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-   -   Official DSP (Axe-Fx, Pod, etc.) Q&A Thread (http://www.ultimate-guitar.com/forum/showthread.php?t=1415782)

Pat_s1t 02-24-2011 11:30 PM

Official DSP (Axe-Fx, Pod, etc.) Q&A Thread
 
GG&A's Official DSP and Signal Processor Thread!

Sponsored by Roc8995



I have noticed in my time here, the last year or so in particular, that there are often threads made regarding different DSP, or Digital Signal Processing units. This would include, but not limited to, the Fractal Audio Axe-Fx, any of the Line 6 Pods, or the Avid Eleven Rack. Questions such as "How do I get a good tube-like tone?", "How do I set this up for a recording/live setting?" or "Why is this thing so bloody complicated?" are quite frequently tossed around here. So, here is a thread for people to ask questions about any DSP unit they have, and (hopefully) have them addressed by knowledgeable members that have used or owned the unit in question. So to start, a simple FAQ:

"What is a DSP unit, and how is it set apart from Solid-State amps?"

A DSP, or Digital Signal Processor, is a piece of equipment that interprets strings of numbers and symbols as real world information, such as images and sounds. In the context of music gear, they are most often singular units that act just as pre-amps for processing a guitar signal into the desired sound. Units such as the Pod and Axe-Fx do this by modelling their circuitry after real amps and effects, along with using varying complexities of algorithms to produce lesser or greater qualities of sound. DSP units are similar to solid state amps in the sense that they traditionally use transistors instead of vacuum tubes in the preamp stage, but they often are used for recording without microphones as well as part of a Preamp -> Poweramp -> Cabinet setup.

"Do these DSP things really sound like tube amps?"

This is one of the more subjective questions. In one person's ears, they may. In another's, they may not. It also depends on the quality of the unit. For example, a $2000 Axe-Fx will sound better than a $130 Pocket Pod. Some artists who have use or have used DSPs live or on recordings are are Periphery, Animals as Leaders, Devin Townsend, Cynic and Meshuggah. A few guitarists that own a DSP, but do not exclusively use it are Jeff Loomis, Chris Broderick, Steve Vai, Greg Howe, Marty Friedman and many others. Demos can be found by simple YouTube searches, such as this, this, this, and this.

"Is it easy to dial a good tone on a DSP?"

This is a very common question amongst users with little experience with digital processors, and there is no straightforward answer. For the most part, you can get half-decent "patches" as they're called (the set of effects, amps and settings you have set up in the particular tone slot) in a few minutes. However, like with any tube rig if you want a really amazing tone, you're going to have to work. This means EQs, complicated knob and signal chains configurations, and sometimes on-board mixing with hours upon hours of tweaking for tone heaven. It all depends on how deep into it you want to go, and again, the quality and complexity of your unit.

"What are a DSP's main uses?"

They are most often used in a home or studio setting, either for practice or recording without microphones. They can be used efficiently by musicians on a budget or noise restraint, so they can produce high quality recordings without cranking a nice tube amp. They can also be used purely for effects in a musicians FX loop or rack. However, a growing amount of artists are also using them in live shows, by running them straight through the PA or by using the DSP with a power amp to act as a normal amp head. In this setting, a footswitch is recommended, that can be simple 2 way switches right up to Fractal's own MFC-101, a $750 unit with tuner, individual effect controls and loads of other features. It is all preference and what the musician needs in terms of versatility that decides what level of control gets invested in a pedal.

Member List!
This is a list of all the regulars and people that offered their assistance in the thread, as well as the gear they have owned or used, currently (C) or previously (P) that they can help with. Any gear that appear as a hyperlink will be to their owners threads regarding that piece of gear.
Bolded are the users that frequent the thread and contribute often.

- Pat_s1t (of course)
- GS Lead 5
- Ignite
- InanezGuitars44
- kutless999
  • Digitech RP355 (c)

- Levi79
- Reincaster
  • Fractal Audio Axe Fx

- Space Frog
  • Line 6 Pod HD500 (c)

- SquierLolz
- Syriel
  • Zoom G2.1 Nu (c)

- Tom 1.0


DSP Brand List
This is a general list of some popular DSPs manufacturers, all pictures being links to their main websites.)



- Digidesign Eleven Rack ($899.99)







That's about it for the OP. Feel free to post any question you can think of, as this thread is made to be a knowledge base for this kind of gear. Cheers guys! :cheers:

- Pat_s1t

nutinpwnsgibson 02-24-2011 11:43 PM

good thread idea, i'll try and answer any pod questions

ibanezguitars44 02-24-2011 11:44 PM

"Do these DSP things really sound like tube amps?"

