Ground problems... Please help...

[blindsjc]

Hi friends,
I'm in trouble with a project ground,
I have a PSU, preamp, poweramp and an effect at the same pcb.
I need to know the best way to ground all these subcircuits to
avoid noise and hum. May I use a star ground, getting all the ground
points in all subcircuits and group then at the chassis ground? The
same with the input and output jacks ground? I'm really lost in
this task, please help. Thanks a lot.

Take a look at the project components:


Link: http://blindsjc.v10.com.br/placas.htm

Ronaldo

[joecool85]

The picture isn't loading.  I will say, however, that star grounding is the way to go.

[teemuk]

First read: http://www.ssguitar.com/index.php?topic=288.0 if you haven't done that already. If you did, read it again.

Have you selected the common point from the PSU board and is it effective choice? At the boards, did you make a separation between audio and power ("dirty") grounds and possible grounds for relays, digital stuff etc - if you use them? Did you route logically so that they will not interfere with each other?

Star grounding scheme is way to go but practically its too "complex" and can begin to act as antenna if the wiring grows too long. Luckily one can often cut the amount of return wires used. Read the tutorial, it should give pretty much insight of the topic.

[blindsjc]

I will read it again, and will search for
something that I probably misunderstood.
After I will post again the results. Thanks
for the help.

Thx

[blindsjc]

Hi friends,
In the text about star ground (aiken), the author talks about
a two stage ground point to separate the preamp section from
the other high gain stages. In my project I have a preamp, power
amp and two effects. One of the problems I think are these high
gain effects and power amp bringing noise to the preamp.

Can you give me a view about the two stage star ground? The text
is no clear to me and I cant understand where the two points are
really located, and how to test it.

[teemuk]

I think he states it pretty clearly: Power supply and high current common returns are connected physically closer to common point (in this case leg of one of the main filter capacitors) and the preamp grounds (that use lower current) are connected physically further from the common point (in this case leg of one of the filter capacitors supplying the preamplifier).

In practice, this IS NOT a star ground - it is just a way to bundle common returns together in a safe way. A true star grounding scheme would NOT bundle any of the common returns together! If people would stop misusing the term "star ground" the whole concept might be easier to understand.

The configuration is pretty much the same as the description in the grounding tutorial of this site:

Lower currents -> Higher currents -> Common

Aiken makes no distinction between preamplifier's supply and signal grounds but you get better result if you separate them from each other.