| red |
Hi guys i really need a little help here.
My brother has a cheap dvd player (pixelview) that has a 5.1 output and I decided to build a 5.1 amplifer.I need no decoder in the amp because the dvd has it.
So the design is as simple as possible.Five TDA2030A with single supply for the 5 channels and a TDA7294 split supply for the subwoofer.
The problem is that I need a preamp for this so I made one using 4 TL072.I have six buffers and a filter designed by rod elliott but i have a problem with volume control and channel separation.What I mean is that if I modify the volume to the center channel It also modify the subwoofer level as well. This happens with the remaining channels as well.I didn't test it on the dvd. I used a simple walkmen and my computer sound card.If i put signal to the surround channels I can hear music to the fronts even if I have no signal on them.So I assume that my schematic is wrong or that i have a problem in wiring.
Here the schematic of the buffer and the pcb.The pots aren't on board.They are 100k linear pots that have a resistor of 15k in parallel with the input of amplifiers.The amplifiers are the recomended schematics by the manufacturers and they are from the data sheets of the Ic's.The TL072 POWER SUPPLY is soldered to the power supply of the TDA7294 which consists of one bridge regulator and 2 capacitors of 2200uF.The amps work fine without the preamp so I assume this is the problem...
Please help!!!!!! |
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| red |
| And this is the board of the preamp |
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| rpapps |
Hi Red
I am assuming that the circuit board layout you posted is shown from the component side with the tracks shown in x-ray.
If that is the case, there is a problem around IC2. It has no +Vcc connection and the input signal from J7 appears to be connected to the +Vcc pin. Also, the IC numbers on the layout don't match the schematic. Can you clarify.
Cheers
Rob |
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| red |
Thanks for the answer...
I found the problem...It was in the wiring...I had 5 ground loops and u can imagine what a mess was there...The pcb is right.
It has four TL072 that has 2 opamps in each capsule.It may have a small error in the pic but in reality really works fine.Now it is almost complete...All i need is a bit of paint for the amp case...I'll show some pic if u r intrested... |
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