This is one of the more subjective questions. In one person's ears, they may. In another's, they may not. It also depends on the quality of the unit. For example, a $2000 Axe-Fx will sound better than a $130 Pocket Pod. or have used DSPs live or on recordings are are Periphery, Animals as Leaders, Devin Townsend, Cynic and Meshuggah. A few guitarists that own a DSP, but do not exclusively use it are Jeff Loomis, Chris Broderick, Steve Vai, Greg Howe, Marty Friedman and many others. Demos can be found by simple YouTube searches, such as this, this, this, and this.

check the sentence starting with "or have used DSPs live..." i tihnk you missed the beginning of it haha.

anyway, just trying to help you clean it up a ltitle. awesome thread idea and i hope it starts growing.

Pat_s1t 02-24-2011 11:49 PM

^ Thanks bro! Fixed it.

Seanthesheep 02-24-2011 11:52 PM

heres the first DSP question, if something like line 6 spider amps dont sound too great, why inverst in something like a pod hd 500? isnt it essentially the same thing? ofc theres different features, but basic sound, wont the be similar? and how good are POD HDs sound wise? IS the distortion as aweful as a spiders distortion?

Pat_s1t 02-24-2011 11:57 PM

Quote:
Originally Posted by Seanthesheep
heres the first DSP question, if something like line 6 spider amps dont sound too great, why inverst in something like a pod hd 500? isnt it essentially the same thing? ofc theres different features, but basic sound, wont the be similar? and how good are POD HDs sound wise? IS the distortion as aweful as a spiders distortion?
The circuits and the algorithms in the new Pod HD series are a huge step up from the Spiders. The Spider's technology just isn't as advanced as the Pod HD, or even the XT and X3 Pods. The designers made sure to use more complex computing to make the sounds more lifelike than the Spider, which they didn't put as much work into because they aren't made to satisfy semi-pro and pro musicians. The distortion in particular is much better than the Spider, which was fizzy and had very low clarity. The Pod is also equipped with more EQs and effects to level out unwanted frequencies and the like.

Seanthesheep 02-25-2011 12:22 AM

ok then, sounds pretty cool i guess. probably not as nice as my half stack will but better than my spider for sure it looks like :P

gumbilicious 02-25-2011 02:49 AM

i like this idea, this is a topic that many aren't prepared to readily understand. way to step up TS.

Quote:
Originally Posted by Pat_s1t
"What is a DSP unit, and how is it set apart from Solid-State amps?"

A DSP, or Digital Signal Processor, is a piece of equipment that interprets strings of numbers and symbols as real world information, such as images and sounds. In the context of music gear, they are most often singular units that act just as pre-amps for processing a guitar signal into the desired sound. Units such as the Pod and Axe-Fx do this by modelling their circuitry after real amps and effects, along with using varying complexities of algorithms to produce lesser or greater qualities of sound. DSP units are similar to solid state amps in the sense that they traditionally use transistors instead of vacuum tubes in the preamp stage, but they often are used for recording without microphones as well as part of a Preamp -> Poweramp -> Cabinet setup.


i don't contest this description, but i feel some key points have been missed and it could be expanded upon. if you want you can use any of this.

"What is a DSP unit"

electric guitars output an analog A/C electric current to represent an audio signal. many guitar effects are designed to manipulate this analog signal (many distortion and modulation effects for example). eventually different concepts like digital representation of an audio signal could be implemented.

the process of obtaining this 'digital signal' (1's and 0's) from the analog signal (A/C electric current) is known as analog to digital conversion (A/D). the process involves sampling the analog signal and representing the sampled voltages as discrete values (usually as group of something like 16 or 24 1's and 0's).

what are the benefits of this cumbersome process? it's kinda complicated, but lets just say we can make pretty cool things that do alot of stuff in a fairly small space using this technology.

so what does this have to do with Digital Signal Processing? well digital signal processing is the practice of manipulating this audio information in it's digital form. the ways in which you can manipulate the data are incredibly flexible and allow for much creativity. the actual manipulation is performed on digital signal processors (DSPs), which look like a fairly unexciting microprocessor. from specs i have seen on the chips, the processing speeds don't seem that fast by modern computer processor standards (but are plenty fast enough for proper seamless audio signal processing), but the machine language of the chip itself is specialized for audio signal processing.

after the signal is manipulated by the DSP chip it is sent to a digital analog converter (D/A) to be feed out to some sorta amplification device.

"How is DSP set apart from Solid-State amps?"

solid state (SS) and tube technology are based on amplifying and manipulating an analog signal (using things like triode tubes and transistors). DSP just processes a digital representation of an analog signal.

