The Swezey Digital Filter Program			April 4, 2012

Advice on Undoing RIAA Equalization using this Program

Note: This is only needed if you record your 78 RPM records at a slower speed such as 45 RPM and then convert them upward.

If you are recording your 78 RPM records at 45 RPM and resampling them later you need to undo the RIAA Equalization built into nearly every phonographs since 1954 before you do the conversion.

As I mentioned in my document:
Advice on Digitizing Phonograph Recordings for use with this Program
this can be done using the Audigy (or some other) Wave Editor.

However, I feel I can get better results using my program to do this.
It is somewhat clumsy so you may decide not to do it this way but if you do here is what you need to do.

This has to be done as a special run.

1. Un-Hide this I/O Configuration Window from under Help on the Main Menu if you have hidden it.

2. Restart the program to see the I/O Configuration Window.

3. If the WAV file was recorded in stereo as recommended below select Stereo.

4. Set the FFT to 4096.
The WAV file will probably not play in realtime using this high of an FFT but it will give you better results in the conversion.

5. Press Enter to  go on to the Main Window.

6. Using the Wave File Input Control select the file you want to convert and open it.

7. From the Main Menu select the Profile that resets everything to OFF.
Reset Profile (Clear ALL to OFF settings)

8. From the Main Menu under Auto Options select to undo the RIAA equalization..
Undo RIAA equalization

9. From the Main Menu under Controls select the WAV Low Pass Pre-Filter control..
WAV Low Pass Pre-Filter Control
This step is optional but will clear out high frequency out of band noise.
Adjust the cutoff frequency as follows:
Remember that the audio is at 45 RPM so the true frequencies are actually shifted lower.
Mature 78's have little above 12,000 Hertz so use 7000 Hertz here.
Early Electrical have little above 10,000 Hertz so use 6000 Hertz here.
Acoustical recordings have little above 3400 Hertz so use 2000 Hertz here.
I useually set the number of Taps up to 151 as well.

10. Adjust Audio Input and Output Level Controls as needed so the output is NOT over loaded.

11. Once everything is ready press Reset on the Wave File Input Control to return to the beginning of the file, press Record on the Capture Output Contol and then press Play on the Wave File Input Control.

12. The program will probably 'chug' (start and stop) while it is converting the WAV data.
Don't worry this is normal and no data is lost during this process.

13. Once it is done you can click on New File on the Capture Output Contol to release the output file.

The output file still needs to have it's speed converted but that works fine and is easy using Audigy.

This process only undoes the RIAA Equalization.

My Web site: http://www.winternet.com/~swezeyt/dsp.htm
Your comments are always welcome, please e-mail me at: swezeyt@winternet.com

Thank you for trying the Swezey Digital Filter Program!

(c) 2012, Thomas F. Swezey. All rights reserved. 04/04/2012)