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How do I know if I am clipping


redbelo
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Use a blank preset with headphones and listen to the guitar played hard through all pickup combinations and see if you can hear any distortion. Digital clipping is not pleasant, so if you’re clipping, you’ll probably hear it. If there’s any doubt, compare the sound with pad on/off (adjusting for equal volume). If they sound the same, you’re probably not getting digital clipping.

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This is something I actually find problematic w/the Stomp... not knowing how much signal you’re sending to foh.  An onboard output vu metre would be useful.

 

Sean Meredith-Jones

www.seanmeredithjones.com

 

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Unless the boys at Line-6 can come up with a "software" signal meter in Helix (or Stomp if it doesn't have one), the meter thing will have to come from your Audio Interface (or something else after the output). Cant hardly add a hardware meter to an already shipped product, but they may be building this as I type this. ; )

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22 hours ago, amsdenj said:

Use a blank preset with headphones and listen to the guitar played hard through all pickup combinations and see if you can hear any distortion. Digital clipping is not pleasant, so if you’re clipping, you’ll probably hear it. If there’s any doubt, compare the sound with pad on/off (adjusting for equal volume). If they sound the same, you’re probably not getting digital clipping.

 

Worthwhile as a quick check when you are in doubt and have no baseline from other tones or no DAW. Be aware though that changing your input pad is like changing your amp model drive dial, which may have an audible impact on your tone, especially if it is on the verge of breaking up. Thus you may think of hearing the onset of clipping, but It’s just amp distortion.

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6 minutes ago, MartinDorr said:

Be aware though that changing your input pad is like changing your amp model drive dial, which may have an audible impact on your tone, especially if it is on the verge of breaking up. Thus you may think of hearing the onset of clipping, but It’s just amp distortion.

 

That's why @amsdenj said "use a blank preset". (no effects, no amps)

The pad come before the AD conversion so it is extremely important not to clip at that stage. 

 

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It's actually pretty darn difficult to clip the input of the Helix or the Stomp. The max input level is like +16dBu. That's higher than what a lot of devices are even capable of outputting. Whether or not you want to use the input pad (or set the input level to line level on the Stomp) has more to do with how the modeling reacts to the signal you're sending. Now, certainly, if you're sending a line level signal, you'd want to have the input set to line level. But as far as guitar, it's really what sounds best.

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5 hours ago, phil_m said:

The max input level is like +16dBu.

I don't think so. According to my measurements Hx instrument level is 11dBu full scale and line level 19dBu FS.
It would be nice somebody can confirm it. I have no true RMS voltometer.

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The key thing is to keep most blocks at unity gain (bypass on/off doesn’t result in a big volume jump). This way you won’t get gain buildup in your signal chain that could result in digital clipping at the output, and you’ll be sending each block a signal that hopefully keeps it in its sweet spot, where it was designed to work best.

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On ‎5‎/‎14‎/‎2019 at 7:35 AM, zolko60 said:

I don't think so. According to my measurements Hx instrument level is 11dBu full scale and line level 19dBu FS.
It would be nice somebody can confirm it. I have no true RMS voltometer.

 

Hi - Im a bit confused with this.   dBFS (Full Scale) and dBu are not the same thing.  dBFS does have two meanings - one more related to electronics testing...but in the Audio world, dBFS usually referes to the digital environment.   Phils comment re =16dBu is an analog measure.  All Digital use of dBFS must be negative , ie, its not possible to exceed 0dBFS....

 

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Please don't be confused. Every AD and DA conversion takes place between dBFS scale and voltage. Voltage can be presented as V units or logaritmic dBu, dBV units with known reference.
Therefore for full scale digital signal (0dBFS) of given converter there is full scale dBu value.
+4dBu is profesional standard for line level signals. It requires some headroom. 14dB headroom is good practice. proposed by BBC (some british radio not Big Black ;) so lots of converters are +18dBu full scale.
Some manufacurers include that data in technical specification of their products. In case of Line6 you have to measure if interested.
There are calculators for V, dBu, dBV conversion: http://www.sengpielaudio.com/calculator-db-volt.htm

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I got the +16dBu rating from some other gear that uses the same A/D converters that the Helix uses. In reality, the Guitar In is probably a little higher than that because Line 6 has some proprietary circuitry that increases the dynamic range of that input from 114dB to 123dB. The other inputs should be rated at +20dBu.

 

I believe the main reason Line 6 doesn't publish this sort of data is simply because they believe (rightfully so, imo) that the vast majority of users 1) don't care and 2) don't really understand what it means. Also, it seems that the main use of such information is for people arguing about the superiority of one platform over another. They end up just being smokescreens.

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1 hour ago, phil_m said:

I got the +16dBu rating from some other gear that uses the same A/D converters that the Helix uses

You assume all gear based on the same converter chip has exact rating. I don't think so. Even Hx return inputs have two switchable full scale values.

 

1 hour ago, phil_m said:

Guitar In is probably a little higher than that because Line 6 has some proprietary circuitry that increases the dynamic range of that input from 114dB to 123dB.

No. Guitar input is exactly the same as Hx return inputs set to instrument level in terms of dynamic range and noise  performance. According to my RMAA measurements S/N ratio for any output/input loop is 110dB A weighted. If return inputs had 114dB and guitar input 123dB that measurements would indicate some difference and would be audible.

 

1 hour ago, phil_m said:

I believe the main reason Line 6 doesn't publish this sort of data is simply because they believe (rightfully so, imo) that the vast majority of users 1) don't care and 2) don't really understand what it means. Also, it seems that the main use of such information is for people arguing about the superiority of one platform over another.

I believe these two sentences contradict each other :D
I can show you  published specifications for far less valuable gear than Helix. If someone does not read, care or understand so his arguments are ether non existent or stupid. I have never seen an argument that +24dBu interface is better than +12dBu. All info I need is if I connect non clipping Helix via analog to another AD converter can iduce clipping and if return input is worse than guitar input when I want to connect another guitar.  These are the basics. I do not care if THD value is 0,00034 or 0,00152%
I personally think that the manufacturer that publishes specs is superior to one that doesn't. I still can understand the point Helix is sold as guitar modeler and guitarist are dumb "to the eleven" type of men. :D

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