wire wrap vs. high freq. attenuation

Tony Clark clark at andrews.edu
Tue Dec 2 04:32:41 CET 1997


> I guess I should have thought about this before I wire-wrapped numerous 
> modules, but I recently read something that made me think that making a 
> pcb might be better than wire wrapping in circuits where high 
> frequencies are involved.

   Yes, the main problem here is crosstalk.  In most cases where I've 
seen wirewrapping (old 8-bit computers mainly) you'll have a serious mass 
of wires travelling every which way with NO shielding other than the 
enamel (or plastic) wire coating.
   For those old 8-bit computers, crosstalk doesn't matter too much 
because its either on or its off, who cares if there's 500mV worth of 
noise on the signal?!

> What's the relationship here?  More importantly, has anyone wire wrapped 
> a VCO, VCF, VCA, etc. with no problems in the high frequency ranges?

   Continuing my paragraph above...An analog circuit board is going to be 
more prone to these crosstalks where every small amount of bleed-through 
adds up to a slightly noisier output.

> I know that most people probably make their own pcb's, but I really 
> enjoy wire wrapping.

   Hey, I'm not knocking wire wrapping, it's a legit form of doing very 
small quantity circuits!  Most prototyping methods are prone to the exact 
same problems!  Now whether or not you'll actually _notice_ this 
crosstalk happening is a totally different matter.
   I can say that I haven't seen any side effects of my circuits being 
prototyped in less than ideal circumstances (only slightly better than 
wire wrapping I'd hazard a guess), but then I don't really consider 48kHz 
"high frequency" either.  I'd imagine that I'd categorize that as 
anything above 1MHz or so.
   In conclusion, I don't think you'll run into any trouble wire wrapping 
your circuits.  Hope this is a bit of reassurance!

   Tony

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