Line Level...The Axe III...The Matrix

200man

200man

Power User
The purpose of this thread is to shine the light on the output levels of the axe and the input levels of the matrix. Hoefully if my assumptions are not correct I may learn something in the process. :)

First I took a look at the input level sensitivity of the matrix. Well, I dunno but it seemed a bit dodgy but maybe we can figure it out. First, the matrix has one of those one-size-fits all neutrik connectors. The matrix documentation states for all of their amps that the input level sensitivity is = 0.775v / 0 dBu. So, and I really want to know the answer to this, as they do not specify nor provide an ability to select balanced or unbalanced level: Is there no common mode rejection circuitry if connecting a balanced signal? If there is a balanced circuit are the input levels for both the unbalanced and balanced signals “normalized” to 0.775V? I could not figure this out. Anyone know? The matrix documentation indicates for runs greater than a foot to use xlr cables for greater RF shielding...which one might infer indicates both plus and minus signals are combined? ....i dunno...

Secondly, I’ll reference a wiki article on “Line level” for reference:
https://en.m.wikipedia.org/wiki/Line_level

Next assumption; when matrix says “0.775V” they are referring to 0.775RMS / 0 dBu.

Well, if this is the case then we have the axe’s output levels next to consider.
I think I saw here that you may select -10dBv or +4dBu for output level. I read the sticky thread here on “Output Level” to confirm.

Okay now we can pull the data from the wiki to compare:
the axe output levels...
-10dBv level (consumer) = 0.316VRMS [from the wiki graph: 0.447*0.707=0.316)
+4dBu level(pro) = 1.228VRMS [from the wiki graph: 1.736*0.707=1.228]

the matrix input level sensitivity...
0dBu level(pro) = 0.775VRMS [from the wiki graph: 1.095*0.707=0.775]

The matrix’s documentation also states, under their “Getting Started” section 5, to adjust the input source(the axe’s output level), to a “required level (ideally 0dBu or 0.775V)” and adjust the Matrix output until a “sufficient level” is achieved. Now this made me scratch my head for the following reasons. First, there is almost unanimous consensus that the Matrix sounds better with less attenuation(i.e. crank the volume knob). Second, this means depending on the volume required, one might want to position the output level of the axe fairly low, in order to control a “cranked” matrix amp.... which might be much lower than 0dBu. hmmmm.....Could that make an argument for selecting -10dBv on the axe depending on volume required?
 
FractalAudio said:
You’re way overthinking this.
Click to expand...
I almost typed the same thing last night.

Use whatever arrangement sounds best to you. As long as you can get the volume you need, it doesn’t matter.

As far as the Matrix sounding better when it’s “cranked,” at any given volume, the Matrix is working just as hard, no matter how you got to that volume.
 
Rex said:
I almost typed the same thing last night.

Use whatever arrangement sounds best to you. As long as you can get the volume you need, it doesn’t matter.

As far as the Matrix sounding better when it’s “cranked,” at any given volume, the Matrix is working just as hard, no matter how you got to that volume.
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Thanks Rex.
Yes, it is true I wrote too much last night. ;)
But many times conversations in threads do not present a lot of information technically, which causes weird posts. :)
Anyway I’m not wrapped around the axel with the Matrix volume issue but it is true that many others have testified that it does indeed sound better “less attenuated”.

The question I was most interested in was the input circuitry question WRT the matrix. It’s funny, we know how to model the circuitry of hundreds of tube amps, but when I ask a question about the power amp that many users have implemented to use specifically with the axe noone knows. :)
Now remember that last statement was said lightheartedly so please don’t hurt me. ;)
 
I’ve also heard that with the Matrix GT series specifically, there’s something about the circuitry that makes it sound better when the volume knob is at 2 - 3 o’clock or higher, regardless of what the actual output volume is, like maybe there’s an imperfection in the Matrix’s master volume attenuation circuit design or something.

As in, Axe-Fx with volume maxed and Matrix volume low will sound different than Axe-Fx volume set low, Matrix volume cranked.

Disclaimer: I’ve never personally tried the Matrix amps so I haven’t tested this for myself, it’s just something I’ve read.
 
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Rex said:
As far as the Matrix sounding better when it’s “cranked,” at any given volume, the Matrix is working just as hard, no matter how you got to that volume.
Click to expand...
There was a recent thread written by Metallica's tech (I believe) about the perceived tonal difference with the Matrix GT1000FX when the volume knob was set at 2 o'clock or higher (but keeping overall volume the same by feeding less into the amp).

It doesn't seem to make sense, but a lot of people seemed to have reached the same conclusion...

I think that is the origin of the question being asked.

My answer would be: set the Matrix to the level that you think is best. Adjust what you feed into to work with that for the volume you need.
 
Your question was whether there is common-mode rejection in an unbalanced input. The answer, by definition, is no.
 
unix-guy said:
There was a recent thread written by Metallica's tech (I believe) about the perceived tonal difference with the Matrix GT1000FX when the volume knob was set at 2 o'clock or higher (but keeping overall volume the same by feeding less into the amp).

It doesn't seem to make sense, but a lot of people seemed to have reached the same conclusion...

I think that is the origin of the question being asked.

My answer would be: set the Matrix to the level that you think is best. Adjust what you feed into to work with that for the volume you need.
Click to expand...
I actually called Matrix a few years ago and they told me the system sounded better when the volume was cranked passed 2 o'clock. They don't tell people because if the power up or down sequence is in the wrong order you could damaged the speakers.
 
Rex said:
Here's what you said:
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Now are getting somewhere?
You are stating that regardless of the neutrik connector, the Matrix input is an unbalanced connector because the specification from Matrix says it is 0.775V.
Therefore, additionally you are saying that the Matrix is only using one of the balanced inputs(probably the +) if it is connected thusly.
...anyway that’s what I heard/saw/inferred. ;)
 
Woah. Now I feel stupid. All I ever do is adjust the knobs using my ears so it's low noise and I can achieve the volume I need.

I guess I need to start carrying a multi-meter with me. Then again, I only know how to measure impedence and use the continuity tester so maybe I'll just stick with my ears.
 
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I just talked to Andrew at Matrix. 0 dbu is the optimal input level. -10dbv is too quiet and 4dbu can be too hot and you could damage the speakers.
 
shroomboss said:
I just talked to Andrew at Matrix. 0 dbu is the optimal input level. -10dbv is too quiet and 4dbu can be too hot and you could damage the speakers.
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You have to pick one!

Also, that's not the absolute level... You still have output level knobs on the Axe Fx.
 
200man said:
You are stating that regardless of the neutrik connector, the Matrix input is an unbalanced connector because the specification from Matrix says it is 0.775V.
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No, I’m not saying that. I don’t know whether its input is balanced or unbalanced. You’d have to look at the manual to know that.

You asked whether there’s common-mode rejection on an unbalanced input. And there isn’t.
 
unix-guy said:
There was a recent thread written by Metallica's tech (I believe) about the perceived tonal difference with the Matrix GT1000FX when the volume knob was set at 2 o'clock or higher (but keeping overall volume the same by feeding less into the amp).

It doesn't seem to make sense, but a lot of people seemed to have reached the same conclusion...

I think that is the origin of the question being asked.

My answer would be: set the Matrix to the level that you think is best. Adjust what you feed into to work with that for the volume you need.
Click to expand...

Having used the GT1000FX for many, many years, I can attest to the fact it really does sound better when turned up to 2 c'clock or more.
 
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