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Old 27th November 2012, 03:54 PM   #1
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Default Getting 7.1 Output From Stereo

Hello everybody. I am trying to design a 7.1 audio amplifier circuit. I have a 5.1 speaker system whose amp is damaged and 2 extra speakers lying around. The speaker amp used to take stereo input and give 5.1 channel output. What ICs should i use to split , mix or amp the signal into 7.1 . I use Proteus when designing is there a better sotware with more ICs available for designing.Thanks
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Old 27th November 2012, 11:32 PM   #2
Minion is offline Minion  Canada
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Location: Cowican Bay , vancouver island
you cant get a true 7.1ch system much less a 5.1ch system from stereo , but to do a fake 7.1ch system you would split each stereo channel 3 ways , then sum each channel for a center speaker and then put a low pass filter on that channel for a sub ......
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Old 28th November 2012, 12:42 PM   #3
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Thanks . What IC should i use to split it . What should be the cut off frequency of the filter?
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Old 28th November 2012, 10:41 PM   #4
Minion is offline Minion  Canada
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any audio opamp will work , maybe a ne5532 ?? the cutoff frequency you select would probably depend on your sub , you could also make the filter adjustable .....
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Old 1st December 2012, 03:16 PM   #5
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From Rod Elliot's site Simple Surround Sound Decoder There is a more complex scheme documented elsewhere on the site.

Starting with the Hafler arrangement, you can apply a delay effects box to the rear speakers. You can also do somewhat stereo rear channels by doing a "favors left" and a "favors right" arrangement.

Add a subwoofer amp.

Next, you can create a center channel summing amplifier with inverting stereo op-amp for input, resistor mixer, inverting mono power amp for output. See Decibel Dungeon site for inverting mono power amp, since all of the gainclones there are inverting.

To expand for 7.1 simply place additional copies of the center channel amp in-between any two channels, such left front+left rear = side left.

For the front and/or side channels, a mild "stereo expander" might be helpful for extra fun, especially if the room is narrow.

Instead of analog style decoding, it may be easier to simply use a source with 8 outputs that outputs 7.1 already decoded and ready for use with analog amplifiers.

In hi-fi, we often aim for "open sounding" or slightly euphoric stereo instead of hard-wiring surround sound multi-channel. The open sound hi-fi alternative is less likely to make a blare sensation when run full blast and it doesn't require a mess of cabled speakers cast everywhere. Some of the hi-fi systems can fill a room with enveloping, involving, realistic sound, from just 1 speaker, some use two speakers, and it is rare to use more than two speakers in hi-fi, except for overcoming caveats of seating arrangements.
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Last edited by danielwritesbac; 1st December 2012 at 03:19 PM.
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