Current amp vs Voltage amp

HEy, look, if it weren't for fretting over how well every technical detail of one's system is working in theory compared to others, what else would one do? Listen to music and find out, maybe?

05-09-13: Swampwalker
I'd love to hear Atmasphere and Almarg comment about how that type of amplifier's inherent electrical characteristics interacts w speaker loads.

Hi Michael,

I'm not especially familiar with Class D amplifiers. But in terms of output impedance they are of course firmly in the voltage source camp, with some of them having extraordinarily low output impedances/high damping factors. In terms of feedback, I don't have a particular feel for how much negative feedback most of them use, but I'd imagine that it is not insignificant in most cases.

An exception would apparently be the ARC amps that have switching output stages. Those are described as using no global feedback, and are spec'd as having 1% THD. Which would seem to raise the possibility that their behavior is somewhat tube-like.

Also, the Spectron writeups on their Musician III indicate that although negative feedback is used its adverse effects are claimed to be essentially eliminated as a result of the fact that transit time (aka propagation delay) through the signal path is exceptionally fast. I see no reason to doubt that claim.

As I say, though, I have no particular knowledge of the degree to which feedback may be employed, and the degree to which it may be an issue sonically, with Class D in general.

05-09-13: Bombaywalla
"In the Power Paradigm the box design puts the peak at a lower frequency to take advantage of the extra energy- but again netting fairly flat frequency response, but with the additional benefit of bass extension, which might well be up to half an octave."
Atmasphere, what does this mean? The box resonance peak is where it is. How does the Power Paradigm amplifier move that peak to a lower frequency?

I believe that Ralph was referring here to speakers that are designed per power paradigm principles, not to amplifiers. One of his underlying points is that both must be designed in accordance with the same paradigm, if they are to work well with each other.

05-09-13: Bifwynne
I've picked some LP dogs that are so bad, the neighborhood dogs howl. And I don't think that's because of NF or impedance peaks or negative phase angles. Some recorded music just stinks.

Truer words were never spoken :-)

Best regards,
-- Al

"I've picked some LP dogs that are so bad, the neighborhood dogs howl. And I don't think that's because of NF or impedance peaks or negative phase angles. Some recorded music just stinks."

No doubt.

Personally in my audio "journey" I have been in places in the past on occasion where few recordings seemed worth listening to. Nowadays, no two sound the same, and some are still barely listenable but the vast majority sound good enough for me to enjoy, especially if one takes pleasure in the variety of sounds a recording might deliver rather than futilely attempting to make them all sound similarly good.

FWIW, I use an ARC tube pre-amp and a Bel Canto Class D amp. There is a lot to be sid about pairing a tube pre-amp with a good Class D amp, if a tube amp is not what the speakers ordered.

So my conclusion is that the devil is in the details and the details are what will swing you one way or the other, for better or for worse.

As the great scholar and musician Frank Zappa once said, "you are what you is". Very true when it comes to recordings.

The box resonance peak is where it is. How does the Power Paradigm amplifier move that peak to a lower frequency?
If the resistance in the bass region goes up (due to a box resonance) then the current into that higher resistance goes down. the voltage must go up to keep constant power. Where does the bass extension come from?

This is a matter of design. The peak exists as a relationship of the driver and the box. Change the relationship, change the peak. The bass extension comes from designing the box so the peak occurs at or below the cutoff of the driver, in such a way that the peak maintains the bandwidth. Not hard to do if you understand speaker design.

I believe that a traditional SS amp (one that was not designed for an ESL in mind) will likely sound mediocre 'cuz of the high capacitance load that will tend to make that amp oscillate & eventually fail. OTOH, if a SS amp is designed with an ESL in mind (& a few names come to mind that are being used successfully with ESLs & planars) then these SS amps will be effective.

Belief and reality are usually two different things. In this case I invite you to do the math. How much power will an ideal 400 watt SS amp make into 30 ohms and into 3 ohms? If you answer 'about 100 watts and about 900 watts' then you have some grasp of the problem.

to be fair, when the SPL get's really high, my ears hurt. So what's the point of that exercise?? ;>')

If that happens with less than 105 db, then its an indication that the system has some sort of odd ordered harmonic generation associated with its operation. A sound pressure level meter might be handy to sort out the actual volume level.

"If that happens with less than 105 db, then its an indication that the system has some sort of odd ordered harmonic generation associated with its operation. A sound pressure level meter might be handy to sort out the actual volume level."

Maybe, but levels louder than 80-85 db (much lower) are often cited as the limits of safe listening without causing damage to ones hearing.

Even if you can go 105db, it may not be such a great idea to do so.

Maybe our hearing works a certain way with certain sensitivities for a reason?

I wonder what happens if one listens to nicely produced music, say a big band with lots of brass and high frequency energy live at 105DB? Is it as comfortable as listening to the no NF tube amp at the same level? Its a fair question, I think.

ANyway, its nice to know if one can go to 105db cleanly in any case. That's a pretty good indicator that you have the headroom needed for good results at more moderate volumes, where excessive loudness should not be an issue.