LTspice model for Dynaco A470 Output Transfomer - diyAudio
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Old 17th February 2011, 05:32 AM   #1
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Default LTspice model for Dynaco A470 Output Transfomer

A while back I posted a message concerning LTspice models for output transformers and got some helpful guidance. Thanks to everyone who offered advice.

Rather than tackle a generic U/L transformer model complete with a drop down list, I decided to start small and create a simple .asc file for a single transformer: the Dynaco A470 for the ST-70 power amp. I've attached that file here.

Drawing the symbol was easy enough but determining the appropriate inductances for the transformer sections turned out to be more difficult than I thought it would be. I tried using Robert McLean's excellent spreadsheet but I suppose I don't understand that as well as I thought I did. Could someone help me out with the inductance values for L1 through L7, possibly including series resistances? If it's easier to get the specifications for the Hammond 1650N (which has the same 4300 ohm primary impedance) I'll be glad to use that instead.

My goal is to figure out how to do this once so that I can create additional models for the Dynaco Mark III output transformer (model A431), and the Plitron PAT4004 and PAT4006. Any help you can provide to educate a newbie would be greatly appreciated.

Thanks in advance.

Ray
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Old 17th February 2011, 08:32 AM   #2
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What´s wrong using diyaudio.com search? This was just seconds away!

SPICE Transformer Model Spreadsheet

http://www.diyaudio.com/forums/attac...odels-rev4.zip

Last edited by revintage; 17th February 2011 at 08:35 AM.
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Old 17th February 2011, 01:21 PM   #3
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Quote:
Originally Posted by revintage View Post
What´s wrong using diyaudio.com search? This was just seconds away!

SPICE Transformer Model Spreadsheet

http://www.diyaudio.com/forums/attac...odels-rev4.zip
Thanks, Lars. I guess I need to work on my search skills, not to mention my spreadsheet skills. I'll take a go at using Robert's updated spreadsheet to see if I can answer my own question but I hope it's OK to come back and ask for help if I get stumped. What I will try first is to see if I can arrive at the same parameters for the Hammond 1650T as Robert's example shows, and if I can I'm sure I'll be able to do the others.

Ray
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Old 17th February 2011, 02:21 PM   #4
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Ray,

You didn't post the file you mentioned in your original message.

Rick
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Old 17th February 2011, 02:33 PM   #5
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Hey Rick and Ray,
No need for Rays file, follow McLeans spreadsheet instead. Just type the transformer name in the cell with red/bold text and copy the blue into LTSpice. Also use the transformer schematic shown there.
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Old 17th February 2011, 03:33 PM   #6
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Quote:
Originally Posted by revintage View Post
Hey Rick and Ray,
No need for Rays file, follow McLeans spreadsheet instead. Just type the transformer name in the cell with red/bold text and copy the blue into LTSpice. Also use the transformer schematic shown there.
Sorry about the missing file -- another newbie mistake. My schematic model was the same as Robert McLean's anyway.

I've studied Robert's revised spreadsheet and I think this is going to give me everything I need. I was working with his original version 1 spreadsheet and was having a little trouble following it, but the new revision 4 instructions (not to mention the calculations) helped a lot.

Thanks to all for the help.

Ray
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