AMPS: High Power Vs High Current?

[Hetfield]

I haven't been following this thread that closely but Audioholics tested a Yamaha Aventage receiver w few months and it was only putting out 35 watts per channel. That is pretty pathetic.

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[speakerman39]

The impedance overall means nothing. It is the impedance in the power range that matters especially below BSC.

It really is not difficult. Lets take a 20 volt rail voltage. If the impedance is 10 ohms then the maximum current that could be delivered is 2 amps. In practice it would be a little less, but lets ignore that. So the power delivered would be 40 watts. Now lets assume we have a good linear SS amp. Now lets make the speaker impedance 5 ohms. So the current will up to 4 amps and the power to 80 watts. If it is a really linear amp dropping the impedance to 2.5 ohms will be 8 amps, and the power 160 watts. If it can't deliver the current for the power required by the input then there will be clipping. In practice an real world amps are not that linear, and the power into 2.5 ohms will probably be closer to 120 watts.

Now lets make the impedance 20 ohms. In an SS amp it can't deliver a higher voltage than the rail. So voltage clipping will occur at above 20 watts.

Now lets take a tube amp. We can get any voltage we want, by selecting an appropriate secondary tap on the output transformer. So we can match power to any impedance and have the power constant through any range of impedance as long as it is constant with frequency

However here is the rub. Few loudspeakers have constant impedance. So if we match a tube amp to the mean impedance of say 8 ohms, and say it delivers 20 watts max into the load. Lets see what happens in a real world load. If the impedance is 4 ohms at 200 Hz it will deliver 10 watts at that frequency. Now say the impedance is 6 ohms at 900 Hz, it will deliver 15 watts at that frequency. So this is how at max power at the clipping point a tube amps response starts to follow the impedance curve. So if you have a tube amp speaker selection has a huge impact on the sound you get. The reason being is that tubes can not increase current as load impedance is reduced, like SS amps can.

Now you can see why highly sensitive speakers with very simple, and especially no crossovers, are so popular in the tube community. Back in the tube days I used pretty much exclusively full range drivers with no crossover.

Lastly your quest to look at high current versus high power is just nonsensical. The two are the same side of the coin. A high powered amp is high current. A high current amp is high powered.

A low current amp that was high powered would need a high output voltage and a very high impedance load. That situation is not encountered in real world loudspeakers.

You see power is Voltage X Current, always, no exceptions. So at a given voltage then you can only increase power by dropping load impedance so current can rise.

This is really simple very basic stuff about which there can be no argument. Don't get confused by the ignorant pig dribblers wasting ink in the Audiophool press. These people are unfortunately too numerous to count, and make the Internet full of error, which is inexcusable since this matter is so simple.

Thanks once again TLS for this very informative post. I will come back to this again and again b/c it is very well written. Both of your post will serve me well as an outline of what to read up on more. From the way you describe amps here it sounds like I would be better off with a SS amp of some sorts. That is, tubes can NOT increase current as impedance drops whereas a SS amp can. That is rather significant inmho. Thanks!


Cheers,

Phil

 

[speakerman39]

Yes, that is what it was, an example. You need to see what is the power rating of the amp in question, how it was rated, and into what load.


If you have speakers that dip to 2.5 Ohms, you will need more power capability. And, of course, speaker sensitivity matters as well. Also, rated power is continuous power, hardly what music or movie is about.

With your example above your amp needs to deliver 17.9 Watts. So, if that is the case, speakers 90dB sensitive in room should drive it to 100 dB for sure.

I thought the 10v was just a random example. Just checking to make sure. Have not done this kind of math in a very long time.....LOL!!! None of it is really that hard, but I know it can easily get that way fast and in a hurry. I got an A in college Calculus I, but Calculus II was an entirely different story..........LOL!!!! Thanks!


Cheers,

Phil

 

[speakerman39]

I agree with TLSGuy and others, 95% anyway that it's practically a moot point at best.

As mtry mentioned, ohm's law (okay let's include the power formula too) governs. If you buy an amp that can do 100W into 8 ohms, then as long as it is a well designed class AB amp, it will do around 125 to 150W into 4 ohms, obviously not continuously but for long enough to suit most music listening applications and a lot of speakers with dips to the 3 or 4 ohm range. Even my old Denon AVR-3805 that weighs 37 lbs 10 oz soak and wet had been tested to 2 ohms (even 1 ohm iirc) without going up in smoke and still able to put out close to 100W (again iirc).

So Phil, just re-read some of the S&V reviews on the AVR brands of the one you currently own and sleep well. Or be prepared to restrict your choices to the truly and literally "high current" amps that just keep doubling down (approximately) by Krell, Boulders etc.

Alternatively, you can also consider (or pretend) any mid range to flagship AVR as truly high current design if you de-rate them by a factor of 2 to 4. Example: A 140WPC Denon, de-rated (by you) to 50WPC will qualify as a truly high current amp, much truer than any HK AVR of the old days that were considered by many as high current amps, yet almost always get beaten by Denon's in S&V (HTM back then) by a good margin.

Yeah, I have read many times how well the Denon/Marantz stack up to their advertised power specs. HK was always a different animal from what I garner. My former Pioneer 1015 had plenty of power and sounded terrific back in the day. Owned a few Yammies down the line that always sounded pretty good. However, Audyssey has won me over. Thanks for the info!


Cheers,

Phil

 

[speakerman39]

I haven't been following this thread that closely but Audioholics tested a Yamaha Aventage receiver w few months and it was only putting out 35 watts per channel. That is pretty pathetic.

