all the biquad talk had me remember trying to figure out the riaa filter for vinyl playback/production a couple years back which i never quite figured out. attached is what I had attempted. 

the playback filter seems to be correct but when I switch to the production filter. which should be the inverse of the playback filter, i get nothing but I think im swapping the coefficients incorrectly...

anyway, here is the thread this is based off of:

http://www.musicdsp.org/showone.php?id=122

and here is some help on the inverse:

http://music.columbia.edu/pipermail/music-dsp/2003-February/055408.html

maybe someone can make heads or tails of this and give me a help?

basically I am attempting to 3d print a record cutting head so I mostly need the production (iRIAA) filter as I will be going straight from PD to a record lathe.

thanks!

m

ps. this was helpful too http://jiiteepee.tripod.com/riaa.html

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