Taming Amp Simulation

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Taming Amp Simulation

Post by hhart »

Hello,

i would like to share my experience in working with amp sims and get some tipps.

My problem:
I've tried several amp sims to get the sound I like and ended up with Neural DSP plugins (all with the same issue).

Especially with low gain sounds, i have the problem that the gain distortion as soon as the amp kicks in jumps unnaturally right into your face. It just sounds too "harsh", "fizzy" and "direct".
If I compare it to a real amp and cabinet, I feel the distortion way more "smooth", "creamy" and "gentle", even at high gain.

I cant find a way to tame this down in amp sims. I tried several IRs, many many mics and mic positions, but the distortion still does not feel "molded" in the signal.
Maybe someone can imagine what I'm talking about.

So my questions:
1. Too get rid of this annoying harshness I often end up EQing very hard. High Shelf in the 4k - 8k and often Low Passing down to 4k. Of course this totally kills the brilliance of my sound. Is it normal that an amp sim needs that much Low Passing?

2. One Plugin of Neural DSP (Abasi) has a Low Pass switch in front of the amp. By activating this, i get a way more natural result. But it feels wrong to low pass a DI Signal. Has anyone experience how to EQ a DI Signal to work best with amp sims?

All I'm searching for is a nice rolloff in the Highs without loosing too much brilliance.

Thank you in advance
hhart
Posts: 2 Joined: Wed Jan 25, 2023 1:21 am

Re: Taming Amp Simulation

Post by Wonks »

Hi and welcome.

It sounds to me that you haven’t got the cab sim turned on, as the sort of filtering is what would happen naturally when the amp signal is passed through a guitar speaker.

Looking at the manual for the SLO100 (which I assume is fairly typical in the cab control section for a the amps), there’s an on/off switch for the cab sim section.

But you say you’ve messed about with changing mics and mic positions to no good effect. Did the sound change at all? I’m sure that you could still change the mic positions with the cab sim off.

Assuming the cab sim is on and working, then what you could be hearing is either an inaccurate cab/mic model or just the sound that the amp actually makes through the speaker when you’ve a mic pressed up against it.

You don’t play guitar with your ear pressed against the speaker hearing almost all direct sound. You hear a far less direct sound in the room, with the room reflections smoothing off some of the harsher edges and some sound radiating from the cabinet itself. So definitely use some reverb after the cab sim, not just reverb (if any) on the amp.

Slightly broken-up sounds can often sound harsh as there is only an edge of overdrive and the signal is still very dynamic as you haven’t got close to the point where the sound is naturally compressed. So some compression after the sim should help. Something with a very fast attack will help curb the louder transients.

Open-backed cabs sound different to closed-back cabs as an open-backed cab projects a lot more sound from the rear, so you get a lot more reflected sound in the room. I don’t know what amps you’ve got, but playing an open-backed Fender Deluxe in a room certainly sounds a lot different to putting your ear up to a speaker in a 4x12” cab.

Whilst close-miking is typical for recording, it’s also fairly common to use a couple of mics, say an SM57 and a ribbon like a Royer 121, and to EQ and blend the results as the ribbon has a smoother top end without the presence boost the SM57 has. It’s also common to use a more distant room mic as well, which all helps smooth out the top end.

But it really comes down to how it sounds in the mix, as we know a miked-up amp doesn’t sound that close to the sound we hear in the room when playing it.

I’ve forgotten to mention what guitar you are using? A Strat or Tele is going to be a lot brighter than a humbucker-equipped guitar, and a single coil’s slightly driven sounds will sound more spikey than a humbuckers.

And that low pass filter in the way in you talked about? It’s very common. It’s called your guitar’s tone control! :D

Also, if you are using a very short, very low capacitance guitar just when recording, using your normal length lead might help roll off some of the very high end going into the amp sim.
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Re: Taming Amp Simulation

Post by hhart »

Thank you very much for this detailed response.

