current versus watts

Dangelod:
with the best amps doubling output as impedance is is halved.

you're talking audio, man! what's 'best' for you could be 'trash' for another listener! There's no objective definition of 'best amp' in this hobby - it's all VERY subjective.
So, I'd say that many of the large chassis (think Rowland Model 8, 9, the MBL 1200W/ch used to drive their radial speaker, Gryphon & others in that chassis size) & expensive amps (think top-of-the-line Krells from the late 1980s, present MBLs, Boulder, Rowland Model 8, 9, Gryphon) show this tendency. Most amps in the market do not have this proprty - it's very expensive to make them have this property!!

Dangelod
Seems like all high quality amps clearly describe output in watts........
But, I do not see(often) specs on current ?

That's because Power = Volts * Current = Current squared * Impedance (or Resistance). So, if you know Watts & Resistance you can calcuate the output current. Herman has already done those calculations for you in an earlier post. Those calculations pertain to maximum output DC current of your hypothetical 300W/ch into 8 Ohms i.e. output current when the amp is outputting 300W. You should realize that such an event is unlikely to occur frequently unless you are listening to music at paint peeling high levels (& ruining your ears!).

Dangelod:
Is high current as important to quality dynamic sound as high watts.....
If so, what are the general ranges of current output that would be acceptable for a high quality amp.

yes & no - depends on the speaker you are using. Some speakers are notorious for needing a large reserve of current to drive them to their best performance & other speakers are an easier load on the amp. Hence, there is no clear definition on what is considered a general range of output current. As another member pointed out - depends on the speaker impedance-phase curve.
But, as Atmasphere wrote before, whether you output small amounts of current or large, you need to do so with minimal distortion otherwise the sonics are strident. At high distortion levels it won't matter whether you have the "best" amp or not, the music experience will come up way short.

The conclusion is that the amplifier-speaker interface is a complex one because the speaker load affects the amplifier output impedance & vice-versa. Plus, the speaker impedance & phase varies over frequency. So, as you run up/down the audio spectrum, nothing remains constant! So, you will not be able to take a fixed number (amplifier output current as you are asking) & apply it to an interface that has variable performance....
IMHO. FWIW.

When we are talking 'best', IMO power doubling has nothing to do with it; none of the 'best' amps I have heard have that capability.

I feel that the specs have no meaning if the resulting amp is unlistenable. IOW our ears are more important than the amp is- our ears are the most important aspect of audio. Its important to drop all the preconceived notions about specs, including the ability to double power, if you your goal is for the system to sound like real music. see

http://www.atma-sphere.com/papers/paradigm_paper2.html

for more information

".... output current when the amp is outputting 300W. You should realize that such an event is unlikely to occur frequently..."

Well, measured (MEASURED!!!!) peak power needed to drive B&W 805 bookshelf speakers at musical peaks waw 3500 watts i.e. not three hundred but more then three thousand watts and for 87.5 dB sensitivity bookshelf speakers.

Only Simon Thacher from Spectron (to the best of my knowledge) is trying to "connect" specs of their amp with its musicality and many, me including, compare their amps to the best tube amplifiers.

The problem is not in specs. The problem to read them and understand them. The problem that many of not most amp producers show misleading specs like we discussed above peak current for 20 msec or displaying distrotions at low (typical number is 10 watts) output and not full output and at 1kHz only etc etc.

So, yes - you are better off listening to the component but it does not hurt to understand too...

John and Simon's philosophy is iltra low distortions and then you hear real (well recorded...) music without ear piercing or euphinic colorations.

Rafael

Hi Dob, I agree keeping distortion down is important. Distortion can hide detail. A lot of designers use global negative feedback to reduce distortion though, and this technique often results in subtle enhancement of odd ordered harmonics, specifically the 5th, 7th and 9th, that are used by the human ear to perceive the volume of a sound.

So the resultant sound will sound louder than it really is, in addition it will have brightness. Our ears are so attuned to these harmonics that even 100ths of a percent of distortion of them is audible: harsh, hard, brittle, clinical, bright, chalky, etc are all terms audiophiles use to describe this enhancement.

Thus it is often the case that the use of negative feedback is violating one of the fundamental rules of human hearing perception. So generally an ultra-low distortion figure is often a sign that global negative feedback is being used, and also that the amp may sound like a nice hifi, but will never sound like real music. IOW I am always suspicious when I see super low distortion figures.

"use of negative feedback is violating one of the fundamental rules of human hearing perception. "

Hello Ralph,

I spoke with Simon Thacher from Spectron and he is in full agreement with you as it relates to negative feedback in conventional amplifier.

He said that you are absolutely right and poor neagtive feedback, ripples from the power supplies and few other sources of odd harmonic distortions are "music soul killers" i.e. its not so much obsuring detail by even order harmonics as ear-piercing odd order harmonics.

Yet, Spectron rely heavily on global feedback. He explaiend that the crucial factor in negative feedback is transit time, the amount of time it takes from when an error is detected at the input until it is corrected at the output.

Thacher claims that Spectron use much faster digital logic circuits then anybody in the world. Their amp's transit time is less then 200 nanoseconds. Such an ultra-short transit time allows the amplifier to correct for many small errors; and the control loop can follow the input much more accurately WITHOUT generation of many odd (and even) order harmonic distortions and this is the main reason for positive "musical" reviews their amp receive.

All The Best
Rafael