09 April 2013

Home Studio: Electric Bass & Guitar direct recording using Pro Tools, Rack 003 and Amplitube


Note: this entry was already published in my old Spanish version of this blog around November/2010. I am revisiting it here.

Lucky people will have the opportunity to record their guitars taking the sound of one or more mics directed to their amp's cabs. Less lucky people will have to try to get an acceptable sound by directly recording the guitar, using some kind of amp modeler plugin.
Even if you can mic your amp full kranked, micking technique is complex and, to achieve the best sound is not always so easy. Other techniques, as re-amping, where the clean recorded signal of the guitar is being sent to one or more amps to, finally record back the amplified sound, allows you to work with several mic positions and, several amps and amp' settings until achieve the desired result.
But, this re-amping techniques require good gear (mics, amps, pre-amps) and, you can loose a lot of time moving mics, changing amp settings, etc.

To just record Reference Guitar Tracks, there is nothing as a good amp modeler plugin. You just need to connect your guitar to your audio card, select the right amp in that plugin and take care of the basis sound while recording. If results doesn't convince you, you can later swap the amp model, mics models, speakers models and, whatever other thing that you needed, without having to move yourself out of your chair, until to achieve the wanted sound.

But, sure, amps modelers have their own tricks and limitations.

I'm convinced that Amplitube 3 by IK Multimedia is an excellent simulator, the best in its price range but, I see lot of people that seems to have serious difficulties to get good sound from this plugin. I think you can get decent tone even with Multimedia PC Speakers.

If you are expecting from this plugin to hear the sound of your amp as if you were inside the room where you've put the mics, I think you didn't understand the concept behind Amplitube 3.
Amplitube 3 simulated the recorded sound of an amp that, being catched by a mic, processed by a pre-amp and inserted in a recording track, will be always somewhat different to the "live" sound but, this recording will be very similar to the sound you will hear in any commercial mix.

Evidently, the near field monitors of your home studio aren't able to move the amount of air that an amp cab can move and, therefore, the sensation produced by being in front of your amp disappears and, the sound becomes a bit more compressed, dry and colored by the mic (which position and direction highly affects the recorded sound) and pre-amp.

Studio, Line, Instrument, Mic levels and other stuff

While testing a DI box (see previous blog) I've realized that the input signal was highly superior to the input level I was achieving through other paths, what made me to review the links between my gear, that was previously well configured but, that I've messed up when changing to a new home.

A perfect coupling between the outputs of a device and the inputs of the following one in the chain is of high importance to achieve a clean, strong and free of distortion signal. But.... there are so many types of signal levels!.

Studio level

Gear that processes audio signals (pre-amps, compressors, equalizers, etc) can have inputs or outputs ready for Studio Level signals. The Studio level is the highest signal level of all (+4 dBu).
If we plug a Studio Level output in a input with an inferior level, that high signal will overflow the input, creating a high distortion level and forcing the input to clip the sound.

Usually, Studio Level signals travel thru a cable with connectors type XLR or TRS and, usually they have balanced signals. Impedance is usually around 600 Ohm.

A balanced signal consist into send twice the signal but, with opposite phase to cancel noise.

If your equipment is stereo and has two balanced XLR or TRS outputs (one by channel), they will possibly be a couple of Studio Level outputs.

Line Level

The Line Level is clearly inferior to Studio Level (-10 dB) and, this is the level where the consumer electronics devices usually work (Hi Fi chains, etc.). Apart of such a level, the needs respect of impedances are totally different from those that are required for a mic or an electric instrument (guitar, bass).

Usually, this signal Level travels thru cables with TS (Jack mono 1/4") or TRS (stereo, if it comes from an stereo device) and, they are unbalanced (left channel, right channel and ground).
The impedance level is around 10 KOhm.

Instrument Level

Electric instruments, as the guitar or bass, generate a very low signal but, stronger than a mic. For sure, that signal should be amplified (that's why we use guitar amps!) and, its level is clearly under the Line Level.
Additionally, instruments need of inputs with high impedance levels and, outputs with very low impedance level to achieve their best dynamic range.
The instrument signal usually travel in the same way as the Line signals, trough a cable with Jacks TS (usually) or TRS (if an stereo instrument) and, they are unbalanced.