Wonks wrote: Wed Jan 25, 2023 8:22 am It sounds to me that you haven’t got the cab sim turned on, as the sort of filtering is what would happen naturally when the amp signal is passed through a guitar speaker.

Looking at the manual for the SLO100 (which I assume is fairly typical in the cab control section for a the amps), there’s an on/off switch for the cab sim section.

Yes, totally what i mean. But i have it turned on. But the filtering does not sound naturally. I tried many different ones. Each time I feel that there has to be more filtering. So much, that I would like to chain two cab sims after another. But that should not be the way to go I think. I must be missing something else with my harshness.

Wonks wrote: Wed Jan 25, 2023 8:22 am But you say you’ve messed about with changing mics and mic positions to no good effect. Did the sound change at all? I’m sure that you could still change the mic positions with the cab sim off.

Yes the sound changes drastically. The pure amp signal is of course useless without the cab activated.

Wonks wrote: Wed Jan 25, 2023 8:22 am Assuming the cab sim is on and working, then what you could be hearing is either an inaccurate cab/mic model or just the sound that the amp actually makes through the speaker when you’ve a mic pressed up against it.

You don’t play guitar with your ear pressed against the speaker hearing almost all direct sound. You hear a far less direct sound in the room, with the room reflections smoothing off some of the harsher edges and some sound radiating from the cabinet itself. So definitely use some reverb after the cab sim, not just reverb (if any) on the amp.

Thats a great tip. I dont want to muddy out my tone with to much of reverb, but what you are saying totally makes sense. I think the reverb can be the solution to a certain amount. I'll give it a try.

Wonks wrote: Wed Jan 25, 2023 8:22 am Slightly broken-up sounds can often sound harsh as there is only an edge of overdrive and the signal is still very dynamic as you haven’t got close to the point where the sound is naturally compressed. So some compression after the sim should help. Something with a very fast attack will help curb the louder transients.

Interesting point. Where do you mean to put the compression. After the amp and before the cab? Or compressing it after the full simulation.
I feel like in every single amp sim this edge of overdrive is very absolute. So if you reach a certain threshold with parts of the signal. The overdrive kicks in instantly. There is no fluid transition between the states. And that feels more like digital artifacts, than a smooth drive. You know what i mean?

Wonks wrote: Wed Jan 25, 2023 8:22 am Open-backed cabs sound different to closed-back cabs as an open-backed cab projects a lot more sound from the rear, so you get a lot more reflected sound in the room. I don’t know what amps you’ve got, but playing an open-backed Fender Deluxe in a room certainly sounds a lot different to putting your ear up to a speaker in a 4x12” cab.

Great thing to think about. Thank you.

Wonks wrote: Wed Jan 25, 2023 8:22 am Whilst close-miking is typical for recording, it’s also fairly common to use a couple of mics, say an SM57 and a ribbon like a Royer 121, and to EQ and blend the results as the ribbon has a smoother top end without the presence boost the SM57 has. It’s also common to use a more distant room mic as well, which all helps smooth out the top end.

Yes. The ribbon does exactly the type of rolloff I'm looking for. But i don't get the point with the more distant room mic. My experience with cab sims shows that the top is mostly affected by moving the mic horizontally away from the center. Pushing it back mostly affects the low end for me. Am i doing something wrong?

Wonks wrote: Wed Jan 25, 2023 8:22 am But it really comes down to how it sounds in the mix, as we know a miked-up amp doesn’t sound that close to the sound we hear in the room when playing it.

Totally agree. I think ive got some sounds that are very smooth in the mix. What im searching for is a guitar tone that can stand for it's own. Without other instruments to cut through. So a nearly clean, but still saturated tone. So at the edge of breakup. But all im really getting is too much harshness, than a creamy tone for this. Almost sounds like an error.

