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Jay
Banned

Join Date: Feb 2003
Location: Jakarta
Quote:
 Originally Posted by PauloPT 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

PauloPT
diyAudio Member

Join Date: Jan 2010
Location: Lisboa, Portugal
I attach the simulation file and my bjt and mosfet. So, why the spectrum isn't clean?
Attached Files
 SSA.asc (10.3 KB, 55 views) SSA_models.txt (27.7 KB, 44 views) standard.txt (143.7 KB, 36 views)
__________________
Kind Regards,
Paulo.

Last edited by PauloPT; 8th February 2013 at 12:20 PM.

Banned

Join Date: Jul 2011
Location: Portugal
Quote:
 Originally Posted by Jay 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.

PauloPT
diyAudio Member

Join Date: Jan 2010
Location: Lisboa, Portugal
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?
__________________
Kind Regards,
Paulo.

 8th February 2013, 11:34 PM #3925 Esperado   Banned   Join Date: Jul 2011 Location: Portugal 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.
Jay
Banned

Join Date: Feb 2003
Location: Jakarta
Quote:
 Originally Posted by Esperado 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?

Banned

Join Date: Jul 2011
Location: Portugal
Quote:
 Originally Posted by Jay 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.

 10th February 2013, 08:43 PM #3928 PauloPT   diyAudio Member   Join Date: Jan 2010 Location: Lisboa, Portugal 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? __________________ Kind Regards, Paulo.
Banned

Join Date: Jul 2011
Location: Portugal
Quote:
 Originally Posted by PauloPT Any sugestions about how to build a nice power supply for the SSA?

 11th February 2013, 05:50 AM #3930 Esperado   Banned   Join Date: Jul 2011 Location: Portugal 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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