Dumble note flipping caught on sound file!

[talbany]

The Phenomenon is known as Swirl

Described as a dynamically-changing, slightly "phasey" sound as a note or chord decays, which is common to some tube amps. Typically, "swirl" is caused by a midrange "dip" or varying duty-cycle change in a clipped square wave that changes position as the note decays, giving a sort of mild phase shifter effect.

What happens is that first the phase inverter or output stage clips and produces a flat square wave. As the note decays, the signal level decreases, and the midrange frequencies start getting "unclipped" (either by the fact that their frequency band level is lower, or by phase cancellations due to the unequal phase shift with respect to frequency caused by tone controls and other RC phase shifts that occur in a gain stage) and show up as a "dip" in the top of the square wave, which will move back and forth along the top as the fundamental and other harmonics shift the operating point. Even if the clipping ratio isn't extreme enough to show the "dip" on the scope, the duty-cycle of the square wave will usually be dynamically changing as well.

Since the preamp stages are all AC-coupled to each other, the operating point shifts as the signal gets smaller, due to slight "blocking" distortion, where the gain stage clamps the top peak to a point slightly above it's cathode voltage, while allowing the wave to still increase in the negative direction. As the signal decays, it shifts upward and changes the duty-cycle of the clipping. It is this ever-changing shifting of the operating point that causes the "swirl" effect. The trick to good "swirl" is in the correct staging of the gain and frequency breakpoints of each gain stage in the amp, particularly in the phase inverter and output stage.

A similar effect can be caused by too much drive from the phase inverter to the output tubes. As the note decays, a riding "buzz" can be heard coming in and out. This is crossover distortion aggravated by too much signal swing to the output tube grids. Reducing the signal levels at the output of the phase inverter will cure this.

Another cause of a "swirly" sound is a parasitic oscillation that is riding on the output signal, causing intermodulation distortion.

Hope This clarifys things!!
AXE Note Flipping..

Tony

[Max]

The Phenomenon is known as Swirl

Hi Tony,

Hope you are well!

Which one precisely of the different linguistic methaphors ("note flipping", "straining", "blooming" etc.) discussed here in this thread do you call "the phenomenon"?

Or asking in a different way:

As you will be aware "swirl" is a linguistic metaphor by wich you try to describe a certain kind of your perception of certain guitar tones. So to understand what kind of perception you try to describe by this metaphor I would like to ask you in what part of what clip precisely (from 1:13 to 1:17 as an example) posted here in this thread do you perceive "the phenomenon" you try to describe by using the linguistic metaphor "swirl"?

All the best and a have great weekend

Max

[talbany]

So you know I didn't just make this up.. Here is a thread on TGP from others who have heard this before, but don't really know where it comes from or how and why it's being generated... They refer to it as Swirly or Woosh/ Zhoosh sound..Of coarse the thread turns into a bit of a mess at the end.. I think what some are hearing here and on TGP is some form of this swirl/note flip Phenomenon...IMO


http://www.thegearpage.net/board/showth ... ght=zhoosh

Tony

Max
I am well and hope you are too!!
Depending on how the listener/Player perceives this Phenomenon I suppose it could possibly take the form of all three anomalies ( linguistic metaphors).. note flipping or swirl "straining "blooming or whoosh as some call it...

Disclaimer: Without actually scoping and measuring and listening to the amp while the effect is taking place it's IMHO virtually impossible to say with 100% certainty what is actually taking place by listening to a clip alone..In all honesty it's really just an educated guess..

[Luddy]

I have wondered about this sound. I had thought it had the same sound as when feedback starts to occur. But now I think it has a different sound than that. I can get it at bedroom levels with my Ceriatone OTS. The term "note flipping" is a little misleading, although I do hear the effect as an octave jump. If the octave jump happens consistently with everyone, then I think the name should reflect that. I should mention that for a given note, even numbered harmonics represent the octave.

[stratcat62]

I've followed this thread and decided to put my 2 cents in. I've always considered the term 'note flipping' to represent the vocal quality that some of the Dumble amps seem to be especially good at producing, where it is doing something very phasey. I hear it most dramatically in "Rugged Road", another Ford track, "Village Blues", and maybe the single best example in a clip of a Brown Note Blue Monkey. :12-:20 http://www.youtube.com/watch?v=g1E0Oy6C6Ww

I hear the 'bloom' or slight harmonic thing in many amps, including my Fenders though it may come easier in Dumbles; you can coax it from the amp holding a single note. The vocal and vowel sounds that only seem to occur during runs, are in my opinion, much more impressive and simply cool sounding. I think it mostly comes from the way you articulate and attack notes, but some of the Dumble/Dumble-style amps (especially the Ojai amp) seem particularly suited to bring that quality out.

