"David Looser" wrote in message
...
"fredbloggstwo" wrote

snip

With something as simple as a line amp I'm suprised that you need
auto-routing. Most PCB layout software offers a manual routing option, why
not use that?

David.

Hi David

I am doing the manual routing - I thought that I had mentioned that in my
original post as I like the challenge of doing so even more so on a single
sided board :-).

As regards the RF considerations that Don mentioned. I also seemed to
remember doing university experiments where it was clear that low frequency
signals do radiate at sharp corners and plotting them on conductive paper as
so many volts per metre.

The other points raised such as grounding and power lines are taken for
granted. I was just wondering if there is any evidence on the more esoteric
aspects as a point of interest.

On the point of 'a complicated line amp', its a bit of an unusual one as it
is a Class A design with a constant current output stage, quite elegant,
that drives a chunky transformer, so having 4 transistors and a plethora of
resistors and diodes, its not quite like a straight forward your average
5534 with a beefed up output stage.

Mike

In article , fredbloggstwo
wrote:


As regards the RF considerations that Don mentioned. I also seemed to
remember doing university experiments where it was clear that low
frequency signals do radiate at sharp corners and plotting them on
conductive paper as so many volts per metre.

Its true that 'sharp' features (local curvatures) do increase the local E
field levels around the point. And that the E-field lines tend to 'radiate'
in the geometric sense from them. However it will then depend on other
nearby conductor shapes how much E-field coupling there will be. Also how
long the straight parts are either side of the corner/point.

For low frequencies you can work these things out using quasi-static
approximates, etc. If you want some good books on the theory then my
personal recommendations are "Electromagnetics" and "Antennas" both by
Kraus. His book "Radio Astronomy" is also excellent if you have an interest
in things like RX design, enviromental factors, etc.

Kraus worked for many years designing and developing high-performance
systems. His books explain *clearly* a number of details that many other
books on EM, etc, either gloss over or make a dog's dinner of explaining.

Ramo, Whinnery and van Duser is also pretty good, but IMHO much less
clearly written than Kraus.

The other points raised such as grounding and power lines are taken for
granted. I was just wondering if there is any evidence on the more
esoteric aspects as a point of interest.

On the point of 'a complicated line amp', its a bit of an unusual one
as it is a Class A design with a constant current output stage, quite
elegant, that drives a chunky transformer, so having 4 transistors and
a plethora of resistors and diodes, its not quite like a straight
forward your average 5534 with a beefed up output stage.

One advantage of steady rail current Class A designs is that you don't have
to worry so much about coupling with the rails since they aren't radiating
any ac. Although with more common designs they will of course be showing
variations like those of the signal - but that isn't likely to be a source
of distortion. :-) The downside is that ripple needs more attention in
terms of having an adequate PSU for the high demands.

Slainte,

Jim

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