Cliff, Oh My...The Swirl!

B

Boogieman

Inspired
So I have not been playing a lot for quite some time. Decided to load up 15b and give it a drive tonight. I went through a couple of my Fender/Marshall presets and was astonished at the dynamic swirl I was hearing. Absolutely amazing in that it sounds like some of my tube amps have (and do) when they are performing at their best. Swirl is almost impossible to get if an amp does not have it in the first place, so I can't even imagine how the AFXII can do this. As I recall (Cliff has forgotten more than I ever knew about tube amps), the swirl has to do with the overdriven phase-inverter interacting with the output stage as it goes in and out of clipping. Regardless, it is so amazing I spent the entire night relishing in the magnificence of the swirl as my notes rang out. I'm in awe of this machine and the brains behind it.

Thanks Cliff and crew for what you do.

boogie out
 
Yes, it's related to the PI clipping vs. the grids clipping vs the plates clipping and then all the bias point changes that occur along with that. You have some control over it with the Power Amp Bias parameter.
 
Boogieman said:
So I have not been playing a lot for quite some time. Decided to load up 15b and give it a drive tonight. I went through a couple of my Fender/Marshall presets and was astonished at the dynamic swirl I was hearing. Absolutely amazing in that it sounds like some of my tube amps have (and do) when they are performing at their best. Swirl is almost impossible to get if an amp does not have it in the first place, so I can't even imagine how the AFXII can do this. As I recall (Cliff has forgotten more than I ever knew about tube amps), the swirl has to do with the overdriven phase-inverter interacting with the output stage as it goes in and out of clipping. Regardless, it is so amazing I spent the entire night relishing in the magnificence of the swirl as my notes rang out. I'm in awe of this machine and the brains behind it.

Thanks Cliff and crew for what you do.

boogie out
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Ok... WTF is swirl?
 
Good amps have it.

One of the very best amps I've ever played (and often miss), the JCA Circuits GR 1.6 had the most wonderful swirl to it.

The Savage Glas 30 has it as well.

I find it hard to explain. You have to hear and feel it. But I agree with the OP that FW15b has it.
 
Karl Houseknecht said:
It's like "zhuzzzsh". It's organic, three-dimensional, and touch sensitive. ;)

I have absolutely no idea either.
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:lol now that I know what causes it the term is pretty silly. Like most guitar players that feel the need to invent or assign a word to describe a sound or feel to more easily convey it. InterMod is nothing more then two frequencies combining together to create a third. In the process of a pair of notes that are being bent the product third will sound like it's "flipping" or "swirling" for lack of better terms as it is being moved or "bent" through that range.
 
Sometimes just a tube change does it. In my old Mesa Mk IV, I changed power tubes many times. When I popped in a set of Winged C 6L6's, got the swirl.

It's almost like when you don't have it, the sound stays at the speaker...as far as locating where it coming from. When you get the 'swirl', the sound envelops you, becomes '3D', doesn't stay stuck at the speaker.

(I swear I wasn't smoking anything at the time)
 
FractalAudio said:
It's not IM distortion. It's variable phase shift due to bias shifting.
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Lol. Sounds like something Dr Brown would say. And the Axe rocks because of it!
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Sent from my iPhone using Tapatalk
 
scorch said:
Sometimes just a tube change does it. In my old Mesa Mk IV, I changed power tubes many times. When I popped in a set of Winged C 6L6's, got the swirl.

It's almost like when you don't have it, the sound stays at the speaker...as far as locating where it coming from. When you get the 'swirl', the sound envelops you, becomes '3D', doesn't stay stuck at the speaker.

(I swear I wasn't smoking anything at the time)
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That's because the tubes were slightly mismatched. The Power Amp Bias parameter controls the amount of power tube mismatch. A little bit of mismatch is a good thing. Too much, though, can cause excessive transformer distortion since there will be a quiescent current through the OT at idle.
 
FractalAudio said:
It's not IM distortion. It's variable phase shift due to bias shifting.
Click to expand...

I thought 'swirl' was one of those flowery tone terms only doctors and lawyers use on the internet when they're trading overpriced boutique bedroom amps. Now that I know it's real I'll describe it like this (though I'm still not sure I've ever heard this).
 
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