[LAD] simulating analog audio devices part II

Giuseppe Zompatori siliconjoe at gmail.com
Fri Jun 8 08:02:39 UTC 2007


Some time ago I did a sim using LTSpice
(http://www.linear.com/designtools/software/) under Wine of a Carvin
Legacy tube amp. LTSpice was the only program that had wav in/out and
would run on Linux at the time I tried this.
The schematic for the amp is here
It's a complex beast that ngspice would have lots of troubles
simulating because of the infamous "floating nodes" and other quirks.
Everything is included into the sim, preamp, phase splitter, output
valves , output transformer and even the model of a greenback speaker.
Naively, I haven't set the sim time step to the a sampling freq
related number, nevertheless it sounds Ok to me, I dont know how
LTSpice deals with transient sims involving wav files in details.

The ogg for the sim is here:


I played a bounch of fast licks to have the transient sim finish
before the universe will collapse, yeah you guessed it it's pretty
slow... I think it took 1 day to finish on an AthlonXP 2800+...
Now days I am messing around with GNUCap and QUCS (http://qucs.sf.net)
to which I just ported my first tube model whose plate voltage/grid
current curves look like that:


Hopefully a way to inject wav files in both GNUCap and QUCS will come
true as they both seem better than spice derived programs.



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