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
The syntax for biquad~'s arguments, according to the help patch:
fb1 fb2 ff1 ff2 ff3
In the patch you swap fb2<>ff2 and ff1<>ff3. The syntax in the help file is confusing. For better consistency it could be called:
fb1 fb2 ff0 ff1 ff2
Fill the coefficients for the 44.1 reproduction filter as mentioned in the musicdsp topic:
-0.721892 -0.186052 1 -1.70072 0.702938
But this doesn't seem to produce a minimum phase filter, and it can't be inverted. I guess the signs of feedback coefficients must be flipped to match Pd's biquad implementation:
0.721892 0.186052 1 -1.70072 0.702938
This gives a frequency and phase response much resembling the plots on http://jiiteepee.tripod.com/riaa.html. This filter can be inverted by swapping the feedback and feed forward coefficients and also flipping the signs:
1.70072 -0.702938 1 -0.721892 -0.186052
This gives the exact inverse frequency and phase response.
Katja
On Wed, Oct 15, 2014 at 12:14 AM, me.grimm megrimm@gmail.com wrote:
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
Pd-list@lists.iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
great thanks for the help! that seems to work swell.... attached is the revision.
how would one go about generating / calculating the coefficients in pd using [expr]? then instead of having each in its own message the coefficients could be calculated automatically via global/local sample rate, normalizing gain could be applied/adjusted in real-time, etc.
m
On Wed, Oct 15, 2014 at 7:59 AM, katja katjavetter@gmail.com wrote:
The syntax for biquad~'s arguments, according to the help patch:
fb1 fb2 ff1 ff2 ff3
In the patch you swap fb2<>ff2 and ff1<>ff3. The syntax in the help file is confusing. For better consistency it could be called:
fb1 fb2 ff0 ff1 ff2
Fill the coefficients for the 44.1 reproduction filter as mentioned in the musicdsp topic:
-0.721892 -0.186052 1 -1.70072 0.702938
But this doesn't seem to produce a minimum phase filter, and it can't be inverted. I guess the signs of feedback coefficients must be flipped to match Pd's biquad implementation:
0.721892 0.186052 1 -1.70072 0.702938
This gives a frequency and phase response much resembling the plots on http://jiiteepee.tripod.com/riaa.html. This filter can be inverted by swapping the feedback and feed forward coefficients and also flipping the signs:
1.70072 -0.702938 1 -0.721892 -0.186052
This gives the exact inverse frequency and phase response.
Katja
On Wed, Oct 15, 2014 at 12:14 AM, me.grimm megrimm@gmail.com wrote:
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
Pd-list@lists.iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
"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.""
WHAT??? [image: :)]
2014-10-14 19:14 GMT-03:00 me.grimm megrimm@gmail.com:
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
Pd-list@lists.iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
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Alexandre Torres Porres -
katja -
me.grimm