Best way to eliminate DC voltage at my DAC output? - diyAudio
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Old 3rd January 2013, 10:07 PM   #1
robbbby is offline robbbby  Canada
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Default Best way to eliminate DC voltage at my DAC output?

Apologies in advance if this is posted in the wrong forum, seemed like the best spot.

My dac (not a diy, actual production dac), has about 25millivolts DC at it's output and after passing through the voltage gain of my amp (hypex ncore400) I end up with 500mVDC at my speaker output. This translates into lots of pop when sometimes stopping music playback, powering down amps, adjusting volume or muting. I was just wondering what would be the best way to remove this DC before it gets to my amp without hurting the sound quality.

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Old 3rd January 2013, 10:21 PM   #2
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No way of telling without seeing the actual circuit of the dac. The easy solution is a good quality cap in series with the Hypex inputs. It won't be completely invisible sonically and will definitely be expensive.
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Old 3rd January 2013, 10:39 PM   #3
robbbby is offline robbbby  Canada
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Would a 1uf film capacitor be the right choice?
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Old 3rd January 2013, 10:53 PM   #4
ytsoc is offline ytsoc  Romania
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it might attenuate lower end of the band(aka the bass), maybe a 4.7 or even higher?
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Old 3rd January 2013, 10:57 PM   #5
DF96 is offline DF96  England
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This could be either a fault or design error in your DAC. Faults can be repaired. Design errors can be harder to fix, but a suitable cap (plus resistor to ground) should do it.
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Old 3rd January 2013, 11:14 PM   #6
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Quote:
Originally Posted by robbbby View Post
Would a 1uf film capacitor be the right choice?

It will depend only upon the Hypex input impedance (sorry, too lazy to check).

Why don't you mention anything about the dac? Reluctant to tamper with it?

It may turn out that a simple opamp replacement will reduce the offset sufficiently.
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Old 3rd January 2013, 11:27 PM   #7
robbbby is offline robbbby  Canada
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I am hesitant to tamper with anything made by people who know what they are doing, especially when it is under warranty for 3 years

I actually just did some more tests since some of my setup recently changed.

The dac is actually outputting closer to 50millivolts DC now. I was previously using the built in attenuator on the dac, now I have a preamp so it is set to bypass and the full voltage out of the dac has resulted in more DC as well. Fortunately now, it seems my preamp takes care of the DC, the resulting DC output at my speaker outputs is now only 200millivolts at maximum attenuation of the preamp, at regular listening levels it is only like 20mV
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Old 4th January 2013, 12:10 AM   #8
cotdt is offline cotdt  United States
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Just use some 2.2uF Mundorf Supremes. They are cheap budget capacitors.
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Old 4th January 2013, 12:24 AM   #9
robbbby is offline robbbby  Canada
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Ignorant question but do larger caps lower the cutoff frequency or smaller caps?
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Old 4th January 2013, 02:08 AM   #10
cotdt is offline cotdt  United States
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Quote:
Originally Posted by robbbby View Post
Ignorant question but do larger caps lower the cutoff frequency or smaller caps?
Larger caps, but they also add more in the signal path. Smaller caps are more transparent-sounding.
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