Using Amp Modelers and Effects, Part 1

Using Amp Modelers and Effects, Part 1 Brought to you by: guitar.com

Just Press Play Logo Gif 40581In this era, amp modeling is a way to get many amp sounds in one box. Amp modeling is a process in which the manufacturer dissects guitar amps, analyzing (and then modeling) waveforms from the beginning of the input chain and through all stages of amplification. It's a long story but the concept is very good, especially if you need to quickly dial up a great or specific amp sound.

OK, in most cases, a great sounding guitar amp miked will sound better than a similar modeled amp sound recorded direct. On the other hand, if the amp that was modeled was an outstanding sounding amp, it may sound better than an amp that is tired (old caps; old tubes; tired, loose sounding speakers, etc). In any case, it's nice that we have the option of amp modeling sounds today, so lets get going on this.

 

I am most familiar with the Line 6 products since I am a consultant and Beta tester from time to time, so I will relate to that format. I assume the others have similar traits.

The drawbacks:

No, the modeling may not sound as good as real amps, as mentioned above. This is a digital format. With all digital formats there is an inherent delay (latency). I have run down how latency of the sound (inherent delay caused by analog to digital and digital to analog conversion of the signal) may hurt the feel of the performance, and also mentioned that its not a big deal if you get used to the delay.

The cool stuff:

Select from many amp models and the odds are good there will be a tube direct box pre-amp model. Hey, with amps like the Line 6 VETTA, you can choose a separate model for each side of a stereo spread meaning one amp model on the left side and another amp model on the right side! A great sound for a stereo spread! Typically many effects can be easily dialed in. No need to mic a guitar amp. (Yes, we may want to split off the guitar signal and run it through an amp as well.) Multiple speaker cabinet models to chose from. This opens up many possibilities that really make a huge difference in the sound. One huge advantage is no frequency bumps or suck-outs caused by a speaker cabinet! The modeling of the speaker cabs is their sonic coloration trait only! The outputs are low impedance so there is no need to use a direct box when plugging into the recorder mixer.

Latency 

I'm not sure of the inherent delay of other manufacturers for the units available today but I do know the Line 6 amps spec as of February, 2004.

Basically, the delay time of Line 6 digital units is primarily caused by the A/D and D/A conversion. On a typical 24-bit converter (used by Line 6), the delay is 31 samples on the A/D, and 30 samples on the D/A. Total is 61 samples, which at 48KHz would be 1.27 milliseconds. The delay of the actual processing is much smaller, maybe a few samples, so it isn't really a factor (although that may not be the case with other companies' products). Overall, it stays well under 2 milliseconds and is not a big deal, after you get used to it.

You can save some of the total delay time if you have a digital input on your recording system. The time that you save, though, is the time delay of your system. For example, if you were to take a Line 6 Vetta or PODxt digitally into a computer or recorder, you save the D/A delay time (30 samples). But the signal has to get converted back to analog at some point, so it comes back. What you save is the D/A time of the amp modeler, and the A/D time of the recorder, so overall it is a good thing.

Note: It may be worth mentioning that if you are trying to play live through a software plug-in, the latency is going to be several times bigger because of the buffering of samples required in the computer.

Before we get into routing, etc., a word on using/chaining digital gear: Let's say that you are using a digital effect in front or after the amp model unit. As mentioned, digital gear causes a delay. If you're routing analog, add approximately another 2 milliseconds of delay. Add another digital unit in the path and you get more delay. The delay will surely be noticeable at that point. The key is to route digitally whenever possible! This will cut the delay down big time!!!! (Usually just a few samples per digital gear addition). By the time this article comes out, the odds are good that most all of the manufacturers will have digital ports!!! More on this subject in the next article.

 

Routing the Amp Modeler Using a Mono Analog Path

For our routing example, we are recording the guitar on track #7 and using mixer module #9 for the modeled amp direct input. If you're using a digital recorder with a built-in mixer, and if the modeled amp has a digital port (output) we finally have a different routing! That will be explained in the next article, Recording the Guitar Using Amp Modelers and Effects.

