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Old 17th January 2013, 04:45 PM   #8151
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by mr_push_pull View Post
dvv,

50W enough? pretty much in the ballpark. I'm a regular guy myself, but what's 6dB between friends?
a.wayne will love this discussion (if you haven't already gone through that, haven't read the last few pages)
I'm using 6volt rms when playing loud , ok its nominal 1ohm (300-22k) , only man amplifiers need apply ...
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Old 17th January 2013, 04:56 PM   #8152
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let's see, Apogee?
(look, it rhymes!)
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Old 17th January 2013, 05:21 PM   #8153
a.wayne is offline a.wayne  United States
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Close , but no apogee , This is what I'm currently using ...
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Old 17th January 2013, 05:22 PM   #8154
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DIY? really have no idea.
I'm considering the La Folia, just out of masochism.
obviously, my girly class-D amp won't do
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Old 17th January 2013, 05:29 PM   #8155
a.wayne is offline a.wayne  United States
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Yes DIY, 3way direct drive ribbon (no transformers) hybrid.

Bel Canto class-d mono's did not work , as well as others . Krell,Threshold ,PS audio, adcom(565/555) are the few that has worked , i did not like the sonics of the adcoms ..

The PS audio works amazingly well considering 3pr output ....
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Old 17th January 2013, 06:00 PM   #8156
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Ncore never got back with me on their NC400 , so i will pass ...
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Old 17th January 2013, 11:03 PM   #8157
fas42 is online now fas42  Australia
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Quote:
Originally Posted by dvv View Post
And it had what I love to hear most in any amp, it somehow suggested that it had infinite power, as if you simply couldn't overload it anyhow. An illusion, of course, but quite a number of American amps pull this off, and I daresay nobody pulls it off like the Yanks. Well, maybe Naim a little bit.
That's exactly what all systems should sound like: I found it amazing, 20 years ago, trying some monster amp that would crush my toes if it fell on them, start to collapse as you pushed the volume up. A "miserable", 20W, chip amp should give you that impression if it has a decent power supply; it's what's called "engineering" ...

Frank
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Old 18th January 2013, 02:21 AM   #8158
a.wayne is offline a.wayne  United States
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Then it was not a monster amp
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Old 18th January 2013, 03:53 AM   #8159
gootee is offline gootee  United States
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Originally Posted by dvv View Post
As I understood it from an admittedly brief lookover (no time now, will dive in later on), you got 53,050 uF per channel for a nominally 100W/8 Ohms amp?

Tom, as I see it, no amp ever made satisfied this criteria, or perhaps a few wildcard products did, but I never heard about them.

<snipped>
Hi dvv,

The calculation example that you quoted was not calculating the required reservoir capacitance for a power supply. It was merely to help illustrate what types of calculations could be performed, with an equation that had been derived.

In that particular example, the result meant that IF you needed a capacitance to supply all of the current for the first zero-to-peak rise of a 5-Amp-Peak 30 Hz sine wave, then if that capacitance was not at least 53050 uF, the voltage across the capacitance would drop by at least one volt.

The result was subsequently verified with an LT-Spice simulation.

That equation was actually just an approximate result; a sort of "worst-case estimation" equation:

(13b): C ≥ a / (πfΔv_MAX)

where a is the 0-to-peak amplitude of the capacitor's sinusoidal current waveform, f is frequency in Hertz, and C is capacitance in Farads.

The more-complete picture, for the scenario being considered in that derivation, is this one:

(17): C ≥ Δi / ( 2πf∙(Δv - (ESR∙Δi)))

Equation (17) gives the capacitance value, C, that would be required in order to supply the current for the first quarter-cycle of a sine signal of frequency f (in Hz), with 0-to-peak amplitude Δi Amperes, while causing the voltage across the capacitor to dip by no more than your choice of Δv Volts.

To use equation (17), it will be easier to first set ESR to zero, calculate a C value, find an estimate for ESR for that C value at the frequency being used, and then re-calculate the C value with the ESR value.

If we still want to just account for the whole sine wave, we should be able to simply double the C value given by equation (17), since we're considering only the positive or negative half-cycle, but not both, and the other half of the half-cycle of a sine wave is symmetrical and thus encloses the same area (its integral), i.e. the same amp-seconds value, as the first half.

[Edit: Note, too, that positive capacitor current was defined as current flowing into the positive-voltage-designated lead of the capacitor. So, typically, for this scenario, both Δi and Δv will be negative.]

For more of this exciting story, including some of the considerations involved when Δv - (ESR∙Δi) gets close to zero, go to

Power Supply Resevoir Size

Tom

Last edited by gootee; 18th January 2013 at 04:19 AM.
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Old 18th January 2013, 04:20 AM   #8160
fas42 is online now fas42  Australia
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Quote:
Originally Posted by a.wayne View Post
Then it was not a monster amp
What's in a name ...?

I remember a hulking GAS being quite a disappointment ...

Krell was OK, but tends to sound fairly rough. ME, an Australian brand with an intelligent power supply for its time, a vast array of paralleled small value smoothing caps, did pretty well ...

Frank
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