Inverse RIAA signal generator

Sunsun22 · 7th May 2010, 12:33 PM

Is there a signal generator that incorporates an inverse RIAA circuit available in the market? I don't want to use an external Inverse RIAA circuit because it may be incorrect (and difficult to calibrate) and induces hum.

Conrad Hoffman · 7th May 2010, 12:50 PM

I've never seen such a thing, but my experience is that inverse networks have to be physically placed right at the preamp input, and often a heavy ground strap run to the chassis, otherwise the hum levels will contaminate distortion measurements. RIAA compensation in the signal generator might not be useful and it probably wouldn't be as accurate as what you can build yourself.

Conrad

jackinnj · 7th May 2010, 03:27 PM

If you are using a data acquisition card, you can use the polynomials for the correct time constants to just massage the data in situ.

Numerator: 1 + X* 3.255e-3 + X^2 * 2.385e-7
Denominator: 1 + X*318e-4 + X^2 * 1e-12

I wrote a program for my HP3577a network analyzer to do this via the GPIB, (can't find the program) you should be able to do it with a sound card -- if the data on the sound card is valid to >50kHz.

scott wurcer · 03:37 PM

I have a 24/96 inverse riaa wav file with 100 10th octave tones placed at exact bins for a 64k FFT. The phase is randomized so it is psuedo-random. Better than .0005dB, I've been using it to verify biquad digital RIAA filters.

Nelson Pass · 7th May 2010, 03:39 PM

Quote:

Originally Posted by Sunsun22

Is there a signal generator that incorporates an inverse RIAA circuit available in the market?

Audio Precision has it.

scott wurcer · 7th May 2010, 05:30 PM

Quote:

Originally Posted by Nelson Pass

Audio Precision has it.

I figured he might want something cheaper. It is amazing, rippling only a four coefficient IIR filter through an unequalized file is better than .00057dB and +-2 degrees from minimum phase and perfect channel to channel match. Better than any set of R's and C's. No noise or distortion either.

dumptruck · 7th May 2010, 05:34 PM

There is this: Hagerman Technology LLC: iRIAA Filter for Phonostage DIY Kit

consort_ee_um · 7th May 2010, 05:48 PM

You could put a standard or computer function generator into this:
Reverse RIAA Equaliser

rayfutrell · 7th May 2010, 06:12 PM

Here is an article with a simple inverse RIAA network. http://waltjung.org/PDFs/A_High_Accu...AA_Network.pdf

Ray

Sunsun22 · 7th May 2010, 08:40 PM

Many thanks for the input.

7th May 2010, 12:33 PM	#1
Sunsun22 diyAudio Member Join Date: Jul 2004 Location: Hong Kong	Inverse RIAA signal generator Is there a signal generator that incorporates an inverse RIAA circuit available in the market? I don't want to use an external Inverse RIAA circuit because it may be incorrect (and difficult to calibrate) and induces hum.

7th May 2010, 12:50 PM	#2
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	I've never seen such a thing, but my experience is that inverse networks have to be physically placed right at the preamp input, and often a heavy ground strap run to the chassis, otherwise the hum levels will contaminate distortion measurements. RIAA compensation in the signal generator might not be useful and it probably wouldn't be as accurate as what you can build yourself. Conrad __________________ I used to be an audiophool like you but then I took an arrow to the knee.

7th May 2010, 03:34 PM	#4
scott wurcer diyAudio Member Join Date: Jan 2004 Location: cambridge ma	I have a 24/96 inverse riaa wav file with 100 10th octave tones placed at exact bins for a 64k FFT. The phase is randomized so it is psuedo-random. Better than .0005dB, I've been using it to verify biquad digital RIAA filters. __________________ Clay is embedded in our subconscious. It has been there for at least 50,000 years. Last edited by scott wurcer; 7th May 2010 at 03:37 PM.

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7th May 2010, 03:27 PM	#3
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	If you are using a data acquisition card, you can use the polynomials for the correct time constants to just massage the data in situ. Numerator: 1 + X* 3.255e-3 + X^2 * 2.385e-7 Denominator: 1 + X318e-4 + X^2 1e-12 I wrote a program for my HP3577a network analyzer to do this via the GPIB, (can't find the program) you should be able to do it with a sound card -- if the data on the sound card is valid to >50kHz.

7th May 2010, 05:34 PM	#7
dumptruck diyAudio Member Join Date: May 2010 Location: MN	There is this: Hagerman Technology LLC: iRIAA Filter for Phonostage DIY Kit

7th May 2010, 05:48 PM	#8
consort_ee_um diyAudio Member Join Date: May 2004 Location: Hertfordshire	You could put a standard or computer function generator into this: Reverse RIAA Equaliser

7th May 2010, 06:12 PM	#9
rayfutrell diyAudio Member Join Date: Sep 2004 Location: virginia	Here is an article with a simple inverse RIAA network. http://waltjung.org/PDFs/A_High_Accu...AA_Network.pdf Ray

7th May 2010, 08:40 PM	#10
Sunsun22 diyAudio Member Join Date: Jul 2004 Location: Hong Kong	Many thanks for the input.

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