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I have seen that as well. However, that was with all channels driven too. But, it is hard to deny Yamaha's reliability.


Cheers,

Phil

 

[Hetfield]

I have seen that as well. However, that was with all channels driven too. But, it is hard to me Yamaha's reliability.


Cheers,

Phil

Yahama rocks, have had several receivers from them but will no longer be using receivers. I'm going back to separate. Parasound amp 140 watts per channel, conservative rating by the way, all channels driven. It's clean, pure, dynamic power. My old Yamaha RX-V663 is controlling the system though, for the time being. Sounds absolutely fantastic.

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[speakerman39]

Yahama rocks, have had several receivers from them but will no longer be using receivers. I'm going back to separate. Parasound amp 140 watts per channel, conservative rating by the way, all channels driven. It's clean, pure, dynamic power. My old Yamaha RX-V663 is controlling the system though, for the time being. Sounds absolutely fantastic.

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Yes, the Yammies do sound great. I used to own the 663....LOL!!!! Parasound is very well regarded. But, also very expensive. But, it never hurts for me to dream....LOL!!!!


Cheers,

Phil

 

[highfigh]

I thought the 10v was just a random example. Just checking to make sure. Have not done this kind of math in a very long time.....LOL!!! None of it is really that hard, but I know it can easily get that way fast and in a hurry. I got an A in college Calculus I, but Calculus II was an entirely different story..........LOL!!!! Thanks!


Cheers,

Phil

That's OK, this is Algebra.

 

[Hetfield]

Yes, the Yammies do sound great. I used to own the 663....LOL!!!! Parasound is very well regarded. But, also very expensive. But, it never hurts for me to dream....LOL!!!!


Cheers,

Phil

Parasound is incredible. I bought this beast of an amp back when I was single, no mortgage or kids so I couldn't do it again. I'd go with something from Emotiva or Outlaw audio and they are be slouch themselves. The Parasound amp sounds incredible!

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[Pogre]

I'm really liking my Monoloith. It's legit.

 

[M Code]

I would caution trying to calculate output power into a loudspeaker using Ohms law. Most loudspeakers are not resistors they are reactive and can load an amplifier with a unique, inductive output. Some loudspeakers like the MagnaPlanars are mostly resistive, but we have measured component amplifiers that can output 125 watts into a Dale resistor load (8 ohms) but into a certain loudspeaker the power output drops to 22 watts...

A far more accurate method is to use the PowerCube, unfortunately few testing labs take the time to do this.

Just my $0.02...

 

[Pogre]

Just my $0.02...

You're gonna go broke posting on the forums!

 

[speakerman39]

That's OK, this is Algebra.

Yes, so very true. But, sometimes we also used some simplified calculus as well. But, once I got into Calculus II, things became much more difficult for me. It was a nightmare to say the least......LOL!!!! Glad that is over with and done!

Cheers,

Phil

 

[speakerman39]

I would caution trying to calculate output power into a loudspeaker using Ohms law. Most loudspeakers are not resistors they are reactive and can load an amplifier with a unique, inductive output. Some loudspeakers like the MagnaPlanars are mostly resistive, but we have measured component amplifiers that can output 125 watts into a Dale resistor load (8 ohms) but into a certain loudspeaker the power output drops to 22 watts...

A far more accurate method is to use the PowerCube, unfortunately few testing labs take the time to do this.

Just my $0.02...

Interesting......but what is PowerCube? I am almost afraid to ask......LOL!!!! Thanks!


Cheers,

Phil

 

[speakerman39]

I'm really liking my Monoloith. It's legit.

Yes, I am sure it is being from ATI. Glad that you are liking the Monolith and your new Ultras! Keep up the good work.


Cheers,

Phil

 

[lovinthehd]

https://www.ap.com/technical-library/measuring-power-amplifiers-with-reactive-loads/

 

[Hetfield]

I'm just a fan of separates myself. I understand perfectly well why most people go with a receiver but just me, I like separates. Did it for years and then went back to receivers for 10 years but back up separates and love it.

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[Pogre]

I'm just a fan of separates myself. I understand perfectly well why most people go with a receiver but just me, I like separates. Did it for years and then went back to receivers for 10 years but back up separates and love it.

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I do have separates. My SR6011 is the pre.

 

[Hetfield]

I do have separates. My SR6011 is the pre.

Yeah man, you got a nice system. I bet it sounds incredible. I have a receiver as any processor too. Working out nicely right now. I always loved Marantz. I had a Marantz processor years ago, forget the model number but it sounded incredible.
I'd love to hear the ultra bookshelfs but I can't right now and I'm not the kinda a person just to order them knowing I can turn them with free shipping. I just can't do that, it's not my personality. They look beautiful though. If I didn't have my Def Techs, I'd like to try SVS Ultra and PSA speakers also a listen. I do love the Def Techs though so it's a moot point.

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[Pogre]

Yeah man, you got a nice system. I bet it sounds incredible. I have a receiver as any processor too. Working out nicely right now. I always loved Marantz. I had a Marantz processor years ago, forget the model number but it sounded incredible.
I'd love to hear the ultra bookshelfs but I can't right now and I'm not the kinda a person just to order them knowing I can turn them with free shipping. I just can't do that, it's not my personality. They look beautiful though. If I didn't have my Def Techs, I'd like to try SVS Ultra and PSA speakers also a listen. I do love the Def Techs though so it's a moot point.

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Wish you lived closer. I'd have you over for a listen. Wouldn't mind hearing yours either.