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Tubular simulations - AC30SIM, BC-60, LHX2, 5032796

11/28/2000 9:28 PM
Tubular simulations - AC30SIM, BC-60, LHX2, 5032796
I decided to break this out from the other thread as it was getting rather long and twisted. And it's one of my passions.  
"If that's the one I'm thinking of, it is an approach that is very similar to LXH2's Marshall and Fender simulators."
Not "very similar" to my thinking. Stephan used a *much* more sophisticated approach. Here's the link for Stephan's AC-30 sim  
The AC30 SIM has a total of *4* non-linear stages with interspersed EQ, (not counting the speaker emulation). And so does a *tube* AC-30.  
The Roland BC-60 design also uses multiple non-linear stages with EQ in-between as well.  
In contrast, the LXH2 Marshall design uses *one* non-linear stage (a simple diode clipper, same as a JCM-900 Marshall preamp), with EQ before and after it. But a Marshall amp uses a total of *4* non-linear stages (some new ones use more)with interspersed EQ.  
The LXH2 Fender design uses *one* non-linear stage (although it *is* a complex one implementated using long strings of diodes, a cap and a couple of zeners in parallel to get a more complex transfer curve out of that one stage), with EQ before and after it. But a Fender Twin uses a total of *4* non-linear stages with interspersed EQ.  
Therefore, both the LXH2 designs consist of EQ circuitry before and after a *single* non-linear stage - maybe more than one, if you want to count some op amp clipping in the Marshall emulator, as a non-linear stage emulating a tube (a stretch in my book).  
Not designs I would call "*very* similar" to 4 carefully tailored non-linear stages with EQ interspersed. IMHO, a very *different* approach to designing an amp simulator.  
Of course, I have been justly accused of being excessively "picky" about details at times (yet another one of my character flaws - oh, the shame... ;) ).  
(And this is *not* to belittle the LXH2 designs, just to point out there are *major* differences between his design implementation and the AC30 SIM and BC-60 approaches. LXH2's designs say a lot more about making an amp with tubular tone than patent 5032796.)  
The original point of the post was - patent 5032796 is *not* much of a tube emulator. LXH2 is a step in the right direction (well, minus the *16* op amp active filters in the speaker emulator anyway - jeez, talk about generating NOISE!!).  
BTW - Stephan's design does speaker emulation with 4 inductors, some caps, and generates NO NOISE). Now you probably suspect how I got into winding torroids a few years back...  
So anyway, *IF* you want to understand what makes tubes "magic" besides urban legend....and *IF* you have an interest in analog tube simulation technology as it continues to mature, you can learn *many* more useful concepts and approaches one heck of a lot faster by studing circuits from better teachers (than patent 5032796) - like Stephan.  
But if you're *not* interested in such matters, that's OK, too.  
My point #2 (from the old post)clearer?  
I guess I muddied things up by bringing this subject up here. This *is* Aron's STOMP BOX forum. But what the h*, we talk guitar electronics, power attenuators, channel switching, so why not? And *hey*, why did Jack have to go and put that amp emulator circuit in a stomp box in the first place? [feigned rage] ;)  
Well, IS anyone else out there interested in discussing how to continue to unravel further the magic of tubularity (besides Hartley, who doesn't seem to hang here much lately ;)  

aron Re: Tubular simulations - AC30SIM, BC-60, LHX2, 5032 -- 11/28/2000 11:01 PM
Doug H Re: Tubular simulations - AC30SIM, BC-60, LHX2, 5032796 -- 11/29/2000 6:00 PM
gfr I agree the LXH2 has a diffeent app... -- 11/30/2000 10:52 AM