A friend was telling me that on early 50's LP's the correction curve was not RIAA as we know it today but something called AES.
If I have recorded the LP thru the phono input on the amp, and thus applied the RIAA curve to the sound, is there a plug in or effect that will "reverse" the RIAA curve ?
and a second plug in that will apply the AES curve?
pgmer6809
According to the Wikipedia article on RIAA equalization...
The RIAA equalization curve was intended to operate as a de facto global industry standard for records since 1954. However, it is almost impossible to say when the change actually took place.[1]
Before then, especially from 1940, each record company applied its own equalization; there were over 100 combinations of turnover and rolloff frequencies in use, the main ones being Columbia-78, Decca-U.S., European (various), Victor-78 (various), Associated, BBC, NAB, Orthacoustic, World, Columbia LP, FFRR-78 and microgroove, and AES.
So, it may be impossible to say which equalization curve was used for any particular recording. Then, the trick would be finding the hardware, or software, that could make the appropriate conversion. A simple Google search for AES equalization will bring up a number of useful and interesting websites covering the subject.
Hi
Try experimenting with the Graphic Equaliser to adjust the boost/cut of the audio to approximate the sound you require.
RIAA boosts the lower frequencies relative to the higher frequencies, so you would need to do the opposite in the graphic equaliser.
It may not be perfect, but then listening to audio never is as there is not a system which can produce the original in it purity - you always get some 'colouration' especially from the microphones, speakers/headphones, room characteristics and your age - we tend to lose the higher frequencies as we get older.
HTH
John
Thanks to those that took the trouble to reply.
Since then I have found a solution using Audactiy the Free /Open Source audio editor.
There are plug ins for Audacity that apply RIAA, AES, FFRR and other equalization curves. The plug ins also have an 'invert button'. So the solution would be to load the RIAA curve, click invert, and then apply that to undo the RIAA added to the sound by my audio amp. Then I can load the AES curve and click apply to get the right version of the equalization.
FWIW: 1. Knowing the correct curve to apply is not that difficult. Many audio sites on the net document what curves were in use at which record ompanies during which years.
2. It is not really practical to build an 'inverse RIAA' equalizer curve by hand in ACL (by dragging the mouse etc.) The curves supplied by the Audacity plug ins have over 40 datapoints in them, each specified to one or two decimal places.
pgmer6809