Wonks wrote: Wed Jan 25, 2023 8:22 am I’ve forgotten to mention what guitar you are using? A Strat or Tele is going to be a lot brighter than a humbucker-equipped guitar, and a single coil’s slightly driven sounds will sound more spikey than a humbuckers.

I tried several approaches. The humbuckers are really my way to go. Tried it with a single coil in comparison and it got (of course) worse.

Wonks wrote: Wed Jan 25, 2023 8:22 am And that low pass filter in the way in you talked about? It’s very common. It’s called your guitar’s tone control! :D

Never thought about it in this way.

Wonks wrote: Wed Jan 25, 2023 8:22 am Also, if you are using a very short, very low capacitance guitar just when recording, using your normal length lead might help roll off some of the very high end going into the amp sim.

unfortunatelly i don't understand that point.
hhart
Posts: 2 Joined: Wed Jan 25, 2023 1:21 am

Re: Taming Amp Simulation

Post by Wonks »

Guitar lead length - the longer the lead, the more capacitance the lead has and that capacitance will roll off the top end of the guitar signal.

And whilst a lot of guitar leads have a fairly average capacitance value per unit length, some are made with a value that's about half the average value.

We are used to hearing the sound of out guitars with a certain length of lead connected, so using a longer lead will make it sound a bit duller, and a shorter lead a bit brighter. A low capacitance lead will allow a long 30' lead to sound like a typical 15' lead, but also, if you have say a 6' low capacitance lead you picked up for when recording at home into an audio interface, your guitar sound could be a lot brighter.

Compressor - put the compressor after the amp+cab sim so its working on the output signal from that.

Distant room mic - the further away from the amp the mic is, the greater the amount of reflected sound the mic is going to pick up, so it's going to sound more like you hear it in the room when playing. However it will depend on the room the impulse was recorded in as to how much moving a mic away will affect the sound. In a very dry room with lots of acoustic treatment, maybe not that much as compared to a room with a hard floor and walls .

It will also depend on whether they are modelling the effect of the mic position or using impulse responses and morphing between two or more actual positions.

Amp gain sudden distortion onset - I've no idea how these neural sims work. They obviously use IRs for the cabs but 'Neural capture' for the amps, which could mean anything. It does sound like they are either changing between IRs that have too much of a gap in gain, or their general modelling program is swapping between clean and overdriven modes too quickly. Hard to tell exactly what the issue might be without hearing some examples.

I've only heard the Neural Cortex (not the DSP versions) being used on YouTube and the sounds seem pretty natural to me on that. The Studio Rats YT channel features the Quad Cortex quite heavily. I don't know if it could give you any helpful ideas.

https://www.youtube.com/results?search_ ... uad+cortex

One option on the sound might be to duplicate the track, roll off the treble on one track and then balance the two track's volumes to get a better mix of treble. Or try heavily EQing and compressing one track and leave the other as-is and again balancing the volumes to get a better overall sound.
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Re: Taming Amp Simulation

Post by Wonks »

One other consideration is the signal level going into the amp sim. I don't know if Neural DSP have a recommended signal level, but it could possibly be you're hitting it too hard. Have you tried reducing the input signal level to see if it makes a difference?

I know that modelled hardware units like compressors work best if the signal level going in is equivalent to the level they would see if they were actual hardware units - but I know it's not always obvious exactly what that should be within a DAW. However it's not going to be a signal that's peaking at just under 0dBFS.
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Re: Taming Amp Simulation

Post by Wonks »

You could also check to see if the amp output level has an affect on the sound from the cab IRs. Without knowing exactly how they've captured the IRs and at what volume(s) going through the speakers when they did so, you can only try things out and see if reducing on increasing the volume level to the speaker IR and adjusting the amp sim's output level with another plug-in (to keep a similar overall volume) has any affect on the sound.

Once you start to drive a speaker hard, you are going to get some compression and a different sound to that of the speaker given a low power signal. They may or may not have modelled/sampled that.
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