Your chance to make me buy an AXE FX II!

ok. here you go. AxeFx Ultra from my practice rig. (FWIW, consider the AxeFx II does this and more, and for some things, better.) this is pretty lo-fi iPad 2 video/audio, but gets the idea across. Threw it together real quick, as much an exercise in going thru the process of doing an iPad video and uploading to Dropbox as I'd never done that before.

[video]https://www.dropbox.com/s/yg5sl73p7ccckn0/IMG_1305122105360.mov[/video]
 
clarky said:
wow.... a lot of negative vibes in here....

Velokki - any kind of pitch shifting in real time with a bass if you are playing low notes and shifting upwards will always be difficult
this is because the frequency of very low notes takes longer to detect
you're better off playing an octave up and adding the octave below because it'll track better..
if it's 5ths you're after, I'd add -12 and -5 together so you hear the octave you're playing in, and the octave and 5th below
the Axe's pitch shifting is about as good as it gets when it comes to real-time shifting / harmonising...
Click to expand...

Though I've never found the pitch shifting to present a functional problem for bass, I do agree with clarky here with respect to low note tracking the lowest notes on a bass. FWIW I've owned the Digitech whammy and TC Gforce and found them to be slightly better than the AxeFx ONLY with regards to shifting up these lowest notes, but otherwise prefer the AxeFx shifting overall in terms of flexibility and overall tone. The Gforce has a global bass mode for tracking which probably helps quite a bit with performance. Again, though, I've never found the pitch shifter prohibitive creatively or in performance use. It may not be fine tuned for low bass notes, though (certainly a presumption on my part).
 
clarky said:
Velokki - any kind of pitch shifting in real time with a bass if you are playing low notes and shifting upwards will always be difficult
this is because the frequency of very low notes takes longer to detect
Click to expand...

I may be wrong, but... I think this would only apply to intelligent pitch shifting. Does fixed pitch shifting/harmonizing need to detect the note, or is it just applying a fixed ratio?
 
it's all kinds of pitch shifting
before the note to be added, can be added, the note you are playing needs to be 'discovered'
higher notes have a higher frequency.
this means that there are more cycles per second to measure
for example.. A above mid-C is 440Hz..
although I have no idea how many cycles of the waveform are needed to measure and determine pitch
compare that to the low B of a 7-string bass.. which is just 31Hz..
each cycle is therefore much further apart in time so it takes much longer to detect the pitch..
so for real-time pitch shifting/ harmonisation, very low notes will always take longer and may not be quite so stable..
offline / non-real-time is the only way to nail this properly.. but you won't be doing that on stage.. lol..

that's why [if you want to hear very low notes] you're better off playing high and shifting low
there will be a point where playing low-ish and shifting high works pretty good..
I don't have a bass so I personally don't know where that area is..
the low E on a 6 string guitar tuned concert is only 82Hz.. so even that may be a little slow..

Simeon came up with a super clever trick to overcome the lag using [I think] an ADSR to allow the original unshifted pick attack to sound when the shifter is used with mix=100..
thereby filling the lil' space cause by the delay as the shifter is figuring out the pitch
so as a player, it feels more immediate...
very smart fella..
 
Maybe Cliff can chime in (since he has written some pretty kick ass pitch shifting algorithms), but I think the only time you need to detect what note you are playing is if you are doing intelligent (scalar) shifting and the intervals will change depending on your input note.

Put it this way, if I play a note - any note - and want to take it up an octave, I need to double the frequency. If I want to go down an octave, I need to halve it. In the old days, you could achieve this effect by running your tape at double (or half) speed and your pitch would change accordingly, no matter if it was the low B on a 5 string bass or a piccollo. The algorithm for the notes in between the octaves is pretty straightforward (Google suggests a scaling factor of 2^(n/12) where n is the number of semitones you want to shift), but the point is the only time this scaling changes based on the input frequency is if you need to change n (i.e. to chose a major or minor third interval for that Iron Maiden riff)

Not trying to be pedantic Clarky, and I admit I could be wrong; I just find this stuff fascinating and if I have a skewed idea of how this works I would rather know :)
 
ahh... maybe you should double / half the speed of your Axe-II then... lol...
sorry... couldn't resist that.. lol..

seriously....
I think you have to detect the pitch before you can to anything at all to it in the digital domain..
all digital signal processors [including the Axe] are essentially calculators..
ok... they are extremely fast and insanely clever calculators... but that's cos it's all math based.. even the modelling..
so.. putting it a little crudely, you need to know what freq you are doubling / halving before you throw your x2 or /2 math at it
it's therefore not the same as analogue tape [even when it's trying to emulate it]
in fact.. the digital stuff, whilst changing the pitch actually tries to keep some of the frequencies from the incoming source audio [the formants] the same in order to retain the tonal characteristics of whatever it is that you are shifting the pitch of... that's pretty clever..
essentially.. when you drop a guitar by an octave, you still want it to sound like a guitar [which don't happen when you havle the tape speed of an old CopyCat]..
 
clarky said:
so.. putting it a little crudely, you need to know what freq you are doubling / halving before you throw your x2 or /2 math at it
Click to expand...

