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mrimaging 17th July 2013 01:46 AM

Please help me diagnose a Hypex problem
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I have an older Hypex UCD400 amplifier and I hear a click on my speakers whenever I turn it on. Also, when I turn off the amplifier, there is a low volume whining noise that can be heard as the capacitors are discharging. This behavior has been present since I have had the amplifier, but the noises are not loud enough where I am afraid of damage to the speakers. My guess is that there is a DC offset, but I figured I would see what people more knowledgeable than myself think and what the best solution would be. I have attached some pics of the amp. Any help would be appreciated!

David_Web 17th July 2013 05:00 PM

My UcD180HG have a square/triangle wave sound that lowers in frequency as the capacitors discharge.
As there are no relays disconnecting the speakers the click is probably the oscillation starting creating a small bump before it gets going. The whining noise is probably the oscillation breaking down as rail voltage collapse. I have not seen any DC offset push the cone ether way though.
I figured it to be normal.

If it isn't I'm sure someone will step in and yell "turn it off before you break something".

mrimaging 19th July 2013 03:00 AM

Thanks, glad to hear that I'm not the only one seeing this behavior. Do you have a soft start module on your amp? I was wondering if that would make any difference.

David_Web 20th July 2013 09:28 PM

Yes I have a soft start, simple timed relay that bypasses a resistor after a few seconds.

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