1. Plug the guitar into the guitar amp model box.
2. We are dealing with a mono path here. Plug one of the guitar amp model box outputs (the unit will state which output to use if mono) into mixer module #9 line input. This is important since if youre using the wrong output jack and using stereo effects in the amp model box, you would only get half of the effect. i.e., half of the chorus effect, which would sound strange. Keep in mind that the signal output should be in the line-level category and low impedance and if you have only one input on the mixer module, no problem as usual.
3. On module #9, to start, if you're plugging into the line input, set the line trim to zero dB (unity gain). If you have only one input for mic and line, plug in and set the gain trim pot to zero dB (unity gain).
4. Assign mixer module #9 to bus #7 (bus #7 routes to the recorder track we are using for the guitar). Make sure that module #9 is not sent through the monitor chain and is only routed to record track #7. If the mixer module offers a direct output, you could use and patch into recorder track #7 input.
5. Set recorder track #7 into input mode so we can monitor through the recorder. (In digital land, you may want to monitor the input signal on module #9 BUT only do so if you notice a delay monitoring through the digital mixer and or recorder path.)
6. Bring up module #7 (recorder track return) about half way up on the fader throw.
7. Bring the studio control room monitor level up to a normal listening level.
8. Ask the guitarist to play the part for the song. While the guitarist is playing, slowly bring up the fader on module #9 (guitar mic fader source) to zero (unity gain). This level setting is typically around 3/4ths up on the fader throw.
9. With the guitar volume full up, have the guitarist play and select the modeled sound(s) for the guitar part that will be used for the song.
10. After finding the sound(s), and setting level controls, tone controls, effects, etc., have the guitarist play with all the attack that would be used for the part.
11. Above Step #3 further adjustment: If you're using an analog mixer and recorder adjust the trim level on the mixer to average zero dB on the recorder track meter for now.
12. Above Step #3 further adjustment: If you're using a digital recorder format, adjust the trim to -4 dB on the recorder track meter for now (-4 dB is safe in case the guitarist players louder when recording the odds are good that will happen!) Always remember that going into the red (past zero) on a digital format meter will definitely clip the A to D converter (analog to digital converter) which is not advisable!!! Digital distortion sounds terrible!!!

Regarding #9 and #10 above, If you are the guitarist and engineer, and if you'll be playing chords for the guitar part, play all the open strings when adjusting the level with your other hand. If you'll be playing single notes for the part, simply play one string for now, such as the D or G string and adjust the mixer level with the other hand.

Experiment with EQ settings on your mixer. After EQing to taste, go back to step #11 or #12 (depending upon your recorder format). Make sure to have the guitarist play as loud as will be played for the song. If you are the guitarist and engineer, do yourself a favor and play as loud as you will play for the performance.

If you're using an analog recorder (step #11 above), it is possible to use a higher level other than an average of zero dB if looking for tape compression. In this case, after setting the EQ, compressor (if used), and possible other effects, to set the level for tape compression, you would need to put the guitar track in record and monitor in playback mode (monitoring off the playback head). Bring up the level on mixer module #9 to taste. The VU meter for track #7 will be slamming way past +3 dB. The one consideration is to avoid distortion in the mixer and tape machine electronics, so if you start hearing ugly distortion, back off on the level until it goes away.

Note that when monitoring the guitar in playback mode, there is a major delay, so if the guitarist is wearing headphones, its best to take out the guitar in the headphones while doing the level settings.

 

EQ and Compression

Per the application, review articles on guitar EQ (Parts 4 through 9) and compression (Parts 10 through 13) for details.

 

Using the Amp Modeler and a Real Amp

Its best to record to separate tracks to control the blend, etc. when mixing.

Recording with both an amp modeler running direct and a miked guitar amp are a great concept since you could get the best of both worlds this way. For buzz saw power low 5ths EQ the modeler for the low end stuff and smoothly roll out all frequencies past 600 cycles. On the amp mixer path, you would smoothly roll out below 600. This is a give and take situation since you would need to have the EQ and levels set (between both sounds) for a smooth transition. Thats the logical explanation BUT if the transition is radical instead of smooth, and it works for you, great! Dig, how about two totally different sounds one blends into the other!!! Cool!!!

Since the amp modeler does not have a true throughput that a direct box would have, you need to Y off the guitar cable into the amp modeler and the guitar amp. A simple Y adapter could be used but the guitar level will drop around 6 dB to both inputs. Thats not good if youre using a distortion sound since 6 dB is a huge drop on the front end. The odds are good that some company makes an active mult box for splitting off a guitar signal that does not load down the guitar output, but I haven't found one. Search the Internet and you probably will.

Comb filtering is a possibility in this situation since the amp modeler will have a delay of approximately 2 milliseconds. Review and adapt to the previous direct box articles using an amp as well.

 

Routing the Amp Modeler Using a Stereo Analog Path

Important: This path will only matter if you're using stereo effects included in the amp modeler. Such effects would be chorus, maybe stereo flanging, etc. The manual should state which effects are stereo. If you're not using such effects, you might as well record to one track as explained above.

