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Scott Dorsey Scott Dorsey is offline
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Default Where does the hum come from?

I am -assuming- that the original poster is plugging a DAC that has a TRS
1/4" output into a powered speaker with a TRS input, using a proper
TRS-TRS patch cable and that no speaker wire is involved.

If unshielded speaker wire is used for line level connections, there will
be a hum.

Now.... a thing can hum for two reasons: either something is grounded in
two places (causing a ground loop) or something is not grounded at all
(causing something to be unshielded).

We know the problem is not a ground loop because there is no connection
to the DAC other than the speaker, and there is no connection to the
speaker other than to the DAC and power.

It's quite possible the DAC does not have a pin 1 connection to chassis and
that therefore it is effectively unshielded until an input or power is
connected to it. A multimeter will very quickly show if this is the case.

If so, the hum will disappear when the system is configured for actual use.
--scott


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