DSP itself is NOT an amplifier, although some digital manipulation can either increase effective or perceived volume. usually an analog signal sent to an A/D needs to be properly buffered or even amplified before a favorable digital sampling can occur, this buffering could be achieved with a transistor or vacuum tube. also, after the signal has been processed by the DSP chip and sent to the D/A it may once again need to be amplified or buffered before being sent to the power section. the power section itself consisting of a normal power amp, doesn't matter if it's solid state or tube.

what i want to impress is that DSP does not really compete with solid state and tube amps so much as DSP is actually designed to be used WITH solid state and and/or tube amps. without amplifiers, there is no way to make DSP loud... and there are no 'digital amplifiers' (class D is not digital)

so with this knowledge, now add to the fact that many advanced DSP devices may include power amp distortion emulation and speaker cabinet emulation (among other things) as well. now you'll start to understand why most DSP devices work best on 'flat response' systems (a very sterile sounding amp and speaker system that has a fairly even volume response across the audio frequency range). these advanced emulation devices don't want the coloring from the power amp, the preamp or the speaker; instead the want more transparent amplification the allows the most accurate reproduction of DSP.

"How is DSP used?"

i feel DSP amps are falsely understood to be 'all digital' by some people, amps like Vypyr's and Spider III's have solid state buffers and amps to facilitate it's DSP modeling. also, DSP chips can actually be added onto 'all tube' amps fairly easily (add a Neunabar Wet pedal into you amp instead of that unreliable accutronics reverb tank if you want) and many sound mixers and guitar amplifiers are just basically SS designs with DSP thrown in the signal path. furthermore many DSP is also found in many pedals, Line 6 even offers their own hardware platform to develop your own DSP effects!

DSP effects are actually software that is designed in programming environments with either [fairly universal] machine level languages or higher level languages modified with instruction sets for controlling the microprocessor. languages can monitor controls, I/O, switches and buttons on the pedal and react to events. the language also supplies multiple ways to manipulate digital audio signals as well. after the code for the effect is written, it is compiled and written to the DSP device. thats it.

http://line6.com/tcddk/

Fred the Shred 02-25-2011 06:46 AM

I used to demonstrate Line 6 gear in Portugal and own an Eleven Rack, so I'm more than happy to help people out if needed. :)

One thing that must be said is that, sometimes, using actual tube coloration from power amps (this assuming you are not aiming for a as faithful as possible approximation to the emulated model, of course) manages to breathe new life into your sound and add new nuances to it.

It has been quite rewarding when reamping in the studio, for instance, to take a regular Line 6 amp model (I don't care what people say - some of their native models are beautiful to me) and use the power amp's natural clipping to have it act as if it were a completely new amp. For instance, layering a Line 6 Bayou straight track with another one bypassing the A.I.R. and going through a Boogie 20/20 and a good cab such as an Orange 2x12" imparts gorgeous richness to the tone due to the subtle differences in the way dynamics end up playing their part.

DSP's have been a part of my sessions for ages now, and when well used, the emulations are a precious tool that allows you to get near infinite quality options saving hundreds of hours. :)

Metalmaker 02-25-2011 08:46 AM

Sweet, I know a decent amount about the pods and the axe fx, so I'll also try to answer some questions

As far as DSP processor speeds go:

While they SEEM to be unimpressive in terms of HZ, the reason why they are better than normal processors is because DSP's are almost specifically made to be used in such applications since they are great at real time calculations. Were we to use the new Intel i7 processors, the performance would fall far short since it isn't made for real time A/D conversion and processing

This info is from Cliff, the designer of the Axe Fx

silly6-string 02-28-2011 08:47 AM

would u guys go pod or reg pedals for a cover band? I play a strat thru a deville

gumbilicious 02-28-2011 11:25 AM

Quote:
Originally Posted by silly6-string
would u guys go pod or reg pedals for a cover band? I play a strat thru a deville


depends on the scope of the band and your responsibilities in it.

i personally prefer individual pedals myself, but i don't usually try and stick real close to an original band's tone. something like a POD would quite literally let you set up every tone you want to use in a gig with presets and that can be very useful.

but if you are just a rhythm guitarist and all you need to do is punch you distortion on and off, then you'd prob be fine with just a distortion pedal.

but if you are playing lead and want to really try and nail 'the tone from beautiful disaster' or some other highly recognizable melody with a particular tone then a POD may be a god send for you.

i also notice, in my personal experience, that the more people in the band the more these digital effects set in the mix properly. so if you are doing a 3 piece band, then i'd try and use individual pedals but if you are a 5 piece band then those digital effects actually keep you isolated in the mix better.

