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Old 25th June 2012, 07:12 PM   #6421
DF96 is offline DF96  England
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Quote:
Originally Posted by a.wayne
Best Way to test, is play at listening level and then unplug , it should go for at least 3 seconds before noticeable distortion , if not the power supply caps are too small .
OK, back of envelope calculation (including wild guesses marked by []):
Noticeable distortion means 50% drop [1], so 3 secs means a time constant of 4.3 s.
Assume normal listening level means 10% of full output current draw [2] so at full output would be 0.43 s.
In 10 ms this would give a droop of 2.3%.
So 'play unplugged for 3 secs' is just another way of requiring no more than 2.3% droop between charging pulses. You can adjust this figure up or down a bit but we seem to be talking about a few percent ripple at full output.
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Old 25th June 2012, 07:20 PM   #6422
wahab is offline wahab  Algeria
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According to the "metric" above a power amp with poor caps number
but with low quiescent current could appear as better than an amp
with two fold the capacitance but triple fold the quiecent current....
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Old 25th June 2012, 07:28 PM   #6423
DF96 is offline DF96  England
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Yes, so "x% PSU droop in 10 ms at full output" is a more precise measure than "works unplugged for y secs at normal listening level". I was trying to show that all these rules of thumb end up as rough ripple measures, so it may just be that ripple is what matters.
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Old 25th June 2012, 07:45 PM   #6424
bcarso is offline bcarso  United States
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Quote:
Originally Posted by nigel pearson View Post
I think I am right in saying Hypex is not an H bridge . It almost looks class B in layout .
The basic UcD invention of Bruno's has a half-bridge output. However it's fairly straightforward to connect two of them as a full bridge and synchronize the outputs.

As it is intrinsically a variable-frequency design, the issue of heterodyning and audible artifacts of same in multiple amp systems comes up as a potential problem, although any such behavior using Hypex modules is hotly denied by the company. Philips (the patent owner) will let you use the topology as long as you use NXP semiconductors by the way. I think it is an excellent approach if class D is dictated by considerations of efficiency.

Brad
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Old 25th June 2012, 07:48 PM   #6425
wahab is offline wahab  Algeria
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Quote:
Originally Posted by DF96 View Post
Yes, so "x% PSU droop in 10 ms at full output" is a more precise measure than "works unplugged for y secs at normal listening level". I was trying to show that all these rules of thumb end up as rough ripple measures, so it may just be that ripple is what matters.

Undoubtly.
They estimated the max ripple amplitude at wich the amps s NFB
would be efficient enough to bring it down to the amps s intrinsical output noise.

At 5% ripple , about 2.5V Pk generaly , an amp need 100dB PSRR
to bring it below its own output noise.

At the time this could be easily accomplshed with an RC filter for the
front end and get the remaining rejection with 60 to 80dB NFB , easily
available at 100hz or so...
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Old 25th June 2012, 07:59 PM   #6426
Pano is offline Pano  United States
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Quote:
Originally Posted by jacco vermeulen View Post
What would you have favored/listened to, if they hadn't fckd up your mind in France ?
All that Audio Research junk. And Ampzilla, maybe a Dynaco if i was slumming. Yep, they screwed me up bad, those damn French.
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Old 25th June 2012, 08:18 PM   #6427
Pano is offline Pano  United States
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Quote:
Originally Posted by a.wayne View Post
Using my volt meter (pano test) avg was approx 6 volt -8 volt ..
Cool! Was that 6-8 volts on the -12dBFS signal after you had set your levels?
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Old 25th June 2012, 08:27 PM   #6428
dvv is offline dvv  Serbia
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Quote:
Originally Posted by Pano View Post
All that Audio Research junk. And Ampzilla, maybe a Dynaco if i was slumming. Yep, they screwed me up bad, those damn French.
Actually, I know from experience that Audio Research's killer markets in Europe were France and Italy.

But Ampzilla ... hmmm ... yummy! James's baby which, just like a real baby, seems to grow over time. It matures.

And James is a member of my small Trio Amp Club, with John here and Matti Otala in Finland.
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Old 25th June 2012, 09:31 PM   #6429
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by dvv View Post
No way, Jose, I've seen too many "purist" amps with no protection circuits which were literally fried, and their "protection" fuses were still intact.

It can kill dynamics only if it has been poorly designed, or when the amp is adverstised to do more than it actually can in real life, necessitating aggressive protection.

Mine sleeps and is 100% inactive to 2 Ohms, it triggers at 1.8 Ohms, by when I feel it damn well should trigger.

Wayne, I will guarantee this in writing - you can use or remove the entire protection ciruit and the amp will sound the same. I've been developing it for well over 20 years now, and it has never let me down, but has saved both the amp and very possibly the speakers twice (inadvertent short circuits).

I'll let you take all the risks, thank you. And if your speakers are really 1 Ohm loads, let me tell you, you ARE taking risks.

Have blown fuses , haven't hurt any amplfiers yet , the weak ones had their arms raised before the first note, anyway No protection necessary , just make sure output stage bigger than PSU ..

Quote:
Originally Posted by DF96 View Post
Yes, so "x% PSU droop in 10 ms at full output" is a more precise measure than "works unplugged for y secs at normal listening level". I was trying to show that all these rules of thumb end up as rough ripple measures, so it may just be that ripple is what matters.
Sounds good to me ...

Quote:
Originally Posted by wahab View Post
Undoubtly.
They estimated the max ripple amplitude at wich the amps s NFB
would be efficient enough to bring it down to the amps s intrinsical output noise.

At 5% ripple , about 2.5V Pk generaly , an amp need 100dB PSRR
to bring it below its own output noise.

At the time this could be easily accomplshed with an RC filter for the
front end and get the remaining rejection with 60 to 80dB NFB , easily
available at 100hz or so...
Damn .. you love NFB, use it like Geritol ..

Quote:
Originally Posted by Pano View Post
Cool! Was that 6-8 volts on the -12dBFS signal after you had set your levels?
Nah , RMS meter direct voltage from amplifier ...
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Old 25th June 2012, 09:36 PM   #6430
Pano is offline Pano  United States
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Oh, OK. Hard to know what you had. Might be close if your program material was average -12dB.
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