[sdiy] LTSpice problem: simulating Irwin/Gallo linearised 2164 VCA

Tom Wiltshire tom at electricdruid.net
Thu Aug 22 15:26:40 CEST 2019


Hi Neil,

Thanks for the offer. I’ve managed to find a way around it.

Reading similar problems in forums online suggested to me that the solver struggles to find a workable initial condition for the VCA-in-feedback-loop. It then tries a smaller timestep to see if it can fix that, and finishes up repeating this process until the time steps become tiny and it chucks the error.
Changing LTspice’s default Spice engine solver and altering the DC solution method seems to avoid this problem and I get a sensible simulation result.

(It works using “NoOpiter” DC solution method and “Alternate” Solver, in case anyone needs to know).

Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================

> On 22 Aug 2019, at 14:04, Neil Johnson <neil.johnson71 at gmail.com> wrote:
> 
> Hi Tom,
> 
> I've had good success simulating this circuit (and others based on various models of the 2164), but without your files it is difficult to know what "node n005" is.
> 
> If you can simplify your circuit down to the simplest possible that still shows the problem you're seeing and you can share it maybe we can help?
> 
> Cheers
> Neil
> 
> 
> 
> On Thu, 22 Aug 2019 at 13:02, Tom Wiltshire <tom at electricdruid.net> wrote:
> Hi All,
> 
> I’m having trouble simulating the Irwin/Gallo linearised 2164 VCA. The error I get is: “Analysis: Time step too small; initial timepoint: trouble with node n005”
> 
> I don’t really understand what this is trying to tell me since the .tran transient analysis command I’m using is unchanged since a previous typical 2164 VCA where it worked fine.
> 
> I can simulate other circuits using the 2164 ok, so I’m wondering if it’s something particular to that circuit, and specifically whether the feedback loop needs dealing with some how differently?
> 
> Have other people managed to sim this circuit and if so, what did you do?
> 
> Any pointers appreciated.
> 
> Thanks,
> Tom
> 
> 
> ==================
>        Electric Druid
> Synth & Stompbox DIY
> ==================
> 
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy




More information about the Synth-diy mailing list