GS LEAD 5 02-28-2011 12:21 PM

Nice thread.
How about something on what happens when you run a DSP into an amp without an effects loop? Also a bit on how speaker sims work?
And how about a recommendations chart? Or reviews from users like in the Laney thread?

silly6-string 02-28-2011 01:07 PM

ya im in a 3 piece band

gumbilicious 02-28-2011 01:29 PM

for a 3 piece i'd like to use some rich analog effects to thicken things up.

it is not necessary, but i use multiple amps when playing power trio. usually using at least 1 amp on each side of the stage. the reasoning for this is manifold:

1) stage monitoring: everyone in the band hears you a bit better cuz of the 2 sources of signal on either side of the stage

2) stage projection: the crowd gets better coverage as well and they can hear your signal better and more appropriately in the mix.

3) stereo field: with two or more amps you can create a stereo field and use stereo effects to create 'space' in your tone. stereo delays (dd-7 for example) or stereo phasers (like my mutron bi-phase) sound HUGE in a stereo mix.

4) mix and match: i can reinforce my own tone by using different amps (class A, class A/B, hybrid, SS, etc), cabs (open back, closed back), and speakers(alnico, ceramic, 12", 15", etc). this allows for some pretty big sounds.

5) consistency: i get a built in backup amp. if one amp goes down then you already have another one going without stopping the song! i like that (even if it is noticeable when one goes down).

6) distributes volume: i don't have to run my amps as loud cuz there are 2 of them. i find this really cool cuz many closed back cabs are very 'beamy' (narrow projection path of sound) and volume is inconsistent throughout the room. it won't matter how much you crank up your amp, if they are out of the path then you'll still sound weak in the mix. with this setup, both amps will be at less volume and more people will hear you better (more perceived while running your amps cooler).

i am in no way saying that these techniques create a '2 guitar' feel, but they can make '1 guitar' sound pretty huge and help fill that mix and sound better. you also don't need 2 really badass amps. even 1 good amp with a 'spare' amp on the other side of the stage helps better than you would think.

the downsides are there too. first off, you rely of pedals way more. some people would want to use amp distortion and using multiple amps may make that harder and you'd be relying on that OD or distortion pedal to provide the juice. the setup is also bulkier and can get complicated quick. not many people have the patience i have for the extensive live setup i [may] use.

Meelad360 02-28-2011 01:31 PM

I thought I'd put this here

Some tips for Pod Farm:

Outside of Pod Farm

-Use it after a tuner VST (I use gtune. In fact, all the GVSTs are pretty amazing). You'll always need a tuner if you want to record well. Tune often.

-After Pod Farm, have some kind of impulse loader , such as KeFir, LeCab2, etc. You will need to turn off the cab in Pod Farm.

-Search on google for impulses (especially the Catharsis impulses), and load those impulses into the loaders.

-Also, if using a loader that can handle multiple impulses, mix and match, see what you like.

Inside of Pod Farm itself

-ALWAYS use a tubescreamer right before the amp head when playing high gain/using a high gain model.

-Do not set the threshold on the noise gate too high, because then the fakeness of the simulator will come out, as well as kill sustain.

-Use the fact that you can use more than one signal chain to your advantage.

High gain models I've gotten good results with -
Solo 100
Deity Series
Dual Treadplate
Cali Diamondplate

Seanthesheep 03-01-2011 06:49 PM

quick question about the line 6 POD HD 500

lets say i want something to do the following and well, would that work? because it would have to:

be able to add delays, choruses and random effects to my live rig (it would essentially replace like 3 or 4 pedals id have to buy if it did this)

be able to act as a practice amp with headphones (for when i have play almost silently at night)

be able to go striaght out into my computer to record tracks

and is there something else that might achieve this better?

Pat_s1t 03-01-2011 10:18 PM

^ Yes, yes and yes. There are units that would do it better (such as my Axe-Fx :D ) but it's only marginal, and the HD 500 is a fine piece of gear. I used to use my Pod X3 for all those things, and the HD series is way above the X3.

ibanezguitars44 03-01-2011 10:28 PM

+1 to pat_s1t's advice, and +1 to BTBAM lyrics in his sig :D

Seanthesheep 03-01-2011 10:40 PM

would it be able to add effects, without adding an amp model that would colour my tone?

because the amp im upgrading to has like the perfect ttone for me, and i wouldnt want any extra tone colouration from this unit, and theres no way i would buy the axefx my completed rig wont even cost that much :S id just be looking for something reasonably pricd, because althought the new amp im getting is for the band, im going to university soon and may be living in an apartment, so practice at night will be impossible unless i have a unit that i can plug headphones into and will sound good. and i might as well kill 2 birds with one stone and make my live rig easy to manage for effects switching.

so completed rig will be:

guitar->tuner->noise gate->OD->peavey 6534+->pod hd->peavey 6534+->avatar 212

and its probably my perfect tone :p: (if the pod doesnt colour anything)


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