Hi,
Is there a predefined curve that I can use to remove RIAA Equalization that my preamp introduces? Any help appreciated. I’m trying to remove the RIAA eq, then apply an acoustic eq to record an old acoustic vertical recording
AFAIK there isn’t one in Audacity (I seem to remember a Feature request a while back asking for just this).
Can you not set your pre-amp so that it doesn’t apply the RIAA - or if you are using the amp/preamp from a hi/fi you could try connecting the TT through a Tape input or Aux input (only the input marked “Phono” on such devices appplies the RIAA eq.).
WC
The problem, and I admit it’s not a big one, is that Phono Inputs have a very specific characteristic to match the photo cartridge. Something like 47,000 ohms shunted with 15 pFd of capacitance. That’s what the cartridge is expecting to see at the other end of that wire, and it’s comfortable with that. If you plug into LINE-IN or AUX-IN, the ohms number will certainly be off and the capacitance number will be too. So what you’ll get, in addition to the very much reduced level (increased noise) and no RIAA will be the distortion of the mismatch.
There are some incredibly detailed postings of exactly what the RIAA specification is, cycle by cycle. It should be possible to write the curve, no? One of you two knows how to program that and if you tell me how, I’ll plug the numbers in and test it.
Koz
Hi. Thanks for the responses. Instead of trying to take out the curve that my phono input introduces, I decided to buy a “flat” phono preamp. It provides the necessary amplification without introducing the RIAA curve. Once I’ve recorded my 78prm records (non-RIAA, acoustic recordings), then I’ll apply the appropriate EQ in Audacity, restoring the record to it’s original design sound. This actually will help me in a couple of ways. I also purchased a test record that outputs “pink” noise, so I’ll be able to adjust my system to be totally “flat”, so that what I get from the record is actually what is on the record, and no eq introduced by my equipment. Then i can apply whatever curve (even RIAA) necessary.
eric,
Keep in mind that pink noise is not actually “flat.” White noise is flat, pink noise is filtered and will show up with a downward slope when you highlight the signal and click analyze → plot spectrum.
White noise if equal energy per frequency. Pink noise is equal energy per octave.
<<<pink noise is filtered and will show up with a downward slope when you highlight the signal and click analyze → plot spectrum.>>>
There is a significant variation in that assumption. If you try that in Cool Edit, you do not get that sloping effect in the display. I went round and round with the developers about that. Turns out many analyzer tools work in a mode where white and pink come out the same. There is a rational explanation for this which I remember made my head hurt and I had to lie down for a while.
Koz