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Old 21st January 2013, 06:56 PM   #33211
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Somebody else's opinion:
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Old 21st January 2013, 07:05 PM   #33212
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Simon,
Way to many times, but we didn't have plotters then to do it for us. I still have those pens and they were a major pain in the behind. Smudges always pissed me off to no end.,........ But pen plotters could get you also, I still have a Houston Instruments plotter with printer port connection, have to keep legacy computers just for that type of stuff.
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Old 21st January 2013, 07:10 PM   #33213
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Originally Posted by SY View Post
Wow, that jello sure does splatter. I used your calculation, just without cooking the books like you did. That's apparently "paper warrior" when someone other than you does it.

Neither I nor Scott (who has considerably more experience than both you and I put together) see any signs of the 3k/6k/whatever-new-one ripple harmonics in the output of real-world 797 circuits using basic raw supplies and basic regulators. Apparently you haven't either, or you'd have added that at the end of your lecture.
SY,

Are you really that confused?

The 3K figures are based on weighting because human hearing appears to be most sensitive at that frequency.

The 6K peak in power supply noise is from the single .01F capacitor power supply shown.

Those are separate issues. Why do you confuse them.

The AD797 can reject all the power supply noise that ever will be, when the power supply moves the ground around that is your limit.

But just in case you missed it you will not achieve -90 db PSSR in a circuit with more than one active component, or even one with gain.

Now why does Scott never see 6K in the output, most likely because he doesn't use bad power supplies. He won't see 3K unless he has a Fletcher Munson weighted analyzer.

I gave an example of a real power supply, Waly got confused about ripple before and after regulators. So I gave a bit more of the example. You keep chiming in with paper calculations, that in your opinion disprove my measurements. I think that since you can't even calculate a ripple voltage your opinion is worthless.
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Old 21st January 2013, 07:11 PM   #33214
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Simon,
Way to many times,
I know! Mylar and ink remover were great steps forward.
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Old 21st January 2013, 07:18 PM   #33215
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Originally Posted by simon7000 View Post
But just in case you missed it you will not achieve -90 db PSSR in a circuit with more than one active component, or even one with gain.
That's a statement that can not be proven, first off you don't even specify frequency. At DC it's easy.
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Old 21st January 2013, 07:24 PM   #33216
SY is offline SY  United States
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Quote:
Originally Posted by simon7000 View Post
I think that since you can't even calculate a ripple voltage your opinion is worthless.
Even if I couldn't, PSUD2 certainly can.

So, got that data showing the 3k/6k/whatever-your-latest-dodge from PS ripple on the output of a competently laid out 797 circuit? Or is that hidden away in the lockbox with John's 7th and 9th harmonic data?
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Old 21st January 2013, 07:30 PM   #33217
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OK, then let's do the math without the need for a codex. If I have a bare bones supply (cheap 10,000uF/25V cap, no fancy choke or extra RC) and a whole pile of circuitry (let's say 100mA of draw), raw supply ripple is 120mV. At your chosen 3kHz, harmonics are -40dB wrt 120mV. A 7815 will knock that down another 55dB (and a 317 with cap bypass will be about a hundred times better, but let's stick with a 7815). 797 knocks that down another 95dB. So there's our line stage. The power amp is likely to have 26dB of gain. Overall, then, we deliver a signal -164dB down from 120mV at the speaker terminals (something less than a nanovolt). I haven't taken the math further, but I bet that's pushing the thermal noise of the voice coil.
Just to refresh your memory, Ed. If we change the PSRR to your new number of 95dB, the noise is 5dB worse. But that's based on my earlier estimate of 120mV ripple for the raw supply, which is too high (based on measurements of the components I have on hand). The actual number, as I showed, is about 12dB lower. So change my -164dB to -171dB. The 6kHz numbers are even lower. Drop in a more modern reg than the bell-bottoms and platform shoes 7815 and you can take out another 20dB or more, as if you needed that.

You'd do better worrying about the effect of room light on the Seebeck coefficient of the speaker terminals.
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Old 21st January 2013, 08:07 PM   #33218
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Originally Posted by simon7000 View Post
Lets go over the basics.
Ed
You stuffed that soup with all the herbs of the world.
Each paragraph in your post asks for a dedicated thread.

As is the case with this thread, every subject has a half life of a few hours. Two days later everything is buried deep down in the noise.
So although I agree on most with your points, I will not expand on any but on this .

Quote:
The noise from the primary power supply may be additionally filtered. (I haven't gone into this, but George has shown one way to add resistors.)
In that work I was cascading RC filter stages between the rectifying diodes and the voltage stabilizer trying to see the noise effect of capacitance distribution increasing from rectifiers to stabilizer (something that can be reliably tested with the PSUD2 too)

Thank you for this intriguing post and from your side try to find a way to settle this issue. I would paraphrase you:

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Originally Posted by simon7000 View Post
Now just for you SY,

Pass the Ouzo. The civilized way to settle a non-dispute.
ES
Life is so short SY and the level of noise is destined to increase till the end, all along the universe (you know that).

George
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Old 21st January 2013, 08:09 PM   #33219
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That's a statement that can not be proven, first off you don't even specify frequency. At DC it's easy.
Very true

Now lets try a simple question. If my PSSR at 120 Hz is 90 dB, There is .1 V P-P ripple (120 Hz.) on my negative supply, none on the positive supply and my gain is 60 dB. Can you predict from the data sheet what the output ripple will be?

Can you offer a value based on experience?

Now if I have have the same voltage of ripple on the positive rail, will there be more ripple out if the ripples are in phase or out of phase? Can you answer that question from the data sheet? From experience?

If you want to, assume a chip you are familiar with.

In my article I am trying to avoid brand names as some will jump to conclusion based on a limited sample size of a particular production run that A is better than B. Since sample size is limited and processes change I wish to avoid that.

ES

Last edited by simon7000; 21st January 2013 at 08:13 PM.
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Old 21st January 2013, 08:13 PM   #33220
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Originally Posted by gpapag View Post
Two days later everything is buried deep down in the noise.
... an thus useless. Well said, George. We are moving above thousands of surfaces, nothing in deep. Real world results are not appreciated.
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