Part 2 of "The ultimate IR, NEBULA, REAL DEAL test"

[Omega_Void]

If you push your power amp with Nebula, you will create so much saturation that it will create too much harmonics when you apply this program to an ALREADY saturated sound (the output of your virtual amp).

There is no virtual amp here. The preamp is physical, its output is recorded.

The poweramp and speaker are physical in one clip, and their distortions are added on top of the preamp, just as normally happens in a guitar rig.

In another clip the preamp goes through Nebula instead of any poweramp and cab.

What is hoped is that Nebula will reproduce the distortions from the poweramp and speakers, and add those distortions to the output of the preamp the same way the physical amp and cab did.

You appear to be saying it's a drawback that Nebula is expected to capture the saturation/compression characteristics of the poweramp and cab But that's what is wanted, it's the whole reason for using Nebula. If these effects were unwanted one could just stick with regular impulses.

 

[Skaldir]

Omega Void is correct!
Only when you use the poweramp out with a powersoak or something with the programs you get "double saturation". But in this case its supposed to be used with pre-amp outs.

But thanks anyway for your input Pipotron.
Some things have been very interesting to me.
Btw. you can reduce kernels to 1 in Nebula (playback side) in every program with more kernels. Not neccessary to capture it in Nat with 1 kernel. Just go in the kernels menu and slide the fader from max to 0. That way you can reduce kernels.
When I am back from holiday I will explore the Nebula playback smoothing a bit more. There is "smooth, linear, cubic.." as far as I remember. Sadly its documented nowhere what happens when you change. :/

 

[drew_drummer]

Unless I'm missing something he's talking about the extra saturation from the poweramp WHEN you capture the Nebula program - he's not talking about extra saturation coming from the preamp going into a power amp, then going into nebula.

???

 

[drew_drummer]

You appear to be saying it's a drawback that Nebula is expected to capture the saturation/compression characteristics of the poweramp and cab But that's what is wanted, it's the whole reason for using Nebula. If these effects were unwanted one could just stick with regular impulses.

And I'd disagree with this. The benefit for using nebula is to get dynamic frequency response across the whole spectrum. Where an IR is a static snapshot. The benefit it seems to me is not to be found in the usual application of Nebula - capturing compression characteristics of the power section.

The reason being... most amp sims also have a power section. So you're doubling up on the poweramp, adding extra squish.

IMHO, you should be using a very very linear power amp when taking your Nebula impulses using NAT.

I could be way off base. But this is how I've always thought of Nebula vis-a-vis, cab simulation.

Edit: I realise a real preamp was used for this test. But in general applications, I think people would be using amp sims with power sections with this stuff. It's worth investigating as a separate issue.

 

[Ermz]

I agree. Unicorn has a solid state power amp around, but all the test programs generated with it thus far have been 'less than ideal' at best. I'm unsure why this is, but for a final program release I would certainly hope that some transparent power amp options are provided, as I always record my amps from the speaker out, capturing the power amp.

In this test only the preamp signal of my JVM was used, and it sounds much worse and hairy, as the JVM relies heavily on its power section in order to create the smoothness and hugeness in its tone. If you're only capturing the preamp of an amp head, chances are you're only getting 50% of the picture.

 

[Omega_Void]

I agree. Unicorn has a solid state power amp around, but all the test programs generated with it thus far have been 'less than ideal' at best.

Frequency response of the loudspeaker drivers will differ with amplifier output impedance.

A solid-state poweramp designed for PA or hi-fi will have low distortion, but very low output impedance.

Solid-state guitar poweramps will have rather high output impedance, to better sound like tube amps. But they may not be designed for low distortion.

Transient response is also affected.

Low output impedance means the electrical control of the speaker is more accurate, so when current stops flowing in the voice coil, the coil stops moving faster.

High output impedance means when the current stops the speaker keeps moving. This is called overhang. It's most noticeable at the resonant frequency (around 110Hz for an OS Mesa IIRC).

This also applies when the current drops from one level to another. Basically, poweramps with high Z-out cause the speaker to store some of the energy from the signal, and release it again when the signal drops, so dynamics are smoothed out, giving a fuller but somewhat less detailed sound.

So, if you don't want to (or can't) disable poweramp simulation pre-Nebula, a clean poweramp is necessary, but it must have high Z-out or the speaker won't sound the way it does when driven by a guitar amp.

I'll add that keeping it clean by using low power levels isn't a solution. Speaker colouration can (depending on the speaker) change lot as cone excusions increase. An accurate cab model of cones that are hardly moving wouldn't be very satisfying .

 

[Skaldir]

The benefit it seems to me is not to be found in the usual application of Nebula - capturing compression characteristics of the power section.

I would like explain it in short words. The capturing of harmonics/saturation is not the only thing that happens.
The program also has 48 dynamic volume level steps that are played back according to the input volume. (preamp out volume or ampsim out volume)
So it also would be possible to only capture the level steps and leaving out the whole saturation characteristics like a static impulse. And you can decide that in the playback side of Nebula by reducing Kernels.

Edit: I realise a real preamp was used for this test. But in general applications, I think people would be using amp sims with power sections with this stuff.

Its the question what sounds better. A "sampled" power section from Nebula or an algorithmic coded one.




The real problem we have with the Nebula programs atm I think is only this additional high end. And its not only in my programs. It seems to be there in programs from other people too. I guess it has to do with the interpolation mode between the dynamic steps and frequency bands.

 

[Pipotron3000]

Thanks for reading my posts

I wish OwnHammer will post something about how he captured his cab impulses.
Did you listened to his Mills 412-GTR Acoustics Afterburner 4x12 • Celestion Vintage 30 #1 - Metal Full mix ? Impressive...
http://www.ownhammer.com/media/speak...-GTR_Mesa_V31/
I don't hear any highs trouble

May be you are right Unicorn about troubles related to the engine settings.
There is definitely something strange,may be asking on Nebula forum would help getting in touch with others Nebula programs makers

About the solid state vs tube amp, for sure the sound will be different.
I'm even totally convinced a big part of an all tube amp sound is more in the power amp saturation/compression and interaction with speakers than preamp...but this is another discussion
And i understand it is very cool to get the saturation/compression of a pushed hard tube power amp section...if you use only a preamp (my confusion).
@Omega_Void
I didn't seen Nebula test was running directly from preamp in Nebula, sorry
I thought it was double power amped by any mean (it could have explained a lot...).

Now it is clear it is not the problem, if preamp only was used as input.
I really don't understand the difference between real cab and Nebula on this test.
BTW the previous test REALLY impressed me
Nice job

The mystery still going on...

 

[HOFX]

Not to necromance, but this thread just saved me 75 E on Nebula. Thanks Andy Sneap Forum.

 

[Pipotron3000]

We were speaking about Nebula cab making, not using
If you buy Nebula and use OwnHammer or Kalthallen cabs, you get the BEST (and it is BEST, not best) cabs sim in the digital world.Period.

Now, we all know Nebula is a b*tch to use. I can't even track with it, i use zero latency cab sim (like NadIR) and replace it with Nebula afterward.

But hey, this is the best thing woundwise after the real thing. Even good cab sims like dynamic Axe FX ones don't hold a candle next to it.

After using good Nebula cabs, i would not even think to mix with an IR anymore.
May be a combination of NadIR and TPA-1 ?