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Hello,
Is it normal to have 9.290 VDC common mode DC bias (on the on - the and + relative to the GND) on the balanced outputs?
Is there any way to get this lower?
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Rank: Administration
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Yes, it is normal. Yes you can AC couple.
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Rank: Member
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Russ White wrote:Yes, it is normal. Yes you can AC couple. What caps do you recommend? Will I loose much sound quality ? Im using Hypex nCore amplifiers. It will handle common mode DC, but 8-9VDC will probably clip the input stage before the amp. Will it help if I don't use GND and only - / + ? Or is the best way to use capacitors on the output? Edited by user Tuesday, January 17, 2012 7:01:41 AM(UTC)
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Rank: Advanced Member
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Location: Norway
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As far as I can see from the datasheet from Hypex (NC400), it is a fully differential design. Ground is no part of the audiopath. My guess is that only connecting + and - should work.
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Rank: Member
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steinholien wrote:As far as I can see from the datasheet from Hypex (NC400), it is a fully differential design. Ground is no part of the audiopath. My guess is that only connecting + and - should work. Thanks Stein!
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Rank: Member
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Well, is it after all? If you look at the nc400 datasheet with a magnifying glass, you'll notice that the incoming signal ground is connected to the chassis, same as the nc400 signal ground. So those two things are connected.
I'd like to know the cap values as well. I tried to search the forum with no luck. Can't find the Legato 2 manual or bom either. Everyone is talking about them caps, but no one reveals the values.
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Rank: Advanced Member
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The best way to get a reliable answer on the need for caps, would be to contact Hypex. To calculate capacitor value you can check this calculator: http://www.v-cap.com/cou...capacitor-calculator.phpThey use this formula: C=1/(2*pi*fc*ZL) where C is cap value in F, fc is cornerfrequency and ZL is load impedance (input impedance of poweramp).
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Rank: Member
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Joined: 3/29/2009(UTC)
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Location: Finland
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Thanks! That clears things out. So, i need to put the caps into the amp then. I thought i needed to implement an universal solution to remove the DC from the legato output with caps.
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