Table: amp settings, depending on power amp and speaker

[VegasDude]

This is awesome. Thanks so much!!

 

[lauke-lux]

Regarding this post https://forum.fractalaudio.com/threads/axe-fx-iii-with-real-cab-vs-the-real-thing.191689/page-2
Edit :
"Use a good power amp and try again. Those Powerstage things are budget Class-D amplifiers in a shiny box. The damping factor on them is quite poor at high frequencies."
"
" A lot of it is about transient energy storage. A tube amp stores a LOT of energy. Take a typical 100W tube amp like a Diezel. It will typically have 220uF of reservoir capacitance and a B+ of 450V. The energy stored is 22.3 Joules!!!
Now take a typical consumer Class-D "500W" power amp (actual continuous power about 100W). They usually have voltage rails around 50V and 680uF or so of capacitance. The energy stored (assuming bipolar supplies) is 1.7 Joules.
The tube amp has over 13 times the energy storage. So those palm mute transients are reproduced accurately. The Class-D amp runs out of gas.
For example, if your transient duration is, say, 100ms, and you're pushing a full 100W then the energy required is 10 Joules. The Class-D amp simply can't do it.
It's one of my pet peeves. People use cheap, low-end, consumer grade Class-D power amps and then make bold proclamations that the models don't sound as good as the real amp without understanding even a lick of the physics involved.
I put an Axe-Fx through a Crown X2 once and it Marty McFly'd me."


Does the table hereabove needs an update or clarification? To my understanding there is a different behavior between class A/B SS PA and class D SS PA, and even between "low power storage class D SS PA and bigger Class D PA.

Also, should I understand that FOH must be considered as SS PA plus FRFR speaker?

Thanks a lot for this thread.

 

[yek]

Does the table hereabove needs an update or clarification?

Nope.

And FOH is the same as Direct / FRFR speaker only.

 

[James Freeman]

Bump

NOTE: The SS PA + Cab Mode is NOT intended for use with “current drive” power amps, i.e. tube power amps, Class-D current feedback amps, etc

Would that be most modern Class-D amps?
Let's take the very common Behringer A800 which is Class-D but does it use current feedback?

 

[FractalAudio]

Bump



Would that be most modern Class-D amps?
Let's take the very common Behringer A800 which is Class-D but does it use current feedback?

No idea, you'd have to ask Behringer. Most modern Class-D amps are voltage feedback as AFAIK.

 

[jellodog]

Would that be most modern Class-D amps?

Current drive amps tend to be the ones aimed at guitar amplification only and usually claim to be tube-like, for example Quilter.

Most other general purpose SS PA designs tend not to be current drive.

 

[Vecordia]

@yek After I review this with @FractalAudio, would you mind if I consider this for inclusion it in the appendix of the Blocks Guide? I'd color-code it to highlight non-default settings.

Hi there. I not able find the table in the Blocks Guide. Is it because maybe it was not included in the end? I may be looking at the wrong document, part or revision. Thanks!