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Old 24th June 2012, 06:11 PM   #6361
1audio is offline 1audio  United States
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Bigger caps mean smaller conduction angle and higher peak currents, which cause higher drops on the power source. Following it through leads to an impossible situation.

I suggest looking with both voltage a current probes to see what is actually happening. The peak currents for those big caps could radiate a long way from the cap diode transformer loop.

What good is low ripple voltage if the induced noise swamps it?
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Old 24th June 2012, 06:18 PM   #6362
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Studer/reVox's A740 power amp
Serial production Motorola TO3's (5631/6031 = 200W/140Vce)
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Old 24th June 2012, 06:18 PM   #6363
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Originally Posted by 1audio View Post
Bigger caps mean smaller conduction angle and higher peak currents, which cause higher drops on the power source. Following it through leads to an impossible situation.

I suggest looking with both voltage a current probes to see what is actually happening. The peak currents for those big caps could radiate a long way from the cap diode transformer loop.

What good is low ripple voltage if the induced noise swamps it?
Good point.

Which is why I advocate getting bigger capacities by using parallel "big" and "small" capacitor. Big = 22,000 uF, "small" = 10,000 uF. With good bypass and with bleeders.
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Old 24th June 2012, 06:20 PM   #6364
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I'm not a big fan, either, but what about batteries and caps?
Yes , better with caps , but we all felt at the time better with linear PSU ....
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Old 24th June 2012, 06:24 PM   #6365
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Quote:
Originally Posted by 1audio View Post
Bigger caps mean smaller conduction angle and higher peak currents, which cause higher drops on the power source. Following it through leads to an impossible situation.

I suggest looking with both voltage a current probes to see what is actually happening. The peak currents for those big caps could radiate a long way from the cap diode transformer loop.

What good is low ripple voltage if the induced noise swamps it?
Is this when the top end dies .... ?
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Old 24th June 2012, 06:31 PM   #6366
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Bigger caps mean smaller conduction angle and higher peak currents, which cause higher drops on the power source. Following it through leads to an impossible situation.
Many amps have either an L or an R element in series after the rectifier and 1st cap. That's gotta make a difference.
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Old 24th June 2012, 06:34 PM   #6367
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One could accuse engineering of finding the minimum that will possibly work - for a little while.
If that's the goal. Engineering is finding the right way to hit a target- deciding what that target is lies elsewhere. If the target is high performance and a set of goals are laid out, then engineering is a way of not doing silly things like using "rules of dumb" to accomplish religious goals while sacrificing real performance. The "bigger is better" is a perfect example- higher ripple currents have performance and reliability consequences, and a dumb rule like that ignores the realities of actual amplifiers.
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Old 24th June 2012, 06:53 PM   #6368
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If the target is high performance and a set of goals are laid out, then engineering is a way of not doing silly things like using "rules of dumb" to accomplish religious goals while sacrificing real performance.
How do we know what the rules are?

If we see that a large number of amps judged to have strong power supplies have 1 joule per watt (or whatever) might that tell us something? The goals are interesting, the results more so.

One might engineer an amp for a certain amount of ripple, then find that there sonic advantages to going further. That seems to be what amp builders have been finding, tho I'm sure a lot of it is conjecture. Is all of it just audio voodoo, or do increasingly bigger PSUs bring real, audible benefits? Of course that would not be too hard to test, but might be expensive and time consuming.

Looking at what has already been done and the reported results is another way of finding out if the idea has merit.
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Old 24th June 2012, 06:53 PM   #6369
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If that's the goal. Engineering is finding the right way to hit a target- deciding what that target is lies elsewhere. If the target is high performance and a set of goals are laid out, then engineering is a way of not doing silly things like using "rules of dumb" to accomplish religious goals while sacrificing real performance. The "bigger is better" is a perfect example- higher ripple currents have performance and reliability consequences, and a dumb rule like that ignores the realities of actual amplifiers.
That sounds awfully like the politicians - they are also in total denial of everything, especially their own culpability. Realities they have already discarded as useless baggage a long time ago.

Last edited by dvv; 24th June 2012 at 07:03 PM.
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Old 24th June 2012, 06:56 PM   #6370
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How do we know what the rules are?
That was my point- there are no rules, just a logical approach to getting the performance that you want. John gave a nice explanation, and when he and I are in agreement, you should treasure that moment.
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