See... that's what I don't get. Why do you need to know the frequency? You are doubling/halving/whatever the entire signal, applying the same process and the same math *regardless* of the nature of the content. If you don't like the tape analogy, it is exactly the same in digital world. Record something at 48k. Play it back at 96k. It is exactly one octave up (and half the duration, but there's another algorithm to deal with that). Why does it matter what the original signal was? This works the same for a guitar note, a drum solo, a full symphony score, spoken word etc. This is how digital pitch shifting has worked for many years. It seems to me that any latency would come from the other side of the equation (which seems to be like a kind of granular synthesis to make the shifted notes the same duration).

It is possibly that the Axe is using some other technique to do pitch shifting - Antares autotune uses something more akin to a vocoder, but we wouldn't be seeing that real time and polyphonically just yet. For that to work on something like drop tuning a whole guitar, chords and all... well if Cliff could do that in real time we would have guitar to midi conversion in the axe already because that is exactly the information he would need to be extracting from the signal.

(Just to reiterate, not sniping or arguing. I genuinely enjoy discussions like this :) )
 
Rook said:
Why do you need to know the frequency? You are doubling/halving/whatever the entire signal, applying the same process and the same math *regardless* of the nature of the content.
Click to expand...

Fixed/Whammy modes have a pitch track on/off parameter. Tracking adjusts more than the shift interval, something about cut/splice lengths I'd guess, which usually sounds better.
 
Rook - I'm making an asumption that within the Axe, that pitch shifting, octave dividing and harmonising [given that they all live in the same fx block] are all essentially varient uses of the same fundamental coding.. saves re-inventing the fx block..
so build for the most difficult and everything else is covered...

the reality is that we are both guessing...
only FAS know the actual answers...

btw - I know you're not arguing / sniping.. seems pretty obvious to me.. and I totally get where you're coming from...
my thoughts on this with respect to the Axe are guesses based upon what I think I'm hearing / feeling on a shifted tone
that said... for a real-time pitch shifter... I think it's seriously impressive...
 
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Admin M@ said:
I'm a bit ashamed really, of this thread and how it got off so quickly on the wrong foot.

If you can't say something nice - YouTube

Honestly, Velokki, I thought your question was perfectly reasonable and I'd be happy to personally help you. Reach me through the portal below:

Fractal Audio - Powered by Kayako Resolve Help Desk Software
Click to expand...

Agree.....

Velokki,
M@'s response should demonstrate to you one very big reason as to why you should buy an Axe-II. Customer support is outstanding and the vast majority of the community here go above and beyond to help each other.

I strongly encourage you to take M@ up on his offer and contact him via his instructions. I would be willing to bet though that you would be very happy if you did end up buying an Axe-II.

Good luck and let us know how your decision process goes!
 
Velokki - What is your current setup for guitar & bass?

If money is no object - Axe, Power Amp, FHFH speakers - then you could build an all-in-one rig. If you want to keep run FHFH for guitar and keep your bass cabs, then 2 power amps are going to be required (unless you don't mind unplugging & plugging on the fly).
 
Admin M@ said:
I'm a bit ashamed really, of this thread and how it got off so quickly on the wrong foot.

If you can't say something nice - YouTube

Honestly, Velokki, I thought your question was perfectly reasonable and I'd be happy to personally help you. Reach me through the portal below:

Fractal Audio - Powered by Kayako Resolve Help Desk Software
Click to expand...

It's the title and the last sentence that upset me. Had it been a simple, "Can somebody help me decide if the axe is right for me?" the responses would've been much nicer. What he did was the equivalent to walking into a Sci-Fi convention and saying, "Ok, I'll buy a ticket, but ONLY if somebody can demonstrate that I'll have a good time. Come on, you nerds love to show off your Cosplay. Show me a good time and I'll buy a ticket." This forum is generally very helpful and friendly, but that's driven by mutual respect, not making demands.
 
Sidivan said:
It's the title and the last sentence that upset me. Had it been a simple, "Can somebody help me decide if the axe is right for me?" the responses would've been much nicer. What he did was the equivalent to walking into a Sci-Fi convention and saying, "Ok, I'll buy a ticket, but ONLY if somebody can demonstrate that I'll have a good time. Come on, you nerds love to show off your Cosplay. Show me a good time and I'll buy a ticket." This forum is generally very helpful and friendly, but that's driven by mutual respect, not making demands.
Click to expand...

That was exactly my reaction also. And what I tried to explain, just not as well :-(
 
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