipping IS distortion. You say things like this...

"in the digital realm - clipping = NOTHING. A flat squared off waveform with no shape. "

...without a hint of irony. You are aware that square is a shape, right? Distortion distorts waveforms, clipping distorts waveforms...you are clinging to dogma and looking increasingly petty in your defense of it.

Subject:RE: question about clipping

Reply by: Iacobus

Date:3/6/2007 9:02:34 AM

?

I thought Vocalpoint mentioned that, in the digital realm, data is destroyed past 0 dBFS? It just can't be represented since it's lost.

Clipping can destroy a particular sound, even distorted guitars. I'm not even a sound engineer and I know that. Distorted guitars have rounded peaks too. (They're just a hell of a lot more rough-looking overall.) Lop off a peak during its transition, and it's going to sound like, well, garbage. That wall-of-crunch sound is going to be ruined by the sound of what seems like flies buzzing around.

If that's a person's intention, go for it, but I guarantee it's going to grate on your listener if done consistently.

Iacobus

Subject:RE: question about clipping

Reply by: BradlyMusic

Date:3/6/2007 10:13:13 AM

Wynton,
I don't know if you ever got your answer in all these replies, since it seems like a bunch of bickering back and forth over misinterpretations and slight technicalities.

Let me try and be the voice of reason and get you to a simplified answer.

First off, NO you don't want any clipping to occur when recording in the digital world. The reason why you might not notice it is because your ear can not hear it unless there are consecutive samples clipped. I believe it's 4 or 6 consecutive samples before you will actually hear the negative side effects. So this may be why you are not hearing the distortion, but it is there and there is no benefit of having it there, so you want to elliminate it when recording.

When you purchased the new cartridge the cartridge gave you higher output levels from the turntable. This will increase the overall signal to noise ratio of your recordings and make for a better transfer. You must make a compensation by lowering the the input gain on your soundcard now due to the increased output from the new cartridge.

The optimal goal when recording digitally is to get the highest level possible without exceeding 0dBFS. 0dBFS is the maximum value represented in the digital world and anything that exceeds that will be distortion, since there are no values that can represent it over 0dBFS.

I'm probably gonna go overboard on the technical details right now, and a lot of this is unnecessary for you to understand. Just try to bear with me thru it.

Music in general has 2 levels in the dB world. One is an "Average" level and the other is a "Peak" level. The Average level is the one that your ears detects as being volume and is what you would see displayed on an old analog VU meter. "Peak" level is the one shown on the Acid "Peak" record meters. This will instantaneously show the highest level of the audio when it is being recorded. Music has what is known as a crest factor ratios. These ratio's would be used in technical terms like "2:1 crest factor or 4:1 crest factor". 6dB in the audio world equals a multiplication of "2" and additionally 12dB in the audio world would be a multiplication of "4". Thus when you see a "crest factor" ratio of 4:1, this means that the "Peak" level of the audio is on average +12dB(x4 multiplication) higher than the "Average" level of the audio.

Ok, now that the technical mombo jumbo is out of the way. Modern music today usually has a crest factor ratio under 2:1 and more closely to 3:1. Thus the peaks are usually 6-10dB higher than the average level of the audio. Older recording like you are transferring have a bigger dynamics range since less compression was used on them. They will have a crest factor of at most of 4:1 and probably closer to 8:1. This means that the peaks are usually 12dB-18dB higher than the average level.

So what does this all mean? When you set your levels for your transfers set the meters in Acid should be regularly be reading around -12dB or lower. A -15dB average level would be a good setting. So when you look at the meters, you'll notice it will be constantly lit around the -12dB to -15dB level, then occassional peaks will bump up to the 0dBFS area. The meters in Acid will show numbers at the top of them that displays the "Highest" level that has been seen by the meter. If it shows "Clip" in this display, then that means you have gone over the 0dBFS level and you need to reduce the input gain on your sound card and you should actually start over with your transfer at this point, since you've introduced unwanted distortion.

So here's the bottom line of what to do in simplified terms. Playback your vinyl recording, preferably skip forward to a chorus where the music is loudest. Set the input gain on your sound card, so that it's on average reading around -15dBFS with occassional spikes going over this amount.

