Work flow suggestions

my advice if you are building analog circuits is not to use SPICE and

this goes 10x if they are audio circuits. SPICE will not tell you

whether your circuit picks up hum or radio stations or your cell phone.

It won't let you know about common ground impedance that makes your

circuit ring or distort. It usually doesn't tell you what it will sound

like when your choice of opamp saturates, or nearly saturates.  It will

not tell you whether you want a mica or ceramic or polypropylene

capacitor. In fact, it usually won't tell you anything you don't already

know. Your ears will tell all of these things though.

SPICE is sometimes good for figuring out what function a filter does or

how to modify that and basically for experimenting with parameters in

ideal circuits...but it's no substitute for a real circuit. Audio

circuits, unlike some other types of circuits, are easy to breadboard.

Gary Gofstein wrote on Tue, 23 February 2010 15:28

my advice if you are building analog circuits is not to use SPICE and

this goes 10x if they are audio circuits. SPICE will not tell you

whether your circuit picks up hum or radio stations or your cell phone.

 

It won't let you know about common ground impedance that makes your

circuit ring or distort. It usually doesn't tell you what it will sound

 

like when your choice of opamp saturates, or nearly saturates.  It will

 

not tell you whether you want a mica or ceramic or polypropylene

capacitor. In fact, it usually won't tell you anything you don't

already

know. Your ears will tell all of these things though.

 

SPICE is sometimes good for figuring out what function a filter does or

 

how to modify that and basically for experimenting with parameters in

ideal circuits...but it's no substitute for a real circuit. Audio

circuits, unlike some other types of circuits, are easy to breadboard.

Great advice Gary, and I've heard it from others. For me, I'm using Spice

as more of a learning tool, like you said, figuring out what a filter is

doing, and experimenting. As I said, I'm not doing too much original

design, mostly as a tool to understand circuits others have designed and

for experimenting with designs which already work and which I may or may

not want to actually build. I want to take a schematic into Spice and probe

it so I get an intuition for what signals are doing where, and for

learning, and maybe to help trouble shoot when I stuff the wrong

capacitator on the board

Would you recommend doing the schematic in Eagle, then porting it to B2

Spice?

Thanks for the reply.

David

--

Browser access to CadSoft Support Forums at http://www.eaglecentral.ca

well..if it's easy to port it to SPICE then you have the advantage that

if you want to make a board, the schematic is already in EAGLE. that may

not be such a big advantage if modules are small and easily copied from

one schematic capture tool to another.

again..i would skip SPICE and just play around with the circuit on a

breadboard. to check things in SPICE I would just use circuit fragments

- although maybe your modules are so simple that they are almost circuit

fragments anyway. Really only useful for frequency domain analysis.

If your oscilloscope has builtin FFT, you can often quickly see circuit

response by exciting it with white noise. and if you can average the

spectra ( as opposed to signal) on the scope or computer, you'll get

decent response curves. if you are making an audio synth, that wng will

be your first project anyway.

unfortunately, i believe that the best way to get learn about the freq

domain is to study it. use old books (like from the 60's) that don't

rely on computers and DSP. learn how to use the s-plane. someday I will

have time to do this properly, too

Gary Gofstein wrote on Wed, 24 February 2010 17:37

well..if it's easy to port it to SPICE then you have the advantage that

 

if you want to make a board, the schematic is already in EAGLE. that

may

 

deleted...

 

unfortunately, i believe that the best way to get learn about the freq

 

domain is to study it. use old books (like from the 60's) that don't

rely on computers and DSP. learn how to use the s-plane. someday I will

 

have time to do this properly, too

Thanks Gary. I think I agree. It makes sense to do the capture in Eagle,

then port to B2 Spice. I will be doing less simulation that schematic

capture so I think it's more efficient this way.

For what it's worth, when I started getting back into electronics a year or

so ago, I bought some new tools and I do have a good (not top of the line)

dual trace scope with FFT.

For context, my background includes graduate degrees in physics and

bioengineering, and I took several EE courses as a senior in undergraduate

school. I've done a lot of control system design and analysis so the "S"

plane is (well, used to be) my friend :). I've designed and built

instrumentation/data acquisition systems, and for the past several years,

I've been analyzing dynamical systems and writing some dynamic simulation

code. That said, I never did really learn analog design. I'm still

convinced it's done in dark rooms with chicken bones and black magic

The modules are mostly pretty simple. A few op-amps, a couple of

transistors, and the requisite capacitors and resistors. Even the most

complicated ones typically fit with room to spare on a 160 X 100 mm board.

So far, none are my own design and so their respective designers have done

the breadboarding and confirmed their designs. There are just so many I'd

like to look at and learn from but I'm disinclined to buy the parts and

spend the time breadboarding them. I'm hoping I'll be able to get enough

out of a decent simulation to satisfy my curiosity.

I do appreciate the time you've taken to discuss this with me.

David

--

Browser access to CadSoft Support Forums at http://www.eaglecentral.ca