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Old 24th June 2011, 06:31 PM   #301
Sync is offline Sync  Serbia
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Pass AlephJ and Aleph30 amps don't work with Legato3 if gnd on xlr is lifted...
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Old 29th June 2011, 06:07 PM   #302
orpheus is offline orpheus  United States
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I have built a Legato 3, but haven't installed it yet, in part because I am having difficulty understanding and researching if common mode DC will damage my system.

I have active loudspeakers made by ADAM, and I have emailed them to inquire if common mode DC will work with their equipment. I think that I failed in explaining the situation to them, as they answered as if I was inquiring about offset. I would bet that it would be ok to use the Legato with my setup, but I want to ask the manufacturer to be certain.

Here is what I am thinking of writing to them in response, please let me know if I have made any errors, or if I should add anything.



The DAC I want to use has common mode DC at the balanced output, but no differential DC. At the balanced output of the DAC, there is no DC between + and -, but 7-9 volts of DC between + and Ground and - and Ground. Will the DC between + and Ground, and - and Ground cause problems for the amplifiers, or will it work since the DC between + and - cancels itself out?


Thank you for your time and assistance.

Aaron.
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Old 29th June 2011, 06:13 PM   #303
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Quote:
Originally Posted by orpheus View Post
I have built a Legato 3, but haven't installed it yet, in part because I am having difficulty understanding and researching if common mode DC will damage my system.

I have active loudspeakers made by ADAM, and I have emailed them to inquire if common mode DC will work with their equipment. I think that I failed in explaining the situation to them, as they answered as if I was inquiring about offset. I would bet that it would be ok to use the Legato with my setup, but I want to ask the manufacturer to be certain.

Here is what I am thinking of writing to them in response, please let me know if I have made any errors, or if I should add anything.



The DAC I want to use has common mode DC at the balanced output, but no differential DC. At the balanced output of the DAC, there is no DC between + and -, but 7-9 volts of DC between + and Ground and - and Ground. Will the DC between + and Ground, and - and Ground cause problems for the amplifiers, or will it work since the DC between + and - cancels itself out?


Thank you for your time and assistance.

Aaron.
I would add, "Or can I omit the signal ground all together?" As this would eliminate the DC all together. It is often not needed.
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Old 29th June 2011, 06:43 PM   #304
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May I ask a question regarding removing ground on balanced outputs? A balanced output works by keeping the signal that is equal and opposite in polarity respecting to ground, and discarding the signals that are equal in polarity and voltage.

How can you remove ground with no issues, where is your common reference?

Regards,
Regi
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Old 29th June 2011, 06:49 PM   #305
orpheus is offline orpheus  United States
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Originally Posted by BrianDonegan View Post
I would add, "Or can I omit the signal ground all together?" As this would eliminate the DC all together. It is often not needed.
Thanks so much! I appreciate your time and help.

Aaron
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Old 29th June 2011, 06:49 PM   #306
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Quote:
Originally Posted by regiregi22 View Post
May I ask a question regarding removing ground on balanced outputs? A balanced output works by keeping the signal that is equal and opposite in polarity respecting to ground, and discarding the signals that are equal in polarity and voltage.

How can you remove ground with no issues, where is your common reference?

Regards,
Regi
The derived center point between the differential signals.
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Old 29th June 2011, 06:55 PM   #307
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The derived center point between the differential signals.
That's clear, thanks!
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Old 30th June 2011, 11:33 PM   #308
alazira is offline alazira  United States
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Hi Brian,
So one can try without the ground and if it works great, but if it doesn't then nothing bad will happen, just no sound?
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Old 1st July 2011, 12:37 AM   #309
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Yes, or bad sound. (You will know.)
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Old 2nd July 2011, 02:17 PM   #310
gwikse is offline gwikse  Norway
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Finished my legato 3.1
Playing through some cheap headphones atm. Have never heard them sound this good though

Tried using no ground connection to my icepower 1000asp modules (with attenuator for testing purposes). I had a little background noice through the speakers. Are yours completely silent?

At start up the + - outputs measure 2mV dc but settles down to 0,0 and I was wondering what your numbers are? Do you see the same during warm up?

I had the output at 0mV initially but noticed that after a while I had aprox -2mV so I adjusted it too keep it as close to 0 as possible when warm.
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