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Old 9th September 2012, 07:26 AM   #3011
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p.s. if you want less capacitance and don't mind more some inductance you could try having send on blue/white, orange/white and return on brown/white green/white.
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Old 9th September 2012, 09:15 AM   #3012
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Quote:
Originally Posted by sonnya View Post
Sim of the final circuit tells me less than 2mOhm of the final amp at 20KHz.

Before asking how it is done. This does not leave my doorstep, but it can be done....

So the DFin my final circuit is equal to the Hypex NCD400.
Here's info about output impedance of SSA BIGBT HP before CCS were installed. Real measurement shows that 2 mohm calculated by sim isn't unrealistic at all.
After CCS modules were added SSA was sold so quickly I didn't have enough time to make another set of mesurements, but I believe that the output impedance in latest iteration would go even lower, very close to sim's 2 mohm. OLG + feedback + smart PCB layout can do that.
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Old 9th September 2012, 09:31 AM   #3013
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That's interesting, You & Sonny seem to highly value a very low o/p Z

I found 0.1 - 0.2R sounds nicest except for big bass speaker or sub which need low Z to drive them.
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Old 9th September 2012, 09:44 AM   #3014
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So you would need to tweak TSSA a little bit because it has 0,45 ohm Zout. When do you expect to perform first listening test of Sonny's modules?
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Old 9th September 2012, 10:10 AM   #3015
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Quote:
Originally Posted by mikelm View Post
That's interesting, You & Sonny seem to highly value a very low o/p Z

I found 0.1 - 0.2R sounds nicest except for big bass speaker or sub which need low Z to drive them.
There's Catch 22 involved in a damping factor of specific amp. Higher DF means by definition the amp puts more effort to "correct" the output signal according to an input signal, that's OK at least in theory. But what if the amp is not fast enough, higher DF number would make a lot more of phase-timing distortions than it should, ruined the sound more than if DF would be lower. By high speed amps like SSA is, high DF means only that the output signal would be really close to the original, speaking of time coherence, so very pleasant to listen to even with high DF.
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Old 9th September 2012, 10:29 AM   #3016
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Mine should be 0.33 because I'm using ALF16N16W and ALF16P16W

I now have the parts - now I need to find some time - perhaps within a week
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Old 9th September 2012, 02:18 PM   #3017
sonnya is online now sonnya  Denmark
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Originally Posted by mikelm View Post
Mine should be 0.33 because I'm using ALF16N16W and ALF16P16W

I now have the parts - now I need to find some time - perhaps within a week
You Will not be disapointed.
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Old 9th September 2012, 02:21 PM   #3018
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Originally Posted by Jay View Post
I think it will become a capacitive load for the amp? Do you mean the negative cable shielding the positive one???
Of course, the amp is supposed to have enough phase margin to stay stable under such a capacitive load. Zobel included.

As a general law, and like for a bridged amp, the shield have to be connected at the ground of the amp and free Loudspeaker side (no current).

About Zout of an amp (damping factor) your best value depend of the speakers themselves.
1- Bass reflex are calculated for a given source impedance (cable included). It matters for low end flat response.
2- But best is the damping factor, best is the pulse response.
3- But on some loudspeakers (medium, tweeters or wide band) too much damping can increase the material resonances if the cone fractionate. By example, my JBL 2" motor, highly damped by itself, sound better with a passive attenuator between itself and the amp.

So, best is the damping factor of the amp, best it is, and you can play with external serial resistances. And, because DIY are Gods, they can tune the FB compensations for perfect flat (and square waves) response with their real world loudspeakers installation, including wires.
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Old 9th September 2012, 03:59 PM   #3019
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Esperado, so fine tuning between amp and speakers with optimal serial resistor. Meaning best square waves measured on speaker driver terminals or on axisys microphone's signal?
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Old 9th September 2012, 04:47 PM   #3020
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Esperado, so fine tuning between amp and speakers with optimal serial resistor. Meaning best square waves measured on speaker driver terminals or on axisys microphone's signal?
Unless you use a digital filter or a very good tuned Speakers (regarding group delay) there is no way to look in an understanding way square waves via a mike. But it is the way to tune the group delai of the enclosure (geometrical alignment of speakers)
I prefer to tune the FB compensation, looking at the speaker's outlets of the amp to get no overshoot on square waves with wires and loudspeakers in place, then try different resistances on medium/tweeters speakers (each band separately for a multi band one.
Well, with passive filters, serial resistances of coils or attenuators are often yet too much to can improve anything. Thus it applies mainly on active multy-ways systems or wide band single speakers, and i tune them with ears: too subtle for any measurements.

Quote:
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By high speed amps like SSA is, high DF means only that the output signal would be really close to the original, speaking of time coherence, so very pleasant to listen to even with high DF.
Exactly.

Whatever the point of view from which we observe an amplifier,, slewrate is definitively the goal.
"Faster" is the amp, more you can add Feed back. Despite the wrong bad reputation of feedback, more feedback more DF, less harmonic distortion.
"Faster" the amp, less IM or TIM. better the sound.
We have a perfect example with the current source we were talking about here. It increase bandwidth SO reduce distortion. Everything is stuck together.

L.C you are one of the rare audio designer with have a *complete* view of audio closed loops. Including the signals generated by the loudspeakers when they move, feeding the feedback returns with high level errors signals.

I'm convinced that, when the CSSA (Complete state-of-the-art symetrical amplifier ) will be tuned in the littlest detail, this forum will have his master piece.
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