Record your Vinyl into Acid and pay attention to the highest number value that gets recorded on the top of the meter. It will probably be somewhere around -2dB to -6dB or there abouts. For this example we'll say that the Max level was displayed on the meter as -3dB. Make a note of that value. Now after your recording is done, this tells you how far that the fader on the Acid track can be raised so that your audio is raised to the maximum "Peak" level that it can be raised to in the digital world. So if it was "-3dB" FS, then raise the Acid fader level to "+3dB". Now you have eccentially done a step known as "normalization". Acid doesn't have this feature like Sound Forge, but by adjusting the track fader in Acid by the amount that was "Peak Held" on the record meter you have eccentially done the same thing in a different fashion. In the Sound Forge Normalization process it scans the wave file for the highest Peak and then raises the volume for you that amount. Well when you're recording, YOU are scanning the highest peak level by making a note of the highest value that is on the peak meter in Acid. Then YOU are manually raising the track fader level afterwards.

All this -18dB and -20dB garbage that is being spewed in this forum is worthless information, and tells me people are reading information and not using general audio knowledge. Thus, you're getting a lot of information that is valid to a point, but it's information of "View can't view the forest from the trees" perspective. This -18dB information is only valid if a test tone was included on your vinyl recording along with the actual audio. Thus they would give you a -18dBFS 1Khz test tone and then you would adjust your input on your sound card until your peak meters in Acid read -18dBFS while that test tone was playing. These test tones are only included on the original master recording mix reels and DATs and such. Since your vinyl probably doesn't contain this type of test tone to set your levels, this information is almost worthless in your type of transfer and you need to resort to common audio knowledge in knowing the typical crest factors used in certain era's of music.

Sorry if I went too deep on the technical side, but hopefully this helps you out .

-Brad

Subject:RE: question about clipping

Reply by: Vocalpoint

Date:3/6/2007 10:26:41 AM

Brad,

"All this -18dB and -20dB garbage that is being spewed in this forum is worthless information, and tells me people are reading information and do not have general audio knowledge. This -18dB information is only valid if a test tone was included on your vinyl recording along with the actual audio. Thus they would give you a -18dBFS 1Khz test tone and then you would adjust your input on your sound card until your peak meters in Acid read -18dBFS while that test tone was playing. Since your vinyl probably doesn't contain this type of test tone to set your levels, this information is worthless in your type of transfer and you need to resort to common audio knowledge in knowing the typical crest factors used in certain era's of music."

Garbage is a little heavy handed. And yes - after re-reading my responses - some vital info (like proper a calibration to 0db (Analog) = -18dbFS) was omitted and my apologies for that. And it is certainly not useless for the this type of transfer. A proper calibrated board or input should be able to properly output any input source within a reasonable range - and your example of using the test tone would certainly benefit Wynton in his transfers...it would be a quick exercise for him to see just what kind of levels he is feeding into ACID.

I used to be this way too...just fire in any input at whatever level looked good - usually slamming up to 0dbFS like many in here. After a quick calibration and using accepted industry level setting practices - my stuff turned around fast.

We are all trying to help. Your explanation was very good.

VP

Subject:RE: question about clipping

Reply by: BradlyMusic

Date:3/6/2007 10:30:56 AM

Sorry, my post was not meant to offend anyone and after I posted it, I saw how it could be viewed that way and went back and clarified it further. Your information is valid to a point as I pointed out later by editing my post. But in a way you where really giving information as I later pointed out of trying to view the forest from the trees. The most important factor is knowing the general dynamics range of the era of music being transferred. There are no solid facts on that kind of information, it's just generalization and I saw a lot of information being shovled around like facts because it came from a professional mastering engineer articles and that information was being used in the wrong regards to the original post.

Subject:RE: question about clipping

Reply by: Vocalpoint

Date:3/6/2007 11:10:28 AM

"The most important factor is knowing the general dynamics range of the era of music being transferred. "

But that is exactly the reason that -18dbFS is a great reference spot. Or -15 or even -12. If you can carefully place your transfers somewhere in here - clipping is a distant memory and your tracks will thank you later.

It's this myth about thinking that a digital (peak) meter is the same as the old school analog VU meter. Some self starters into the digital realm see the top of that meter and since their only reference point is an old school analog meter (you know - "just barely touch the red") they figure the top of this meter (and it's result "red" which is actually data that cannot be represented at all) is the same - like their tracks are gonna be hotter or something - which couldn't be farther from the truth.

The real "hotness" comes from taking a properly transferred vinyl track that nicely peaks at say -6dbFS resulting in a 23 bit file that can be finalized into shape (with room for 6 DB of EQ/limiting etc etc) in something like Sound Forge. The track will stay out of the clip zone and sound fantastic.

VP

Subject:RE: question about clipping

Reply by: wynton

Date:3/7/2007 12:10:05 PM

I just want to thank everyone for their contributions to this thread. This has all been very helpful.