Does Out 1 (Main) effect anything other than volume?

It has been stated that Out 1 is only an attenuator - I cannot remember the source.

@austinbuddy 's and my video about Out 1 are both concerned about getting the same level on the VU meters in the AX8 (just before the D/A converter) and the VU meters in a DAW. To achieve this, we need unity gain across Out 1 (= all the way up) and unity gain across the audio interface/mixer input (= a +4 dBu line input). Not all mixers and audio interfaces will give unity gain even with the channel gain / input trim set to minimum. I found with my own audio interface that if I didn't use the dedicated +4 dBu line in and went through one of the combo inputs that something like 3-5 dB gain was added as a minimum.

If you run a guitar signal into a +4dBu line input, I think you would get an input level around -40 or -60 dBFS (haven't tested). -12 dB(FS = Full Scale) is a very healthy input level. Generally, you want to hit your digital audio interface or mixer with peak levels between -18 and -12 dBFS. That gives you plenty of headroom before clipping (occurs at 0 dBFS). But the daw level really has nothing to do with unity gain. Unity gain, is (in the context I use) that the level that comes out of the AX8 D/A converter is the same level as I get into my DAW/mixer. If the level out of the AX8 DAC is -40 dBFS, unity gain ensures that the level in my DAW is also -40dBFS.

A fader at the 0-line should definitely be unity gain across that fader.

I think @chris is right that a lot of people struggle with 'simple' audio engineering issues and that causes a great deal of questions. To some extent that is a skill we need to learn, when we use the AX8. We have taken over the mic and the mic preamp from the audio engineer, we should know how to handle this - some people also insist on taking over the channel EQ and ask the sound guy to leave the channel EQ flat. I agree that a flat EQ would probably be the best starting point, but if the sound guy think it needs adjustment, I certainly hope he adjusts :)

There is much to learn; peak levels, VU levels, input sensitivity, input impedance, gain staging etc. Sometimes, it is not possible to learn everything, and there may very well be other variables than optimal gain staging to consider. If turning down Out 1 saves the day, or makes interfacing with your other audio equipment easier, JUST DO IT :)

EDIT, added: Turning down Out 1 does not affect your tone at all. The only 'penalty' is increased signal to noise ratio (this is a fact, whether you can hear it or not). However, the AX8 has a very very good signal to noise ratio under optimal conditions. So in many cases, especially live, optimizing your signal to noise ratio may not be your primary concern. If your signal to noise ratio goes from 100 dB to 90 dB because your gain staging is not optimal, it probably does not matter. If you play passive single coil pickups, it surely does not matter.
 
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Out 1 Main should NOT be set to maximum in all situations.

Unity gain is measured with Shunts only. Once you add other blocks, you are probably louder than Unity Gain.

Use the volume knob as a volume knob. It will not change anything other than volume/level coming out of the AX8. Here are more of my thoughts on this:

https://forum.fractalaudio.com/threads/a-few-questions-about-foh.142368/#post-1689559


Chis,

I still did not understand the concept.
In ax8 manual we can read:

"Unlike the FX8, the AX8 is NOT specifically designed for unity gain, but when you’re using it “direct” this really should not be a concern."


What is unity gain used for? Why is FX8 designed for unity gain and Ax8 not?

I understood that out 1 (main) is a Volume Knob only, and it doesn't matter if I set it for 9 o'clock or 15 o'clock, because it is just a volume knob. It does not change my tone in anyway.

But I would like to know why unity gain is important is some context?

Thank you
 
Some have experimented and they say that Unity Gain is achieved when the preset is leveled at the mid-line on the VU meter and the Out 1 knob is all the way up.

Regardless, the main thing I see popping up all the time is “I read I need to turn the Out 1 knob all the way up for best tone/usable noise level.” That part is just not true at all.

Further, people tell their soundguys that it needs to be all the way up and there are issues at the gig because of it - mostly because the soundguy won’t adjust things. But it happens so often and I get Private Messages from many people at the gig frequently. Then they are eventually forced to turn down and I get questions like “I was forced to turn down and I just think my tone was way worse because of it - how do I prevent that.” It then becomes a psychological conversation like I described above, where I get them to hear there’s actually no added noise at all by simply turning down.


I completely agree with you, that volume knob does not affect the tone.
But I still did not get why people want to achieve unity gain.
 
I still did not understand the concept.

What is unity gain used for? Why is FX8 designed for unity gain and Ax8 not?

I understood that out 1 (main) is a Volume Knob only, and it doesn't matter if I set it for 9 o'clock or 15 o'clock, because it is just a volume knob. It does not change my tone in anyway.

But I would like to know why unity gain is important is some context?
Unity gain is useful as a starting point in some situations when you’re using other gear.

