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Reverse RIAA curve
Posted: Sun Oct 18, 2009 3:21 am
by billw58
There have been a couple of posts recently about transcribing 78 rpm records. The problem is that virtually all phono pre-amps (and USB turntables) apply the RIAA playback equalization curve. This is not appropriate for 78s. What is needed is the ability to reverse the RIAA playback EQ, then apply the appropriate 78 rpm EQ for the particular disc you are transcribing. One could painstakingly draw the reverse RIAA curve and save it, but why not include it as a standard pre-set? Audacity already includes many 78 rpm presets, and it makes sense to me that anyone wanting to use one of those presets would first want to apply the reverse RIAA EQ first.
-- Bill
Re: Reverse RIAA curve
Posted: Sun Oct 18, 2009 10:36 am
by 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
http://wiki.audacityteam.org/index.php? ... e_Requests
and pending FRs at
http://wiki.audacityteam.org/index.php? ... e_Requests
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).
Re: Reverse RIAA curve
Posted: Sun Oct 18, 2009 3:28 pm
by billw58
I
knew I'd seen a similar request somewhere, but couldn't for the life of me figure out where. I
did search the forum, but overlooked the wiki Feature Requests page.
waxcylinder wrote: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 own Eq curve - and sometimes more than one). unless ALL the 78 curves were reconfigured for first strip the normal vinyl 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 of me find it on the forum (or on the Wiki Pending Feature Requests or Feature Requests pages).
There's another reason for separating the reverse RIAA curve from the 78 rpm EQ curves. Most users today will be transcribing their 78s at 45 rpm. You need to first reverse the RIAA EQ, then change the speed, then apply the correct 78 rpm curve. Combining the curves only works if the transcription was done at 78 rpm in the first place.
-- Bill
Re: Reverse RIAA curve
Posted: Sun Oct 18, 2009 11:42 pm
by steve
You may be interested in the second half of this thread from the audacity developers mailing list:
http://n2.nabble.com/P4-EQ-Can-t-save-a ... l#a3733515
Re: Reverse RIAA curve
Posted: Mon Oct 19, 2009 10:15 am
by waxcylinder
Aahhhh .....
I've just seen Bill's updates in the manual for the upcoming 1.4/2.0 release - and see why this request has been posted right now.
Awkward to explain to users how to reverse the curve and awkward for users to do the work ....
a reverse RIAA would simplify things.
WC
Re: Reverse RIAA curve
Posted: Mon Oct 19, 2009 12:36 pm
by billw58
waxcylinder wrote:Awkward to explain to users how to reverse the curve and awkward for users to do the work ....
Steve:
I went and read that thread, and learned about the existence of EQcurves.xml. Very simple to create a reverse RIAA curve. Just copy and paste the existing RIAA curve then negate all the values!
-- Bill
Re: Reverse RIAA curve
Posted: Mon Oct 19, 2009 1:20 pm
by waxcylinder
Bill,
does that mean that you consider this FR to be redundant?
WC
Re: Reverse RIAA curve
Posted: Mon Oct 19, 2009 2:26 pm
by billw58
waxcylinder wrote:Bill,
does that mean that you consider this FR to be redundant?
No, I think it is so trivial to add it to the default EQCurves.xml, why not do it?
The RIAA curve is only useful for people who connect a turntable directly to their stereo mic input and then need to apply the curve. We tell people not to do this (who has a stereo mic input?), but to use a phono pre-amp that applies the RIAA curve.
The reverse RIAA curve is useful for people who are transcribing 78s. This is admittedly a small proportion of Audacity users, but probably at least as large as those who connect a turntable to their mic input.
-- Bill
Re: Reverse RIAA curve
Posted: Mon Oct 19, 2009 2:41 pm
by waxcylinder
Plus my vote then - I recall several times in the past few years when I have responded to folk who are (or planning to) transcribe 78s - telling what to do would be much easier with a reverse-RIAA.
OFF-TOPIC - Sady I am not one of those who has 78s to transcribe. I used to have a reasonable collection when I was younger (and a resonable collection of wind-up gramophones to play them on) all garnered from jumble sales when I was in the Scouts. But unfortunately my parents threw them all out when I left home to go to University - it's a long story .... 
Still, looking on the bright side, it saves a transcription chore I suppose 
WC
Re: Reverse RIAA curve
Posted: Mon Oct 19, 2009 2:58 pm
by billw58
Here it is. Until this is added to the default EQCurves.xml I'll keep this around to give to people who need it.
Code: Select all
<curve name="Inverse RIAA">
<point f="30.000000000000" d="-18.600000381470"/>
<point f="31.000000000000" d="-18.500000000000"/>
<point f="50.000000000000" d="-16.899999618530"/>
<point f="63.000000000000" d="-15.899999618530"/>
<point f="70.000000000000" d="-15.300000190735"/>
<point f="100.000000000000" d="-13.100000381470"/>
<point f="125.000000000000" d="-11.600000381470"/>
<point f="200.000000000000" d="-8.199999809265"/>
<point f="250.000000000000" d="-6.699999809265"/>
<point f="300.000000000000" d="-5.500000000000"/>
<point f="400.000000000000" d="-3.799999952316"/>
<point f="500.000000000000" d="-2.599999904633"/>
<point f="600.000000000000" d="-1.799999952316"/>
<point f="700.000000000000" d="-1.200000047684"/>
<point f="800.000000000000" d="-0.800000011921"/>
<point f="900.000000000000" d="-0.300000011921"/>
<point f="1000.000000000000" d="-0.000000000000"/>
<point f="2000.000000000000" d="2.599999904633"/>
<point f="3000.000000000000" d="4.699999809265"/>
<point f="4000.000000000000" d="6.599999904633"/>
<point f="5000.000000000000" d="8.199999809265"/>
<point f="6000.000000000000" d="9.600000381470"/>
<point f="7000.000000000000" d="10.800000190735"/>
<point f="8000.000000000000" d="11.899999618530"/>
<point f="9000.000000000000" d="12.899999618530"/>
<point f="10000.000000000000" d="13.699999809265"/>
<point f="15000.000000000000" d="17.200000762939"/>
<point f="16000.000000000000" d="17.700000762939"/>
</curve>