Is there a simple EQ circuit for adding RIAA recording EQ to an audio recording?

[audioxcel]

I can find many simple IRIAA RC circuits for reversing the RIAA EQ present on vinyl records but none for adding RIAA EQ to an audio tape. Every phono preamp has an IRIAA circuit but I cannot find a schematic for a simple RC circuit that adds RIAA EQ.

Is there such a circuit or is it just not possible?

I would like to input a flat EQ 2mv signal and output a vinyl recording RIAA EQed signal of about 0.5mv.

[Soulbear]

I can find many simple IRIAA RC circuits for reversing the RIAA EQ present on vinyl records but none for adding RIAA EQ to an audio tape. Every phono preamp has an IRIAA circuit but I cannot find a schematic for a simple RC circuit that adds RIAA EQ.

Is there such a circuit or is it just not possible?

I would like to input a flat EQ 2mv signal and output a vinyl recording RIAA EQed signal of about 0.5mv.

Hi there,
Did you take a look at Rod Elliots site??? Here :- https://sound-au.com/articles/eq.htm
Maybe you will find something useful there
Regards Soulbear

[audioxcel]

That is a very cool site but I didn't see anything for a circuit that adds RIAA EQ to a flat EQ signal. It is easy to find circuits for reversing RIAA EQ because every audio phono stage preamp has that circuit built into it to make playing 33 1/3 RPM records possible.

Because people who make records have to add RIAA EQ to whatever audio source signal that they are cutting onto vinyl I thought this would be the place where I would be most likely to find expert information.

What I find frustrating is how the terminology regarding RIAA EQ seems to be hard to discuss because so many people use RIAA EQ and IRIAA EQ interchangeably when they are actually direct opposite EQs. I tried to get advice on a DIY audio forum that I participate on and everyone kept posting IRIAA circuits (reverse RIAA) and the discussion quickly degenerated into people calling me ignorant not because it is true (even though it is true on this subject at least) but because I refused to concede that IRIAA EQ is the same as RIAA EQ. I began to get some usable info after we agreed to start using the terms "recording RIAA EQ" and "playback RIAA EQ".

I hope we don't have that issue here but to prevent it, what I am asking for is a simple RC circuit for adding "recording RIAA EQ" to a flat EQ signal that is passed through it. I don't want to use op amps or software programs. I just want to use a simple RC circuit.

[audioxcel]

Correction I would be inputting a 20mv signal not 2mv.

[mratx]

There are a lot of designs for this out there, people use them for testing phono preamps (you feed a flat signal into it to give it the RIAA curve, run the modified signal into the preamp, and theoretically you should get the flat signal out.) An article on one well-known design is attached.


Mark

[audioxcel]

I have read that article before and am just as confused as every other time that I have read it. My understanding is that an "inverse" RIAA EQ circuit is the same circuit (which reverses the RIAA EQ applied during record making) that is built into every modern phono preamp. When I put an LP (which has been cut using pre-emphasis RIAA EQ) on my turntable and start play, the output from my phono cartridge passes through the phono stage of my preamp where my phono stage uses a de-emphasis "inverse" RIAA circuit to output a flat signal by reversing the pre-emphasis RIAA EQ that was added to the signal that was cut into the LP.

I cannot understand how passing a signal though another "inverse" RIAA EQ (low frequency boost and high frequency cut) circuit and then passing that signal through my preamp's phono stage would not result in the output from my phono stage having the square of the LF boost and the square of the HF cut that it already has built into its circuit instead of the desired flat signal.

[farmersplow]

A phono amplifier, as used for record players, is an RIAA EQ. It boosts the low frequencies and reduces the high frequencies.
An IRIAA EQ reduces the low frequencies and increases the high frequencies. This IRIAA is actually ‘ONLY’ used in the production of record cuts. Nobody needs it in ‘normal’ audio life.
If you pass a linear input signal through an ‘ideal’ IRIAA EQ and then through an ‘ideal’ RIAA EQ, the result is a linear output signal again.
There are hundreds of examples of RIAA EQ on the Internet. Some with RC circuits only, some with tubes and some with operational amplifiers. There are also digital versions.
There are not so many examples for IRIAA-EQ, but there are also.
You just have to search.
Here is an simple example of an RIAA-EQ with circuit diagram you can use. (low frequencies are boosted and high frequencies are cut). This circuit is not 100% perfect but works very well.

RIAA.jpg

Best regards from Austria
Thomas

[audioxcel]

Thanks. This seems odd to me. The RIAA EQ curve was created to allow the groove to be better cut into records but the implementation of this EQ is call inverse RIAA EQ The playback circuit that is used by phono preamps to reverse the EQ that was applied during the making of records is called RIAA EQ. It boggles my brain.

I spent 3 whole days searching for an circuit to apply EQ to the flat output of a DAC that would result in a flat frequency response when that EQed signal was passed through the phono stage of my preamp. I couldn't find any results because I thought that RIAA EQ was used to cut records. SMH

[farmersplow]

well then the knot is untangled now