Simple Phase Shift Circuit (for midrange) ??

QuadraphonicQuad

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kfbkfb

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I'm interested to know if anyone has designed a simple phase shift circuit that is accurate in the midrange of sound (about 300Hz to 5kHz), IMHO, since this is an arbitrary surround sound creation method, significant phase shift errors outside of the midrange don't seem important.

My purpose for the circuit to be able to make a simple SQ (270 degrees) stereo enhancement preprocessor.

All that would be needed (AFAIK) is 2 input buffers, 2 phase shifters, 2 summing circuits to output an SQ stereo enhancement encoded stereo signal (for a Surround Master in SQ decode mode, for example).

Anyone have such a circuit design or be willing to design one (and share it here in QQ)?


Kirk Bayne
 

jimfisheye

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I could dial it up in a DAW. One can use a DAW app as a "plugin" in their home theater audio chain and thus run it live. Or if this was aimed at an upmix project that was DAW work to begin with... then we're done.

I'd use linear phase cross-over style eq's for the splits. Move the phase around as you please on the midrange split. Mix back together and output.

You'd have unlimited control over cross-over points and phase manipulation and you could jump in right now with no cost.
 

kfbkfb

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I was thinking of a easy way to preprocess stereo to get the 270 degree surround sound creation output from an SQ decoder (w/ or wo/ logic), using hardware only.

Limiting the phase accuracy requirement to the midrange should make the circuit about as simple as possible.

(making the summing circuit with switchable gain could also be used to preprocess for the 180 degree mode)


Kirk Bayne
 

par4ken

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I was thinking of a easy way to preprocess stereo to get the 270 degree surround sound creation output from an SQ decoder (w/ or wo/ logic), using hardware only.

Limiting the phase accuracy requirement to the midrange should make the circuit about as simple as possible.

(making the summing circuit with switchable gain could also be used to preprocess for the 180 degree mode)


Kirk Bayne
Using hardware only you are back to simply using an SQ decoder (non logic, no blend) and a phase inverter to pre-synthesize the signal. The original CBS circuit using the MC1312P SQ decoder chip is the way to go if building from scratch. Featured in "Radio Electronics Oct 1975" but watch out for the many errors in that article. You have already pasted the correct CBS circuit!
 
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