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Real Mesa Dual Rectifier vs Axe-Fx III and input impedance woes...

ML SOUND LAB

Cab Pack Wizard
And what I'm saying is that they do sound the same and there are clips to prove it.
Even my clip proved it. I'll add time codes to avoid confusion:


0:00-0:07 Guitar straight to the Dual Recto

0:07-0:15 Guitar to the Axe-Fx III input, empty preset, Output 3 to the Dual Recto

0:15-0:24 Guitar to the Axe-Fx III input, empty preset, Output 3 to the Dual Recto but I matched the volume with the first clip as this was a hotter signal

0:24-0:32 Axe-Fx III Dual Recto amp sim with default settings

0:32-0:46 Axe-Fx III Dual Recto amp sim with default settings but master on 5 like I had on my real amp and this sounds just like it should sound. Really close to my amp but actually sounds a bit better even.
 

Raab90

Inspired
Still no idea what you're saying. How do you put a "real amp through guitar"?

One clip is guitar->Axe-Fx->Ouput 3 to amp.
Another clip is straight into the amp.
The third clip is one or the other to keep you guessing.
Let me rephrase:

a) Recording of the real amp (signal chain: Guitar->Real amp)

b) Recording of the real amp (signal chain: Guitar->Axe->Real amp)

c) Recording of the tone matched model (Signal chain: Guitar->Axe-Real amp)

I’m basically saying that putting both units in series shifts the resonat freq. and taking the real amp out on a fourth recording should produce a brighter sound like the one on case a)

But nevermind it
 

ML SOUND LAB

Cab Pack Wizard
Let me rephrase:

a) Recording of the real amp (signal chain: Guitar->Real amp)

b) Recording of the real amp (signal chain: Guitar->Axe->Real amp)

c) Recording of the tone matched model (Signal chain: Guitar->Axe-Real amp)

I’m basically saying that putting both units in series shifts the resonat freq. and taking the real amp out on a fourth recording should produce a brighter sound like the one on case a)

But nevermind it
I understood what you were trying to say but, that's not ideal in so many ways for what I'm trying to do. Thank you though. :)
 

Raab90

Inspired
I hope to find a solution and wish and sincerely hope that I'm doing something wrong. This is not only about the Axe-Fx, like the test that I did with the DI box: guitar into passive DI with input through going to the amp in sounds completely normal, plug an XLR from the DI to anything and it changes the sound. If the sound difference was small I wouldn't care but it's really big right now. Here's a pic of the waveform difference:



Here's an audio clip:

https://www.dropbox.com/s/ciosr430mzmyxp7/Problem.wav?dl=0

And this happens on both my Mark V and Dual Rectifier.
By “Input through” you mean the DI is bein bypassed? That would mean it’s not loading down the pickup. If you plug into something you’re producing a similar effect than cascading the axe into the recto, loading the pup down and shifting the res freq
 

ML SOUND LAB

Cab Pack Wizard
Correct. See my test clips.
Your clip sounds like it works perfectly. This is where I start to lose my sanity. :D I tried different cables, different outputs, different I/O settings, different everything. Eventually did a factory reset and I'm still experiencing this. Could there be a problem with other things connected to the Fractal?
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
Let me rephrase:

a) Recording of the real amp (signal chain: Guitar->Real amp)

b) Recording of the real amp (signal chain: Guitar->Axe->Real amp)

c) Recording of the tone matched model (Signal chain: Guitar->Axe-Real amp)

I’m basically saying that putting both units in series shifts the resonat freq. and taking the real amp out on a fourth recording should produce a brighter sound like the one on case a)

But nevermind it
There was no tone matching. Putting the units in series does not shift the resonant frequency because the output impedance of Output 3 is very low.

There are three clips, each with an E chord played three times:
One clip is guitar straight into amp.
One clip is guitar into Axe then into amp.
One clip is one or the other but I'm not telling you which.

Here's a spectrogram. Notice that the spectrums are basically identical apart from minor differences in my performance.

spectrogram.JPG
 
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FractalAudio

Administrator
Fractal Audio Systems
Moderator
Your clip sounds like it works perfectly. This is where I start to lose my sanity. :D I tried different cables, different outputs, different I/O settings, different everything. Eventually did a factory reset and I'm still experiencing this. Could there be a problem with other things connected to the Fractal?
Could be something wrong with the input but I doubt it. Try using the rear input.

