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audiorob
diyAudio Member

Join Date: Apr 2006
Location: Dallas, Texas
Re: spice, output_impedance, damping factor, and more

Quote:
 Originally posted by audiorob As I understand it, damping factor is the output impedance / the nominal impedance of the speaker (or close enough...). In the paper, Nelson mentions that the damping factor is about 4 for the Zen 5. I assume that is the output impedance of about 2 ohms divided by a "normal" speaker's impedance of about 8 ohms. If spice is correct, that brings the damping factor value to about 11.
Uhh... Oops!

I'm sure it is obvious to everyone that I have the equation inverted. It
should say that damping factor is the speaker's nominal impedance
divided by the amplifier's output impedance.

I hate when I do that...

Robert

 24th October 2006, 09:36 PM #82 audiorob   diyAudio Member   Join Date: Apr 2006 Location: Dallas, Texas Rail voltage vs output voltage As mentioned in Babowana's, "Papa, I want a zen 5 amp" thread, I did some experiments with rail voltage. I posted the results there, but they really should have been posted here, as this is the "problems wth zen 5" thread. That is to say, sorry for the cross post... As weird as this sounds (or, *I* do not understand this), this is what I have discovered. With the "standard" (ie: per Nelson's paper) Zen 5, and re-biasing for the different rail voltages: +/- 20V Rails -> +/- 17V (34Vpp) output before clipping +/- 25V Rails -> +/- 18V (36Vpp) output before clipping +/- 30V Rails -> +/- 17.8V (35.6Vpp) output before clipping I guess +/-20V rails is the sweet spot. Does anyone have an idea why the output voltage does not rise above +/- 18V, regardless of rail voltage? Could this be due to a max Vgs of 20V for the IRFP240 and IRFP9240? I guess I need to trace voltages on the gate to see if that might be it. Other than that, I'm out of ideas... thanks, Robert
audiorob
diyAudio Member

Join Date: Apr 2006
Location: Dallas, Texas
Re: Rail voltage vs output voltage

Quote:
 Originally posted by audiorob As weird as this sounds (or, *I* do not understand this), this is what I have discovered. With the "standard" (ie: per Nelson's paper) Zen 5, and re-biasing for the different rail voltages: +/- 20V Rails -> +/- 17V (34Vpp) output before clipping +/- 25V Rails -> +/- 18V (36Vpp) output before clipping +/- 30V Rails -> +/- 17.8V (35.6Vpp) output before clipping I guess +/-20V rails is the sweet spot. Does anyone have an idea why the output voltage does not rise above +/- 18V, regardless of rail voltage? Could this be due to a max Vgs of 20V for the IRFP240 and IRFP9240? I guess I need to trace voltages on the gate to see if that might be it. Other than that, I'm out of ideas...
Uhh... never mind. My scope seems to have a 25V, apparenty pp scale, that
I thought was +/- 25V. I discovered this while measuring gate and source voltage
with the scope and got strange results. As the source pins are (almost directly)
tied to the rails, I measured rail voltage with the scope and got bogus numbers. I
found the different scale, and... well... there you have it.

Another example of a gibbon at the controls.

I haven't measured rail voltage vs output voltage yet. I wanted to post this
first, to hopefully stop any waisted effort caused by my stupidity.

My apologies to any following my bad info.

Robert

Babowana
Formerly "jh6you". R.I.P.

Join Date: Jul 2006
Re: Project summarization

Quote:
 Originally posted by audiorob I think the Zen 5 has better bass than my X150. The midrange is also very good. However, *I* have not heard anything with better midrange than an X150, and I still have that opinion. I also think the Zen 5 has very good high end - almost as good as the X150.
My experience on J-Low

Bass: very good +
Mid: very good +
Treble: very good +

Warm and sweet
Even at high volume, never bawl at me
Lovely

For your info, today I use input coupling caps of 6.8uF film,
replacing the original 47uF electrolytic

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