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Started by Koreth, February 09, 2010, 04:16:59 AM
Quote from: rowdy_riemer on February 12, 2010, 06:34:36 PMThis sounds like the theory behind the Fetzer Valve article on runoffgroove.com. I might play with the Fetzer Valve design using your figures for calculating Rs. BTW, JFETs are more like triodes than Enhancement MOSFET's, but not more triode like than depletion mode MOSFETs, which can be pushed into enhancement mode.
Quote from: Koreth on February 14, 2010, 04:39:37 PMWhen speaking of this 3/2 law or 1.5 law, are you referring to the spacing, or the slope/curvature of the grid curves in a triode, or both?
Quote from: J M Fahey on February 27, 2010, 11:51:00 AMLet us not forget that curve or slope cloning emulates a *clean* triode.The *clipping* triode emulation is a whole other game, and then we will be able to emulate Preamp distortion only.We still need to emulate power pentodes, both clean and overdriven, transformer nonlinearities, the works.Just as a side note: it can and *has* been done.A very intelligent guy I know from a Brazilian Forum ("Amplificadores Valvulados" in Orkut) did an amazing work as his final Project to become Electronics Engineer there.AFAIK what he did was to create this *huge* Spice model of a Mesa Boogie, a DC-5 or something like that, including transformer nonlinearities, speaker response, power supply sag, everything. :duhI told him he was crazy, a Champ would do to prove his point.End of the story: he reached a point (after 1 year work, involving almost all of his class and a couple Professors) where he could play 10 seconds of Blues with his trusty Strat into his soundboard, and hear them some 30 seconds later, undistinguishable from his miked Mesa whatever.Almost real time. Mind you, it was not DSP work, but fully a Software solution.Yea, I know, you have Guitar Rig and others there who *claim* to emulate 500 classic amps. Do they? :troubleThis one did emulate just *one* .... faithfully.Unfortunately he became Engineer and now he's working full time in a completely unrelated field, say Electrical utility company or something like that.
Quote from: Steve Conner on February 27, 2010, 08:30:07 AMHi all... I've been a long time contributor to the MEF, but this is my first post here, and I've been thinking about this subject a lot lately.You can copy the transfer function of a tube as closely as you like, with circuits of ever increasing complexity, but what I'm wondering is: How close does it really need to be?It seems to me that all a "tube simulator" needs is a gradual, soft clipping characteristic that starts with low-order harmonics, moving to higher-order as you push it harder. It shouldn't hang up from saturation effects, and it should draw "grid current" so that you can have duty cycle modulation.I don't think any finer level of detail than that really matters. It might change the "flavour" of the tone a little, but it won't make the difference between caviar and cr@p.Thoughts?
Quote from: J M Fahey on February 27, 2010, 11:51:00 AMLet us not forget that curve or slope cloning emulates a *clean* triode.The *clipping* triode emulation is a whole other game, and then we will be able to emulate Preamp distortion only.
Quote from: Findeton on March 23, 2010, 11:45:34 AMI've got a simple question: is Ik=Ig+Ip or Ik=Ip? Of course I need to know this to properly emulate grid current saturation.