Reverse RIAA curve

[whomper]

@waxcylinder

Bill,

there is a posting in the Wiki Feature Requests page that relates to this, which says:

“Equalization:
Automatic 78 RPM EQ from RIAA-recorded 78’s: Flattens the curve to negate the RIAA EQ then applies the required 78 RPM EQ in one button press. Add more 78 RPM presets to facilitate this. (7 votes)”

See full list of FR’s at Missing features - Audacity Support
and pending FRs at Missing features - Audacity Support

I think that yours is a better idea as there are several 78 equalization curves that can be applied (there were no standards back in the earlydays of recording - each company had its oqn Eq curve - and sometimes more than one). unless ALL the 78 curves were reconfigured for first strip the normal vinyla RIAA and than apply it’s own RIAA the equalization would be incirrect.

I do vaguely remenber some discussion about a reverse RIAA curve - but can’t for the life oof me find it on the forum (or on the Wiki Pending Feature Requests or Feature Requests pages).

i would think we have a bigger need to fix dolbyb andor chrome bias tapes that are played on a boom box for moving to cd.

[theSeaHawk]

Unless you have dozens of clean 78s and pre-RIAA lps waiting to be recorded in which case it is invaluable.

[waxcylinder]

It gets even easier with the latest 1.3.12 RC2 (Alpha) version of Audacity - there is a new “Invert” button in the EQ effect - which enables you to easily invert any of the exisiting pre-set curves - including,of course, the RIAA curve.

BTW just be aware that there is some discussion currently going on on the developer email list as to whether or not the current RIAA curve is quite accurate or not - inconclusive as yet …

WC

[ebrjvd]

BTW just be aware that there is some discussion currently going on on the developer email list as to whether or not the current RIAA curve is quite accurate or not - inconconclusive as yet …

The reverse RIAA function should undo the de-emphasis introduced by the preamp used, but most preamps deviate somewhat from the theoretical values (3180, 318 and 75 µs) due to component tolerances, so what’s the point re. accuracy?

In 1976, the IEC60098 standard introduced a fourth time constant to reduce sub-sonic rumble on playback: 7950 µs (20 Hz).
http://webstore.iec.ch/webstore/webstore.nsf/artnum/018568
http://shop.bsigroup.com/en/ProductDetail/?pid=000000000000192214
http://www.webstore.ansi.org/RecordDetail.aspx?sku=IEC+60098+Ed.+3.0+b%3A1987
http://www.bonavolta.ch/hobby/en/audio/riaa.htm

RIAA equalization

Most modern phono preamps have a 20 Hz rumble cutoff built-in.
However, care should be taken not to amplify rubbish (rumble…), hence one should not implement this 7950 µs time constant in a reverse RIAA function.

A better solution would be a linear (flat) preamp for non-RIAA records, or an adjustable preamp for the various record brands / EQ settings,
e.g. 78 RPM and RIAA Preamplifier

Jos

[vethraxx]

Hello. New to the forum and very intersted in the posted reverse RIAA curve. I have been uning Audacity to transcrive nearly 1000 78rpm records to uncompressed .wav files. My turntable does apply the RIAA curve. I don’t mind it so much as it helps to bring down the hiss and adds a warmness to the recordings. However I would like to hear it as unaltered as possible.

I see the text in the window for the reverse curve. Do I just hit copy all then past to notepad and save it as a .txt file? I see .xlm mentioned do I change the file extention from .txt to .xml? A little help please Thanks.

[Gale_Andrews]

@vethraxx

Hello. New to the forum and very intersted in the posted reverse RIAA curve. I have been uning Audacity to transcrive nearly 1000 78rpm records to uncompressed .wav files. My turntable does apply the RIAA curve. I don’t mind it so much as it helps to bring down the hiss and adds a warmness to the recordings. However I would like to hear it as unaltered as possible.

I see the text in the window for the reverse curve. Do I just hit copy all then past to notepad and save it as a .txt file? I see .xlm mentioned do I change the file extention from .txt to .xml?

Make sure you have the current Audacity 2.0.5 ( Audacity ® | Downloads ) .

Then as waxcylinder said, choose Effect > Equalization then just select the shipped RIAA curve and press “Invert”. Press “Save/Manage Curves…” then “Rename…” to save the inverted RIAA curve as a preset, then it will be selectable from the “Select Curve” list. See Audacity Manual .


Gale

[waxcylinder]

@vethraxx

…I have been uning Audacity to transcrive nearly 1000 78rpm records to uncompressed .wav files…

You might find this workflow from the manual useful: Audacity Manual

The following web site: http://www.videointerchange.com/vintage_78s.htm gives a very detailed purist approach to capturing good quality transfers from 78s - well worth a read if you are serious about this subject.

WC

[vethraxx]

Thank you very much for your input.