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Old 14th October 2012, 01:28 PM   #1441
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Thanks!
Quote:
Originally Posted by DF96 View Post
Yes, provided that the frequency, amplitude and phase of these sine waves are such that they add up to some approximation to a low frequency square wave. I thought we established much earlier in the thread that an LF square wave is the hardest thing for a PSU to cope with, in terms of current delivery and hence required reservoir capacitor value. Anything else is easier. There may be a separate issue with things like IM caused by capacitor nonlinearity, but that is for another thread.
Well, that was interesting. So, what do you think of this?:

Comparing the below amplifier examples (they're both single rail for simplicity). Text symbols of "<" and ">" indicate DC transient charge flow right after a powerful bass beat. Both examples have the power supply on the same board as the amp, but one of them isn't dull.

Example 1:
transformer > bridge rectifier > power supply reservoir < small 1cm trace < amp board caps
both the DC and noise returned while power supply reservoir awaits charge
amp board caps discharged/disturbed, an open door to noise

Example 2:
transformer > bridge rectifier > power supply reservoir > D//C series filter > amp board caps
only the noise returned while the power supply reservoir awaits charge
amp caps stay full, Shields UP!

Tomfoolery:
That was mild, but now I have plugged both examples into an old fashioned Christmas tree lights blinker!
Example1 plays dull and cuts out when connected to the blinker
Example2 didn't play dull and the blinker didn't make it cut out
(Both did work better without the blinker, so I've now removed it.)

Question:
On Example 2's D//C series filter, how big does the "C" (or an RC) need to be to provide a return path to send noise away from the amplifier? I had only 3.3n.
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Last edited by danielwritesbac; 14th October 2012 at 01:32 PM.
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Old 14th October 2012, 03:20 PM   #1442
DF96 is offline DF96  England
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Sorry, Daniel, I have no idea what you are talking about. Where/what is this noise you are talking of? Do you mean noise in the same sense that the rest of us mean noise?
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Old 14th October 2012, 03:25 PM   #1443
AndrewT is offline AndrewT  Scotland
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Daniel won't use normal technical nor simple english language.
As a result most of his posts are lost to me.
eg,
blinker?
a eye guard for a horse, or a turn indicator on an automobile?
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Old 14th October 2012, 03:39 PM   #1444
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Quote:
Originally Posted by DF96 View Post
Sorry, Daniel, I have no idea what you are talking about. Where/what is this noise you are talking of? Do you mean noise in the same sense that the rest of us mean noise?
Yes. Instead of noise return path question howabout this instead: How big of a cap or RC would damp a 6a05? I didn't use a 6a05 but those are fairly noisy, and if the bypass could take care of that much, then that's probably enough to get the job done.
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Old 14th October 2012, 04:04 PM   #1445
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Quote:
Originally Posted by AndrewT View Post
Daniel won't use normal technical nor simple english language. As a result most of his posts are lost to me. eg, blinker?
a eye guard for a horse, or a turn indicator on an automobile?
The latter. The Christmas tree lights blinker was a device sold a long time ago, and quite similar to the turn indicator blinker, it made the lights blink. This can be used to cause very bad quality power for a test.

And then I compared two examples; both are the compact sort with the power supply on same board as the amplifier. One of the examples had its 1cm "umbilical" trace cut and D//C installed (in-between reservoir capacitance and amp caps). That one succeeded despite bad power.

Likewise, the example with the filter also succeeds with a smaller transformer than the example without the filter. The amp board caps don't instantly lose charge every time the power supply reservoir waits on the transformer.

Other way to see it: Which can deliver a charge into the power supply faster, the amp board caps or a bogged down transformer?
Well, I didn't want the amplifier's caps to lose charge needlessly.
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Old 14th October 2012, 04:55 PM   #1446
DF96 is offline DF96  England
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Quote:
How big of a cap or RC would damp a 6a05?
I assume you mean a 6a05 rectifier? What has damping got to do with reservoir cap size?

What is a D//C?

Quote:
Which can deliver a charge into the power supply faster, the amp board caps or a bogged down transformer?
Why do you want to deliver charge quickly 'into the power supply'? In most PSUs the charge flows one way: from the rectifier, via the reservoir, to the smoothers/decouplers. Charge does not usually flow back from the smoothers to the reservoir. Once again, I have no idea what you are talking about.
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Old 14th October 2012, 11:19 PM   #1447
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Quote:
Originally Posted by DF96 View Post
I assume you mean a 6a05 rectifier? What has damping got to do with reservoir cap size? What is a D//C?
transformer > bridge rectifier > power supply reservoir > D//C series filter > amp board caps
D//C is exactly as it says, 1 diode paralleled with 1 capacitor.
The amplifier works, therefore the diode is NOT installed backwards.

If that doesn't do it, the following explanation won't help either:
A large capacity fuel container of 120cm high. -and-
A small capacity fuel container of 220cm high.
I want to connect them but I don't want fuel to flow out of the small capacity container.
Do I use an ordinary pipe or do I use a one way valve?

