Hope this is an easy answer. I’m not a programmer and did my best to find the answer searching various manuals. I want to have both of these Nyquist biquads applied to the waveform simultaneously. It seems that if you just run them sequentially, the second cancels out the first.
Thanks, that worked. Much appreciated; would have taken me forever to figure that out.
The source is an article by Scott Wurcer in Linear Audio magazine. I’ve been corresponding with some more knowledgeable engineers on the diyaudio forum about this, too. A similar source for such a curve is Wayne Stegall’s website:
I’ve tested the curve and it is accurate to about +/- 0.1 dB up to 36 kHz. That’s impressive for an IIR filter.
If you have any (very) old records, this page in the Audacity wiki may be of interest: Missing features - Audacity Support
Unfortunately those curve specifications are not directly compatible with current versions of Audacity, but there’s a “EQ XML to TXT Converter” in Audacity’s “Tools” menu to convert to the new format. More info here: EQ XML to TXT Converter - Audacity Manual
I would be willing to pay a modest price for someone to write this for me–this would be a big timesaver in the long run, e.g. if I’ve transferred something at 250 / -5 but I realize later it would be better to have it set at 250 / -8.5 or if I use a displacement-sensitive cartridge with a hardwired RIAA integrated preamp to transfer a record from 1930 with a curve of 500 / -8.5 and want to conservatively get the curve correct without drastic gain changes. I could do it now, but it will take a lot of tedious templating. There are so many permutations that it would be better to have something that has the code built in.
This really should be baked into future versions of Audacity. While it’s probably true that the FIR filters are virtually the same, the famous Gary Galo article discussing FIR vs IIR filters and phase relationships and waveforms have me wanting to use IIR filters for all my re-EQing. All of the above curves are accurate to 0.005dB or thereabouts with roughly three degrees of phase accuracy.