Why is my SPDIF clipping when input 1 isn't?

Orvillain

Orvillain

Power User
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I'm running into the front of my Axe3 - so instrument input 1. This patch splits input 1 to an amp chain, and then dry goes straight through to the mixer. Amp chain panned left, dry signal panned right.

Input 1 is not going into the red zone on the front of the unit at all.

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But it is clipping at the output 2 block. Bigly. I don't understand why.


Here's how things are setup:
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Honestly, I'm still a bit confused how to capture a DI through the Axe FX III, when not using it as a USB soundcard. Just trying to capture a unity gain copy of input 1 to a dedicated track in my DAW to be honest!
 
GlennO said:
This is a confusing thing about the AxeFX, but Out1 and Out2 boost the signal, even when their level parameter is set to 0 dB. you'll have to turn the output down by about 20 dB to compensate.

Here is one of many threads about this: https://forum.fractalaudio.com/threads/out-1-block-clipping.200974/
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Right. I see. Hmmmm. Yes, that more or less works.

If I compare the same input signal split between my Neve DI box and using its THRU connection to also go to the Axe III at the same time, doing a -20dB adjustment on the Output 2 block, gets me within tolerance.
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But I have to set that up per patch I guess???

Do I need to do anything special when I reamp this signal later on through the Axe FX? Any additional attenuation or boosts?
 
Ultimately I'm just trying to figure out a good recording and reamping workflow. I want to record a rough take with any preset, whilst also recording a DI.... and later on I want to be able to reamp that DI without really having to make any changes to patches or signal levels. Y'know.... just straight forward like.
 
Orvillain said:
Ultimately I'm just trying to figure out a good recording and reamping workflow. I want to record a rough take with any preset, whilst also recording a DI.... and later on I want to be able to reamp that DI without really having to make any changes to patches or signal levels. Y'know.... just straight forward like.
Click to expand...
Simply set SPDIF/AES Out Source to Input 1. See manual for more details.
 
Orvillain said:
Ultimately I'm just trying to figure out a good recording and reamping workflow. I want to record a rough take with any preset, whilst also recording a DI.... and later on I want to be able to reamp that DI without really having to make any changes to patches or signal levels. Y'know.... just straight forward like.
Click to expand...

It would be unusual to clip a guitar DI output, even with the 20 dB, so you could do the compensation at your DAW DI input channel. But if it is clipping, you could put a global block in the DI path to turn it down, but of course you're limited to a mono wet output if you do it this way. For both stereo wet and a DI recording, you'll find instructions here:

https://forum.fractalaudio.com/threads/axe-fx-for-the-recording-musician.177592/
 
FractalAudio said:
Simply set SPDIF/AES Out Source to Input 1. See manual for more details.
Click to expand...
So use spdif for the DI capturing, and use analog connections for the "amped wet" recordings?

That makes sense. Means I can keep stereo effects on the amped stuff too. Hmmmmmm. Interesting. Could be a go-er.
 
GlennO said:
He wants to record wet and DI at the same time. That's a common way to record. That way you get a usable take, but have the option of replacing it later.
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Yeah, and trying to keep it in the digital realm as much as possible, without using the Axe3 as my audio interface because I have 16 channels of other bits of gear connected to my two main cards.
 
Orvillain said:
Yeah, and trying to keep it in the digital realm as much as possible, without using the Axe3 as my audio interface because I have 16 channels of other bits of gear connected to my two main cards.
Click to expand...

Configurations #3, #4 or #5 in the recording guide will allow you to record a stereo wet and a DI and re-amp, while allowing for other inputs.
 
Actually... it sorta stands to reason that I could do this:

1. Use my Neve DI box as the dry DI signal. Record to a track in Reaper.
2. Use the THRU output on the Neve to go into the front of the Axe3.
3. SPDIF to Reaper from the Axe3. Stereo goodness if I want it.
4. When reamping from Reaper, route it via SPDIF into the Axe3.

In this scenario I assume I would need to set the AES/SPDIF input level to the correct value so that it aligns with the original signal level of the Neve DI box - thus the Axe3 in reamping scenarios would still see the same signal level as if I was plugged straight in.

It is an extra stage of conversion in there, but to be honest I'm not that fussed about it. The Neve DI box and the Discrete 8 Pro interface I use are both very high quality.
 
Orvillain said:
Actually... it sorta stands to reason that I could do this:

1. Use my Neve DI box as the dry DI signal. Record to a track in Reaper.
2. Use the THRU output on the Neve to go into the front of the Axe3.
3. SPDIF to Reaper from the Axe3. Stereo goodness if I want it.
4. When reamping from Reaper, route it via SPDIF into the Axe3.

In this scenario I assume I would need to set the AES/SPDIF input level to the correct value so that it aligns with the original signal level of the Neve DI box - thus the Axe3 in reamping scenarios would still see the same signal level as if I was plugged straight in.
Click to expand...
This will work fine, but you don't really need to use the thru on the Neve DI. You can use your interface's control software to route the DI input directly to the interface's SPDIF output and into the axefx and save yourself a cable.
Orvillain said:
It is an extra stage of conversion in there
Click to expand...
I don't think so. The only conversions happening are your dry into your interface and your dry into the axefx if you want to use the Neve's thru. When reamping with SPDIF the signal stays digital in both directions.
 
