Best way to eliminate DC voltage at my DAC output?

[robbbby]

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.

Thanks

 

[analog_sa]

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.

 

[robbbby]

Would a 1uf film capacitor be the right choice?

 

[ytsoc]

it might attenuate lower end of the band(aka the bass), maybe a 4.7 or even higher?

 

[DF96]

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.

 

[analog_sa]

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.

 

[robbbby]

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

 

[cotdt]

Just use some 2.2uF Mundorf Supremes. They are cheap budget capacitors.

 

[robbbby]

Ignorant question but do larger caps lower the cutoff frequency or smaller caps?

 

[cotdt]

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.

 

[WithTarragon]

Let's get serious here!
Do a google search on RC high pass filter. The cap is in series and resistance (to gnd) is mostly the input impedance of the amplifier (load). The number you get is the -3dB down point.

 

[robbbby]

So the hypex ncore400 has a differential input impendance of 104k ohm. With a 1uf cap I get a cutoff frequency of 1.53Hz.
Is that not low enough, should I be going bigger?

I have absolutely no idea what -3db down point means.

 

[cotdt]

Yes go with the 1uF. Such cap values tend to be very transparent, as if not even there, so long as you get a decent quality capacitor.

 

[robbbby]

I'm afraid to ask but what would be a good cap?
Was looking at the mundorf supreme silver/oil or silver/gold/oil/etc but they seem a little rich for my blood, especially since i'm running balanced and need 4, so I started looking at the regular mundorf supremes which aren't bad at $18.90 a piece.
Then there are the other mundorf MKP M caps (white with red writing), only $3 each.

 

[cotdt]

The regular Supremes are the way to go. They are two standard poly capacitors combined together to cancel inductance. The Silver/Oil has a little more treble emphasis, but I think the regular Supremes are more neutral. ClarityCap MR is another excellent option.

 

[robbbby]

The silver/oil are unfortunately 3x the price of the regular.
I'll definitely take a look at the claritycaps.
Appreciate the recommendations.

 

[analog_sa]

I'm afraid to ask but what would be a good cap?

It would really depend upon how good your unnamed dac is and how high are your expectations. Count yourself lucky the Hypex is so high impedance

 

[fiscal]

Hi

Are you shure That your amp have a 200x gain? May be your amp generate CC. Did you mesure it?

 

[analog_sa]

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

50mV of offset is outright defective in my view. Your preamp is being used effectively as an attenuator, so this explains the reduction of DC as well as AC at normal listening levels. Still, not listing your equipment when asking for advice is wrong.

 

[fiscal]

Oops