Why Don't We See More High Current Electronics?

Although I always have the greatest respect for opinions expressed by Ralph (Atmasphere) and Grant (Tvad), and I almost always find myself in agreement with both of them, in this case I think that their posts are commingling two separate issues.

ANY amp having negligibly small output impedance, such as most solid state amps, WILL double the amount of power that is delivered into a halved load impedance, PROVIDED that it is operated within the limits of its maximum voltage, current, power, and thermal capabilities. That is a matter of basic electrical engineering principles. If in fact Harley disagrees with that he is wrong.

Most, and perhaps nearly all, tube amps will not do that, BECAUSE their output impedance is not negligibly small.

All of that is essentially a separate issue from the one I believe Emerson (Foster_9) was asking about, which I believe concerns whether or not the MAXIMUM power ratings of a solid state amp are twice as much for a 4 ohm load as compared to an 8 ohm load.

03-15-11: Tmsorosk
...there may be other reason's it doesn't sound bright other than just the double down aspect.

I suspect this is correct.

Best regards,
-- Al

03-16-11: Unsound
Tvad, I for one would hate to lose you, and your valued balanced contributions to this forum. This particular thread doesn't seem that contentious to me. I do hope you'll reconsider.

I strongly second these thoughts. Grant, as I indicated earlier I have nothing but the highest respect for your innumerable contributions to this forum, from which I and countless others have benefited greatly. I too very much hope that you will reconsider.

Best regards,
-- Al

Irv, thank you for offering the words of reconciliation to Grant.

03-16-11: Irvrobinson
For a good voltage-source amp with 100w into 8ohms, if the speaker has a peak impedance of 16 ohms into 4KHz the amp will clip at 50w, and if the lowest impedance occurs at 40Hz with 4ohms the amp will clip at 200w, but the frequency response at 50W will still be flat (within the amp's spec) across the entire spectrum up to 50w.

Trick question - what happens if the speaker is reproducing 4KHz and 40Hz *at the same time*?

Well, since one frequency is far higher than the other, there will be instants of time at which their peak amplitudes will simply sum together. If both frequency components have the same amplitude (which is highly unlikely with music), the amp could provide half of its maximum output voltage at each frequency, without clipping. Since for a given impedance power is proportional to volts squared, power delivery at each frequency at the clipping point would be 1/4 of the numbers you cited above: 12.5W at 4kHz, and 50W at 40Hz.

At least, I think so :-)

Regards,
-- Al

Thanks Kirk. But note that Irv specified a 40Hz impedance of 4 ohms, so I believe that my indication of 50W (rms of course) at 40Hz was correct.

Also, I think that when you referred to 40V and 20V "peak-to-peak," you meant to say "peak." The 100W figure, presumably rms, corresponds to 28.28Vrms into 8 ohms, which would be 40V peak, or 80V peak-to-peak.

Dividing by two, to reflect each of the two frequency components of equal amplitude, whose peaks will add in phase at some instants of time, we have 14.14Vrms (equivalent to 20Vpeak or 40Vpeak-to-peak), which equates to the 12.5Wrms into 16 ohms and 50W into 4 ohms that I stated.

Best regards, and thanks for spotting the "summons." :-)

-- Al