Amplifiers: High Current? High Voltage?

Gs5556- Nice to see your post. The seemingly 'simple' fact that you outlined seems to be missed by many in the audio community- the current in a speaker is the same for a given amount of power regardless of the technology that created the power- Ohm's Law cannot be denied.

In reality all power amps are in fact that: *power* amplifiers, and are incapable of producing current without voltage, or voltage without current. I wish the industry would get this fact straight (and get right with the Law :)

Peter_s, Additional filter caps with help smooth out a power supply of noise created by the operation of the amp. The less noise, to a certain extent, the less distortion. The result is smoother sound with greater authority.

Peter, you are correct. Most amps are designed to act as voltage sources. An amp designed to be a current source is called a transconductance amp and their use is limited because they don't work well with most conventional 2 and 3 way speaker designs due to the design of most crossover networks. Nelson Pass does make one that is intended for single speaker systems such as Lowther based systems.

First Watt article

Gs5556, I don't follow your logic in explaining output power in terms of transfromer ratings. Yes, there is some relationship there, but not as you described. The VA rating on a transformer tells you how much power it can consistently deliver without overheating. The transformer does not choke off the current as you described in your second example (only 8 watts because only one amp can flow to the speaker). It is true that the amp has a maximum voltage that it can produce that is limited by the secondary voltage of the power transformer, but there is no "current resevoir" determined by the transformer.

The current resevoir consists of capacitors in the power supply. A power amp with a large capacitor bank can deliver huge amounts of current for brief periods of time that far exceed the current rating of the transformer secondary. The amp will try to maintain the requested voltage and only starts to dip when it can't deliver the current demanded by the load at that voltage, and even though the dcr of the transformer secondary does play into the complete analysis, the limiting factor is not the VA rating of the transformer.

That is a bit simplified but the basics of the situation.

Thanks Herman. That's what I was getting at with my question about capacitors. I assume all prior discussion about transformers has been input transformers.

the law is current times voltage equals power. in the case of speakers, all a voice coil is, is an inductor used as a motor. for inductors, the larger the current, the stronger the magnectic field. voltage isn't really that important when it comes to pushing a speakers. the higher the current, the more powerfull the electromagnetic field is. high voltage has its advantage, it saves a lot of power, but for subwoofers, high current wins hands down. when looking at amplifier specs, people don't know what to look for, power equals watts, but peak doesn't equal rms, the difference between regular amplifiers and high current amplifiers, is that, regular amplifiers us more voltage in the equation then current (which is like 50volts times 2amps= 100watts when you could use 10volts times 10amps to get the same power but create a stronger magnetic feild), when it is current that is pushing the relitive motion of the induction (voice coil). but another thing is, voltage is what pushes your current through, and with out that voltage, no current would flow, voltage in equals voltage out, and all voltage is, is electronic pressure.

the difference between regular amplifiers and high current amplifiers, is that, regular amplifiers us more voltage in the equation then current (which is like 50volts times 2amps= 100watts when you could use 10volts times 10amps to get the same power

"Regular" amplifiers don't use more voltage in the equation. All voltage amplifiers, which is what almost all amps are, whether or not they are capable of producing high currents , try to maintain a constant voltage out for a given voltage in. The amount of current that flows will be the voltage divided by the impedance, and the impedance is whatever it is. So called "high current" amps are the ones that have the ability to deliver more current if the impedance dips real low, but don't somehow magically push more current through the speaker than one with less reserves.