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Old 23rd August 2004, 02:15 PM   #1
Triox is offline Triox  Australia
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Join Date: Jul 2004
Location: Australia
Default Bypassing DVD amp

The amplifiers in my Digitrex DVD player which are LM4731,s have been destroyed. These don,t seem to be available in Australia.

These are National 25W /25W.

To cut a long story short , I removed the amplifier chips and heatsinks , put extra sockets on the back of the unit and attached these to what were the inputs of the LM4731.
These inputs are fed by a 1 uF cap and a 1K resistor in series.

I have hooked these new outputs to an external amplifier and all seems well.

Does anyone see any potential problem with this and maybe offer some tips.

I have built some Digi 125s , but am not overly impressed with the sound volume, as my old 35W amplifier seems louder and clearer.

I will probably build some P3A amps or similar and attach
these new outputs to the amp inputs.

My only problem now is I need 6 amps to cover the 5:1 outputs.

I wonder if it,s worthwhile to spend so much buying ready made PCB,s?


ALso do you think I,ll need a pre amp?
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Old 25th August 2004, 01:33 PM   #2
Triox is offline Triox  Australia
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Join Date: Jul 2004
Location: Australia
Default Re DVD player with built in amplifier.

I tried a 741 pre amplifier to drive the digi 125 from my dvd and
it sounds a lot louder, but its a bit noisy, seems to pick up hums and buzzes ,

Any ideas how to make a simple quiet pre-amp?
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Old 25th August 2004, 04:06 PM   #3
jaycee is offline jaycee  United Kingdom
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Join Date: Apr 2004
Location: Norwich, UK
You will probably need a buffer preamp stage because I would guess that the 4731's were being directly driven by the output from the DAC stage.

Do not use the 741 op-amp for audio. It is awful. If you want it simple, build one around an 5532. Elliot's P88 will do if you are into his designs.
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