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Old 8th February 2012, 03:29 PM   #20491
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Jan, you are debating design experts. Including published ones. Tread softly.
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Old 8th February 2012, 03:30 PM   #20492
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Quote:
Originally Posted by janneman View Post
Come on Ed, the large Vout will give a lot more load-induced noise from an oscillator that anything you can remove!
Let me put it this way: if you would apply for a job with me as audio designer, and you would propose this for a low noise supply, you would not get the job ;-)
Which may be my loss, but still.

jan
I assume you meant R not V, and this is not a design for an audio power supply!

Remember rule #2. "When the boss is wrong refer to rule#1!"
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Old 8th February 2012, 03:31 PM   #20493
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Quote:
Originally Posted by john curl View Post
Jan, you are debating design experts. Including published ones. Tread softly.
And Jan is one of them!
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Old 8th February 2012, 03:43 PM   #20494
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Hi,

Quote:
Originally Posted by janneman View Post
Did anybody actually do some measurements on the Finesse regulator? Does the claim hold?
I found that in practice 20dB are achievable with reasonable ease, however the circuit is quite sensitive to differences in the transistors (manufacturers, batches etc.) so without adjusting the real circuit with the real parts it is not a given that even the 20dB will attained.

Higher attenuation into the 30dB+ region is possible but now you need to explicitly tune for a specific batch of transistors and even then you may have quite a number of rejects.

Trimming these Finesse Noise Shunts in practice is a challenge, as there is very little ready instrumentation that cab be used. The low noise pre-amplifier also shown on the Wenzel site is an excellent tool for low noise measurements, however it too is not "ejit-proof" to build (we now use building one of these as test for new engineers to see if they are competent - most fail miserably) and may need trimming.

Another issue is that the output impedance of the "Finesse Noise Shunt" becomes quite high. This is of little concern in the intended application (cleaning up noise from the supply for a clock oscillator), but may not be acceptable for some other circuits.

The large dependence of the noise rejection on the precise active parts led to me designing the dual cascaded Finesse Noise Shunt I originally used out and replacing it with a circuit of my own design that has almost exactly the same component count as the dual Finesse noise Shunt, similar noise limits (self noise of a 2N4401 transistor) but around 70dB to 80dB noise rejection without any trimming and minimal component dependence.

This design is a simple capacitor follower (around 35dB noise rejection) combined with an AC current source and an AC Shunt (combined over 46dB noise rejection). The output impedance is also around 1/10 of that of the Finesse Noise Shunt.

Of course, it is again just another dumb, stupid and obvious application of the CCS & Shunt Reg principle, no finess, no innovation, just brute force and reliable noise killing.

And credit is due to Mr Wenzel, without his article and his circuits quirks I might have never tried and instead used just another dumb, stupid and obvious application of the op-amp & pass transistor circuitry instead.

Ciao T
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Old 8th February 2012, 03:58 PM   #20495
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Quote:
Originally Posted by simon7000 View Post
I assume you meant R not V, and this is not a design for an audio power supply!

Remember rule #2. "When the boss is wrong refer to rule#1!"
Yes Rout, or Zout.
No matter whether it is for audio or not, any design that works, sort of, depending on temp, and with carefull adjustment unit-to-unit, is bad engineering.
My rule # 1.

jan
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Old 8th February 2012, 04:01 PM   #20496
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Quote:
Originally Posted by john curl View Post
Jan, you are debating design experts. Including published ones. Tread softly.
Sorry John, you know I look only at content, not titles.
I live by the adage from a person you also respect: the late Dick Feyman.
I quote: Never believe anything that is based on authority, tradition or religion.
My rule # 1, & 2.

BTW Thanks for the list of publications. I agree that some of those 'general design' pubs often publish articles pertinent to audio design.

jan
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Old 8th February 2012, 04:10 PM   #20497
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Audio design is part of the general electronic engineering world. I get new ideas, and understanding of the fundamental concepts of what is going on from ALL the publications that I scan. It helps me keep an open mind to new developments, like those in wire, quantum devices, etc. It makes more sense of new audio tweaks when I see that the world outside audio is also using strange concepts (at least strange from what I learned in college) and is going forward with them.
Feynman was a great physicist, I have most of his books, and Jack Bybee tells me about working with him, and HOW he would always try something before condemning it outright. You take Richard Feynman out of context, in my opinion.
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Old 8th February 2012, 04:11 PM   #20498
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Quote:
Originally Posted by john curl View Post
You take Richard Feynman out of context, in my opinion.
Have you read his essay on Cargo Cult Science? Worthwhile.
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Old 8th February 2012, 04:13 PM   #20499
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Quote:
Originally Posted by Bonsai View Post
.....ripple eaters aka cap multipliers.....
Since I seem to be misunderstood.

A "ripple eater" is NOT a cap multiplier.

See what I understand as a cap multiplier:

Using a low noise transistor or JFet, you get very low noise at the output, of course at the expense of a not so low output impedance...

Click the image to open in full size.
Attached Images
File Type: gif cap multiplier.gif (25.4 KB, 396 views)
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Old 8th February 2012, 04:45 PM   #20500
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Quote:
Originally Posted by john curl View Post
[snip] You take Richard Feynman out of context, in my opinion.
Speculation because you haven't read it yourself.

Let me fill you in. It is a literal quote from his letter to his daughter on her birthday, don't remember the exact age I believe it was 13th.
The letter was to prepare her for her adult life where she would be herself responsible for separating myth from reasoned fact and take firmly ground-based decisions, in the light of assaults by lots of quacks, snake-oil salesmen and religious fanatics. Just hope she steers clear from audio .

jan
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