The input impedance for an instrument should be over the 20 KOhm and, usually around 1 MOhm.

Mic Level

Mics generate very weak signal levels, the weakest of all. The mic needs of an input impedance level lower than the Line or Instrument levels and, needs to be HIGHLY amplified.
Mic signals usually travel through cables with XLR connectors and, they are balanced.
Additionally, some mic types requiere Phantom Power so, they would need an input that can provide those 48V that are a must for the mic to produce some signal (by example, condensor mics).

Impedance level is around 600 Ohm.

This kind of signal is one of the most used in Studio. The reason is that their technical characteristics allow to send signals in longer distances with less lost of quality of such a signal.
In instrument cables, you can notice some degradation around 10 meters (depending on the quality of cable and connectors).

Sample of Signal Level pairing using the Rack 003

Rack 003 inputs from 1 to 4 are inputs with pre-amp. That means that they will accept weak signals that should be lately amplified.

Each of these inputs has to connectors, one XLR connector and one TSR, both balanced (the device will unbalanced them, depending on what are you pluggin in there).

The XLR input is waiting for a Mic Level signal, with the right level and impedance used for such a signal. To connect there any other kind of signal will produce a highly distorted signal, due to the fact that the output gain in this input is the higher one.

In Rack 003, each couple of inputs (1 & 2 and, 3 & 4) have some switch to activate the phantom power. The drawback is that once you switch it on, both inputs have the phantom power active and, this will mean that you cannot link there any equipment that doesn't requires Phantom Power. Be careful, then.
So... what do I have linked to the pair of XLR inputs 1 and 2?.

  • Phantom Power is active
  • In input 1 I'm directly pluging mics that require phantom power (condenser mics)
  • In input 2 I'm connecting the output of the Radial J48 Active DI, that converts the Instrument Level signal of its input into a Balanced Mic output that's being sent thru its output XLR connector.
But, Inputs 1 to 4 have an additional possibility. There is also a balanced stereo jack connector, labeled as DI that waits for Instrument or Line level signals that will be amplified with the help of the pre-amp assigned to that input.

You can not simultaneously use the XLR and DI inputs, even that you can leave the equipment linked there, just one of the two input paths will be active at once.
We will select the input type with the button "Mic/DI" that you will find in the front panel of your Rack (mic = off, DI = light). If the led of that button blinks, this means that this input is clipping and therefore, the level of the signal that you are providing there is higher than foreseen.

What do I have connected to inputs 3 and 4?

  • I am directly plugin any kind of instrument to input 3 DI, manipulating the gain level labeled as "Input 3" in the front end of the rack.
  • To input 4, I've plugged the output FANTA of the TAD Silencer. This output with speaker emulation of this attenuator/load box has a very low level, as a mic, is balanced and works with an XLR connector. Since it doesn't needs Phantom Power, I am connecting it to input 4, instead of 1 or 2 (with phantom power) to avoid damaging the unit. The gain level of this input can be regulated with the gain knob labeled "Input 4" in the front panel of the rack.
Inputs from 5 to 8 are of type balanced TSR. All them are labeled as DI and, none of those will be amplified (no pre-amp assigned). Therefore, this inputs are waiting for signals already at Studio or Line levels, provided by some external amplifier.

A button in the back panel close to each entry allows you to select the Line level (-10dB, button pushed) or Studio Level (+4dB, button pulled).

What do I have in inputs 5 to 8?

  • To input 5 I've connected the LINE output of the Silencer. It has a Line Level (-10dB) and, the gain for this signal is being controlled in the Silencer itself, with the volume control of the line output.
  • To input 6, I've connected the balanced output of the SPL Track One (pre-amp). It provides an Studio Level output (+4 dBu), with an XLR connector, converted to TSR in the input side.
Anyway, whichever the method you use to record a guitar, directly to a DI input of the Rack, thru a DI box or, thru a pre-amp or thru a speaker/simulator or attenuator, you should ensure a high, clean and free of distortion signal for Pro Tools.

