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Old 23rd June 2013, 10:58 AM   #9021
hesener is offline hesener  Germany
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Quote:
Originally Posted by Joachim Gerhard View Post
Here is the variety of the K-multiplier i used in the headphone amp. The negative one is build the same way. Do you think it is dimensined resonable ?
Circuit 2 shows a more conventional circuit i would like to build for comparison. It came out of the simulator well. I see the main advantage of circuit 2 in the use of a quite small shunt cap. There is a really small 4.7uF Wima foil so it could work without electrolytics.
Circuit 1 will need a higher input voltage compared to circuit 2.... how about using a CCS instead of the diodes that connect to the base of the NPN? A simple JFET might be enough, and give tons of noise isolation....
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Old 23rd June 2013, 11:06 AM   #9022
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The circuits should have very similar voltage drop because of the 17uA base current. 17uA through 3 diodes is 1.2V. 17uA through 68k is also 1.2V.

A CCS won't improve noise isolation because it is the Early effect of the driver that limits that. More filtering for the reference is not an improvement except at bass or subsonics.
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Old 23rd June 2013, 11:24 AM   #9023
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by hesener View Post
Circuit 1 will need a higher input voltage compared to circuit 2.... how about using a CCS instead of the diodes that connect to the base of the NPN? A simple JFET might be enough, and give tons of noise isolation....
Quote:
Originally Posted by keantoken View Post
The circuits should have very similar voltage drop because of the 17uA base current. 17uA through 3 diodes is 1.2V. 17uA through 68k is also 1.2V.

A CCS won't improve noise isolation because it is the Early effect of the driver that limits that. More filtering for the reference is not an improvement except at bass or subsonics.
That is exactly true, the circuits where tuned to exactly the same output voltage (the difference in the simulation is only 16mV). (post #9007 left).

Edit: Oops... this is about #9016 (the output voltages of left and right are about the same). Joachim will build and analyze both lets wait and see...

Last edited by FdW; 23rd June 2013 at 11:33 AM.
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Old 23rd June 2013, 12:32 PM   #9024
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Originally Posted by sq225917 View Post
Jackinnj, what is the second reg in your example?
The Jung Regulator with LM317 pre-regulator and AD825AR error amplifier.
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Old 23rd June 2013, 01:06 PM   #9025
MiiB is offline MiiB  Denmark
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I do have a preference for making R-C og L-C type of circuits, where the PSU impedance mainly relies on single passive components.

I once made a DAC with a tube rectified power supply. And i must say the blackness and tone colors I got there was truly outstanding.

Tube rectifiers really eliminates diode switching noise.
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Old 23rd June 2013, 01:28 PM   #9026
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I will now build the two circuits, both with 47 Ohm to supply the pass transistors.
I have no problem to understand you Keantoken but you look at this circuit from another angle. For example i have seen other cap multipliers that have massive filtering of the base current. You are the first one that said that filtering is limited by the early voltage ( at higher frequencies ) and i have to digest this.
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Old 23rd June 2013, 01:29 PM   #9027
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Here is an example of massive filtering :
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File Type: png CFB cap multi syn.png (237.3 KB, 119 views)
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Old 23rd June 2013, 01:34 PM   #9028
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Here is another example with conventional darlington :
Capacitance Multiplier Power Supply Filter
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Old 23rd June 2013, 01:57 PM   #9029
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by Joachim Gerhard View Post
Here is another example with conventional darlington :
Capacitance Multiplier Power Supply Filter
Using a darlington makes for a larger voltage drop and thus a lower value of the filter resistor (or both, or any of these )
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Old 23rd June 2013, 02:01 PM   #9030
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by Joachim Gerhard View Post
Here is an example of massive filtering :
The LM needs 5V drop and the multiplier is configured for 10% that is a lot to drop and I do not see very great benefits. If you want a absolutely stable voltage, and you are spending all these components, also the complexity, then a Jung 2000 Regulator may be a better bet.
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