Hypex ucd180 buzzing

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Hi

I have just rebuilt my 10*ucd180 amplifier in a new chassis with a new power supply. but it has now developed a buzzing sound. I cannot recall having this on the last build so i must have messed up somewhere.

i can hear the noise sitting 2-3 meters away from speakers, so its more than the normal tweeter hiss you expect. its coming from both left and right, a little bit more from right i think.

The buzzing was louder when the signal cables rested against the smps, so i suspect the noise is coming from here. it lessened when i moved the cables away from the smps but i cannot move them any further. Im using the "Ucd signal cables" from the hypexshop.

The sound resembles the one you get from a poorly grounded electric guitar amplifier, so i suspect it could be a grounding issues. The smps rooted noise may be completely gone but the grounding noise persists.
The last chassis was a bit rougher and i think i involuntarily grounded the signal cables to the chassis, could this be the difference?

What is the recomended distance between smps and signal cables?
Should i ground the signal cable to the chassis?

attached is pictures of the two builds, the old build is the one with the smps to the right and ucd180s to the left in chassis. It has much greater distance between smps and signal cables
 

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Joined 2005
You also have the AC lines much closer to the signal cables in the new chassis. It probably would have been better to put the RCA jacks closer to the modules and have the AC connector in the middle of the chassis.

And, as anonymous mentioned, you should connect the IEC jack earth ground to the chassis.
 
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You also have the AC lines much closer to the signal cables in the new chassis. It probably would have been better to put the RCA jacks closer to the modules and have the AC connector in the middle of the chassis.

And, as anonymous mentioned, you should connect the IEC jack earth ground to the chassis.


I tried to move the AC lines to opposite end of chassis, doesnt seem to help much. There may be slightly stronger buzzing when i moved the AC chord closer to the unshielded part of signal cable...

Grounding the chassis is for safety in case insulation breaks and wires gets into contact with chassis right? it shouldent remove any buzzing sounds?
 

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Ex-Moderator
Joined 2005
Grounding the chassis is for safety in case insulation breaks and wires gets into contact with chassis right? it shouldent remove any buzzing sounds?

If the chassis is earth grounded and something shorts out internally it will blow a fuse or trip a circuit breaker instead of potentially putting lethal voltage on the chassis. It may also help with noise.

Are there any other differences in the wiring between the two layouts? The only other difference I can see is that everything was mounted to the same exposed metal panel in the first amp (all UCD modules had their heat sinks effectively connected together, and possibly to the SMPS ground). Your new amp has the SMPS on the bottom panel and the modules on the side heat sinks but all the panels are anodized/powder coated. Was the SMPS grounded to the metal panel in the first amp through the mounting standoffs?
 
Here is a update.
Noise is now gone, only very slight hissing from tweeters when i put ear close to it :D

The noise must have come from the smps. I moved the smps as far away from the signal cables as possible, and viola!...silencio!

I will ground the chassis at a later time for for safety. it doesent seem necessary for audio quality on this system.

Thanks everybody :)
 

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