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Old 10th January 2013, 12:27 PM   #1011
Waly is offline Waly  United Kingdom
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Quote:
Originally Posted by PMA View Post
This we can see from Bode plots.
FWIW, those are not Bode plots.
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Old 10th January 2013, 12:37 PM   #1012
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Quote:
Originally Posted by Waly View Post
FWIW, those are not Bode plots.
They ARE the Bode plots. The post (985) was here:

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Your posts like this are completely useless, you are bringing no insight here. Similar as in case of your not understanding how the DC servo works.
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Old 10th January 2013, 12:41 PM   #1013
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Originally Posted by Waly View Post
Get used with it, or AC couple the pre.
Sorry, not sure what your link points to.

AC coupling is a possibility, maybe even a must in case this is followed with a dc coupled line stage. It does feel a bit of a waste to have a servo though. In order to minimise coupling cap size i may consider providing a bias resistor ahead of the output buffer and including the cap between the riaa and buffer. That is, unless someone comes up with a smarter suggestion. In any case, even without the servo and going for ac coupling it will be useful to achieve good thermal coupling between the input devices.
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Old 10th January 2013, 12:47 PM   #1014
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Originally Posted by PMA View Post
Are you sure .....
Normally the shielding box should be connected in one point with board ground, reference 0V or something like this. In case you leave metal box floating, it will NOT serve as a Faraday cage. It will act as an antenna and it will couple the EMI noise received on its surface thru coupling capacitance (just geometrically defined) into the circuit board (do not forget you have the wires going IN and OUT of the box). If you connect the box with board reference ground, then it WILL act as a Faraday shield.
I'm sure, a metal box, grounded or not, will alwais work as a cage of Faraday. No radiation can escape (a true) cage of Faraday.
Faraday cage - Wikipedia, the free encyclopedia
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Old 10th January 2013, 12:52 PM   #1015
FdW is online now FdW  Netherlands
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Quote:
Originally Posted by PMA View Post
Are you sure .....
Normally the shielding box should be connected in one point with board ground, reference 0V or something like this. In case you leave metal box floating, it will NOT serve as a Faraday cage. It will act as an antenna and it will couple the EMI noise received on its surface thru coupling capacitance (just geometrically defined) into the circuit board (do not forget you have the wires going IN and OUT of the box). If you connect the box with board reference ground, then it WILL act as a Faraday shield.
In the box-in-a-box-in-a-box case the outer box should be chassis ground (and (at the star point) be connected (using a DDRC I would suggest) connected to the signal ground).
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Old 10th January 2013, 12:55 PM   #1016
FdW is online now FdW  Netherlands
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Quote:
Originally Posted by PMA View Post
Are you sure .....
Normally the shielding box should be connected in one point with board ground, reference 0V or something like this. In case you leave metal box floating, it will NOT serve as a Faraday cage. It will act as an antenna and it will couple the EMI noise received on its surface thru coupling capacitance (just geometrically defined) into the circuit board (do not forget you have the wires going IN and OUT of the box). If you connect the box with board reference ground, then it WILL act as a Faraday shield.
And (last point) if it is an inner box there is nothing to receive (for the antenna, from the outside any way). On the other hand, an gage of Faraday could be looked upon as a shorted antenna. In the proposed case, the antenna would 'receive' all radiation that is in the box, and then short it into oblivion (actually heat ) as long as it is not bouncing around (Hermann von Helmholtz http://en.wikipedia.org/wiki/Helmholtz).

Last edited by FdW; 10th January 2013 at 12:58 PM.
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Old 10th January 2013, 01:02 PM   #1017
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Stay tuned for an update of the assembly guide, then
Thanks Hessener. It is greatly aprreciated.
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Old 10th January 2013, 01:06 PM   #1018
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Originally Posted by FdW View Post
Also, it is a good indication for the need to put the prereg in a separate metal enclosure The question is, how far are you (the builder) prepared to go .
Good question but I now can say that MyParadise R2 is prety quiet
Good (realy good) board design prety good Power suply and regulators
It does not oscillate as far as I can tell and the litle bit of ofsset on the output do not seem to bother mine or another pair of speakers I have eard

So tick box for trafo and box Phonos tick main filter supressor and tick for buss of star on earth.

And use Steinless Stell 304 and a further jacket of cooper but is it realy necessary as it performs quite well just sitting on a carpet

Wuld one design new board for separate power suply and one for phono addressing thermals?
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Old 10th January 2013, 01:32 PM   #1019
Waly is offline Waly  United Kingdom
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Quote:
Originally Posted by PMA View Post
Your posts like this are completely useless, you are bringing no insight here. Similar as in case of your not understanding how the DC servo works.
Man, you are one nervous guy! And I though I clarified the servo problem (and also the input bias current red herring) .

They are not Bode plots, at least not in the sense required for a complete circuit stability analysis. A simple plot of the crcuit transfer function vs. frequency is pretty much useless for analyzing a circuit stability.

But perhaps I am wrong, so please specify the Y units on the loop gain plot and the method used to determine the gain and phase plots, also the feedback loop(s) you are analyzing. Otherwise, everything is mirrors and smoke.
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Old 10th January 2013, 01:40 PM   #1020
Waly is offline Waly  United Kingdom
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Originally Posted by analog_sa View Post
Sorry, not sure what your link points to.

AC coupling is a possibility, maybe even a must in case this is followed with a dc coupled line stage. It does feel a bit of a waste to have a servo though. In order to minimise coupling cap size i may consider providing a bias resistor ahead of the output buffer and including the cap between the riaa and buffer. That is, unless someone comes up with a smarter suggestion. In any case, even without the servo and going for ac coupling it will be useful to achieve good thermal coupling between the input devices.
You almost got it. In a very high gain servo controlled, DC coupled amp, noise fluctuations are visible at the output, that's unavoidable, happens even in proffessional metrology equipment. Input noise has a quickly increasing power with decreasing frequency, so .1Hz fluctuations have a much larger amplitude than, say, 10Hz. If you get 200mV, that's a lot though, could be another additional cause as well (like a bad contact, or a joint thermoelectric contact pile).

Somewhere in the audio chain, there is a high pass filter removing those fluctuations. If you want to control these, just add a 5Hz (or even less) pole somewhere.
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