For example, let’s say you’ve got your FX8 hooked up in 4CM with your favorite amp. If you dial in the FX8 for unity gain, then there’s no inherent change in signal level when you’re running all shunts. If you drop in a Phaser block at default settings, it just adds the Phaser effect, without changing how hard you’re driving the amp you’re connected to. On the other hand, if you’re running at higher-than-unity gain, your FX8 will be pushing the preamp harder, giving more distortion than what you’ve carefully dialed in on your amp.

Let’s put it another way. If you’re running a traditional pedalboard and you bypass all your pedals, you want your guitar signal to pass through your pedalboard unchanged, and hit your amp at the same level as if there was no pedalboard at all. No boost or cut. That’s unity gain. The level you put in is the level you get out.

The AX8 is a different beast. It’s intended to be an all-in-one rig. It has the amp built into it. And amplifiers...well...amplify. They’re supposed to add gain. By definition, guitar amps don’t have unity gain. So the AX8 isn’t designed for unity gain.
 
And I’ll repeat what others have said. Unity gain means that the signal level you put in is the signal level you get out. It doesn’t mean that that two different things have the same level. It only means that one thing puts out the same level that it takes in.

When you dial in two presets to have the same volume as each other, that’s not unity gain — it’s level matching. When you set up your AX8 so its analog level matches its digital level, that’s not unity gain either — it’s level matching.


Where does the name “unity gain” come from, anyway? “Unity” means “one.” A device that has unity gain has a gain of one. When you multiply a number by one, you get the same number. If you send a two-volt signal through a device that’s running at unity gain, you get a two-volt signal out, because 2 X 1 = 2.
 
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what would you call the Fader position on a typical mixer at the -0- line? genuinely asking.
I can't speak for every single mixer in the world but, in my experience, if you set a channel fader and mains fader at the -0- line (not to be confused with 0 on any metering provided by the mixer) and use no EQ, compressor, etc. on the channel, then the line output of the mixer will be equal to the output of the mic pre (i.e. "unity gain"). Same deal as an all-shunts AX8 preset or with my "replace the knob with a wire" scenario. Mixers need to allow both boosting and attenuating signals on the fly, hence the typical +10dB above -0- of headroom on the fader.

If you anticipate needing to adjust your OUT1 up on the fly like you might with a fader (e.g. you play with a stereotypical drummer who gets louder and louder as the show goes on and your band is running their own sound), then dropping OUT1 as a starting point to give you that headroom is a totally valid use of the knob. I've done exactly that in the past but, in the ideal world, I'd prefer to just keep the knob at 100% and have a drummer who can play consistently. Again, I'm speaking of ideals and there are certainly real world scenarios where dropping the knob is necessary.

has it been confirmed that the Out 1 knob is an attenuator?
Not sure if it has been officially confirmed but my metering has me convinced that it is i.e. it is impossible to produce a signal too hot for line level at 100% OUT1 so, from a practical standpoint, anything lower than that would be attenuating. I have no idea what the AX8 is actually doing internally though I suspect it may be a simple multiplication of 0.0-1.0 in the digital domain before the D/A as I believe it affects SPDIF as well.

you can see that AustinBuddy above just stated that his goal is -12 dB in a DAW. can you comment on how that factors in to all this Unity Gain talk?
Setting OUT1 to 100% and gain at 0 on your audio interface means you should be matching your DAW's dbFS metering perfectly with the AX8's VU meter (which can reasonably be called "unity gain" in this case, if you wish) and will never clip if your preset itself does not clip on the AX8. This gets you max signal-to-noise ratio on your recorded clip. If -12 dB is your goal, I would not recommend tweaking anything on the AX8 or on the audio interface to hit this as most DAWs either have a clip gain feature or bundled plug-in that lets you adjust the recorded audio to the level you want for processing in the DAW. Your rhythm tones vs. lead tones probably aren't going to be at the same output levels from the AX8 anyway.
 
Setting OUT1 to 100% and gain at 0 on your audio interface means you should be matching your DAW's dbFS metering perfectly with the AX8's VU meter (which can reasonably be called "unity gain" in this case, if you wish)...
No it can't, because that's not unity gain — it's level matching.

I agree with pretty much everything else that you wrote.
 
Setting OUT1 to 100% and gain at 0 on your audio interface means you should be matching your DAW's dbFS metering perfectly with the AX8's VU meter
This is assuming that the VU meter and the meter in every DAW and 0 on every audio interface is exactly the same, right? Is that a standard they all meet?
 
There are a number of caveats and pitfalls right there :) A VU meter is not a peak meter, it has a time constant, so in material with a lot of transients a peak meter will read higher numbers than a VU meter. This is why I always use the synth block with a 1 kHz sine wave to match between AX8 and my DAW.

No it can't, because that's not unity gain — it's level matching.

