RIAA phono eq curve

[Phil]

On Thu, Mar 19, 2009 at 3:23 PM, Philip Schleihauf
<phil at adjacentfilms.com> wrote:
> On Thu, Mar 19, 2009 at 9:21 AM, suemac at empire.net <suemac at empire.net> wrote:
>>
>> >
>> >
>> >
>> >Original Message:
>> >-----------------
>> >From: Sean Corbett seanbutnotheard at gmail.com
>> >Date: Thu, 19 Mar 2009 08:56:36 -0400
>> >To: ubuntu-studio-users at lists.ubuntu.com, phil at magnustudios.com
>> >Subject: Re: RIAA phono eq curve
>> >
>> >
>> >> ------------------------------
>> >>
>> >> Message: 3
>> >> Date: Wed, 18 Mar 2009 12:31:54 -0400
>> >> From: Phil <phil at magnustudios.com>
>> >> Subject: RIAA phono eq curve
>> >> To: Ubuntu Studio Users Help and Discussion
>> >>        <ubuntu-studio-users at lists.ubuntu.com>
>> >> Message-ID:
>> >>        <d20263c0903180931y2903247di36f1d8379bff89ed at mail.gmail.com>
>> >> Content-Type: text/plain; charset="iso-8859-1"
>> >>
>> >> Hey,
>> >>
>> >> I've got a large collection of vinyl records I need to record onto CD, or
>> >> some other digital format. I've got a stereo with phono inputs, so I
>> could
>> >> use that for the preamp, but I'd rather take the phono player directly
>> into
>> >> my firebox and correct the EQ digitally.
>> >>
>> >> I've done a bit of research on what I need to do. I need a really
>> accurate
>> >> diagram of the RIAA phono curve. The best I've found so far is the one at
>> >> wikipedia, http://en.wikipedia.org/wiki/File:RIAA-EQ-Curve.svg . It's
>> only
>> >> got the markings for 20, 1000, and 20000 Hz. I guess it's got to be a
>> >> logarhythmic graph so I should be able to use it to acurately find the
>> other
>> >> frequency levels.
>> >>
>> >> What I'm hoping for is that someone has already done this and has made a
>> >> preset for a ladspa plugin, or for jamin. Does anyone know of this?
>> >>
>> >> If not, I'll make mine publicly available when I do it.
>> >>
>> >> Thanks,
>> >>
>> >> Phil
>> >> phil at magnustudios.com
>> >
>> >Audacity has the RIAA curve built in... Just record your vinyl, select
>> >the whole recording, and go to Effect>Equalization... and select
>> >'RIAA' from the 'Select Curve' dropdown at the bottom.  I've never
>> >done this myself though, so I can't vouch for its accuracy.
>> >
>> >--
>> >Sean Corbett
>> >
>>
>> Also nicely done RIAA kit from Elliot Sound:
>>
>> http://sound.westhost.com/project06.htm
>>
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>
>
> Alright thanks for all the responses.
>
> In terms of the noise from the firebox: I'm going to try it out, and
> see how good it is. I'm going to hook up the phono and look at the
> noise I get through jamin - I think it's mostly high-frequency, so it
> shouldn't be to much of a problem after the RIAA curve is applied. If
> it's not working, I'll just run the signal through my stereo, which
> has phono inputs.
>
> All the other info is useful. Although using audacity looks easy, I
> think if the firebox works out I will be using ardour, probably routed
> through JAMin for the hdEQ. That way I can just stick in the CD track
> markers and go right to a CD. If I do this I'll make my .jam file
> publicly available somewhere so other people can use it too.
>
> That RIAA kit looks really neat. Maybe I'll have a go at it when I get
> some time.
>
> Thanks!
>
> Phil
>

...sorry for using different email addresses, I always forget to check
which one I'm sending from.

anyway did some digging:
Turns out that you get an RIAA curve with the jamin source code. That
makes it even.

I also found this though:
http://www.mail-archive.com/linux-audio-dev@music.columbia.edu/msg19348.html

"Second, the general 1/F slope of the RIAA curve when combined with
cartridge equalisation should produce a -90 degrees phase shift
over most of the audio band. When you synthesize such a curve with
a multiband EQ, you will not have that phase shift, and any percussive
or transient sounds will be affected. You can easily hear this on
some instruments.

It's quite simple to make an RIAA filter with for example two
first order lowpass LADSPA plugins. Put them in parallel, set
one to 50 Hz and the second to 2120 Hz. Mix the outputs in the
ratio 9 to 1, and the result will be a *perfect* RIAA filter."

I think I'll do some tests with JAMin RIAA vs this guy's RIAA suggestions.

There's quite a bit of info on that thread to sort through, but I
think I'll have enough info to get this going.

Thanks,

Phil
phil at magnustudios.com
http://magnustudios.com