My DIY Matrix Decoder (one picture)

[kfbkfb]

My Fire 7 tablet seems to take a fair quality picture (first attempt, CD for size reference).

I finished building this, my first matrix decoder, in 1983-05.

I haven't switched it on since 2000-09 when I got my Pioneer VSX-D209 receiver which has (original) DPL and a few fake surround sound modes.

I might switch it on again and see how well it creates fake surround sound, I have a fire extinguisher nearby in my basement

IIRC, the front panel switch changes the decoding coefficient "x" from 0.5 to 0.25:
LF=L+xR, RF=R+xL, LB=L-xR, RB=R-xL


Kirk Bayne

 

[kfbkfb]

Just connected my DIY decoder and listened to songs 1 and 5 from the stereo mix on the WAR Quadio.

(no smoking/flaming [41 year old] parts, didn't need my fire extinguisher)

The sound quality and fake surround sound were good although the 0.5 mode (the 1971 Pioneer Quadralizer fake surround sound creation mode) had obvious reduced channel separation.

Both the 0.5 and 0.25 modes worked, I used National Semiconductor LF347N opamps, the 0.5/0.25 switch switches in and out resistors in parallel in the opamp feedback loop which changes the gain to get the 0.5 and 0.25 matrix coefficients.


Kirk Bayne