It's not level matching. You are connecting two points in your signal chain with two unity gain connections, and therefore you have the same level at both points.
You are going from one level measurement at the AX8 VU meters across the Out1 knob set at 100%, so it is giving unity gain across the knob. Then across the audio interface input stage with 0 dB (= unity) gain. As a result, the meter in your DAW shows exactly the same as the meter on the AX8 (provided they are the same kind of meters).
 
You are going from one level measurement at the AX8 VU meters across the Out1 knob set at 100%, so it is giving unity gain across the knob.
i'm truly trying to understand here. i'm not trained in electronics or anything so please use simple terms if it helps :D

does this mean that the middle line of the AX8 VU meter represents "Unity Gain"?

there's just a disconnect for me and i don't see how anything done on the AX8 means "unity gain." how does the AX8 VU meter get you to Unity Gain?
 
The middle of the line does not mean unity gain.

Unity gain means that the level does not change from one point to another. If you measure from the AX8 input to the AX8 output (with a normal/factory preset and out1 all the way up), the level probably changes by 60 dB or more, so that is clearly not unity gain.

When I talk about unity gain, I reference the level at AX8 output block. To me, unity gain is about maintaining that level all the way to the fader in the mixer. I don't really care, what the actual level is in the output block, but the level should be the same at all points between the output block and the fader.

In the output block, we have a digital level, but that represents a specific level in the analog domain, so I think we can say, we have unity gain across the DA converter. With Out1 all the way up, the level does not change either, so we have now reached unity gain from the output block to the AX8 output, and then if the mixer/audio interface adds 0 dB gain, we have unity gain all the way from the output block to the mixer.

The line in the AX8 VU meters is a very healthy level to aim for. There is sufficient headroom before clipping, while it is still a good and strong level. The benefit of unity gain from the output block to the fader/DAW is that then you still have a very healthy level in your DAW/mixer with sufficient headroom before clipping.
If you reduce Out1 and bring the level back up with the input trim/gain on the channel, it is possible to match the same levels, but then you have reduced the volume only to subsequently amplify it, and that introduces unnecessary noise (but as we said often before, a quite low level of noise).

Does it make sense?
 
Unity gain means that the level does not change from one point to another. If you measure from the AX8 input to the AX8 output (with a normal/factory preset and out1 all the way up), the level probably changes by 60 dB or more, so that is clearly not unity gain.

...

To me, unity gain is about maintaining that level all the way to the fader in the mixer. I don't really care, what the actual level is in the output block, but the level should be the same at all points between the output block and the fader.
i guess this is where i'm getting confused.

you aren't factoring in the guitar input to the discussion of Unity Gain. you're considering the output of the AX8 as the start of the Unity Gain determination.

so regardless of where "internal" preset levels are set, regardless of how the guitar input level is compared to the AX8 output, none of that affects your definition/use of Unity Gain.

to me, that right there is 2 different definitions of Unity Gain being thrown around in the same discussion.

one is "turn Out 1 knob all the way up - that is Unity Gain as I define it and my starting point for keeping the same level between the AX8 and Mixer."

other is "Unity Gain is defined as measuring level using all shunts from Input to Output of the AX8, therefore keeping the same input level from Guitar Input continuing through the remaining signal path."

right? still just trying to define things here - not judging any methods or anything now.

i thought "Unity Gain" had a specific "constant" starting from the guitar, rather than some level that you can determine as the starting point from anywhere else within the signal path?
 
i thought "Unity Gain" had a specific "constant" starting from the guitar, rather than some level that you can determine as the starting point from anywhere else within the signal path?
Gain is the ratio between output level and input level in a "two-port network." The AX8's signal path is essentially a two-port network. It has an input and an output. And you're right — it rarely operates at unity gain. A patch cable is also a two-port network. Signal goes in one end and out the other. At line levels, a signal cable has unity gain — you get out what you put in.

Your total signal path includes both the AX8 and at least one cable. That total path doesn't operate at unity gain, even though one of its components (the cable) does operate at unity gain. The total gain is the sum of the gains of all of the components in the signal path. If your AX8 is giving you 30 dB of gain, and the cable is giving you 0 dB of gain (unity), your total gain is 30 + 0 = 30 dB.


The idea behind cranking Out1 all the way up is that 0 VU on the AX8 will give you pretty close to 0 VU in your DAW. That leaves both devices operating near their sweet spot, without having to adjust levels.

Is that unity gain? Not exactly. IIRC, 0 VU on the AX8 is 20 dBFS (20 dB before clipping). On many DAWs, 0 VU is only 18 dB before clipping. On some, it's even less. And in the digital realm, the whole concept of gain sort of breaks down at the interfaces. For example, a 32-bit digital system has more dynamic range than a 24-bit system. At the interface between analog and digital, it's hard to define gain at all, let alone unity gain. The closest you can get is to match reference levels. And that match happens when Out1 is dimed.


