No, Marco, sorry. I wish I did. The result is very good, and a huge leap from the sim in the CX-3. Very annoying that they don’t support MIDI switching of the speed…
http://www.earlevel.com/main/2013/02/16/ventilator-adapter-in-a-mint-tin/ On Jun 18, 2014, at 10:11 AM, Marco Lo Monaco <marco.lomon...@teletu.it> wrote: > Ciao Nigel, talking about the VENTILATOR, do you know something more about > its secrets/internals? > :) > > M. > >> -----Messaggio originale----- >> Da: music-dsp-boun...@music.columbia.edu [mailto:music-dsp- >> boun...@music.columbia.edu] Per conto di Nigel Redmon >> Inviato: mercoledì 18 giugno 2014 08:22 >> A: A discussion list for music-related DSP >> Oggetto: Re: [music-dsp] Simulating Valve Amps >> >> Well, some people think it’s close enough for rock n rock (amp sims), > others >> don’t. It’s the same with analog synths and virtual analog. But there’s > also >> the comfort of tube amps, and there’s the comfort of the limited sound >> palette of using the amp that you know and love. Amp sims are really about >> variety (can’t afford a Plexi, a Twin Reverb, SLO, AC-30, and a few > boutique >> amps? Now you can). >> >> I appreciate the old stuff, but I appreciate the convenience and > flexibility of >> the new stuff—to me it *is* close enough for rock n roll (new stuff in >> general—I don’t play much guitar). I play a B3 clone because I hauled a >> Hammond decades ago, and I hauled and still have (needs work) a Leslie, > but >> I’d just as soon use my Ventilator pedal on the CX-3 (yes, with > programmable >> leakiness and aging of the tone wheels, etc.)—more convenient, and gets >> the sound I want. Others would shudder at the thought. Well, until their >> backs start giving out…I know a hardcore, old-time B3 blues player > (“Mule”— >> a nickname he earning for hauling around his B3 and Leslies) who picked up > a >> clone for his aging back after hearing my CX-3 though the Ventilator. Not > for >> all gigs, mind you, but as an option to go with for some gigs. The point > is that >> if the tradeoffs are attractive enough, it’s easier to let yourself try > new things >> even if you feel that it falls ever so slightly short of what you’re used > to, or >> strays from your comfort zone. >> >> So while some might feel that amp sims haven’t arrived yet, other might > feel, >> “where the heck have you been the past decade?" ;-) >> >> >> On Jun 17, 2014, at 6:59 PM, robert bristow-johnson >> <r...@audioimagination.com> wrote: >> >>> On 6/17/14 8:24 PM, Nigel Redmon wrote: >>>> (Thinking outside the nest…) >>>> >>>>> (...maybe that means opening up the LPF as the gain knob setting is >>>>> reduced) >>>> Yes >>>> >>>> And good discussion elsewhere in there, thanks Robert. >>>> >>> yer welcome, i guess. >>> >>> you may be thinking outside the nest; i'm just thinking out loud. >>> >>> i think, like a multieffects box, we oughta be able to simulate all > these amps >> (don't forget the Mesa Boogie) and their different settings in a single > DSP >> box with enough MIPS and a lotta oversampling. dunno if simulating the >> 50/60 Hz hum and shot noise would be good or not (i know of a B3 emulation >> that simulates the "din" of all 60-whatever keys leaking into the mix even >> when they're all key-up). but they oughta be able to model each >> deterministic thing: the power supply sag, changing bias points, > hysteresis in >> transformers, capacitance in feedback around a non-linear element (might >> use Euler's forward differences in doing that), whatever. whatever it is, > if >> you take out the hum and shot noise, it's a deterministic function of > solely >> the guitar input and the knob settings, and if we can land human beings on >> the moon, we oughta be able to figure out what that deterministic function >> is. for each amp model. it shouldn't be more mystical than that (but > there >> *is* a sorta mysticism with musicians about this old analog gear that we > just >> cannot adequately mimic). >>> >>> and thanks to you, Nigel. >>> >>> L8r, >>> >>> r b-j >>> >>> >>>> On Jun 17, 2014, at 4:07 PM, robert bristow- >> johnson<r...@audioimagination.com> wrote: >>>>> On 6/17/14 3:30 PM, Nigel Redmon wrote: >>>>>> This is getting…nesty... >>>>> yah 'vell, vot 'r ya gonna do? :-) >>>>> >>>>>> On Jun 17, 2014, at 10:42 AM, robert bristow- >> johnson<r...@audioimagination.com> wrote: >>>>>> >>>>>>> On 6/17/14 12:57 PM, Nigel Redmon wrote: >>>>>>>> On Jun 17, 2014, at 9:09 AM, robert bristow- >> johnson<r...