Legato 3, Common Mode DC and You. How do you choose to deal with it? - Page 9 - diyAudio
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Old 16th September 2013, 04:29 PM   #81
goober5 is offline goober5  Canada
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I've run my Legato directly to a Aleph J. Works fine but there is a slight hum without the ground connected. The noise disappeared when I connected the ground to the amp through a cap. Sounds pretty good.
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Old 16th September 2013, 04:48 PM   #82
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Default Legato-Ncore

It turns out one of my Ncore modules had a problem. It is now back in NL getting repaired/replaced.
I suspect that when I have two properly operating modules I will be bale to run the Legato 3 without coupling caps directly into the Ncores, with no ground connection.
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Old 20th October 2013, 02:30 PM   #83
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Default Update, Legato 3-Ncore stereo amp

OK. I got a new Ncore module, and tried it. Frustrating, as I still have significant hum trying to run from the L3 direct to Ncore.
I would give up and cap couple, except that some appear to have success with this combo. So I am going to ask again for ideas. Here are my details:

Legato 3: balanced outputs only. +/- connected to pins 2 and 3 of XLR connector, G no connect.
Ncore stereo amp: +/- connected to pins 2 and 3 of XLR, pin 1 connected to chassis, G wire from Ncore modules connected to chassis.

+/- output from L3 DC offset nulled to <5 mV

Connecting G from L3 to pin 1 makes noise worse.

Another option is to transformer couple the input of the Ncore amp, taking the center tap for G to the Ncore modules and only connecting pins 2 and 3 to the input side of the transformer. I think this will work, but comes with the expense of two good coupling transformers.
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Old 23rd October 2013, 10:09 PM   #84
miero is offline miero  Czech Republic
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No hum here, but I'm using the coupling caps at the B3 caps.

I've not tried it, but what about connecting GND via cap, and keeping hot/cold conected directly?
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