Carefully check technical specifications related to inputs and outputs of all your gear to be sure that your are properly matching each output to the right input and viceversa.
This can sound obvious but, this creates me a lot of headaches and disappointing results in the past.

What's a good input level?

Mi own experience with Pro Tools and Amplitube 3 say that it's better to have to highest signal level in your input track and, then to regulate the output level with the Master knob of Amplitube 3.

The higher your input signal level, the higher the difference between signal and floor noise and, the best the different amp models and stomp boxes will react in Amplitube 3. A very weak signal makes this plugin to sound really awful.

The average sound (RMS) should be between the yellow zone of the input meter and, peaks should be under the red area but, close to its border. Strum hard chords to control peaks level.

Even that Amplitube 3 has a gain knob (input) and, that knob allows to you to raise the input level inside the amp simulator, results are way worst than leaving the knob in its default position and, providing a higher input level.
Reason is that a weak signal has a very low dynamic range and, signal and floor noise are very close in loudness so, increasing the gain to this kind of signal is also increasing the gain of the floor noise, what results in a noisy sound, noise that is being increased to higher levels by the several amp models and gain stomp boxes.

This is true for every input signal in Pro Tools. It's better to send the input track to an auxiliary track and, to lower the output volume in such a track (after being processed by other plugins or outboard gear).

Searching for the right amp' sound

Once we've achieved a high and clean input signal, this is time to choose the amp model and to tweak controls until getting the wanted tone.

I'm always recording a clean track of the guitar sound, in a mono track that I'm sending to an auxiliary stereo track. This is where I insert that plugins that directly affect to the guitar' sound and, therefore, where Amplitube 3 is being inserted (usually as the first plugin).

First step will be to select one of the available amps, depending on your target sound and, tweak the tone stack, gain and volume to taste.

Since the input volume will be high, the amplified volume will be really higher and, therefore, your auxiliary track will start clipping. It's better to lower the output volume of this plugin by using the Master Knob, without reduce the rest of controls of your amp model. Since we are in Digital Audio world, your peaks should be maintained below -3dB, to avoid clipping the input of the next device/plugin/track in the chain.

Hum and rest of candies

Amplitube 3 are modeling really well the originals, so good that they even model the natural noise of the modeled gear. Therefore, if the original is noisy, your model will be also.

Guitars, and very specially those loaded with single coils, are introducing their own noises and hum. The noise generated by the own amp model couldn't be avoided but, you can get rid of your guitar noises in several ways.

You can use some Noise Gate or Noise Reduction pedal between your guitar and the Rack 003 (as the ISP Decimator G-String) or, you can rely in the Noise Gate that provides the own Amplitube 3 plugin or, you can insert a Noise Gate plugin in your auxiliary track, just before the Amplitube 3 plugin.
To check that you are effectively reducing the guitar noise, put Amplitube in Bypass mode, to be sure that you aren't mixing amp and guitar noises.

Any kind of Gate you can use there, can have its own drawbacks and, you can even ruin your guitar sound if your weaker sounds are very close the the floor noise. To accurately adjust a Gate can be a real headache.

Sometimes, it's better to reduce the noise at the beginning and end of the track and, during the "void" parts or, better, deleting "no info" parts or, doing an automate fade to zero in such a sections (where there is only noise).

This is a concept that many people doesn't realizes about, tube amplifies have their own floor noise. Being Amplitube 3 a great emulator, it will reproduce also such a characteristic noise.

Adjusting the Gain Level

Some of amp models are vintage amps. Vintage amps were more oriented to achieve a clean sound than other thing. By example, the power of an amp meant the power that would provide while standing clean (so, 50W meant, 50W clean but, some more watts after beginning to distort!).

Since the goal was to keep the amp clean at high power levels, you will need to help such a kind of amps to break up with the help of some stomp boxes.
Typically, you used some overdrive, fuzz or distortion pedals to force those tubes to start to distort.

