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Old 25th November 2010, 04:10 PM   #11
cbdb is offline cbdb  Canada
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Quote:
Now in reality i do doubt that my amp actually get below 1% THD since spice is ideal component models in an ideal environment.
The spice components are not ideal but for accurate results you need accurate models, and a lot of the models out there are not very good.
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Old 25th November 2010, 04:15 PM   #12
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also noticed that in ltspice i can have a much smaller Cdom before the amp oscillates than in circuitmaker 2000.
I woudnt trust using the the .tran function to test for stability. Better to use the traditional loop gain/phase calculations (gain/phase margins) within LTSpice. Check the Spice thread and the spice examples for Middlebrook probe.
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Old 25th November 2010, 04:41 PM   #13
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Originally Posted by Tekko View Post
0.01% THD at 100-140W output when using command: .four 1kHz V(output) in spice directive.

Click the image to open in full size.
The amp you used Blameless as the basis for your project, keep darligton in VAS this should reduce the THD
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Old 25th November 2010, 05:05 PM   #14
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Smile LT Spice modeling audio

Keep in mind LT Spice was developed by them to mainly model their components, mainly in power products. Most good engineers use spice as a general tool to prove a concept. To go further, complicated math models have to be formulated taking into account every concievable parasitic. Best alternative is good old bench testing with some half decent equipment!
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Old 25th November 2010, 05:30 PM   #15
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Originally Posted by Rafael L View Post
The amp you used Blameless as the basis for your project, keep darligton in VAS this should reduce the THD
Not just that ,but the sine gen. in spice generates .005% just by itself. you can get a blameless to do "parts per million" with proper models and without "tricks".
Get that "Andy C. sine gen." linked to a few posts back.
PS. The IRF models "suck". Still... one can get .0001% or below with them.

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Old 25th November 2010, 07:57 PM   #16
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I never understood this "blameless" name i keep seeing in threads here, what does it mean ?
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Old 25th November 2010, 08:04 PM   #17
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Originally Posted by Tekko View Post
I never understood this "blameless" name i keep seeing in threads here, what does it mean ?
Douglas Self amp, "blameless" ... the prime example he references to in his "power amplifier design handbook"
Audio power amplifier design handbook - Google Books

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Old 25th November 2010, 08:32 PM   #18
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Ohh

Despite 100% outta my head it turns out i did a outright copy of an already existing amp design and then calling it my own.

I will remove all schematics of "my" amp.
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Old 25th November 2010, 08:46 PM   #19
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Is a circuit of the book, is to be used in studies/simulation, I found similar to "Blameless", recognize his authorship on the project.
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Old 25th November 2010, 09:08 PM   #20
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Originally Posted by Tekko View Post
Ohh

Despite 100% outta my head it turns out i did a outright copy of an already existing amp design and then calling it my own.

I will remove all schematics of "my" amp.
The basic design is linn/RCA , long in the public domain. Mr. Self does not have patent on topology. So it can be "your" amp , "My" amp ... the monkey's uncle amp.... Nobody owns it. keep your schematics up.. NO issue.
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