1. Plug the guitar into the amp modeler.
2. Plug the left output (amp modeler) into mixer module #9s line input and plug the right output into mixer module #10s line input. Keep in mind that the signal output should be in the line-level category and low impedance and if you have only one input on the mixer module, no problem.
3. On module #9 and #10, to start, if you're plugging into the line input, set the line trim to zero dB (unity gain). If you have only one input for mic and line, plug in and set the gain trim pot to zero dB (unity gain).
4. Assign mixer module #9 to bus #7 (bus #7 routes to the recorder track we are using for the left side of the stereo path). Make sure that module #9 is not sent through the monitor chain and is only routed to record track #7. If the mixer module offers a direct output, you could use and patch into recorder track #7s input.
5. Assign mixer module #10 to bus #8 (bus #8 routes to the recorder track we are using for the right side of the stereo path). Make sure that module #10 is not sent through the monitor chain and is only routed to record track #8. If the mixer module offers a direct output, you could use and patch into recorder track #8 input.
6. Set recorder track #7 and #8 into input mode so we can monitor through the recorder. (In digital land, you may want to monitor the input signal on modules #9 and #10 BUT only do so if you notice a delay monitoring through the digital mixer and or recorder path.)
7. Bring mixer modules #7 and #8 (recorder track return) about half way up on their fader throws.
8. Pan mixer modules #7 and #8 to full left and full right as to start. You can pan wherever you like but its best to start with the full left and right pan positions checking to hear if you want the full stereo image.
9. Bring the studio control room monitor level up to a normal listening level.
10. Ask the guitarist to play the part for the song. While the guitarist is playing, slowly bring up the faders on modules #9 and #10 (guitar model amp faders source) to zero (unity gain).
11. With the guitar volume full up, have the guitarist play and select the modeled sound(s) for the guitar part that will be used for the song.
12. After finding the sound(s), and setting level controls, tone controls, effects, etc., have the guitarist play with all the attack that would be used for the part.
13. Above Step #3 further adjustment: If you're using an analog mixer and recorder adjust the trim level on the mixer to average zero dB on the recorder track meter for now.
14. Above Step #3 further adjustment: If you're using a digital recorder format, adjust the trim to -4 dB on the recorder track meter for now

Regarding #11 and #12 above: If you are the guitarist and engineer, and if you'll be playing chords for the guitar part, play all the open strings when adjusting the level with your other hand. If you'll be playing single notes for the part, simply play one string for now like the D or G string and adjust the mixer level with the other hand.

Experiment with EQ settings on your mixer. After EQing to taste, go back to step #13 or #14 (depending upon your recorder format). Make sure to have the guitarist play as loud as will be played for the song. If you are the guitarist and engineer, do yourself a favor and play as loud as you will play for the performance.

If you're using an analog recorder (step #13 above), it is possible to use a higher level other than an average of zero dB if looking for tape compression. In this case, after setting the EQ, compressor (if used), and possible other effects, to set the level for tape compression, you would need to put the two guitar tracks in record and monitor in playback mode (monitoring off the playback head). Bring up the level on mixer module #9 and #10 to taste. The VU meter for tracks #7 and #8 will be slamming way past +3 dB. The one consideration is to avoid distortion in the mixer and tape machine electronics so if you start hearing ugly distortion, back off on the levels until it goes away.

Note that when monitoring the guitar in playback mode, there is a major delay, so if the guitarist is wearing headphones, its best to take out the guitar in the headphones while doing the level settings.

 

EQ and Compression

Per the application, review articles on guitar EQ (Parts 4 through 9) and compression (Parts 10 through 13) for details.

Using the Amp Modeler and a Real Amp into a Stereo Analog Path

It's best to record to separate tracks to control the blend, etc. when mixing.

In this case, you would be using a stereo amp modeler using a stereo effect and at least one amp. The following states the cross-over concept and with that in mind, there are so many possibilities, such as the effect on the model sound fading out when the guitar amp(s) takes over the majority of the sonic space. Maybe you might have another effect on the guitar amp. The possibilities are endless!!!

Recording with both an amp modeler running direct and a miked guitar amp are a great concept since you could get the best of both worlds this way. For buzz saw power low 5ths EQ the modeler for the low end stuff and smoothly roll out all frequencies past 600 cycles. On the amp mixer path, you would smoothly roll out below 600. This is a give and take situation since you would need to have the EQ and levels set (between both sounds) for a smooth transition. That's the logical explanation BUT if the transition is radical instead of smooth, and it works for you, great! Dig, how about two totally different sounds one blends into the other!!! Cool!!!

Since the amp modeler does not have a true throughput that a direct box would have, you need to Y off the guitar cable into the amp modeler and the guitar amp. A simple Y adapter could be used but the guitar level will drop around 6 dB to both inputs. That's not good if youre using a distortion sound since 6 dB is a huge drop on the front end. The odds are good that some company makes an active mult box for splitting off a guitar signal that does not load down the guitar output, but I haven't found one. Search the Internet and you probably will.

Comb filtering is a possibility in this situation since the amp modeler will have a delay of approximately 2 milliseconds. Review and adapt to the previous direct box articles using an amp as well.

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