How much truth is there to the so called "high" current designs

[MichaelJHuman]

Some receivers like Onkyo and HK are lowered powered at a given price point than their quality competitors (or used to.)

The salespeople will then tell you that they use a high current design, and that make a huge difference.

I believe high current is useful for load under 8ohms. An amp that can drive down to 1ohm loads needs to be able to provide more current as I understand it.

But let's say you are using nominally rated 8ohm speakers which are pretty easy to drive.

Are the so called high current amps going to help you?

What about dynamic power? To what extent does the power supply factor into ability for a receiver to handle sudden demands? And how important IS that ability? If your amp is rated at 100 watts/channel and it has a dynamic rating of 130 how much louder does that allow you to play your system?

 

[Seth=L]

Simply, high current power means very little.

Dynamic power is short term power, few manufacturers specify how long it can produce it's dynamic power. And what difference there is between 100 watts and 130 watts is very little, only just short of 1 decibel difference.

Say you are watching a movie, and in most scenes and sequences your receiver will likely use as little as 20 watts even with the volume up. Explosions demand more power, but only momentarily. If there is a scene with lots of explosion or music with constant bass then a that could cause normal receivers to compress the sound. It may be loud, but lack dynamics especially in the bass department. If you have a powerfull sub and a mediocre receiver then all should be fine if your speakers are set to small.

I will now direct you to the all channels driven fallacy, which can tell you a lot more than I can.

Here is the article by Gene- http://www.audioholics.com/techtips/audioprinciples/amplifiers/allchannelsdriven.php

Here is the thread that sparked the controversy- http://forums.audioholics.com/forums/showthread.php?t=14222&highlight=channels+driven

 

[mtrycrafts]

Dynamic power is short term power, few manufacturers specify how long it can produce it's dynamic power.

This is specified or used to be, under the FTC amp testing protocol, 20ms signal twice in a second.

 

[Seth=L]

Thanks, I am no good when it comes to numbers, unless I am counting money, but I don't have any.

 

[PENG]

Here is the thread that sparked the controversy- http://forums.audioholics.com/forums/showthread.php?t=14222&highlight=channels+driven

If you look at the numbers I quoted in post#17, at roughly the same price point, HK came in last, behind Denon, Pioneer and Yamaha in both 8 and 4 ohm power ratings. HK came in first however, in being closest to "doubling down" as Buckeyefan1 pointed out. That's doesn't mean much though as they can achieve the higher 4ohm to 8 ohm power rating ratio by simply specifying a lower 8 ohm power output rating. The fact remains HK gets you less power and/or current for the dollar. You get more weight, Buckeyefan1 thought the weight may be due to more robust power supply and heat sinks/amp sections. My problem is, if that's the case why are the robust P/S & Amps not producing results comparable to the competiting Denon/Yamaha/Pioneer. Perhaps the others use more Aluminum in the chassis, and more advanced alloy in the P/S.

As I mentioned before, to get the really powerful high current capable HK you have to go all the way up to the 7XXX/8XXX series. They are not just heavy, they are powerful......

 

[warnerwh]

One thing to always look for however is that the amplifier is capable of putting out more power into four ohms than 8 ohms. If it is at least 25% more power into the lower impedance that's much better.

It can be important with many speakers to have good current capability. Speakers like Electrostatics can dip very low and I suspect most all receivers would shut down trying to drive most of them. Even many high end amps don't like it. In other words a truly high current amp which puts out much more power into 4 ohms than 8 will be much more stable all else being equal.

With speakers like Vandersteens it's pretty much a non issue. Many speakers like Thiels will however sound better with a quality amp if you listen to loud levels at all. An amp that doubles or close to it as the impedance is halved will prove stable with all kinds of speakers where less expensive amps in receivers will not.

That may or may not matter. See what speakers and volumes you need before deciding on amplifiers is the best route.

The best advice I have is to get more power than you think you'll need so the amp will never clip. And remember to only gain 3db in loudness it takes double the power.

 

[PENG]

One thing to always look for however is that the amplifier is capable of putting out more power into four ohms than 8 ohms. If it is at least 25% more power into the lower impedance that's much better.

It can be important with many speakers to have good current capability. Speakers like Electrostatics can dip very low and I suspect most all receivers would shut down trying to drive most of them. Even many high end amps don't like it. In other words a truly high current amp which puts out much more power into 4 ohms than 8 will be much more stable all else being equal.

I agree in principle but a 55W into 8 ohm and 110W into 4 ohm at the same power factor (say both inductive) amp is hardly high current when compared to a 100W into 8 ohms and 140W into 4 ohms at the same price point. The latter will still put out more current into a 4 ohm load. One can even (not saying it happens but just for argument sake) specify a lower 8 ohm power rating in order to give the impression that it doubles down to 4 ohms.

 

[Ampdog]

Or you turn your amp down until it just does not clip. As Seth=L said, the difference between 100W/140W is negligible. Does one want to pay for that? There is also the old addage (probably well-known on this forum) that when choosing an amplifier, one does not consider between outputs less than X2 (3 dB). Just not audible enough.

In a slightly different vein, I frown on so-called superior loudspeakers with the impedance all over the place, especially on the low side. In this year of computer programs, I have great difficulty believing that reactive networks that smooth the loudspeaker impedance still seem "inaccessable". Must the amplifier designers always stand in for such products?