And as you've noted elsewhere, cranking Out1 all the way up can be entirely impractical in a live situation.
 
Gain is the ratio between output level and input level in a "two-port network." The AX8's signal path is essentially a two-port network. It has an input and an output. And you're right — it rarely operates at unity gain. A patch cable is also a two-port network. Signal goes in one end and out the other. At line levels, a signal cable has unity gain — you get out what you put in.

Your total signal path includes both the AX8 and at least one cable. That total path doesn't operate at unity gain, even though one of its components (the cable) does operate at unity gain. The total gain is the sum of the gains of all of the components in the signal path. If your AX8 is giving you 30 dB of gain, and the cable is giving you 0 dB of gain (unity), your total gain is 30 + 0 = 30 dB.


The idea behind cranking Out1 all the way up is that 0 VU on the AX8 will give you pretty close to 0 VU in your DAW. That leaves both devices operating near their sweet spot, without having to adjust levels.

Is that unity gain? Not exactly. IIRC, 0 VU on the AX8 is 20 dBFS (20 dB before clipping). On many DAWs, 0 VU is only 18 dB before clipping. On some, it's even less. And in the digital realm, the whole concept of gain sort of breaks down at the interfaces. For example, a 32-bit digital system has more dynamic range than a 24-bit system. At the interface between analog and digital, it's hard to define gain at all, let alone unity gain. The closest you can get is to match reference levels. And that match happens when Out1 is dimed.


And as you've noted elsewhere, cranking Out1 all the way up can be entirely impractical in a live situation.
From this I gather that Unity Gain just simply isn’t the correct term to use in all this? That’s why you mentioned “level matching”?
 
The definition of Unity Gain:

Unity gain is a term used when establishing the balance between pieces of audio equipment. The idea is that input should equal output, level-wise. Audio that goes into a device at one level and comes out of that device at the same level is said to be at unity gain.

If there is a standard definition of a term, the “reasonably meant” definition might not be accurate.

Unity Gain has always been measured on the Axe series as Shunts only. What goes in is what comes out. There shouldn’t be a 2nd definition of Unity Gain which means “as loud as the unit will go.”

Imagining that the knob is not there seems silly to me because the knob IS there. You can use it and it’s designed exactly for that. As I mentioned before, the FX8 does not have a knob and is therefore designed to be at that level which happens to be a Unity Gain design.

Of course if you experience noise, then gain stage as needed. In some setups I do run the AX8 knobs all the way up, but not for noise concern, more for repeatable knob position. I’m in full control of the mixer and adjust my volume there during the gig.

I personally have not experienced any noise added when running the knob at 9 o clock. I do that 3x weekly at 3 different venues with 3 different mixers and there is absolutely no issue whatsoever.

Because of various posts here and elsewhere, new users are getting the impression that turning the knob low like 9 o clock creates some very audible amount of noise that renders the AX8 useless. I’m not exaggerating - I’ve been told that and when we work through it, at first they don’t even want to try turning that low. When we “act silly” just to test things, they finally turn it low and ultimately discover that it sounds the same.

I actually had to talk some people through it when they turned down and “suddenly heard a ton of noise.” We were on Skype and I could see and hear everything. They turned the AX8 volume down and I heard no difference (they balanced the speaker volume up). They were certain they heard “a noise just as loud as their guitar.” It just wasn’t there. Strangely multiple people swear they heard the tone go to complete crap. I figured out that they had to stop playing, leave the room for a minute then come back. “Wait, did you do something?” someone asked me, actually thinking due to Skype that I adjusted their AX8 (it doesn’t work like that).

For whatever reason, these few people thought it got unusable noisy when simply turning down. But there was no added noise at all. It was in their head and they convinced themselves it was unusable. This happens often with various topics during my consultations. People have an idea in their head, and because it’s audio and not visual, people can tend to have a tough time reacting to what’s actually happening vs what they think should happen. (I’ve had someone not hear any difference in Input Gain on the amp block - sometimes they don’t know what their listening for either.)

Anyway, all that to say that this still is a confusing topic and people sometimes have predetermined notions of certain things and convince themselves of it regardless of what’s actually happening. Sorta like when someone says “oh that’s a real amp recording”, is then told it’s the Axe, and only then do they say “oh right I knew that because it sounded digital.” (I’ve done that test a few times too.)

As mentioned by Dave76 and others, adjust settings as needed to prevent noise. The Output knobs are variable for a reason, so use it as needed.

If you actually do want Unity Gain, that’s one thing. But turning all the way up for no reason can cause issues.


Chris, Does it make any sense talking about Unity Gain while handling an Ax8? This question is for all us. I was trying to understand all of these concepts and ideas... But, How to achieve Unity Gain with Ax8?? It makes no sense at all...
 
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