The fact that the same thing happens with the Kemper points to cable issues though.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
I'm using a borrowed loadbox for these clips, a Two Notes Captor, could that have something to do with this?
It's possible but I've never tried one. Load boxes can do all sorts of strange things due to the creation of feedback loops and such. I struggled with this with the LB-2. It took six iterations to get it right.

Another thing to check is to make sure your Input Impedance is set to 1M. If you have it set to Auto and there's an active block after the input it might be switching the input impedance.
 
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ML SOUND LAB

Cab Pack Wizard
It's possible but I've never tried one. Load boxes can do all sorts of strange things due to the creation of feedback loops and such. I struggled with this with the LB-2. I took six iterations to get it right.
I will try this with a real cab next time I'm at the studio.

Another thing to check is to make sure your Input Impedance is set to 1M. If you have it set to Auto and there's an active block after the input it might be switching the input impedance.
I read about this on axewiki and tried all the different options out just in case.
 

BillyZeppa

Power User
I'm using a borrowed loadbox for these clips, a Two Notes Captor, could that have something to do with this?
I'd be curious to know if the box is coloring the sound. Maybe record a quick few notes without loadbox (at 4:00AM so everyone will be too sleepy to complain about it.. :))
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
of Cliffs clips I liked 1 and 3 , 2 I did hear a slight muffling .
2 was direct into the amp. 1 and 3 were through the Axe-Fx then into the amp with 1 being the front input and 3 being the rear input. This is what would be expected given that the Axe-Fx input has slightly greater high frequency extension than a Recto.
 

ML SOUND LAB

Cab Pack Wizard
@FractalAudio I found the problem: Two Notes Captor Reactive Loadbox. I tried these tests again and I was still having the problem. Plugged straight into my cab and used the Mesa slave out and I'm not having this problem anymore. :) Once again the lesson learned is:

THE PROBLEM IS NEVER WITH THE FRACTAL!

I actually found a way I can use the loadbox. Placing a DI inbetween the amp and loadbox is one way and also using the slave out on my Mesa amps. These work perfectly. It's the output of the loadbox that's messed up.
 
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FractalAudio

Administrator
Fractal Audio Systems
Moderator
@FractalAudio I found the problem: Two Notes Captor Reactive Loadbox. I tried these tests again and I was still having the problem. Plugged straight into my cab and used the Mesa slave out and I'm not having this problem anymore. :) Once again the lesson learned is:

THE PROBLEM IS NEVER WITH THE FRACTAL!

I actually found a way I can use the loadbox. Placing a DI inbetween the amp and loadbox is one way and also using the slave out on my Mesa amps. These work perfectly. It's the output of the loadbox that's messed up.
Doesn't surprise me. Like I said I struggled with this with the LB-2. There's so much power being dissipated that you end up with these funky ground loops that end up feeding current into the ground and right back to the guitar.

You should use a Suhr RL or an LB-2 though. Much more accurate impedance curves. The Two Notes (and the UA OX) don't use inductors for the low-frequency response so there's no low-frequency resonance. Instead the impedance curve has a "bathtub" shape. With the inductor you get a true low-frequency resonance but that inductor is big, heavy and expensive.
 

ML SOUND LAB

Cab Pack Wizard
Doesn't surprise me. Like I said I struggled with this with the LB-2. There's so much power being dissipated that you end up with these funky ground loops that end up feeding current into the ground and right back to the guitar.

You should use a Suhr RL or an LB-2 though. Much more accurate impedance curves. The Two Notes (and the UA OX) don't use inductors for the low-frequency response so there's no low-frequency resonance. Instead the impedance curve has a "bathtub" shape. With the inductor you get a true low-frequency resonance but that inductor is big, heavy and expensive.
Yeah I did some tests with a miked cab vs Two Notes and an IR shot of that mic up. I essentially got a straight line but the low end had a scoop on it. Nothing too big though.. it was like 1dB or so but still, not flat.
 
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