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Old 4th August 2008, 04:42 PM   #1
Buzzy is offline Buzzy  Singapore
diyAudio Member
Join Date: Apr 2007
Default Need help with UCD400

I have built a hypex ucd400st amp to power my 4 ohm passive subwoofer. I ran the line out from my PC soundcard to the rca input on the ucd400 amp. Slowly increased the play volume control on my PC. It worked fine.

However when i connect the ucd400 amp to my pioneer 1015 receiver's sub preout. I got no sound at all. I also tried connecting it through behringer feedback destroyer and still no sound at all. The same sub worked when i hooked it up thru the PC.

I followed the manual closely when building the sub. I have made one change though. I have connected the ON pin (the one that is together with signal cable) to supply ground directly instead of having a switch. Would this be a problem ?
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Old 4th August 2008, 04:44 PM   #2
Buzzy is offline Buzzy  Singapore
diyAudio Member
Join Date: Apr 2007
I also need some sort of volume control. Can i use a potentiometer ? If yes may i know what value would be suitable ?
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Old 6th August 2008, 11:01 AM   #3
Buzzy is offline Buzzy  Singapore
diyAudio Member
Join Date: Apr 2007
I have tested the UCD400 again.

This time I connected the UCD400 amp to the left preout of my pioneer vsx1015 receiver and a 8ohm speaker to the UCD400 speaker out terminals to it to see if the amp works. With this i can hear the amp play well. Then i connected the UCD400 speaker out to the 4 ohm passive subwoofer with the left preout from the receiver still connected to the UCD400. This time i can feel the cone vibrating but the sound is not loud enough. I do not have any volume control on my UCD400.

The passive subwoofer is tested to be working fine when i connect it directly to the speaker out of my receiver.

Do i not have enough gain ? Or is there something to do with input impedance ?

I really need help.
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