Concerned about DC output comment of Audiophonics Hypex Amp.

[wiredrob]

I could use some guidance from the ASR community.

I’m looking at helping my daughter setup her system and am planning to buy an Audiophonics MPA - S250NC Hypex based amp.

FYI I plan to pair this amp with a Wiim Ultra, Elac DBR62, and Pro-Ject Carbon EVO TT.

I see a prominent warning on the website for this amp that is the reason for this post:

“This amplifier does not have a decoupling capacitor, so it lets the DC component of the signal through. Make sure your source has no DC component present at the output. The DC protection of the module switches on at 12VDC which is very permissive.”

Before I buy…Should I be concerned? How can I protect against this being a problem? How the heck would DC get in there?

Thanks in advance for any guidance.

 

[Sokel]

The warning is probably the result of @pma 's tests here on ASR (and rightfully so).
Every DC coupled amp should warn against it and this one is not the only one,there are a lot.

Lots of reasons why a device earlier in the chain can output DC,failure is one of them or bad design,etc.
Even music works can output DC as we have seen some examples here.

One should check every new device for DC before even connecting it to the chain,is so simple that anyone can do it with a simple DMM.
Even a perfect device can have a bad trip ( = bad shipping,poor packaging,etc) that can cause it to misbehave.

 

[meooms]

Agreed. On another note: the Hypex has balanced XLR inputs, the Wiim seems to have unbalanced RCA outputs.
It can be done, but it is not ideal, as the line output level will be lower.

 

[wiredrob]

The warning is probably the result of @pma 's tests here on ASR (and rightfully so).
Every DC coupled amp should warn against it and this one is not the only one,there are a lot.

Lots of reasons why a device earlier in the chain can output DC,failure is one of them or bad design,etc.
Even music works can output DC as we have seen some examples here.

One should check every new device for DC before even connecting it to the chain,is so simple that anyone can do it with a simple DMM.
Even a perfect device can have a bad trip ( = bad shipping,poor packaging,etc) that can cause it to misbehave.

OK good to know. Many decades of my audio enthusiast knowledge has just been updated. I have some follow up questions then:

• Do I test when playing music or at idle?
• Should the DC voltage reading equal zero? I imagine if measured while playing music the DC voltage reading might jump around as I think AC is nothing but varying DC.
• Even if initially testing OK, a failure of a component causing DC in the chain would only be measurable during failure not initially. How should I protect against that or is it not practical do so?

 

[Sokel]

OK good to know. Many decades of my audio enthusiast knowledge has just been updated. I have some follow up questions then:

• Do I test when playing music or at idle?
• Should the DC voltage reading equal zero? I imagine if measured while playing music the DC voltage reading might jump around as I think AC is nothing but varying DC.
• Even if initially testing OK, a failure of a component causing DC in the chain would only be measurable during failure not initially. How should I protect against that or is it not practical do so?

- Doesn't matter as a music does not go down there (well,it shouldn't but as wrote above some,very rare samples do)
- Ideally zero as any of it will be amplified down the road and we don't want that.Close to it anyway and no more than 50mV (single digit number though is a good sign of quality) at the final destination,speaker's binding posts.
- There are various ways to protect against DC,simplest one is a capacitor.With it's own implications of course and that's the reason some designs avoid it.

As for last question,it shouldn't be our concern as consumers to worry about it,sane design should include such protections against most incidents (not all though,unusual failures can always happen) .What I would look for is a good history record of the device(s) and some good luck.

 

[wiredrob]

Agreed. On another note: the Hypex has balanced XLR inputs, the Wiim seems to have unbalanced RCA outputs.
It can be done, but it is not ideal, as the line output level will be lower.

I'm getting the version with RCA inputs just like the one @Amir tested.

- Doesn't matter as a music does not go down there (well,it shouldn't but as wrote above some,very rare samples do)
- Ideally zero as any of it will be amplified down the road and we don't want that.Close to it anyway and no more than 50mV (single digit number though is a good sign of quality) at the final destination,speaker's binding posts.
- There are various ways to protect against DC,simplest one is a capacitor.With it's own implications of course and that's the reason some designs avoid it.

As for last question,it shouldn't be our concern as consumers to worry about it,sane design should include such protections against most incidents (not all though,unusual failures can always happen) .What I would look for is a good history record of the device(s) and some good luck.

Thanks for the greater detail.

I realized I could measure my home setup (NAD M10 V2 into Wilson Audio Sophias). Measured at the M10 speaker binding post I get 12 and 15 mV left and right. So less than 50 mV. Also changes slightly (+/- 10%) with different source material and volume although this could be due to poor connection of probe and vibration.

I will check the new setup once assembled. I'll measure first at the source (Wiim Ultra), then connect to the power amp and measure binding posts.

Thanks for the knowledge to help me be reassured.