Aliasing in the ICONS plugin? No oversampling? (Spoiler: it's a bug)

[DLC86]

Seeing the same thing on that preset (disabled everything but the amp) - I think it's related to the input boost?

View attachment 167141

With input boost off:
View attachment 167143

This doesn't seem to solve the issue here, same preset as above with input boost off... aliasing is reduced in level due to the lower gain but harmonics still clearly reflect back at 24 kHz


And btw, the fm9 seems to have the same issue too!
Input boost off:


Input boost on:


This surely wasn't the case before

EDIT: just for comparison, here's a spectrogram of the fm9 taken last september (it was a different amp though, the Plexi 100W Jumped IIRC).
As you can see harmonics don't reflect back at 24 kHz here.
Judging by the date of this screenshot, I was on FW 10.00 beta2 at the time, so the culprit must be some change made in following firmwares (10.00 stable or 11.00)

 

[davidespinosa]

Explain why this is needed or important.

That's a pretty rude thing to say for someone trying to learn about something new. Richard_G did it right. Dan Worrall is the man. Spreading knowledge to those looking to learn is the better option. Gate keeping and saying those kinds of things to people looking to learn is weird and strange.

Nice post, very helpful-The guy asked a question. I didn't know why either......................

No, MSS didn't ask a question.
He commanded us to explain, implying that aliasing tests are unimportant and unnecessary.

He could have said:
"Could someone please explain why aliasing is important in modelers ? Thanks !"

 

[AlbertA]

This doesn't seem to solve the issue here, same preset as above with input boost off... aliasing is reduced in level due to the lower gain but harmonics still clearly reflect back at 24 kHz
View attachment 167170

And btw, the fm9 seems to have the same issue too!
Input boost off:
View attachment 167171

Input boost on:
View attachment 167172

This surely wasn't the case before

EDIT: just for comparison, here's a spectrogram of the fm9 taken last september (it was a different amp though, the Plexi 100W Jumped IIRC).
As you can see harmonics don't reflect back at 24 kHz here.
Judging by the date of this screenshot, I was on FW 10.00 beta2 at the time, so the culprit must be some change made in following firmwares (10.00 stable or 11.00)
View attachment 167173

What's the range of the color map here? i.e. what is the dBFS value corresponding to black?

 

[DLC86]

What's the range of the color map here? i.e. what is the dBFS value corresponding to black?

-90 to 0 dBFS.
With plugin doctor set at -200 dB you're probably making the quantization noise visible and masking other signals.
Btw, there's also my online spectrogram generator available for free: https://shop.thetonescientist.com/pages/tts-spectrogram-generator

 

[AlbertA]

-90 to 0 dBFS.
With plugin doctor set at -200 dB you're probably making the quantization noise visible and masking other signals.
Btw, there's also my online spectrogram generator available for free: https://shop.thetonescientist.com/pages/tts-spectrogram-generator

Yes, that was just a quick capture, I usually set it to -60dBFS

 

[Randalljax]

Can anyone actually hear this though
Because if it’s been in FM9 and it’s in the AM4 one has to think it’s been there since launch ?

 

[Johnkenn]

Can anyone actually hear this though
Because if it’s been in FM9 and it’s in the AM4 one has to think it’s been there since launch ?

If I put plugs (effects/delays) in Bluecat patchwork and then use oversampling in that, I can hear the top end get more pleasant. Don’t think it’s confirmation bias. Need to try icons in it with oversampling. Don’t know if that is the same thing as having control of it within the plugin, but gonna see if I hear any difference.

 

[blandified]

Can anyone actually hear this though
Because if it’s been in FM9 and it’s in the AM4 one has to think it’s been there since launch ?

According to DLC, he did this aliasing test on the FM9 a year ago and it wasn't showing this issue, so it wasn't there since launch but was introduced at some point.

 

[DLC86]

According to DLC, he did this aliasing test on the FM9 a year ago and it wasn't showing this issue, so it wasn't there since launch but was introduced at some point.

Yep, actually just a few months ago, it was introduced somewhere between official FW10.00 and FW11.00 on the FM9, or corresponding firmwares on other devices (since it's both on the fm9 and am4, I suspect all devices might be affected).

 

[vangrieg]

just for comparison, here's a spectrogram of the fm9 taken last september

Well judging by those images, there’s more aliasing regardless of input boost.

 

[FractalAudio]

This bug exists in all products. Overdriving the input of the Amp block, whether using the built-in boosts or externally can result in excessive aliasing.

I fixed the bug yesterday. The particular preset in question with the Dweezil's Bassguy model and the boosts now exhibits 35 dB less aliasing.

We need to do some internal testing before releasing public versions. We should have fixes ready next week.

 

[MayPRS]

This bug exists in all products. Overdriving the input of the Amp block, whether using the built-in boosts or externally can result in excessive aliasing.

I fixed the bug yesterday. The particular preset in question with the Dweezil's Bassguy model and the boosts now exhibits 35 dB less aliasing.

We need to do some internal testing before releasing public versions. We should have fixes ready next week.

Always on top of his game! Thanks Cliff!

 

[taracatac]

This has been an interesting read, prior to this thread, I knew nothing about aliasing. That being said, can anyone actually hear it? I have an AF3 and FM3, and I haven't knowingly heard aliasing. Maybe I haven't hit the conditions that cause it.

 

[vangrieg]

That being said, can anyone actually hear it?

Everybody can. Not everybody can recognize it for what it is and point to it saying, this is aliasing.

In most extreme manifestations, it sounds like something metallic, or on lower frequencies maybe like something's out of tune. I can't say I can recognize it in more subtle cases, but when something produces a lot of aliasing, I just get tired listening to it over time, if we're talking guitar processors I literally play less.

Generally, it's noise and distortion. You have more aliasing with distorted tones, so it's somewhat masked in other harmonics. But it doesn't sound right because it's unrelated to actual notes you're playing. So something's just not right...

 

[taracatac]

Oh, ok. That makes sense.

 

[FractalAudio]

This has been an interesting read, prior to this thread, I knew nothing about aliasing. That being said, can anyone actually hear it? I have an AF3 and FM3, and I haven't knowingly heard aliasing. Maybe I haven't hit the conditions that cause it.

In this particular case probably not. The aliasing occurs mainly for high frequency input and the aliasing itself is concentrated at high frequencies.

Once you put a cab in there, which rolls off rapidly above 5 KHz, and account for the fact that most of us can't hear much beyond 10 KHz the aliasing isn't audible.

However, ideally it shouldn't be there.

 

[yek]

Metallic aliasing, more distortion, more harmonics? Hmm, must be nice. Can we get a control to dial in the amount of aliasing please?

 

[TheUser]

Everybody can. Not everybody can recognize it for what it is and point to it saying, this is aliasing.

In most extreme manifestations, it sounds like something metallic, or on lower frequencies maybe like something's out of tune. I can't say I can recognize it in more subtle cases, but when something produces a lot of aliasing, I just get tired listening to it over time, if we're talking guitar processors I literally play less.

Generally, it's noise and distortion. You have more aliasing with distorted tones, so it's somewhat masked in other harmonics. But it doesn't sound right because it's unrelated to actual notes you're playing. So something's just not right...

See, my trick is to always play out of tune. That way you can't tell if it's aliasing, or just my terrible skill.

 

[vangrieg]

Metallic aliasing, more distortion, more harmonics? Hmm, must be nice. Can we get a control to dial in the amount of aliasing please?

I can point you to some plugins that have tons of this bliss

 

[FractalAudio]

BTW, there's also a bug in the Drive block that causes excessive aliasing for some models. That was fixed a couple days ago and will be in the next release.