Spice Simulation of Adcom GFA-555

I did some quick LtSpice simulations of the Adcom GFA-555 and am making the asc file available here. I was in a rush used good Fairchild transistors for all the small signal devices and plan to substitute correct models as I find them. Used andy_c's output models which are probably much faster but will do for now - thanks andy! This file has SPICE directives to provide analysis of the distortion; use "view" "spice error-log" to see the results.
Remove .txt from the file names to use them with LtSpice.
I quickly collected some models that I had on this system, my main LTSpice install is on another system. These models are in the attached .LIB file. I have many models but probably not for the remaining transistors so if anyone has them please post them, especially looking for the correct outputs.
 

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  • ADCOM-GFA555.asc.txt
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  • PLB-SPICE-1.LIB.txt
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I believe that there is an example in the audio amp tutorial LTspice file. Comes with the installation. I don't think it uses any of the advanced methods. There is a "loop probe" that is probably more accurate discussed here, see andy's post #29:
http://www.diyaudio.com/forums/solid-state/144719-open-loop-gain-phase-margin-etc-3.html#post1839758

and here:
http://www.diyaudio.com/forums/software-tools/101810-spice-simulation-86.html#post1793923

Are you a member of the Yahoo LtSpice user's group?
 
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Hi Pete,
I did download it a while ago now. I haven't had a chance to even run the install yet. Just as well since the copy I have is now out of date, and my hard drive went from 130 GB free to about 3 point some odd GB free. The 'puter doesn't recognize the larger HD either, so I am forced to move over to a newer machine running Lunix instead of XP. I can't afford to buy yet another license from u$oft because the MD is different.

Once I get computers figured out again, I will do an install and try to learn how to use it. One thing that is a real drag is that I have to do schematic capture twice. One for the simulator, and one for the PCB layout program.

I really appreciate your help Pete, thank you. I have failed you completely though, by not having the program installed yet. Our younger members will be teaching me next!

-Chris
 
Since I am still mainly lurking and trying to learn I figure maybe I'll offer my assistance to help you out with your computer problem...if you need/want my help just PM me. While I am a Materials Scientist/Chemist, I have moon lighted as a sys admin for an office in the past.

As for LTSpice, I have been using it a lot to teach myself electronics and theory. It wasn't until really playing around with LTSpice that I understood things like FlipFlops, Logic Gates, etc. (I understood the concept but didn't understand their power).

Hi Pete,
I did download it a while ago now. I haven't had a chance to even run the install yet. Just as well since the copy I have is now out of date, and my hard drive went from 130 GB free to about 3 point some odd GB free. The 'puter doesn't recognize the larger HD either, so I am forced to move over to a newer machine running Lunix instead of XP. I can't afford to buy yet another license from u$oft because the MD is different.

Once I get computers figured out again, I will do an install and try to learn how to use it. One thing that is a real drag is that I have to do schematic capture twice. One for the simulator, and one for the PCB layout program.

I really appreciate your help Pete, thank you. I have failed you completely though, by not having the program installed yet. Our younger members will be teaching me next!

-Chris
 
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Hello

I was using Tina as a simulator but now I use LTspice who are much better in distortions analysis, and wen you have good spice models the LTspice simulations are quite close to a real amps, the amps prototypes I've done was very close to the simulation.

Bye

Gaetan
 
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Closed Loop Gain Avf-3dB = 110KHz
 

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  • GFA-555 Closed Loop Gain.JPG
    GFA-555 Closed Loop Gain.JPG
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