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Old 28th August 2012, 08:42 PM   #431
RNMarsh is offline RNMarsh  United States
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Originally Posted by Wavebourn View Post
I can proto it, but I have much more things to do than to prove lessons that I learned 35 years ago. Including design of frequency-stable control loops in systems. Problems of stability of control systems are the same like in opamps, for example. Thermo-stabilization as well can oscillate.
I am not asking to 'prove' it but to give an example that this thread can take and run with or it will generate more new ideas for various topologies. In the spirit of this thread I am asking. Thx -RNM
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Old 28th August 2012, 08:42 PM   #432
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The potential problem with INTEGRATING the servo into the design, is that you get the SAME downsides of an external servo, without the ease in DECOUPLING the servo to really be just a DC offset control.

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Old 28th August 2012, 08:48 PM   #433
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Originally Posted by RNMarsh View Post
We have one good idea so far From Wavebourn....
Come on... This ideas were implemented long before Wavebourn was born. For example, steam machines contained stabilizers of sped of rotation that used weights on springs.
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Old 28th August 2012, 08:49 PM   #434
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Originally Posted by john curl View Post
The potential problem with INTEGRATING the servo into the design, is that you get the SAME downsides of an external servo, without the ease in DECOUPLING the servo to really be a DC offset control.
Right. Because DC is zero frequency, and zero is strictly mathematical term that does not exist in our physical word.
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Old 28th August 2012, 08:50 PM   #435
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Originally Posted by Chris Hornbeck View Post
bore a hole in the ground about six or eight feet
Overhere, that's a strategy to drown yourself.
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Old 28th August 2012, 08:53 PM   #436
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Originally Posted by john curl View Post
I put that topology up, because it was DIFFERENT, not necessarily practical.
Wavebourn, I think your approach to bias stability is very elegant.
Yes, it was different. And with ideal devices it would be ideal. However, it would require also ideal power sources...
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Old 28th August 2012, 08:57 PM   #437
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Anatoliy, if your servo injecting anything other than VERY slowly varying DC at the amp input, it is either a very badly designed amp or a very badly designed servo.
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Old 28th August 2012, 09:05 PM   #438
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Anatoliy, if your servo injecting anything other than VERY slowly varying DC at the amp input, it is either a very badly designed amp or a very badly designed servo.
...or, it is a very real view on servo where "VERY slowly" it undefined in engineering terms.
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Old 28th August 2012, 09:08 PM   #439
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Scott's posting #135 and the related circuitry is a beauty.
Unfortunately the component count is high.
And most DIY enthusiasts would struggle with a discrete built of such high gain at 20kHz. Slowing down the dominant pole most likely would be necessary to ensure DIYability, unfortunately this impacts performance....

Nevertheless, to me it is the most educative circuitry of this thread IMHO,
thanks for that !!
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Old 28th August 2012, 09:15 PM   #440
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Quote:
Originally Posted by Wavebourn View Post
...or, it is a very real view on servo where "VERY slowly" it undefined in engineering terms.
Let's say sub-0.01 Hz. At least after a minute or two of warmup. This is certainly the case with my preamp's servo, and it uses old fashioned thermionic FETs.

Really, it's no different than an "integrated" approach except it's cheap and easier and potentially far more accurate (higher sub 10 Hz loop gain in an IC).
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