Hypex NC252MP pop sound from tweeters when turned off

[Davide]

Hi everyone,

lately I've noticed that when I turn off my NC252MP (DIY) it produces a pop from the speaker tweeters.
It's not particularly strong but I'm worried it might be DC and ruin something at some point.
These modules have a PS Enable PIN which in theory allows you to go from standby to on, with no such noise.
But strangely turning it on with this produces an even louder pop (with both NC252MP and NC502MP) and in fact the PS Enable Pin is generally left shorted, and an upstream switch on the 115/230V power is used.
This is what happens in my case and this is also what all the various resellers of these modules seem to do, looking at their internal photos.
Ghent also sells the connector with jumper for PS Enable in the wiring kit.

Since both my NC252MP and NC502MP exhibit the problem I'm pretty sure it's due to the design rather than a defect, so I didn't contact the manufacturer.

What do you recommend?

Considering that these modules also have poor DC protection, is there any board that allows me to protect the speakers and prevent pops?

 

[Newman]

Hi everyone,

lately I've noticed that when I turn off my NC252MP (DIY) it produces a pop from the speaker tweeters.

It is normal. Not sure if your word ‘lately’ above means it was not there before?

It's not particularly strong

Then it won’t do any damage.

but I'm worried it might be DC and ruin something at some point.

If it is DC then the DC Error will be activated.

These modules have a PS Enable PIN which in theory allows you to go from standby to on, with no such noise.
But strangely turning it on with this produces an even louder pop (with both NC252MP and NC502MP) and in fact the PS Enable Pin is generally left shorted, and an upstream switch on the 115/230V power is used.
This is what happens in my case and this is also what all the various resellers of these modules seem to do, looking at their internal photos.
Ghent also sells the connector with jumper for PS Enable in the wiring kit.

Since both my NC252MP and NC502MP exhibit the problem I'm pretty sure it's due to the design rather than a defect, so I didn't contact the manufacturer.

Hypex themselves have acknowledged it and the latest modules apparently have resolved it.

What do you recommend?

As long as the Standby PS is enabled it should be okay. If you like you could measure the speaker voltage when powering down, and come back if it alarms you.

Considering that these modules also have poor DC protection, is there any board that allows me to protect the speakers and prevent pops?

How do you reconcile “poor DC protection” with the DC Error function?

I use a DC protection capacitor on my tweeters, sized so that its roll off point is 1/10th the crossover frequency.