Software Db meter, or Hardware Db meter?

C

Cadbury

New member
Hi Guys,

I have recorded a few songs in the past, and have always had the same problem and managed to work round it rather than solve it. I use a Phonic Helix Firewire 24CH board and record it into Logic Express. I understand that you should always record audio at 0 Decibels, however should I be going by the decibel meter on the Phonic Mixer, or the one on the Logic mixer? As they don't match up the same when a signal is going through.

I have been going by the logic mixer, which makes the phonic meter clip, although I dont hear this. When I have several tracks playing in logic, the output controller in logics mixer starts clipping, so I have to start sacrificing levels on tracks to stop it, which I feel hinders the mix.

Any advice would be super appreciated!

Cheers,

Jack, UK
 
Cadbury said:
I understand that you should always record audio at 0 Decibels
Click to expand...

Hell no, that's waaay too loud. 0dbFS is borderline clipping level. 0.000000000000000001 over that and you're going to clip. You'll want to be inputting at an average (not peak) of around -18dbFS (this varies, it's rough approximation of 0dbVU (analog), but it depends on your A/D converters. That's definitely why the logic mixer clips when you have multiple tracks playing.

Recording that loud, even if by some miracle you manage not to clip, you're leaving yourself absolutely no headroom.
 
Cadbury said:
I understand that you should always record audio at 0 Decibels,
Click to expand...

Unfortunately, you understand wrong. If you're recording in 24bit digital, you can (and should) record WAAAYYYY below "0db".
 
Well that depends on if the meter you are using is 0dBFS, or 0VU at some lower level of dBFS that is more sensible. -18dBFS is supposed to be the standard, but it's more honored in the breach.

Anyway, if you are clipping a preceding analog stage you have no choice but to turn things down.
 
Ok, this makes obvious sense now, I will allow myself way more headroom from now on. I was just worried I would be recording initially to quiet. Should I be following the db meter on my preamp or software though? I believe my preamp hits the reds before my software does.

Cheers for the help on the amateur questions,

Jack, UK
 
You don't want to push the preamp into the red; you don't want that distortion. Record with your preamp at 0VU (nominal operating level, usually +4dBu or -10dBV), and don't worry so much about low digital levels.
 
If you have VU meters on your preamp/mixer use those and just check the logic meter to make sure that you aren't clipping (hitting 0dbfs) in the software.

The analog meters are calibrated to a different standard than the software meters.

0dbVU on the analog meters is line level, that is what you want to shoot for

0dbFS on the software meters is the absolute ceiling, the most signal that can be recorded without distortion.

Since 0dbVU is aprox. -18dbfs, you can see that you have to be running your preamps very hot in order to hit full scale in Logic.
 
Good mixer by the way. I think they are and incredible bang for the buck.

I own the Phonic Helix 18 Universal.

The signal from the preamp knob to the firewire chip is attenuated by -18db. I read this on their website.

I discovered this while I was tracking my motif and wondered how come when recording something the play back was always quieter than the original tracking sound.

Anyway, like all have said here on the post, You can't always be curtain what your meter is actually measuring. I use the software Reaper for my tracking, and when I do try never to go over -12db on tracking meters. I have no idea how the meters calculate the visual results. I've even tracked +6db and never had heard clipping.

Without a long discussion on how to count in binary, this is what you need to know. Your recorded digital bits can only count so high and that high is 100%. In the digital world there is no such thing as 110%. It's sort of like old hand held calculators that would display *error* when you entered 9,999,999+1.

If you clip a signal lightly it will sound like rice crispies, and when that happens your signal is lost forever. Clip too hard and you might possibly burn out your speakers. You want this head room as a safety net. I once a tracked a excited vocalist who started to spank the mic while singing. Sounded just like a bowl of Snap, Krackel, Pop on beats 2 & 4. That's probably not an effect your after.

With the current ability to record at 24 bits. You have 256 times the resolution of 16bit audio. In the real world this means tracking too low is almost impossible.

Tracking lower also gives your recorded signal less distortion. My phonic's preamps give almost zero harmonic distortion(I did a loop back test) but only when the preamp gain knobs are at sane levels.

Don't worry about tracking too low. Don't even worry about mixing too low. During the finial stages of mastering is when you have the mastering engineer boost the digital signal to close in on the 100%.

You might not have discovered this yet, but I always record the signal from the preamp direct, there is a switch labeled pre/post fader on each of the channel strips. Set it to pre, this keeps the raw signal from passing through the EQ, Pan, & Fader circuits keeping hiss noise to almost zero.

Little off topic. Another trick I found is to use an Active Direct Box power by phantom power when recording bass instead of just plugging direct into the board. I'm speculating but I don't think the Helix board has ideal impedance to record bass direct.

Racherik
 
Cadbury said:
Hi Guys,

I have been going by the logic mixer, which makes the phonic meter clip, although I dont hear this. When I have several tracks playing in logic, the output controller in logics mixer starts clipping, so I have to start sacrificing levels on tracks to stop it, which I feel hinders the mix.

Any advice would be super appreciated!

Cheers,

Jack, UK
Click to expand...

As I said the signal recorded by the firewire chip is attenuated by -18db. The mixer itself is analog plus a digital firewire. When tracking I monitor by sending the signal I want to listen to to either the main bus or an aux bus. This is the steps I go through.

First, I set all preamps knobs and channel faders to -infinity.

I start by turning on as few channels as required. If I only need 1, I use 1.

Next, I slowly raise the channel & mains fader to zero unity while playing. Zero unity means to multiply by 1. Means your faders are keeping the signal at 100% neither boosting it or decreasing it.

Once this is done, I then slowly turn up the preamp gain knob while playing until my led output meter on the mixer is using up about 3/4 of the green LEDs. If I remember I don't think I ever turn the preamp gain knob past 2 o'clock.

While turning up the preamp knobs I also watch the faders in Reaper software to make sure those are sane.

After I'm happy I punch record.

Something I do when tracking my band, is I tell them, "Play your loudest...Yes, louder....louder....." I then check the software meters to make sure they didn't clip, add in some safety headroom. Then I tell them, "Ok now you have to turn back down to gig volume. Do you understand you can not play louder than you just did, no matter what? If you do the recording is screwed."

Racherik
 
Racherik said:
As I said the signal recorded by the firewire chip is attenuated by -18db.
Click to expand...

I'd be willing to bet that there is no attenuation. Most likely this is a reference to the difference between the analog scale and the digital scale, where 0dB on the analog meter corresponds to -18dBFS.
 
bouldersoundguy said:
I'd be willing to bet that there is no attenuation. Most likely this is a reference to the difference between the analog scale and the digital scale, where 0dB on the analog meter corresponds to -18dBFS.
Click to expand...

That would make more sense. So you might want to take Phonic's FAQ Answer with a grain of salt.

Racherik
 
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