Help a newbie - modify an old amp to use it's multichannel power amp capabilities

[marquis@mweb.co]

I am a "newbie" to this site. I'm not certain that my request does not violate one of the rules, but here goes anyway....

I have acquired a Creative Labs Audigy 2 soundcard for my PC. I've been
using my PC to play DVD's for about 4 years - hooked into an amp via SPDIF
for audio and the output to a video projector. The amp handles the Dolby Digital decoding.
I upgraded to this card because I was keen to experiment with DVD-Audio -
but of course I have a major problem getting the sound from the card into my
amp - the normal SFDIF connection is not supported when playing DVD-Audio disks (a combination of unresolved requirements by the recording industry I understand, but also bcause of the much higher data bandwidth produced by Audio-DVD). My
current amp does not support multi-channel analogue audio inputs.
But I do have an older Yamaha RX-V1070 amp - this supports Dolby Pro-logic,
so it does provide 5 speaker amplification (though the rear pair at a lower
power level than the front and centre).
My wife will kill me if I buy a new
conventional power amp - she seems to feel that food and kids education (for
example) is more important! So I got to thinking that it may be possible to
do a mod to this old amp and "tap into" the power section circuitry - feed
it the analogue audio output from the Audigy 2 card, let it do the
amplification as usual and hence drive my current surround sound speaker -
which should sound a great deal better than the sound I'd get from currently available PC 5.1 sound systems.
I've opened this amp and can identify the power board, but as it has multiple connectors to other boards I'm not sure I have identified the right one for the pre-amp's input signal. I'd appreciate some guidance.

If this is not the right place to ask such questions - any (polite) suggestions regarding other sources?
My thanks in anticipation.

[UrSv]

If I am not mistaking the RX-V1070 has a 5.1 input, possibly by DB-25, which you could use straight away?

[marquis@mweb.co]

I wish that was the case - if there is such a thing - it is well hidden.
Thanks for the response though.

[MadMax]

You could makeup a signal tracer using an small electro cap with a fairly high voltage rateing and another power amp with voulme control, check for dc voltage first on likly pins, stay away from outputs and power supply, use an isolating transformer or rcd to protect yourself, input singal to one chanal at a time and go looking for it. dont forget to check for voltage first and stay away from power supply.

[paulb]

Or use an oscilloscope to help you find the path. Have you got a friend or acquaintance that has a scope and could help you out?
If you can identify the power board, it's probably not too big a step to find the right connections.

[marquis@mweb.co]

Thanks MadMax and PaulD. I WAS hoping that I wouldn't have to do the R&D myself - that someone had gone there before me....
I'm surprised that this "need" isn't more widespread - with the advent of multi-channel sound sources (and I was around at the early Quadraphonic "experiments" in what, the early '80's I think), multichannel power amplifiers are necessary. It certainly gives more flexibility if the individual channel signals can be driven by the user's choice in addition to whatever pre-amp decoding the manufacturer has decided to support.

[leadbelly]

The mod you're describing is common in the DIY world. But you have to remember that there are thousands of different receivers/int amps out when you consider brand, model, production rev. It's always a gamble to find someone who's tweaked exactly the same box, unless it's an audiophile box where production numbers are lower and production runs are many more years.

When you start digging, you'll probably find that it's easy to figure out the power amp board.