duncanamps.com

[RichardD]

I'm still using a very old copy of PSpice, and I think some modernisation is due. Is there any agreement on which is the best (free) software for playing around with valve circuits?

Thanks.

[Ray Moth]

LTSpice is free, so this post might sound somewhat ungracious. Let me say, firstly, that when it works it's OK; however, it has a few warts that rather spoil it.

Firstly, the HELP function and the error log are not very helpful, in my estimation, probably because LTSpice was written by academics who are notorious for not being able to explain things well. The error log might mean something to one of the programmers who wrote LTSpice but it's mostly meaningless to me.

Secondly, the method of referring to numbered nodes in the circuit without identifying them meaningfully makes it difficult to understand things like the output of the DC operating point analysis. The user interface in this respect is rather primitive.

Thirdly and worst of all, there are BUGS:

- It's inclined to be temperamental and goes into 'sulking' mode, when it just refuses to simulate, especially using the 'normal' algorithm; the 'alternate' (I guess they mean 'alternative') algorithm seems a bit better.

- It invents excuses, like complaining that the timestep is too small but with no hint as to what can be done about it, or complaining about 'floating nodes' that don't actually exist. I've tried fiddling with the Spice Control parameters and that seems to have an occasional effect but I don't really know what I'm doing there and, guess what? the HELP function tells me absolutely f**k all about it!

- In the Transient analysis, I have experienced wildly varying run-times for circuits of similar complexity, for no apparent reason.

[DonnyJaguar]

This may seem like a silly question, but if LTspice is fraught with so many bugs, is there something else I should try first? I'm trying to determine idle current through various triode sections to choose my power supply resistors accordingly.

DJ

[Tubewonder]

MicroCap8 from http://www.spectrum-soft.com/

Free demo version is limited to 50 components but it usually is enough. Only a few tube models are included with the demo but it's easy to use and stable.

Another is Superspice fromhttp://www.anasoft.co.uk/, rather cluttered GUI.