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Scott Dorsey Scott Dorsey is offline
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Default Mic preamp output transformer question

wrote:
On Wednesday, September 12, 2018 at 2:36:07 AM UTC-4, =
wrote:
I notice this circuit uses only one ground, rather than different groun=

d and
chassis earth. This may come to bite you if you're trying to get noise=

down.
=20
Cool. I wondered about grounding and have drawn the power supply ground s=

eparately to the "everything else" ground in KiCAD. I suspect that's not wh=
at you're suggesting though. How would you configure the ground(s), and whe=
re would you advise connecting them together?
Thanks!


the most important ground issues involve signals that enter and exit

1) the + and - leads from the wall wart should go directly to the 470 uf c=
ap so that large ripple currents do not flow through any grounds. I would =
also use the one point to tie the circuit to chassis ground.

2) the pin 1 connections for the XLRs should go directly to the chassis so =
that any large ground currents do not flow through the circuit grounds. Yo=
u can google "pin 1 problem" to learn more about this.


This is a good description.

If you're hand-wiring the thing, try and have a chassis ground and an
internal ground and connect them at only one point. If you're using
a PC board, make a ground plane and connect that to the chassis ground at only
one point. You don't want circulating currents through the chassis at any
time.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."