You asked for it. Please summarize in understandable terms...
May have dated info (like urls) and Dutch mixed in.
DEPTH / DEEP
- solo-act, 2007: This is just me, but I tend to use the deep as a pseudo "cabinet" EQ to match how hard the speakers are working for whatever tone I'm going after. >> javajunkie: This is what I do as well.
- Cliff, 2/2008: If you increase the depth too much with the deep parameter on, the power amp sim can go unstable, just as a real amp would under those circumstances. I can't say any more as it would be disclosing proprietary information.
- Sebastian, 12/2010: [do you use depth?] Totally depends on:
* amount of gain/distortion (i.e. clean sounds, rhythm sounds, lead sounds)
* if the tonestack is pre or post (if it's pre, the bass control has a very different effect on the sound, compared to depth)
* where the low cut (adv. page) is set; depth can bring back the bottom the low cut removed.
- Clark Kent, 12/2010: I hate depth... they should change the name to boomyness. Whatever it's doing it's wrong IMO.
- Yek, 12/2010: Turn down the Depth parameter for less bass. Depth is the same as what’s called Resonance, Fat, Whomp etc. on real amplifiers. The same as Presence but on low frequencies. Higher values give a fuller, looser sound, while low values can be used to achieve a more focused sound. Note that Depth is non-functional when Power Amp sim is off.
DAMP
- Cliff: Damp is the amount of negative feedback around the virtual power amp. Increasing it makes the power amp stiffer and tighter. / Damp defaults to value appropriate for model selected.
- BK-Amps, 9/2010: The control does not behave like a real amplifier. "Damp" control on 10 will be ~12db higher in volume than "Damp" at 0! This is not right. [...]
>> Cliff: The Axe-Fx attempts to normalize the volume as you change the damping. Since the overall gain of an amplifier with negative feedback is A = Ao / (1 + Ao * B), the closed-loop gain can be calculated and corrected for. So when you change the damping the Axe-Fx calculates the resulting closed-loop gain and compensates accordingly. However, if you are driving the "power amp" hard, the equation falls apart because it assumes linear operation. Therefore there may be some volume change. This is done since otherwise you would constantly have to adjust your output volume as you change the damping. Unfortunately it is impossible to predict how saturated the power amp is since that depends on input level. The compensation isn't perfect, the idea is to minimize the volume fluctuations, since without compensation the volume would fluctuate wildly. >> Smilzo: Great idea, because our minds judge louder sounds as better ones! / It must be underlined that if the poweramp is saturated, both Damp and Level must be increased to maintain the same level. forum.fractalaudio.com/threads/29243-The-quot-Damp-quot-Control-is-Strange
- Cliff, 5/2007: The DAMP control is the Class A/AB control. It doesn't actually change the class of operation since there aren't really any guitar amps that are Class A. The AC30 is advertised as Class A but it's really just a cathode biased Class A/B biased hot with no negative feedback.
- zap 2007: Does reducing negative feedback allow more 2nd and 3rd harmonics on the Axe-FX as the "Silk" feature of the Rupert Neve Potico Series 5012 (see last par.)? eqmag.com/story.asp?storycode=14187
>> Cliff: Reducing negative feedback increases harmonic distortion including 2nd and 3rd if operating below clipping. This is because feedback linearizes the amplifier. The Axe-Fx has a non-linear "power amp" just like a real tube amp and if you turn down the feedback (damping) then the power amp will be less linear and will therefore introduce some distortion products. The distortion products tend to be low order (2nd and 3rd).
Once you enter clipping, negative feedback can actually increase the distortion products since the onset of clipping is sharper. A power amp with no negative feedback (i.e. AC30) will produce distortion even when not clipping. However, it will go into clipping gently, since the transfer function tends to be smooth. A power amp with negative feedback will produce less distortion when not clipping but will enter clipping more abruptly since the smooth curve is essentially turned into a piecewise linear function with an abrupt gain reduction at the supply rail. setbb.com/axefx/viewtopic.php?p=11678
- Cliff, 2/2010 v9.02: If you set Damping to zero it detects that and changes the Presence control to a shelving filter, since the control would otherwise be ineffective. Set Damping to just greater than zero and you'll hear the filter turn off and revert to a feedback circuit.
