‘Studio Diary’ is an occasional series where I talk about building a home recording setup for hobbyists and enthusiasts like us. I share my personal experiences, and the thinking behind some of the decisions that I’ve made along the way.
Fractal Audio have recently overhauled their amp modelling in the Axe-FX 3 / FM-9 / FM-3. And my recent dive into the Orange Getaway Driver has shown me that I need to revoice my signal chain. I’m taking this as an opportunity to re-evaluate everything about the pedal preset I’ve built for the Axe-FX 3.
Back in July, I tackled the major cause of noise by sorting out the gain-staging for my pedal platform preset. However, that hasn’t completely eliminated all noise in the signal chain. (Some noise is inevitable.) What can I do about the noise that’s still getting through?
That’s what I’m going to look at in this blog post.
Table of Contents
- Series Tracker
- What Kind Of Noise Am I Tackling Here?
- The Noise I’m Managing – Noise Floor of -48 dB 😱
- How Much Noise Is Acceptable?
- My Approach To Noise Reduction
- Step 1: Adding A Noise Gate Block
- Step 2: Dialling In Input 1’s Noise Gate
- Step 3: Dialling In Input 3’s Noise Gate
- Final Thoughts
Series Tracker
This is the 13th post in this series.
You can see the full list of these blog posts over on the dedicated FW 25 Pedal Platform Preset page.
What Kind Of Noise Am I Tackling Here?
There’s two types of noise that I want to reduce / eliminate (or at least hide): amplified noise and external noise.
Amplified Noise
A guitar signal chain takes a very weak origin signal (the signal from the guitar’s pickups) and amplifies it into a very strong final signal.
Every device in the signal chain acts as a signal amplifier. Some of these devices introduce noise (in the form of overdrive or distortion). Others (such as compressors, and any source of dirt that heavily clips the signal) raise the noise floor.
Gain-staging (making sure each device is receiving the right input signal level) is important. It keeps the amount of amplified noise as low as possible, so that the unavoidable noise is drowned out by our roaring guitars.
But what happens when our guitars aren’t roaring? What happens when we’re trying to play more delicate pieces in a sparse mix? How do we stop the amplified noise from poking through at that point?
Part of solving that is to tackle external noise too.
External Noise
External noise is any sort of noise caused by anything outside your signal chain.
It might be 50/60 cycle hum. It might be electromagnetic interference from your computer screen (or the TV, or your neighbour’s TV). It might be noise from the fridge downstairs in the kitchen.
In our case, it’s also noise from old electrical wiring in the house, noise from the UK power grid, and (at times) noise from our solar panels. Oh, and we also had noise caused by the house’s electrical wiring being poorly-grounded too.
Wherever it is coming from, all of this external noise contributes to the amplified noise. It gets amplified along with your guitar playing.
The Noise I’m Managing – Noise Floor of -48 dB 😱
I’ve grabbed my noisiest guitar (my PRS Paul’s Guitar), disabled all noise gates in my pedal platform preset, switched on a boost pedal AND a drive pedal together …
… and fed that signal into Apple’s Logic Pro.
I’m still new to Logic Pro. If there’s a dedicated tool or workflow for accurately measuring the noise floor, please let me know in the comments below.
If I’m using the stock MultiMeter right, my noise floor currently sits at around -48 dB:
This blog post isn’t about sorting out the causes of this high noise floor. (And they do need sorting … I believe a good target noise floor is -60 dB? That’s a lot lower than what I’m achieving here.)
I’m going to look at how to use tools in the Axe-FX 3 to cope with it.
How Much Noise Is Acceptable?
Zero Noise Appears To Be Impossible
Us home hobbyist players, we’re not playing in amazing spaces that have been built from the ground up to be world-class recording studios.
We’re playing at home. Maybe we’re in a spare bedroom, or we’ve got a corner of the living room to ourselves for this. Or maybe we’re out in the garage, or in a converted loft space. It might be our main hobby (it might not!), but it’s sharing space with regular, domestic life and everything that goes along with that.
Some amount of noise seems inevitable.
How Much Noise Is On Professional Recordings?
As a home hobbyist, I’ve been surprised at how little seems to be written about this. For example, the excellent Produce Like A Pro site only seems to have just the one article on this topic!
So instead, I turned to Google and started looking for isolated guitar tracks to listen to.
It’s a bit tricky to put too much stock into what I found. There’s no providence explaining where they came from, or what stage of the mixing / mastering process they’re from. And I have no way to measure the noise floor in the tracks that I’ve listened to.
All I can for sure is that … it varies.
- Some of the tracks are incredibly clean of noise, as-if they were played with an aggressive noise gate or have been post-processed with modern digital tools.
- Some of the tracks are surprisingly noisy. Some of these are using pretty clean amps too, so the noise can’t be blamed on the hiss of a dimed amp. They contain more audible noise than the recordings I’ve been producing this summer.
