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

11/28/2000 9:28 PM
Bart
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Tubular simulations - AC30SIM, BC-60, LHX2, 5032796
Doug/All,  
 
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.  
 
quote:
"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  
 
http://www.geocities.com/ResearchTriangle/System/2787/All-Cirquits/all-cirquits.htm  
 
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 ;)  
 
Cheers,  
Bart

 
Replies:
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