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Old 1st March 2006, 09:54 AM   #1
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Default spice transfer function for riaa testing

Hi,
recently, someone posted a 'voltage source' that simulates an inverse riaa for the spice simulation software. Unfortunately, I can't find it anymore. Anyone remembers where it is?
Rüdiger
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Old 1st March 2006, 03:18 PM   #2
burbeck is offline burbeck  United Kingdom
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try this link

http://waltjung.org/PDFs/A_High_Accu...AA_Network.pdf

or http://www.hagtech.com/pdf/riaa.pdf

regards
bob
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Old 1st March 2006, 04:33 PM   #3
Ghianni is offline Ghianni  Greece
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Hi all,

The attachment is a theoritical inverse riaa for simulation taking into account that the 1kHz gain is about 40 dB. I copied it from AudioXpress magazine by Gary Galo.

Ghianni.
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File Type: png inv_riaa.png (3.7 KB, 579 views)
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Old 1st March 2006, 05:53 PM   #4
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if your SPICE machine allows it the most acurate method is to use Laplace transform -- search under LAPLACE on the DIYAUDIO forum and you can cut and paste the equations into a component model.
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Old 1st March 2006, 06:35 PM   #5
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I use LTSpice, but, being a novice with spice, I have not found out how to incorporate a laplace transform.
I have, however, found the corresponding formula that I searched:

http://www.diyaudio.com/forums/showt...619#post849619
thanks,
Rüdiger
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Old 1st March 2006, 10:34 PM   #6
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Marshall Leach has an article using SPICE and the LAPLACE transform -- the article deals with horn loudspeakers but from it you should be able to glean how to incorporate the LAPLACE function.

http://users.ece.gatech.edu/~mleach/papers/hornmod.pdf
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Old 2nd March 2006, 10:12 AM   #7
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Hi,

I am not familiar with LT-Spice (I am using Microcap 7) but the generic PSpice syntax is:

LAPLACE:

E|G{name} {+node} {-node} LAPLACE {expression} {s expression}

Example:

E_LOPASS 4 0 LAPLACE {V(1)} {10 / (s/6800 + 1)}

So if your Pspice version does not provide a dependant Laplace source as a schematic entry you can make a sub circuit yourself for the Laplace expression and put it in your library.

A good link for Pspice syntax:

http://www.ecircuitcenter.com/SPICEsummary.htm at http://www.ecircuitcenter.com

Cheers
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Old 2nd March 2006, 10:28 AM   #8
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Quote:
...........theoritical inverse riaa...........
Or just RIAA .

BeigeBag Software A/D V4.x and higher can do this.
The equations can be included in the voltage source or at the output of the circuit . Eliminates any errors that real world components can cause.

Look for "resources " at www.beigebag.com
There is an RIAA example with all details and examples that yoiu can run.
You can also download a free time limited version of A/D V4.x and
run the simulations yourself. Very easy after the first try.

Cheers,
Ashok.
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Old 2nd March 2006, 12:15 PM   #9
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Hi,
I'm lost. The formula as spice command:
E_RIAA In Out LAPLACE {V(Out)}={(1+0.00318*S)*((1+0.000075*S)/(1+0.000318*S))}
does something, but it's wrong and I don't know what happens.
If someone could confirm whether the formula in itself is senseless or should work at all?
The nodes 'in' and 'out' are just that...
Rüdiger
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Old 2nd March 2006, 01:32 PM   #10
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Hi,
that was deadly wrong, after reading w.jung again I would suppose
E_RIAA out 0 LAPLACE {1117*V(in)}={(1+0.00318*S)*((1+0.000075*S)/(1+0.000318*S))}
to work, but it doesn't!
attached is the circuit and the plot,
Rüdiger
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File Type: jpg spiceboy.jpg (46.8 KB, 487 views)
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