Well OK...but I would always try to do without screening, and as far
as possible without insulation too. But if you are dealing with an
amp that is already crowded, with preamp and ps on same chassis,
then I suppose you must do what you can.

My only guitar amp is a converted PA...same circuit as a Marshall.
There are no screened wires, BUT there is a shield between power
valves and input valves...just a sheet of aluminium sticking up from
the chassis about half way.

The screen and anode wiring to the bases is all in one plane with
the other wiring, arranged so there are ground and other
low-impedance circuits between them and the input stage wiring.

I guess combos, with tight 3-dimensional layouts, are more
problematic.

Perhaps Tony might also try screening cans on the input valves.

cheers, Ian

"Choky" wrote in message
...

"Ian Iveson" wrote in message
...
Doesn't the capacitance to ground blur your microtransients? Or
risk new HF squeals in feedback amps?

nope with clever arrangement of grounding


But seriously, this is an equation with several variables.
Horses
for courses and all that. Or do you think it is always better
to
screen high-amplitude signals?

yes,I think-especially when chassy is small,OPT is relativelly
near input
wiring etc
naturally-when trouble arrive,cure can be also removing of that
shielding
and mebbe some other shielding also;
there is not any absolute rule,remember?
only many rules of thumb to help us in avoiding trouble.
but sometimes ,nature (or physic laws-if you prefere) play little
games with
us,so we must use some other approach.
same as that there is not one absolute best grounding scheme (
plane,star
,bus etc) ;
one is always better than others,but just for exact case.


Why is it better to screen the HV wiring, rather than the high
gain
+ high impedance wires that it radiates to?

screen everything if ya can;
or screen nothing if ya can;
what is better you choose.
but,in any case you must have starting strategy,don't ya think?

cheers, Ian