[qtone]

Note bloom flipped note I always thought that was note saturation
where it sustains into the harmonic.

It can be done with chords too
ie playing a triad and moving position in front of the amp

Stevie Ray used to do this standing out front of the rig
he would get the chord into saturation and move his position
to the amps and the chord would bloom through first inversion
second inversion third inversion....

Flipping the 3rd atop or the 5th atop while during saturation
or feedback...

Stevie said the amp could get up and run away with you
if you were not careful.

Saturation of one note blooming into the harmonic .
If your playing one note it goes into the saturated
almost bell like whistle but in a great way...

Like the clips posted....
It can be done holding chords or triads as well and simply
moving the guitar around or position of your body facing the speakers...

I use the westbury tube boost pedal and it will do this same thing
through a solid state amp or tube amp.

location or proximity to the amp with guitar and position
of guitar to amp speaker will play a role in this ....

Its a neat thing to behold.

[Bob Simpson]

The Phenomenon is known as Swirl

I always called it Fred...

Bob

[talbany]

The Phenomenon is known as Swirl

I always called it Fred...

Bob

Bob
Technical clarification.. FRED only takes place in amps that swril covered in red tolex only..

Tony

[Bob Simpson]

The Phenomenon is known as Swirl

I always called it Fred...

Bob

Bob
Technical clarification.. FRED only takes place in amps that swril covered in red tolex only..

Tony

Thanks, Tony! I remember now...

[Harald.Nowak]

Interesting thought, but from my understanding of this it's preamp sag.

I've measured the preamp voltages under load. With a 400Hz sine wave input and OD engaged, master on 0 on a dummy load. The voltage on V1 plate drops 20-30V with signal as opposed to without. Turning up the master makes no difference.

It's also interesting to watch the sine wave changes as you raise and lower the input signal. The peak AC voltage doesn't change much, but the shape of the distortion does.

This all makes since when you realize that lower preamp voltages tend to sound duller, higher voltages have more complex harmonic structure.

Very interesting discussion.

Bob, does this observed preamp sag (with MV set to 0) happen in all your amps - or to the "public": who else can confirm these values? I ask, because in my Amp (which is not exactly a Dumble while its Clean+OD stage and its power supply are very similar) nothing the likes happens:
no matter how hard I strum, the voltages at B4 and B5 do never go lower down than 1-3V; sometimes they even go up (depending on the OD gain setting). It a low plate - all 100k/1.5k btw.
So - while I recognize that my Amp is different in some places - e.g. the dropping res which was part of this discussion is only 10k, not 22k - I figure, I should at least have something around 10-15 V sag then (half the value observed by you); which cannot be observed! My capacitors are typical for Dumble Amps by the way.
So ... any other observations on this?
Thanks!

[LeftyStrat]

I haven't built a Dumble yet, but I've spent a lot of time with my scope trying to get a better understanding of what is going on in a Trainwreck clone. I think Tony's response is dead on.

Ken Fischer does it a little differently in his amps, but the goal is the same. You can get a highly animated waveform, that responds well to playing style, with amplitude dependent asymmetrical clipping.

In the synth world, you can vary the duty cycle of a pulse wave to animate the sound. At 50% duty cycle, you have a square wave with no even harmonics. As you deviate from this it sounds a lot like phasing.

The way Ken Fischer accomplished this was to use that third-stage as an asymmetrical clipper. However, it is tuned such that first the output tubes clip, then the PI, and then the asymmetry starts kicking in.

If you clip only one side of the waveform, since it is AC coupled to the next stage, you shift the crossing points of the waveform and produce something similar to pulse width modulation.

Now there are other ways to do this. Power supply sag will shift the operating point of a tube stage, such that it starts to clip on only one side. The PI can be driven in and out of balance. In a distortion pedal you could probably do it with an envelope follower introducing a DC offset before being sent to a clipping stage.

Oh, and thanks for all the clips. Very inspirational for my own ongoing build.

[Harald.Nowak]

Ken Fischer does it a little differently in his amps, but the goal is the same. You can get a highly animated waveform, that responds well to playing style, with amplitude dependent asymmetrical clipping.
...
The way Ken Fischer accomplished this was to use that third-stage as an asymmetrical clipper. However, it is tuned such that first the output tubes clip, then the PI, and then the asymmetry starts kicking in.

Interesting! Reminds me heavily of my late 1974 Traynor YBA-1 - its 3rd stage also does asymmetrical clipping (68K Anode, 6.8k Cathode, clips rather early asymmetrically) and I LOVE that sound - it makes the attack very crisp! However I also still want to find out whether or not there is a decent amount (say 10V or more) of B4 and B5 sag in a Dumble style preamp.