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What I used to do was run my guitar into my interface's Instrument input. Then route that input directly SPDIF out using the interface's mixer, and put the AxeFX in the SPDIF loop. That way you only get one stage of A/D, and the latency was around 3-4 samples, not even perceptible.
 
Orvillain said:
Actually... it sorta stands to reason that I could do this:

1. Use my Neve DI box as the dry DI signal. Record to a track in Reaper.
2. Use the THRU output on the Neve to go into the front of the Axe3.
3. SPDIF to Reaper from the Axe3. Stereo goodness if I want it.
4. When reamping from Reaper, route it via SPDIF into the Axe3.

In this scenario I assume I would need to set the AES/SPDIF input level to the correct value so that it aligns with the original signal level of the Neve DI box - thus the Axe3 in reamping scenarios would still see the same signal level as if I was plugged straight in.

It is an extra stage of conversion in there, but to be honest I'm not that fussed about it. The Neve DI box and the Discrete 8 Pro interface I use are both very high quality.
Click to expand...

Yes, that's a variation on configuration #5 in the recording guide, although I'm not sure the DI box is serving a useful purpose. You might as well just follow the instructions for configuration #5 and plug into the interface. You'll find complete instructions for adjusting levels and re-amping in the guide.

Personally, if you're on a Mac, I'd recommend configuration #4 as a first choice. It's dead simple and allows all kinds of inputs and re-amping with minimum fuss.
 
Orvillain said:
So use spdif for the DI capturing, and use analog connections for the "amped wet" recordings?

That makes sense. Means I can keep stereo effects on the amped stuff too. Hmmmmmm. Interesting. Could be a go-er.
Click to expand...
Yes,
 
strabes said:
You can use your interface's control software to route the DI input directly to the interface's SPDIF output and into the axefx.
Click to expand...
I actually can't do that with my current setup. The Presonus Quantum that is my master card, doesn't allow any mixing or routing like that. You have to do it all in the DAW. So you will always incur some latency penalty. It isn't much, but it is there.

The Discrete 8 Pro SC I have is slaved to the Quantum using ADAT and word-clock BNC connection. I more or less use it as a standalone 8 channel preamp.

strabes said:
The only conversions happening are your dry into your interface and your dry into the axefx if you want to use the Neve's thru. When reamping with SPDIF the signal stays digital in both directions.
Click to expand...
Yeah I know that. What I mean is...

Scenario A:
  • Plug into Axe 3
  • Use SPDIF Left for the mono amp signal
  • Use SPDIF Right for the mono DI signal
== 1 AD conversion

Scenario B:
  • Plug into Neve and record DI via regular XLR input
  • Plug THRU connection into the front of the Axe3
  • Use SPDIF left+right for stereo amp signal
== 2 AD conversions

Scenario C:
- Route recorded DI signal into the Axe 3 via SPDIF for reamping
== No AD conversion


so basically scenario B gives me stereo, at the cost of an extra conversion.
 
For the best fidelity you shouldn't use a DI box.

The A/D on the Axe-Fx is optimized for guitar and will vastly outperform any general purpose audio interface. The Axe-Fx uses multiple channels of the A/D to increase dynamic range.

If you set SPDIF/AES Out Source to Input 1 you get a bitstream copy of the signal from the A/D.

Route the analog outputs to your interface and use those for monitoring the wet.
 
FractalAudio said:
For the best fidelity you shouldn't use a DI box.

The A/D on the Axe-Fx is optimized for guitar and will vastly outperform any general purpose audio interface. The Axe-Fx uses multiple channels of the A/D to increase dynamic range.

If you set SPDIF/AES Out Source to Input 1 you get a bitstream copy of the signal from the A/D.

Route the analog outputs to your interface and use those for monitoring the wet.
Click to expand...
Thanks Cliff!
 
Orvillain said:
so basically scenario B gives me stereo, at the cost of an extra conversion.
Click to expand...

I think Strabes is right. There are two conversions, but they are in parallel, so each path only has a single A/D. Basically, you're using the DI box as a splitter because you can't route a single input to your interface to two outputs.
 
Orvillain said:
View attachment 134357

I'm running into the front of my Axe3 - so instrument input 1. This patch splits input 1 to an amp chain, and then dry goes straight through to the mixer. Amp chain panned left, dry signal panned right.

Input 1 is not going into the red zone on the front of the unit at all.

View attachment 134358

But it is clipping at the output 2 block. Bigly. I don't understand why.


Here's how things are setup:
View attachment 134359

View attachment 134360



Honestly, I'm still a bit confused how to capture a DI through the Axe FX III, when not using it as a USB soundcard. Just trying to capture a unity gain copy of input 1 to a dedicated track in my DAW to be honest!
Click to expand...
Cuz out1 and out2 blocks boost the signal by 18 dB (iirc), you can simply add a level block in the DI path and set the level to -18dB
 
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