Pspice preamp simulation

Antonix · 27th December 2005, 11:53 AM

I have make the preamp circuit by Norman Koren in Pspice Orcad 10.3
http://www.normankoren.com/Audio/Tub...e_article.html

When I run Transient analisis 1KHZ with 1V AC signal for VLINE IN at V LINE OUT I have only 1,5uV .

The circuit is OK, I have checked 1000 times, the alimentation and ground is ok.

Where do I wrong ?

ray_moth · 28th December 2005, 01:38 AM

You can get incorrect results if you don't run the simulation for long enough to allow capacitors to charge up. When I model a power amp with PS, I allow the simulation to run for 12 seconds, with a delay on the IP signal of 11.95 sec. to avoid excessive run time.

padamiecki · 28th December 2005, 07:43 AM

Quote:

Originally posted by Antonix
I have make the preamp circuit by Norman Koren in Pspice Orcad 10.3
http://www.normankoren.com/Audio/Tub...e_article.html

When I run Transient analisis 1KHZ with 1V AC signal for VLINE IN at V LINE OUT I have only 1,5uV .

The circuit is OK, I have checked 1000 times, the alimentation and ground is ok.

Where do I wrong ?

Just do not use an option "use initial conditions" or do as ray_moth proposed.

Robert McLean · 28th December 2005, 04:50 PM

I have just run the circuit in question in LTSpice without any problems, 1 volt in gives me 4.8 volts out at 1KHz.

What ray_moth said about charging capacitors is true, but in this particular circuit the capacitances are too small to be a problem, you can start your simulation at time zero.

One thing to check is that you have 3.3MEG and 1.2MEG for R4F and R4G. Spice treats 3.3M as the same as 3.3m, ie milliohms. When I run the circuit that way I get 120mV out. Still way more than 1.5uV, but it is something to check.

Also double check the pot formulas. They look unnecessarily complicated to me and a possible source of error. I do not use the same pot model, so I cannot much more. You may want to temporarily replace the pots with pairs of fixed resistors just to eliminate them as a source of error.

Antonix · 8th January 2006, 08:56 PM

Thanks for suggestions I have "only" used the M for mega in place of MEG.

Now all works fine.

Antonix · 10th January 2006, 12:23 PM

Now I have simulated the circuit in spice and I have 12V RMS out with 1V RMS in.

How can I reduce the output ? Decreasing the gain ?

padamiecki · 10th January 2006, 12:29 PM

Quote:

Originally posted by Antonix

How can I reduce the output ? Decreasing the gain ?

1. Larger value for Rk resistor? rather not
2. Voltage divider at the output? rather not
3. Smaller input voltage - via a potentiometer - this is most popular method used in practice!

jackinnj · 10th January 2006, 01:32 PM

remember that the output of a moving magnet phono-cartridge is around 15 mV.

i've modeled Koren's design -- the RIAA performance is quite good --

fwiw -- the best and truest RIAA curve I have modeled is for the Audio Research SP8

Antonix · 10th January 2006, 01:51 PM

Thank for suggestions.

At the moment I am studying the pure line stage whith a CD player as source and I have to optimize this project.

Now I have made a preamplifier based to a Marantz M7.

I have some trouble with a "hum" generated by power supply of plates (I have used a battery for heater).

27th December 2005, 11:53 AM	#1
Antonix diyAudio Member Join Date: Apr 2005 Location: BA	Pspice preamp simulation I have make the preamp circuit by Norman Koren in Pspice Orcad 10.3 http://www.normankoren.com/Audio/Tub...e_article.html When I run Transient analisis 1KHZ with 1V AC signal for VLINE IN at V LINE OUT I have only 1,5uV . The circuit is OK, I have checked 1000 times, the alimentation and ground is ok. Where do I wrong ?

28th December 2005, 04:50 PM	#4
Robert McLean diyAudio Member Join Date: May 2005 Location: Stittsville, Ontario, Canada	I have just run the circuit in question in LTSpice without any problems, 1 volt in gives me 4.8 volts out at 1KHz. What ray_moth said about charging capacitors is true, but in this particular circuit the capacitances are too small to be a problem, you can start your simulation at time zero. One thing to check is that you have 3.3MEG and 1.2MEG for R4F and R4G. Spice treats 3.3M as the same as 3.3m, ie milliohms. When I run the circuit that way I get 120mV out. Still way more than 1.5uV, but it is something to check. Also double check the pot formulas. They look unnecessarily complicated to me and a possible source of error. I do not use the same pot model, so I cannot much more. You may want to temporarily replace the pots with pairs of fixed resistors just to eliminate them as a source of error. __________________ Robert McLean

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28th December 2005, 01:38 AM	#2
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	You can get incorrect results if you don't run the simulation for long enough to allow capacitors to charge up. When I model a power amp with PS, I allow the simulation to run for 12 seconds, with a delay on the IP signal of 11.95 sec. to avoid excessive run time.

8th January 2006, 08:56 PM	#5
Antonix diyAudio Member Join Date: Apr 2005 Location: BA	Thanks for suggestions I have "only" used the M for mega in place of MEG. Now all works fine.

10th January 2006, 12:23 PM	#6
Antonix diyAudio Member Join Date: Apr 2005 Location: BA	Now I have simulated the circuit in spice and I have 12V RMS out with 1V RMS in. How can I reduce the output ? Decreasing the gain ?

10th January 2006, 01:32 PM	#8
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	remember that the output of a moving magnet phono-cartridge is around 15 mV. i've modeled Koren's design -- the RIAA performance is quite good -- fwiw -- the best and truest RIAA curve I have modeled is for the Audio Research SP8

10th January 2006, 01:51 PM	#9
Antonix diyAudio Member Join Date: Apr 2005 Location: BA	Thank for suggestions. At the moment I am studying the pure line stage whith a CD player as source and I have to optimize this project. Now I have made a preamplifier based to a Marantz M7. I have some trouble with a "hum" generated by power supply of plates (I have used a battery for heater).

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