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Triox 23rd August 2004 02:15 PM

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?

Triox 25th August 2004 01:33 PM

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?

jaycee 25th August 2004 04:06 PM

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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