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Old 8th February 2013, 11:41 AM   #3921
Jay is offline Jay  Indonesia
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Originally Posted by PauloPT View Post
I get a lot of harmonics. See the pic below. Is this a concern or just a simulation glitch?
Something is wrong. It should look better than that. Compare with THD shown in the log file.

But I don't understand what Esperado is trying to say
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Old 8th February 2013, 12:16 PM   #3922
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I attach the simulation file and my bjt and mosfet. So, why the spectrum isn't clean?
Attached Files
File Type: asc SSA.asc (10.3 KB, 43 views)
File Type: txt SSA_models.txt (27.7 KB, 33 views)
File Type: txt standard.txt (143.7 KB, 26 views)
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Last edited by PauloPT; 8th February 2013 at 12:20 PM.
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Old 8th February 2013, 05:00 PM   #3923
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But I don't understand what Esperado is trying to say
Look at the first file: Signal is at +20dB, H2 at -55dB.this give 75dB =<0.02% of H2 distortion.
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Old 8th February 2013, 10:25 PM   #3924
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Quote:
Look at the first file: Signal is at +20dB, H2 at -55dB.this give 75dB =<0.02% of H2 distortion.
So is not a concern because the harmonics are below audible levels even if it's an almost continuum spectrum of harmonics?
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Old 8th February 2013, 11:34 PM   #3925
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Not the right place to explainaudible effects of harmonic distortions.
Nothing real after 100Khz, only FFT calculation artifacts. Absolutely normal.
No distortion you can hear after 20Kz neither.
Make a measurement at low frequency if you want to know high order harmonics inside the audible bandwidth.
And do not forget, it is just simulation, not real world.
Now, you decide if the level of distortion you can read up to 20Kz meet your goals.
But 0.02% is a good value for a power amp.
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Old 9th February 2013, 12:01 AM   #3926
Jay is offline Jay  Indonesia
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Originally Posted by Esperado View Post
Look at the first file: Signal is at +20dB, H2 at -55dB.this give 75dB =<0.02% of H2 distortion.
As Paulo said "so it is not a concern?". That's how it sounded like.

Many of us don't have a problem with H2. But with such graph the total HD will be not as good.

I don't have access to LTSpice (and my computer) for a few months now. But the graph seemed to show lack of bias.

I'm not saying that the graph is bad. What I'm saying is that I'm familiar with the amp simulation and what I have seen is better than 75dB. Actually, 75dB is below my standard.

I have been biasing latfet around 120mA-150mA. So may be this one is less?
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Old 9th February 2013, 03:13 AM   #3927
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I have been biasing latfet around 120mA-150mA. So may be this one is less?
Too make your measurements at -3dB (half power) or at least 5v margin from clipping.
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Old 10th February 2013, 08:43 PM   #3928
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I've been listening all day long to beautifull music with my SSA. The female voices are rendered with an unbeliveble presence and realism. And the piano notes are sweet and extended. Melody Gardot, Jane Monheit, Eliane Elias, Diana Krall, among others never sound so wonderful! Today is sunday but I had other things to do besides listening to the SSA. Guess what, the day is over and I just couldn't switch off the amplifier!

I'm going to build this amp the best I know how, with nice parts, nice chassis, nice psu. I'm waiting for some parts including the fets. I ordered these from here:Mosfets I Hope they aren't fakes.

Any sugestions about how to build a nice power supply for the SSA?
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Old 10th February 2013, 09:02 PM   #3929
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Any sugestions about how to build a nice power supply for the SSA?
www.esperado.fr - Alimentation Crescendo
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Old 11th February 2013, 05:50 AM   #3930
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An other positive review about the SSA topology:
Update for Elektor Crescendo Power Amplifier 1982
and , in a private message:
"Thank you very much for putting together the article on the Crescendo. I am very excited with the results I am getting. As you say it must be one of the best amplifiers in the world now!"
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