You will need to do the same in Amplitube 3. Some vintage models can sound really cold until you insert some gain pedal before (overdrive, fuzz. booster...).
So, if you feel that your amp lacks some guts, try first some typical overdrive (Tubescreamer) or, some typical distortion (RAT), to get the sweet spot of those "virtual tubes". It works really well.

Once, you've achieved a nice tone, lower the output signal of this plugin with the help of the Master Knob (don't modify your volume or gain). This will allow to further plugins to have some headroom to process the dynamics of this output signal. My recommendation is that the output RMS will be around -20 dB. You will push the complete mix later, with the help of some compressor in the mix buss.

Fine tuning the sound: cabs and mics emulation

This is probably the modules of Amplitube that more evoluted respect of previous versions of this plugin.

The possibility to change your cab, mics and spatial position of mics, brings to you as many possibilities to experiment with the sound as you would have in a real Studio but, without having to leave your chair!.

You can try swapping the cab model. Maybe, you will like more the sound of such an amp paired with different speakers. It always depends on what are you after.

The mic type and, its position, together with the distances to speakers and to other mics have a lot of impact in the sound. Just check different mics for each position, one at once and, play with the respective position of each mic, separately and together.
The rule of 3 applies as in the real world. To avoid phase issues, one mic should be place 3 times to the distance of the the other, respect of the source of the sound. But, for sure, you can play with any position and, maybe some cancellation of phase is just what you were looking for.

Once you have positioned the main mics, you can concentrate in the ambience mics. You can only control here the gap between both mics and, the volume with which this mics will be blended with the main mics.

Don't be lazy trying several possibilities. You have no physical effort, tests are easy and fast, with immediate results. And, the best of all, once you keep your guitar clean take, you can change everything at any time achieving totally different results.

Adding Effects

Not a good idea to start checking stompboxes (other than those that just put the tubes in their sweet spot) before having achieved your foundational amp tone.
Then you can check the stomp boxes and, try as much as you liked trying to get the exact sound you are after. Those stomp boxes are really well modeled and behave really close to the real thing.

Amplitube 3 gives you the opportunity to swap the order in your chain of pedals so, you can check the effect of each pedal before or after others and, choose the combination that better works for you. Everything, without changing a cable or moving a pedal physically so... play with that!. And, remember that if you don't like the results at the end, you will be able to change everything next day.

Note: guitar amplifiers tend to be recorded WITHOUT amp's reverberation. The reverb effect (as well as the delay effect) is usually added in the mix, by using some quality plugin to give the right deep to your mix.
The good thing of Amplitube3 is that with the same recorded clean track, you can try for ever up to get what you wanted. You just need a single good performance over which work later.

Cutting the Mix

Once you fine tuned the sound of your guitar/amp/effects and achieved a nice sounding guitar track alone, it's possible that your track cannot cut the mix with authority.

In previous blog entries, I've discussed about the 3 dimensions of the Mixing process. Please read those entries to understand how to equalize the guitar and rest of instruments, in a way that every instrument is well represented in the stereo image.

EQ usually goes after Amplitube, to enhance or dismiss wanted frequencies, once your foundational tone was achieved.

Giving strength and consistence to guitar' sound

Even not being always strictly necessary, a light processing of the guitar sound, through a compressor can work in several ways: leveling peaks and valleys, providing a more homogeneous and louder volume, adding some touch of color, modify dynamics, adding or resting punch, increasing sustain, etc. We discussed about it in previous blog entries also.

My personal preference for guitars is a light touch of the plugin Fairchild 670 by IK Multimedia. I am more interested on the coloration that gives that plugin to the sound than on a pure compression.

For basses, it's very usual to combine the LA-2A and 1176 plugins but, I also like the results of the Dynamics plugin by Sonnox.

You can increase the "meat" of the instrument' sound, adding one more plugin that can enhance the harmonical content, like the BBE or, Inflator by Sonnox, among other harmonics exciters.

You could use a colorant equalizer also, as the Pulteq EQP-1A, at the end, to enhance bass frequencies to the bass guitar and give more punch.
At the end, the chain of sound processors that you will choose for your particular project can be so variate as your imagination.

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