SPICE transfer function for RIAA testing
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Onvinyl
diyAudio Member

Join Date: Aug 2002
Location: Germany
...the plot

edit: bad pic, well, the range is -30dB at 1Hz till +77 dB at 20kHz. It rather should be at 0dB
Rüdiger
Attached Images
 spiceplot.jpg (35.4 KB, 622 views)

 2nd March 2006, 12:47 PM #12 ashok diyAudio Member     Join Date: Jun 2002 Location: 3RS Did you check the "resources tab" at the Beige Bag web site ? www.beigebag.com The formula is given in that article about the RIAA correction. Application might be slightly different in that GUI but you get the idea. __________________ AM
 2nd March 2006, 01:04 PM #13 Onvinyl diyAudio Member     Join Date: Aug 2002 Location: Germany Hi, The formula itself seems to be ok, my problem is the actual implementation. I'm sure, the beigebag-spice software is good, but I shall get it working with ltspice, Rüdiger
 2nd March 2006, 05:08 PM #14 Pjotr diyAudio Member     Join Date: Nov 2002 Location: Netherlands Hi Rudiger, In plain pspice text as a sub circuit this works for me: .SUBCKT I_RIAA IN OUT PARAMS: tau_1=3180u tau_2=318u tau_3=75u +tau_4=3.18u * E1 OUT 0 LAPLACE {V(IN)}={(1+tau_1*S)*(1+tau_3*S) +/((1+tau_2*S)*(1+tau_4*S))} R1 OUT 0 1meg * .ENDS For a normal invers RIAA make tau_4=0 and for a corrected RIAA incorporating the 3.16 us time constant, make tau_4=3.18u Maybe that works in your pspice? Cheers
Pjotr
diyAudio Member

Join Date: Nov 2002
Location: Netherlands
Quote:
 Originally posted by Onvinyl E_RIAA out 0 LAPLACE {1117*V(in)}={(1+0.00318*S)*((1+0.000075*S)/(1+0.000318*S))}
The plus for extending the expression on the next line is missing. It must be:

E_RIAA out 0 LAPLACE +{1117*V(in)}={(1+0.00318*S)*(1+0.000075*S)/(1+0.000318*S)}

Btw. Why that factor "1117"?

Onvinyl
diyAudio Member

Join Date: Aug 2002
Location: Germany
Quote:
 Originally posted by Pjotr The plus for extending the expression on the next line is missing. It must be: E_RIAA out 0 LAPLACE +{1117*V(in)}={(1+0.00318*S)*((1+0.000075*S)/(1+0.000318*S))}
Pjotr,
there is no next line. however, the expression computes without error warning, but shows strange behaviour. This is not related to the gain modifier (1117*)
I give up for today,
Rüdiger

Pjotr
diyAudio Member

Join Date: Nov 2002
Location: Netherlands
This is what I get with the sub circuit mentioned.

Attached Images
 i_riaa.gif (4.9 KB, 636 views)

jackinnj
diyAudio Member

Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
In beigebag and multisim there is a transfer function utility -- just multiply and apply the constants:
Attached Images
 inverse_riaa.gif (19.4 KB, 611 views)

Pjotr
diyAudio Member

Join Date: Nov 2002
Location: Netherlands
Hi,

That sub circuit should work in any standard pspice compliant simulator. Since we are most time interested in the gain at 1 kHz I have modified the model so it gives 0 dB gain at 1 kHz:

.SUBCKT I_RIAA IN OUT PARAMS: tau_1=3180u tau_2=318u
+tau_3=75u tau_4=3.18u CORR=9.897
E1 OUT 0 LAPLACE {V(IN)}={(1+tau_1*S)*(1+tau_3*S)
+/((1+tau_2*S)*(1+tau_4*S)*CORR)}
R1 OUT 0 1meg
.ENDS

Cheers
Attached Images
 i_riaa_2.gif (4.0 KB, 564 views)

nuvistor
diyAudio Member

Join Date: Jun 2004
Location: Richmond CA
Here's an LTSpice example of Laplace for inverse RIAA. This inverse RIAA includes the "Neumann" 3.18us or 50kHz lead in addition to the usual 50/2122Hz lags and 500Hz lead. The laplace works well in LTSpice only for AC analysis, for transient analysis you should use an RC network. Of course you need the RC network or a test record for frequency response verification if you built something.

The example uses the "El Cheapo" feedback network with an ideal 1-pole opamp, results are similar to OPA637 model.

I have built and tested frequency response of both tube and solidstate phono preamps modeled in LTSpice, agreement between simulation and measurement from 100Hz and 10kHz normalized at 1kHz is usually within 0.2dB, 0.7 to 1dB from 20Hz to 20kHz. I doubt it is possible to verify frequency response this closely with a test record and phono cartridge, if you have done this please let me know.

The E source with the Laplace formula used adds 19.9dB gain at 1kHz, so for 5mV on the preamp input the AC source (V3 in this example) should be 505.8uV.

The example circuit for Laplace:
Attached Images
 elcheapo_1a.png (10.7 KB, 646 views)

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Holton Precision Audio         CSS         Dx Classic Amplifiers         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post jenks Solid State 31 24th April 2008 08:28 PM NIC1138 Digital Source 9 15th July 2007 12:15 AM Limhes Solid State 3 26th April 2007 05:17 AM jclouse Multi-Way 22 1st July 2006 01:19 PM cm961 Multi-Way 1 31st August 2004 06:42 PM

 New To Site? Need Help?

All times are GMT. The time now is 12:26 PM.