@audioimagination.com> wrote: >>>>>>>> >>>>>>>>> On 6/17/14 5:30 AM, Nigel Redmon wrote: >>>>>>>>> >>>>>>> ... >>>>>>>>>> Anyway, just keep in mind that the particular classic amps >>>>>>>>>> don’t sound "better" simply because they are analog. They sound >>>>>>>>>> better because over the decades they’ve been around, they >>>>>>>>>> survived—because they do sound good. There are plenty of awful >>>>>>>>>> sounding analog guitar amps (and compressors, and preamps, >>>>>>>>>> and…) that didn’t last because they didn’t sound particularly >>>>>>>>>> good. Then, the modeling amp has the disadvantage that they are >>>>>>>>>> usually employed to recreate a classic amp exactly. So the best >>>>>>>>>> they can do is break even in sound, then win in versatility. >>>>>>>>>> And an AC-30 or Matchless preset on a modeler that doesn’t >>>>>>>>>> sound exactly like the amp it models loses automatically—even >>>>>>>>>> if it sounds better— because it failed to hit the target. (And >>>>>>>>>> it doesn’t helped that amps of the same model don’t necessarily >>>>>>>>>> sound the same. At Line 6, we would borrow a coveted amp—one >>>>>>>>>> that belonged to a major artist and was highly regarded, for >>>>>>>>>> instance, or one that was rented out for sessions because it >>>>>>>>>> was known to sound awesome.) >>>>>>>>> what did you guys do with the amps when you borrowed/rented >> them? was your analysis jig just input/output, or did you put a few high- >> impedance taps inside at strategic places and record those signals >> simultaneously? >>>>>>>> Yes. For instance, sweeping the EQ with incremental settings >> changes. >>>>>>>> >>>>>>> yes, another issue (which i didn't really touch on) is mapping the >> settings of the knob to the internal (to the DSP) coefficients and > threshold >> values and such. that is "coefficient cooking" and is the same issue as >> defining Q in EQs so that the knob behaves like the ol' Pultec or > whatever. >> your digital implementation might work very well, but if the position of > the >> knob in the emulation is not nearly the same as it was for the venerable > old >> gear (to get the same sound), someone might complain. >>>>>> Oh yes, they *will* complain ;-) >>>>>> >>>>>>>>>> On Tue, Jun 17, 2014 at 6:58 PM, Nigel >> Redmon<earle...@earlevel.com> wrote: >>>>>>>>>>> On Jun 16, 2014, at 7:51 PM, robert bristow-johnson< >>>>>>>>>>> r...@audioimagination.com> wrote: >>>>>>>>>>>>> one thing that is hard to replicate is a sample rate that is >>>>>>>>>>>>> infinity (which is how i understand continuous-time signals >>>>>>>>>>>>> to be). but i don't think you should need to have such a >>>>>>>>>>>>> high sample rate. one thing we know is that for *polynomial >>>>>>>>>>>>> curves* (which are mathematical abstractions and maybe >> have >>>>>>>>>>>>> nothing to do with tube curves), that for a bandwidth of B >>>>>>>>>>>>> in the input and a polynomial curve of order N, the highest >>>>>>>>>>>>> generated frequency is N*B so the sample rate should be at >> least (N+1)*B to prevent any of these generated images from aliasing down >> to below the original B. >>>>>>>>>>>>> if you can prevent that, you can filter out any of the >>>>>>>>>>>>> aliased components and downsample to a sample rate >> sufficient for B (which is at least 2*B). >>>>>>>>>>>>> >>>>>>>>>>>> This really goes out the window when you’re modeling amps, >>>>>>>>>>>> though. The order of the polynomial is too high to implement >>>>>>>>>>>> practically (that is, you won’t end up utilizing the >>>>>>>>>>>> oversampling rate necessary to follow it), >>>>>>>>> this is a curious statement *outside* of the case of hard > clipping. >> oversample by 4x and you can do a 7th-order polynomial curve and later >> eliminate all of the aliasing. oversample by 8x and it's 15th-order. do > *no* >> oversampling and you can still make use of the fact that there's not a lot >> above 5 kHz in a guitar and amp (so 48 kHz is sorta oversampled to begin >> with). you can fit a quite curvy curve with a 7th-order polynomial. >>>>>>>>> >>>>>>>>>>>> so >>>>>>>>>>>> you still be dealing with aliasing. Modern high gain amps >>>>>>>>>>>> have huge gain >>>>>>>>>>>> *after* saturation. In practical terms, you round into it >>>>>>>>>>>> (with a polynomial, for instance), then just hard clip from >>>>>>>>>>>> there on out, and there goes your polynomial (it can be >>>>>>>>>>>> replaced by an approximation that's very high order, but what’s >> the point). >>>>>>>>> yes, we splice a constant function against a curve. if at the > splice as >> many possible derivatives are zero as possible, that splice appears pretty >> seamless. this is why i had earlier (on this list) been plugging these > curves: >>>>>>>>> >>>>>>>>> x >>>>>>>>> f(x) = C * integral{ (1 - u^2)^M du } >>>>>>>>> 0 >>>>>>>>> >>>>>>>>> (C gets adjusted so that f(1) = 1 and f(-1) = -1.) >>>>>>>>> >>>>>>>>> you can splice that to flat values at +/- 1 and the nature of the >> function will not change appreciably from the polynomial in the region of > the >> splice. >>>>>>>>> >>>>>>>>> anyway, the whole point is to give the guys with golden ears no >> cause to complain about hearing aliases. same with emulating sawtooths > and >> hard-sync synthesis. >>>>>>>>> >>>>>>>>>>>> Anyway, you pay your money, you make your choices. >> Obviously >>>>>>>>>>>> some really good musicians making really interesting music >>>>>>>>>>>> use modeling amps. They don’t have to be better than tubes, >>>>>>>>>>>> in order to be a win, just good enough to be worth all the >>>>>>>>>>>> benefits. If you’re a session music, you can bring in the >>>>>>>>>>>> truck with all of the kinds of amps that might be called on, >>>>>>>>>>>> or you can bring a modeling amp, for instance. And going >>>>>>>>>>>> direct into the PA or your recoding equipment…etc. I’m not >> going to make judgments on what people should like, so I’ll leave it at > that. >>>>>>>>>>>> >>>>>>>>>>>> One happy thing about the aliasing is that, given a decent >>>>>>>>>>>> level of oversampling, it won’t be bad at lower overdrive >>>>>>>>>>>> levels. At the higher the overdrive levels, the harder it is >>>>>>>>>>>> to hear aliasing through all that harmonic distortion you’re >> generating. So it could be worse... >>>>>>>>> i really agree with this, Nigel. with *some* oversampling (but >> theoretically not sufficient oversampling), you can get away with a lot > (like >> hard limits or whatever stuff goes on inside a transformer with core > loss). i >> would not say that you have to oversample to a ridiculously high degree > just >> because there is a hard-limit saturation in there or that your tube model > is >> not a polynomial approximation (but i wonder why you wouldn't try to fit > the >> grid-to-plate tube curve to a finite-order polynomial). >>>>>>>> What I mean is... for a modern high-gain amp, the gain is on the >> order of 2^16 (and the curve starts it’s significant bend up near 1). So > most of >> the signal, when you’re playing maxed out, is simply clipping hard. If > your >> goal is to not alias in the audio band at all, by figuring the max > harmonic >> component based on the order of the equivalent polynomial and the highest >> freq of the guitar input coming in…well, your oversampling factor is going > to >> be a lot higher that you’re willing to implement. >>>>>>> i understand. hard-hard-limit and you got harmonics going up to >> infinity anyway. >>>>>>> >>>>>>>> There’s really no point in calculating a continuous polynomial > over >> that range that I can see. >>>>>>> well, if it splices *well* to the clip region, it might *still* have > a point. >>>>>>> >>>>>>>> It’s no big deal—I just brought it up because I often see people, > here >> and elsewhere, go down the thought path of... "OK, I want to make a guitar >> distortion unit…if I keep my polynomial to order N, I only need to > oversample >> by (N+1)/2...", completely forgetting that when, in their code, they > branch to >> limit the output to +/- 1, their polynomial order just went out the > window. >>>>>>> yes, that's true (sorta). at least *if* the splice to the limited > constant >> value is not smooth. >>>>>>> >>>>>>> but you can make a polynomial match as many derivatives (equal to >> zero) of the hard limit as possible (but that might be at cross-purposes > to >> getting the polynomial to follow a tube curve) and for levels that hit > that limit >> (so the code branches to the limit), if the overflow or spike isn't so > bad, the >> behavior isn't so far away from the "ideal" polynomial and the total >> behavioral issue remains inside the window, i would think. >>>>>> Yes, Robert…but, with the kind of gain necessary…OK, so you have the >> y-xis as you output level, x-axis as input. To view the entire curve for a >> Soldano Super Lead Overdrive, for instance, you draw the curve of your >> choice to rise from y=0 and give you a soft bend into y=1 (full output). > The >> bend will be somewhere around x=1, ballpark (maybe it’s x=2 or 3, to allow >> for lower input levels, but the point is that it’s a small number compared > to >> what’s coming next)…then you allow for x=30000 or so (a flatline from the >> x=1..3 area). Is that not a pretty high order polynomial? >>>>> well, yeah, and it might better be described as a function that is >> discontinuous with most of its derivatives, even the 1st. >>>>> >>>>> so >>>>> >>>>>> The point being, yes the polynomial would be handy at low gain >> settings, but you still need to build this thing to work at extreme gain > settings >> at the same time. >>>>> okay, you mean with it cranked up so that it virtually hard limits. > that's >> not exactly what comes to mind about "warm" tube distortion. like those >> DevilDrive guys (or was it the Kemper guys) built a 12AX7 preamp to model >> (and i wonder how much that tells us about how a Fender Twin Reverb >> cranked up to arcweld behaves like). >>>>> >>>>> but this is hard clipping distortion, not zero-crossing distortion, > right? in >> between the nasty hard limits, you might be able to decently model the > tube >> curves with finite-order polynomials. specifically the mapping curve from >> biased grid voltage to biased plate voltage given a specific load line > (which >> may be affected by power sag). maybe you can cover that quite well with a >> finite-order polynomial and emulate that with a finite sampling rate. but > if it >> clips, might be nasty, regarding aliases. >>>>> >>>>> the only thing i know how to tame down a hard limit (and it may very >> well not be compatible with the characteristic tube curve) is to set as > many >> derivatives as possible to zero and splice the hard limit to that thing. >> continuity to the 2M-th derivative including the hard limit. >>>>> >>>>>> So anything at the low gain settings is pretty insignificant for > something >> designed to handle the high gain settings. >>>>> well, we gotta think sorta like the string theorists. we gotta > imagine how >> to seamlessly glue together two ostensibly incompatible systems. like how >> do we crossfade from the low-gain behavior (the "warm tube sound") to the >> behavior we like when it's cranked up to arc-weld? >>>>> >>>>> >>>>>> Hence my feeling that there not much point to calculating how much >> headroom you have—you can pretty much count on infinity. There may be >> some reasons to do it—I’m not demanding that I have the right idea, just >> simply explaining what I meant by my comments. In reality, it’s not so > clear >> cut, because as I mention before, the more you get into a situation where >> aliasing will be big, at the same time you are in a situation where you’ll > have >> more generated harmonics to mask the aliasing. In the end, aliasing is >> *mainly* a problem if you bend a guitar note and you heard harmonics going >> in the wrong direction. For some reason guitarists just can’t get around > that >> (lol). >>>>>> >>>>>>>> BTW, the more the overdrive, the less the weaker upper harmonics >> of your guitar matter, so you can cheat by rolling them off as you > increase >> drive. >>>>>>> a useful idea. more pre-LPF as the grunge gets cranked up. >>>>>>> >>>>>>>> But you can’t rely on that too much, because guitar players like >>>>>>>> to hang analog distortion stomp boxes in front of your modeling >>>>>>>> amp, giving you powerful higher harmonics. :-) >>>>>>> yeah, but can't you *still* pre-LPF that signal (the output of the >> distortion stomp box) as the amp drive is cranked up? i dunno. >>>>>> Yes, it’s definitely one place where you can win, and help yourself >>>>>> make the best of a practical amount of frequency headroom. Probably >>>>>> the biggest difference (between assuming direct, clean guitar >>>>>> strings as input, and one that’s be pre-crunchified with a >>>>>> stompbox) is that for the former you might get by with a >>>>>> lower-order filter, because guitar string harmonics drops of >>>>>> pretty quickly by themselves. (So, you might design an amp sim that >>>>>> seems relatively alias-free, then get a customer or beta tester >>>>>> complaining about the aliasing, and that's were you find out that >>>>>> guitarists will still want to run their stuff into your sim, even >>>>>> if you give them those functions in DSP.) >>>>> well, i know there can be different specs. but for a 32-tap FIR LPF, > you >> can put the same brick-wall LPF on both guitar (that might not need it as > bad) >> and the grunge box. it's just that for clean amp setting, you might hear > the >> difference between your straight-grunge pedal and the LPF'd one (and it's >> less necessary, maybe that means opening up the LPF as the gain knob >> setting is reduced). >>>>> >>>>> -- >>>>> >>>>> r b-j r...@audioimagination.com >>>>> >>>>> "Imagination is more important than knowledge." >>> >>> >>> -- >>> dupswapdrop -- the music-dsp mailing list and website: >>> subscription info, FAQ, source code archive, list archive, book >>> reviews, dsp links http://music.columbia.edu/cmc/music-dsp >>> http://music.columbia.edu/mailman/listinfo/music-dsp >> >> -- >> dupswapdrop -- the music-dsp mailing list and website: >> subscription info, FAQ, source code archive, list archive, book reviews, > dsp >> links http://music.columbia.edu/cmc/music-dsp >> http://music.columbia.edu/mailman/listinfo/music-dsp > > -- > dupswapdrop -- the music-dsp mailing list and website: > subscription info, FAQ, source code archive, list archive, book reviews, dsp > links > http://music.columbia.edu/cmc/music-dsp > http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
