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Old 24th June 2012, 03:40 PM   #6341
dvv is offline dvv  Serbia
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Quote:
Originally Posted by Pano View Post
And that's basically what I was looking for.

For some reason when you ask for a rule of thumb or general practice, people fly into a fit and want to hit you over the head about "no Magic Answers" or "You can't generalize" or some such. Sheesh..... All I wanted to know is if anyone had noticed a relation between energy stored/output power and sound quality. (Sound Quality vs Measurements). It appears that no one posting here thinks in those terms, fair enough. Tho we can see that someone at Motorola did.

FWIW, many deluxe amps have much more than 1.5 joules per 10W. Is it just overkill?
Indeed? Please give one or two examples of having more than 1.5 Joules/10W and we can try to find out if that's an overkill.

Theoretically, as you add more and more capacitance, at some point you will reach a state which would equal full electonic voltage regulation, even if that point would, pricewise, be higher than with electonics. I mean in terms of effects - quite simply, your nominal power output into say 8 and 4 Ohms would not cause any appreciable voltage drop (sag) of the powers supply lines. I fear that would cost you a pretty penny indeed, but it is possible.
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Old 24th June 2012, 03:42 PM   #6342
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Originally Posted by nigel pearson View Post
I beg to differ a little . Say whatever maximum current will be . Times it by 1.5 for safety . Job done . The manufacturer will give the ripple ratings . Then add caps as your ears require . I would admit that the currents that might be required baffle most of us . Would anyone like to say ? Lets talk daft speakers and stupidly high wattage's ( 1 ohms 600 W ) . One problem is that the big amps draw current at the crest of the sine wave . Sometimes the caps hardly get a look in . My friends in the PA world use 3 phase power as it helps replenish the caps more often . They find there comes a time when no matter how big the caps are 3 phase does it better .
A quick, sure fire way to bankruptcy, Nigel.

On a per item basis, NOTHING in an amp is as expensive as capacitors.
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Old 24th June 2012, 03:47 PM   #6343
dvv is offline dvv  Serbia
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Originally Posted by DF96 View Post
Not necessarily. Motorola were mainly hard-headed engineers, so it is very likely that their rule of thumb was derived in the way I explained i.e. the criterion was not 'sound quality' but x% droop in 10 ms (or 8.33 ms in US). This could be regarded as a ripple calculation, but ripple calcs usually assume full power sine-wave; I assumed full power square wave.

If your amp has good PSRR (including low power supply IM) then it may be the case that there is nothing more to be said: low enough ripple guarantees good enough sound. When people try to explain anything further they usually quickly fall back on myths and legends rather than genuine explanations. Now it may be that we don't know how much hum is low enough, or how much ripple IM is low enough, given that we can't have zero of either unless we use battery power. 'Too low to measure' is meaningless, as you can always measure lower if you try a bit harder.
I beg to differ.

Measuring say THD and/or IM at say 0.001% under worst case conditions is going down to academic values. I honestly see no point fighting now to make that 0.000,9%. That's just making the inaudible even more inaudible.

In my book, that is simply brainless. I prefer to stay on this side of sanity.
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Old 24th June 2012, 03:55 PM   #6344
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by nigel pearson View Post
I beg to differ a little . Say whatever maximum current will be . Times it by 1.5 for safety . Job done . The manufacturer will give the ripple ratings . Then add caps as your ears require . I would admit that the currents that might be required baffle most of us . Would anyone like to say ? Lets talk daft speakers and stupidly high wattage's ( 1 ohms 600 W ) . One problem is that the big amps draw current at the crest of the sine wave . Sometimes the caps hardly get a look in . My friends in the PA world use 3 phase power as it helps replenish the caps more often . They find there comes a time when no matter how big the caps are 3 phase does it better .
Are you calling my speakers daft ..

Ok , they are , but the sound isn't , my findings , too much hurt the top end , too little muddies the sound , so I agree with John , there's no set formula, now how do we combine the two ..?

Ohh.....

Battery power kills dynamics , been there done that .....!
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Old 24th June 2012, 03:58 PM   #6345
a.wayne is offline a.wayne  United States
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Originally Posted by dvv View Post
A quick, sure fire way to bankruptcy, Nigel.

On a per item basis, NOTHING in an amp is as expensive as capacitors.
And nothing in the amp hurt the sound more ....
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Old 24th June 2012, 04:06 PM   #6346
Pano is offline Pano  United States
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Originally Posted by dvv View Post
Indeed? Please give one or two examples of having more than 1.5 Joules/10W and we can try to find out if that's an overkill.
I thought I did yesterday. See this post:
http://www.diyaudio.com/forums/showthread.php?p=3070031

Or am I not understanding Motorola's 1.5 joules/10W? I see that as 0.15 joules per output watt.
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Old 24th June 2012, 04:07 PM   #6347
Pano is offline Pano  United States
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Originally Posted by a.wayne View Post
Battery power kills dynamics , been there done that .....!
I'm not a big fan, either, but what about batteries and caps?
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Old 24th June 2012, 04:25 PM   #6348
popilin is offline popilin  Argentina
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The old holy grail of science:

-The unified field theory.

The new holy grail of science:

-An equation for optimizing an analog power supply.

And do not speak of a rule of thumb, and even less of a rule of Dumb.
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Old 24th June 2012, 04:28 PM   #6349
SY is offline SY  United States
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Quote:
Originally Posted by Pano View Post
Bigger is better.
If you like higher ripple currents, sure. This is another audiophile legend, I'm afraid, one to which I succumbed for many years until I started looking more carefully at what was actually going on in the power supply. As well, adding capacitance until there's no more ripple (whatever "no more" means) is an invitation to make the overall system noise performance worse.

Maybe I'm just a nutcase, but the more sensible approach seems to be to specify the required noise level at the amp output, and knowing the power supply rejection of the signal circuit, work backward to see what acceptable ripple is. Then design the supply for something lower than the maximum acceptable ripple, but not too much lower in order to keep ripple current to a minimum.

Of course this is engineering, not "design."
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Old 24th June 2012, 04:39 PM   #6350
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Quote:
Originally Posted by dvv View Post
examples
Only two ?

Metaxas Soliloquy monaural, 1984.
About 1 J/W, +1600VA transformer for 100W/8.
See post 6159

2nd one, post 6241
1 J/W, +3000VA toroidal for 500W/8

(plenty more, up to some years ago i used to calculate every imaginable correlation factor/coefficient of commercial amps, professional disease)
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