Ground Busses
"Ian Iveson" wrote in message
.uk...
Iain Churches wrote:
My experience with ground buss amps is limited. I have never been
able to make them quiet enough. I found that the exact position in
which a wire was placed on the buss was critical, and that a difference
was audible.It may be there is something lacking in my implementation
of the buss.
I guess the order in which connections are made along a bus is
significant. If you think of the bus as a resistor, then a high-current
return placed furthest from the ground will produce a voltage gradient
along the bus. If the next connection is, say, the signal ground from the
first gain stage, that voltage could be significant.
OTOH, if the connections to the bus are made in order of highest current,
the voltages they produce will be minimised.
But perhaps there is countervailing argument? If a sensitive connection is
close to the ground, then a voltage produced by a high-current connection
further along will be attenuated. So perhaps the order is important, but
it doesn't matter to which end of the bus the ground is connected? What
you don't want is a high-current connection and a sensitive connection
both distant from ground.
Very interesting. Thanks.
Next time I build a prototype, I will try this out.
I find a genuine star earth is hard to implement if there are many ground
connections to make. Exactly how do you fashion a star?
My stars are not symnmetrical with the ground point in the
middle if that what you mean. On a power amp I put the
chassis bonding terminal close to the AC socket, and on
a preamp close to input 1.
I usually make up the star on the bench, as a cableform,
and then fit, trim the loose ends and solder.
The signal ground must be safe to touch if it is brought out to exposed
external connectors. If a resistance is placed between the 0V and chassis
ground, then it should be a low enough value and high enough power to
ensure that the fuse, and not the resistor, will blow quickly if the
signal ground becomes live due to some fault. Perhaps some statutory
regulations apply?
Not a "pro", or an "expert", as usual, thankfully.
Ditto. But thanks for your thoughts, Ian. This is an
interesting business.
Regards
Iain
|