- rpurdue, 9/2010: Even though the JVM isn't the mecca of the Marshall line it sounded great on the crunch channel...better than the Axe. It was spongier and seemed more alive. I was determined to emulate this characteristic. After looking at the manual i found the answers right in front of me...the SAG and DAMPING!!! DUH! I thought because I was using a tube poweramp I should set the SAG very low and the DAMP high....BUZZZZZZ WRONG ANSWER!!! As soon as I upped the sag into the 2-3 range and turned off the Damping entirely, there it was! It not only sounded as good as the JVM but better!! It was much fuller and open sounding. I found the Corncob and Marsha BE really nailed it and then some!
- Cliff, 11/2010: The difficulty is that I allow people to adjust the damping so I needed a way to allow for a hi-cut when the damping was set to zero and a presence control when not. So I came up with the dual-function presence control. When an amp has no negative feedback (i.e. AC-30), the speaker impedance has a much greater effect on the tone and causes the tone to be much brighter. Additionally, there is no way to adjust the tone by modifying the negative feedback (because there isn't any). So a non-negative feedback amp classically employs a hi-cut filter in the power amp. The Axe-Fx allows you to turn on negative feedback, even for amp models that don't normally have any. In that case the high-frequency emphasis due to the speaker impedance will decrease and you then may want to increase the highs to compensate so you need a presence control. Thus was born the presence/cut control. At settings less than zero it acts as a simple hi-cut. At settings greater than zero it acts as a presence control if the amp model has negative feedback by manipulating the feedback or by boosting the treble if there is no feedback. thegearpage.net/board/showthread.php?p=9456143
- fuzznut, 12/2010: So I turned up presence all the way, and was playing with the damp parameter to see what effect it had on the presence range. I put damp to zero and... woah! It got louder, very bright and RAW. Cool tone! It is not mentioned in the manual or wiki manual, but searching here revealed that putting damp to zero completely disconnects the feedback loop in the power amp. What I didn't find is, since presence and depth work off the feedback loop, are these controls now shelving filters as when the power amp is disabled? / Having fun with this one! 2 Das Metal amps in parallel. #1 with bass, depth and damp off (bass is flubby with no feedback). #2 normal, initially with mids and high/presence off, adjust output level until bass sounds right in the mix. Then adjust mids & highs on both amps for various mixes. Tight bass, hairy mids and loose highs! Gotta love this black box... >> Cliff: The presence becomes an active shelving filter. I forget what happens with depth. Probably the same thing or nothing at all.
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http://forum.fractalaudio.com/threads/29243-The-quot-Damp-quot-Control-is-Strange?p=428883
- JM: I am not a big fan of the sound of distortion in the power amp portion of the amp block with very high values of damping. To my ears, the transition to distortion is too abrupt and the character of the distortion too harsh.
http://forum.fractalaudio.com/share-request-patches/35216-fractal-patch-contest-4.html#post524502
- widrace, 3/2012: I would add that Damp is closely tied to the Sag/Master relationship. Damp to me is the main dynamic adder/subtractor and is dialed in to work with the amount of gain your using. Sag follows as a tool to fine-tune the result. High SAG values act like compression where sustain is added at the expense of dynamics. The combination is everything when it comes to feel at any given gain level. Jay noted that high levels of Damp will cause the onset of break-up to be more abrupt and I agree. If chasing the elusive Robben Ford break-up qualities/mannerism it all starts there. Get this part right before you add any upstream/downstream compression too. FWIW, I generally use Damp settings that are rather high compared to Sag. For live use the Damp/SAG combo is key to correctly fitting within overall dynamics of the band. I like to dial in a bit too much dynamics and trim it with a little bit of high-threshold/high-ratio compression to keep the peaks in order. Same goes for recording. Spend some time twiddling various combinations of only the Drive, Master, Damp and Sag parameters while maintaining a perceived output level. If you do this along with a SPL meter you will find the two don't agree much. The goal is to maximize the perceived levels, minimize the SPL, while keeping the right feel and dynamics to suit. No one but you can do this.
http://forum.fractalaudio.com/axe-fx-ii-discussion/48588-i-have-question-about-sag-2.html