:: 3d multimedia amplifier ::

[dhengkoel]

Dear all;

I’ve finished building satellite-subwoofer amplifier for multimedia active speaker. It apply 2 chips TDA 2005, 1 in stereo mode for satellite amplifier, 1 in bridge mode for subwoofer amplifier, 2 transistors for buffer, 1 transistor for subwoofer mixer & filter. But the subwoofer amp make noise: ‘broooommmmm’. I suggest it’s low frequency oscillation.

I attached some pictures. Please give me some suggestion & help.

Regards: ragil.hastomo

 

[dhengkoel]

.. the filter ..

 

[dhengkoel]

.. bottom layer ..

 

[dhengkoel]

.. helloooooouuuwwww .. anybody there? ..

 

[bigparsnip]

do you have the schematic you used to build the amps, as it is rather difficult to tell what you have done simply from a few picturs of the circuit boards.

 

[soundNERD]

try disconnecting the input of the sub amp from the transistor output, and short it to ground. turn it on, and see if the hum is there. if it isn't, there is a problem with the transistors. if it is, there is a problem with the amp. check all the soldering and stuff.

-Mike

 

[palesha]

TDA 2005A is not good for mains supply operation. It is developed for auto use. It has very poor SVR (Supply Voltage Rejection). Hence put big power supply capacitors.

 

[soundNERD]

whats the wattage of that chip? And who makes it?

 

[palesha]

made by ST. It is 6 watt each channel & 20W when bridged.

 

[soundNERD]

well, since that is such low power, why don't you just use higher power chips designed for mains operation (2 x lm1875 or 1 x lm1876 for the tweeters/midranges, and something like a 3886 for sub?

 

[palesha]

Even there r no thick tracks for power & speaker outputs. Don't understand easily by looking at the layout about the grounding.
The PCB should be redesigned and the schematic must be here to give comment or help.

 

[dhengkoel]

Here the filter schematic. For amp i use st recomended schematic: http://www.electronic-kits-and-projects.com/kit-files/datasheets/tda2005.pdf

regards:
ragil.hastomo

 

[dhengkoel]

Here the pcb layout

regards:
ragil.hastomo

 

[palesha]

U can change TDA 2005 to TDA 2009A. It is pin to pin compitable & mains operated. Few changes only. Further it is Class AB. The power & output tracks in ur PCB must be thick as in ST layout. U will get far bettr quality with TDA 209A. Only difference will be in subwoofer output impedance changed to 8 ohms. Enjoy!

 

[dhengkoel]

If I change the filter like picture attached, the bass sound is better .. but in the virtual bode plotter [i use multisim 6], why there's a hole at frequency 4 khz? .. any comments is welcome

regards:
ragil.hastomo

 

[dhengkoel]

the bode plotter