Similar to (but not exactly the same as):
I want to connect a power board, but I DON'T want charge stolen out of the amplifier board.
Do I use an ordinary wire or do I use a diode?

P.S.
(no fuel was used except for analogy)
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Last edited by danielwritesbac; 14th October 2012 at 11:49 PM.
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Old 14th October 2012, 11:29 PM   #1448
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Quote:
Originally Posted by DF96 View Post
Why do you want to deliver charge quickly 'into the power supply'? In most PSUs the charge flows one way: from the rectifier, via the reservoir, to the smoothers/decouplers. Charge does not usually flow back from the smoothers to the reservoir. Once again, I have no idea what you are talking about.
I want the DC never to leave the amp board. I want the AC to travel the reverse path (away from the amp power circuit) as quickly as possible. The resulting filter is D//C.
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Old 15th October 2012, 02:55 AM   #1449
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Default Umbilical Cable Substitute for compact amplifier+power combination boards.

Quote:
Originally Posted by AndrewT View Post
Daniel won't use normal technical nor simple english language. As a result most of his posts are lost to me.
I seriously apologize for the frustration. After a little drive in the car, pondering along the way, I realized that maybe we lost sight of the target.

Could you do me a favor and go look at the MyRef and see what's missing from the power circuit? The umbilical cable that would connect a power board to an amplifier board is missing. When the 10,000u caps need charge, it is most unfortunate that the umbilical cable is missing, because the 1cm trace is not an adequate substitute, since the features are much different. What substitutes may fit 1cm?

Due to the missing cable, after replaying bass (or anything significant) the charge leaves the 1000u caps (normal amps have more like 330u size there, but LM3886's shout needs the bigger caps). The very first thing that happens is amp decoupling cap discharge error, and that's as good as a flat tire. That amplifier is briefly defenseless for every transient. It is the same blunder as an air compressor with temporarily less pressure than the tire you're trying to inflate. This problem is typical of compact combination amp+power boards.

The error causes lower resolution audio (the dull effect that Nico described earlier). I suppose that amplifier would be extremely dull except for the LM3886's harmonic noise that is neither dull nor pleasant. The tuning is appropriate if one must use that part; however, that particular power circuit (omitted umbilical cable) is still causing lower resolution audio.

After that discharge mistake (due to the missing cable) the 1000u amp decoupling caps are in charging condition, temporarily opening the door to noise (a "defenseless" condition). Lastly, both the 10,000u and 1000u charge back up and the defense role of the 1000u is restored. . . until the next bass note. This seems so much like trousers that won't stay up.


We need "umbilical cable substitute"

Of course we could install an umbilical cable and we could give the MyRef an external power board. However, I have proposed D//C as a compact umbilical cable substitute that will fit nicely in the 1cm space provided.

Umbilical cable could slow down the unwanted reverse charge from the 1000u to the 10,000u as could a resistor or D//R. The D//R has an error of two paths forward at two different times, which may or may not be suitable. However, I'm working with D//C right now since it is OK if HF noise exits via return path the 1000u, but not okay if the DC exits the 1000u due to mistaken/compact layout.

Of the several possible umbilical cable substitutes, D//C was the most interesting because of the 1 thing it does differently--blocks some of the caveats of a too small transformer. A too small transformer makes "wrong way charge" even more likely to result in a defenseless amplifier; however, D//C blocked that path. Indeed, it was a surprisingly effective against my crude bad power test procedure. I gave it the power equivalent of poison, and it simply ignored that.

As seen with regulators, the amp decoupling caps weren't mistakenly discharged, since return path for DC didn't work. This is different than umbilical cable which merely hinders both right way and wrong way charge flow. This is not different than umbilical cable that's long enough to guarantee that transient charge for the 10,000u power supply reservoir will always come from the transformer but never from the 1000u amp decoupling caps; and that size umbilical cable is when the amplifier and power supply are in two different boxes. But, if you wanted one little compact all-in-one deal (like the MyRef), try D//C as a substitute for the umbilical cable.

Did I finally manage to explain it?
I wish I had Not picked an LM3886 example that employs power circuit noise to level its response. A compact, discrete amp+power board (or an STK with the bridge rectifier and power supply reservoir aboard with the amplifier) would have given a better example. . . of employing "umbilical cable substitute"

P.S.
If I could only manage to explain this, it is half of answering Nico's question--No need for avoiding large capacitance, just use a regulator, a capmulti, a long-enough umbilical cable, or my cheap little compact substitute. For Nico's 80,000uF example to avoid dulling the audio, he would have to either greatly increase the length of the umbilical cable or install D, D//C, D//R or capmulti or regulators.
Tom is working on the other half of Nico's question.
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Last edited by danielwritesbac; 15th October 2012 at 03:23 AM.
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Old 15th October 2012, 03:34 AM   #1450
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Default One of Nico's questions

Q: Why does extra large power supply capacitance make my amp sound dull?
A: The power supply board to amplifier board umbilical cable is too short.

P.S.
In extreme circumstances or for compact layouts that don't have an umbilical cable at all, Diode//Capacitor (like MR//3n3) can substitute instead of the long cable.
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