- Some of the noise sounded like it was mic bleed from a drum kit in the room or something like that. It didn’t sound like the kind of noise I’m fighting with at home.
What interested me the most, though, was how some of the guitarists managed their dynamics. In isolation, it sounded to me like the guitarists were keeping their notes full and loud and actively cutting them off in a way to manage / reduce the amount of amplified noise that made it into the recording.
I’m guessing it’s the kind of thing you learn if you’re playing loud electric guitar at decent-sized venues over the years?
My Personal Targets
When I’m not playing, I want to get the recorded noise floor down below -60 dB – and, preferably, down to -70 dB or lower.
I say “when I’m not playing” because the noise reduction tools aren’t going to actively remove (much) noise from the signal. All they can do is hide it when I’m not playing, by turning down the output signal.
And that’s how it’s been done for decades, even before we had hybrid or digital rigs.
My Approach To Noise Reduction
How We Used To Do It, Before Hybrid/Digital Rigs
I used to own an ISP Decimator ProRack G noise gate / expander. It operated on the 4-cable method (4CM for short):
- channel 1 sat between your guitar and your pedalboard (or your guitar and amp, if you didn’t have a pedalboard); and
- channel 2 sat in the effects loop of the guitar amp
Channel 1 was responsible for filtering noise out of the signal from the guitar (such as single-coil pickup hum). If I remember right, there was a little filter control that I could adjust to set how strong the filtering was.
Channel 2 was responsible for muting the amp when I wasn’t playing. It did this by listening to my guitar going into Channel 1. The idea here was to cut off the signal going into the power amp, in case pedals and the amp’s preamp section were producing lots of amplified noise.
I always found Channel 2 to be the most useful for managing my noise issues. But maybe modern digital signal processing can make for an effective Channel 1 too?
Recreating This Approach In The Axe-FX 3
Fractal Audio’s Axe-FX 3 gives me all the tools I need to recreate the ProRack G’s 4CM approach entirely in the box.
First off, the Axe-FX 3 lets me add up to four Gate blocks to any one preset. Each Gate block seems to consume about 2% of CPU on my unit, so they’re pretty affordable. And if I can’t afford the CPU cost, each Input block also has a built-in gate too and which doesn’t use any extra CPU at all.
Channel 1 on the old ProRack G wasn’t just a gate, though: it also included active noise filtering. That’s not something that the Axe-FX 3 Gate blocks offer.
The gates built into each Input block do offer a noise reduction mode though. I’m going to try that out, and see if it’s effective for me.
Step 1: Adding A Noise Gate Block
What Does The Noise Gate Do?
The most obvious thing to do is to add a noise gate to the preset. It’s the digital equivalent of adding a noise gate pedal to your pedalboard. It also mimics the behaviour of Channel 2 from my old Decimator ProRack G unit.
The noise gate in the Axe-FX 3 offers four modes:
- Classic Gate
- Classic Expander
- Modern Gate
- Modern Expander
As I understand it, the two ‘gate’ modes either allow sound through or they don’t. There’s no gradual cut off or anything. When the signal drops below the chosen threshold, the gate modes mute the signal entirely.
The ‘expander’ modes, on the other hand, don’t mute the signal. Once the signal drops below the chosen threshold, the expander starts turning the signal level down. Think of it as fading out the signal, rather than muting it.
‘Classic’ and ‘modern’ modes just use two different algorithms to work out when to start affecting the signal.
Choosing A Noise Gate Algorithm
Having tried both, I prefer the ‘expander’ mode. And I’m going with the ‘modern expander’ mode because it offers a little more control.
Here, I’m also following advice from ‘Guerrilla Home Recording Second Edition’ by Karl Coryat (ISBN 978-1-4234-5446-5). Although it’s an older book from 2008, and it wasn’t written for the Axe-FX 3, it focuses on the principles of audio engineering – and they’re just as relevant today as they’ve always been.
Chapter 4 opens with an introduction to expanders, and some advice on how to set them. But first, I need to decide where to put it.
Placing The Noise Gate After The Amp Block
Because I’m using this noise gate to mimic the effect of Channel 2 of my old Decimator ProRack G, it’s going between the Amp and Cab block in my presets.
(Fractal Audio and YouTube guitarist aficionados will have also seen Leon Todd do this a lot in his presets too!)
In this position, the Gate block will mute the signal coming out of the virtual guitar amp. Perfect for me, because I run my delays and reverbs after the Cab block (for reasons I’ll cover in a separate blog post). The Gate block will give me very clean-sounding delay and reverb tails whenever I stop playing.
Configuring The Noise Gate To Listen To My Guitar, Not To The Amp
First things first, I’ve told the Gate block to use Input 1 as its sidechain source. This means that the Gate block will use my (much cleaner) guitar signal to decide when to act, instead of my (much noisier) guitar amp signal.
