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Old 31st July 2012, 07:48 PM   #1101
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Quote:
Originally Posted by EUVL View Post
> This particular circuit (Zen, etc.) is sensitive to the output impedance of the floating supply.

I am sorry, but the SEN / CEN IV are completely different circuit principle than the ZEN IV, as already explained in the article.

> Unless the batteries are heavily bypassed, the source impedance will have a negative effect on the performance of the circuit.
> The circuit requires that the floating supply cancel out all differential mode signals and the only way to do that is to make sure it is a dead short for AC signals.

Really ?
BTW, have you actually built and tested one ?


Cheers,
Patrick
I'm sorry, I was in fact talking about your circuit, which is inspired by the one by Dr. Leach. I'm sorry you apparently do not understand what I'm talking about.

Your article does not discuss batteries vs. regulators for the floating supply, or at least I can't find it.

Did you submit your article to Dr. Leach for his feedback before publishing it? I would consider it rude not to do so myself. He complains about people ripping off his circuit in the article, so it's obviously a sore point for him.

Last edited by dirkwright; 31st July 2012 at 08:06 PM.
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Old 31st July 2012, 08:04 PM   #1102
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Quote:
Originally Posted by qusp View Post
I posted the graph to simply show the discharge curve of NIMH and how radically it changes with lower currents and I fail to see how a higher capacity battery will behave any differently at such low currents. myself I use much higher current single cell lifepo4 cells that put the above graph to shame as far as current, but NIMH are no slouches either. basing your argument on zero experience and decades old research is pretty meaningless i'm afraid.

I wonder when people who have no experience of using quality batteries in their gear will stop quoting that article to back up their present day arguments? its getting pretty tiresome, the number of times its been covered is right up there. I dont have the gear to test or I would be answering the call to update it.

also notice the voltage scale on the side, this is not a big battery

AC and batteries and switching supplies all have pros and cons, areas they do well and others where each is a pita, but low current low noise line level gear is most definitely an area where batteries excel
"decades old research"? are you serious? The copyright on that web page is 2004.

If you don't have the gear to test it yourself, then you have no basis to say your way is better or worse than anyone else's.

I'm sorry, but the facts about batteries do not support their use in circuits that are sensitive to power supply impedance and absolute voltage.
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Old 31st July 2012, 08:25 PM   #1103
EUVL is offline EUVL  Europe
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Inspired yes, as I promptly acknowledged in the first section of the article. Copied certainly not. In fact, the use of JFET cures one of the deficits of the Leach circuit, namely the base current.

And I am certainly not aware that, even in academic publications of which I have had quite a few a decade or so back, one has to submit one's article to the author of a previous publication for approval, when the later publication is a further development of the former, and that the former article has been properly referenced to and acknowledged.

If you have any solid experimental evidence of the detrimental effect of the internal resistance of the power supply in this particular circuit, I am sure all of us would be glad to discover and learn from you.


Best regards,
Patrick
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Last edited by EUVL; 31st July 2012 at 08:27 PM.
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Old 31st July 2012, 08:36 PM   #1104
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Quote:
Originally Posted by EUVL View Post
Inspired yes, as I promptly acknowledged in the first section of the article. Copied certainly not. In fact, the use of JFET cures one of the deficits of the Leach circuit, namely the base current.

And I am certainly not aware that, even in academic publications of which I have quite a few, one has to submit one's article to the author of a previous publication for approval, when the later publication is a further development of the former, and that the former article has been properly referenced to and acknowledged.

If you have any solid experimental evidence of the detrimental effect of the internal resistance of the power supply in this particular circuit, I am sure all of us would be glad to discover and learn from you.


Best regards,
Patrick
You published in a commercial magazine, not an academic one. You're selling evaluation boards from the article also. So, this is different than an academic environment. I never said you had to submit anything to anyone. I merely stated that I thought it would be rude not to do so given the tone at the beginning of Dr. Leach's article in particular. That is my opinion obviously.

Even so, a collaboration with Dr. Leach could have possibly achieved an even better design. I don't see a huge difference between your circuit and Dr. Leach's.

If I wanted to pursue the battery issue further, I would contact Dr. Leach about it myself. I'm not that interested. I'm convinced by the article I cited above and that's good enough for me.
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Old 31st July 2012, 08:38 PM   #1105
EUVL is offline EUVL  Europe
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> I don't see a huge difference between your circuit and Dr. Leach's.

I do.
But we don't have to agree.


Patrick
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Old 31st July 2012, 09:27 PM   #1106
EUVL is offline EUVL  Europe
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As I do not have a working circuit with me to do real measurement, the least I can do is a Spice simulation.

The attachments show two standard SEN IV circuit variants with 2SK170s.
The first one has ideal current and voltage sources, so that the distortion is only due to the circuit itself.
The 2nd is the same, except that a 1R series resistor has been added to the voltage source.
This is as bad as a battery power supply without any decoupling capacitor can ever get.
The corresponding distortion spectra are shown and can be easily compared.

I also attached the Spice model I am using, so that anyone can repeat the results for themselves.


Patrick
Attached Images
File Type: png Standard SEN IV w Ideal PSU.png (27.4 KB, 452 views)
File Type: png THD Standard SEN Ideal PSU.png (42.5 KB, 451 views)
File Type: png Standard SEN IV w PSU 1R.png (28.0 KB, 450 views)
File Type: png THD Standard SEN PSU 1R.png (43.9 KB, 444 views)
Attached Files
File Type: zip Spice Model SEN IV 2SK170 PSU 1R.zip (1.3 KB, 37 views)
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Last edited by EUVL; 31st July 2012 at 09:30 PM.
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Old 31st July 2012, 09:52 PM   #1107
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by EUVL View Post
Actually Nic, you can do an experiment for us.
I would be happy to do this little experiment, but I'm not going to spend my time on it since it's very unlikely to stop dirkwright from trolling the thread independently of the result.

Also my scope is currently abroad and I have about 2000 FETs on my table looking at me for sorting
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Old 31st July 2012, 09:58 PM   #1108
EUVL is offline EUVL  Europe
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Happy matching ....


Patrick
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Old 31st July 2012, 11:18 PM   #1109
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by EUVL View Post
Happy matching ....
As Davide say: matching is Zen work
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Old 31st July 2012, 11:28 PM   #1110
bcarso is offline bcarso  United States
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Default Power supply rejection of Sen and cascode Sen

This is helpful to assess the appropriate levels of concern. In each case the low-frequency attentuation is noted, and the point at which things are up by 3dB, after which they rise (that is, attenuation falls) at 6dB/octave out to VHF.

The cornering occurs a little lower in frequency when the PS noise is in the positive leg of the battery. But it's pretty decent, even without the cascode structures, and when fed from a lowish presumed DAC output resistance.
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File Type: jpg simple sen PS rejection 07-31-12 001.jpg (254.1 KB, 431 views)
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