I’ve also set the sidechain filters to focus on the guitar’s mid range: Low Cut of around 190 Hz and a High Cut of around 3500 Hz. I’m trying to get the Gate to ignore some of the noise that my guitar is picking up. These settings are definitely a work in progress!
With that out of the way, I can find the expander settings that work best for me.
Dialling In The Noise Gate
This is a little tricky, because I have to take into account the noise gate on Input 1 and this separate Gate block interact with each other.
As a starting point, I set the noise gate on Input 1 to ‘intelligent’ mode, and set the threshold to -60 dB. According to the MultiMeter in Logic Pro, this drops my noise floor to below -60 dB.
I’m hoping this helps me avoid making the noise gate settings too aggressive. (I am guessing here, and could be going about this completely the wrong way.)
Next, following Karl Coryat’s advice, I’ve added the noise gate in ‘modern expander’ mode. I’ve set the ratio to max (20:1), and turned the threshold all the way down, so that I can hear the noise floor, and see it being measured in Logic Pro’s MultiMeter.
From here, I’ve picked a ratio (I’ve gone for 2:1, because I don’t want it to be too aggressive), and then turned up the threshold until (according to MultiMeter) I’m just getting total silence into my DAW (as shown by the LU-S value in MultiMeter).
I ended up with a Gate block threshold of around -53 dB.
Step 2: Dialling In Input 1’s Noise Gate
What Does This Noise Gate Do?
There’s a noise gate built into every input block on the Axe-FX 3. It has three modes:
- Classic – a basic downward expander
- Intelligent – a downward expander with Fractal’s most advanced noise filtering algorithm
- Noise Reducer – a noise filtering algorithm that aims to preserve note attack
Of the two noise filters, the Noise Reducer is designed to be as unnoticeable as possible – at the cost of sometimes letting more audible noise through.
Choosing An Input Noise Gate Mode
In the past, I’ve always gone with the Intelligent mode, because it works the hardest to compensate for my awful external noise. I’ve never noticed it causing problems, and I’ve never had any feedback from anyone else that suggested that the Intelligent mode was affecting the tone in any way.
But, this time, I’m going to go with the Noise Reducer.
Basically, I’m willing to take the risk of a little more noise in return for trying to get the most natural sound possible in my audio demos for the blog. If it doesn’t work out, I’ll just switch back to the Intelligent mode.
Dialling In Input 1’s Noise Gate
As far as I know, we don’t have any control over how the noise reduction algorithm behaves. We choose which algorithm to use by selecting a ‘mode’, and that’s that. All we can do is dial in the downward expander in the noise gate.
In the past, I’ve gone for quite an aggressive threshold of -43 dB or higher.
This time, though, I’m going to stick with the -60 dB threshold that I dialled in earlier. Sure, it’s letting some noise through, but the Gate block after the amp catches that, so I’m okay with it.
I’ve decided to put Input 1’s noise gate into Easy mode, and have left the Release time at the stock 100 ms for now.
With these settings, Input 1 is now acting like Channel 1 from my old Decimator ProRack G. Combined with the Gate block after the Amp block, I’ve recreated that old rack unit in my current hybrid rig.
But I can go even further.
Step 3: Dialling In Input 3’s Noise Gate
Wait, What? A Third Noise Gate?
My pedals (and the cables to-and-from my pedalboard) are a significant source of noise for me. With all pedals off, my noise floor falls to -80 dB. Depending on what pedals I have on, they can drive the noise floor up to above -50 dB.
Input 1’s noise gate, combined with the Gate block, already kill the noise effectively when I’m playing. Input 3’s noise gate isn’t going to make my recordings any cleaner.
So why do I need to do anything here?
Disabling Input 3’s Noise Gate
Because I think that the noise gate can’t do anything to help, I need to make sure that Input 3’s noise gate is completely disabled:
- set the expander’s Threshold to ‘off’; and
- set the algorithm to ‘Classic’.
If the Threshold is set to ‘off’, I don’t know if the noise reduction algorithm is still active. The manual doesn’t say either way. So I’m going to assume that it is, and disable all noise reduction by choosing the ‘Classic’ algorithm.
Final Thoughts
These new settings are less aggressive than I’ve been using up until now:
- switched to Noise Reduction in Input 1;
- stopped using any sort of noise reduction algorithm in Input 3;
- thresholds are lower in both Input 1 and the Gate block; and
- Input 3 is doing no noise gating at all now.
I’m hoping they’ll translate into audio recordings that sound more natural than before.
And, in particular, I’m hoping that (along with Firmware 27, which I will upgrade to towards the end of this series), these new settings get rid of a slightly artificial / plasticky sound that I sometimes hear in the note attack.
I’m willing to accept a little bit of recorded noise to achieve that.