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Old 19th February 2004, 10:17 AM   #1
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Default Cascode PSUs

I am preparing to build a split rail preamp supply for (probably) a DACT CT101 line stage. HAving looked at a lot of options, I am quite taken with the Cascode PSU PCB available from White Noise Audio (http://www.wnaudio.com/cascode.html).

Is this configuration the same as a tracking pre regulator or have I misunderstood something in the description. Also, how is this likely to compare to a Jung type super regulator?

Cheers,

Ed
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Old 19th February 2004, 10:39 AM   #2
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Hi Ed,

From the description it sound conceptually like some of the preregulated regulators floating around on this forum, but hard to say without a schematic.

I don't agree with all the claims, some snippets:

- "You can see the triangular wave at the output etc" - I find that nonsense. In any reasonably well executed "jung" type regulator, any control noise would be buried in the thermal noise. So, the problem they want to solve doesn't exist;

- Even if the problem would exist, it is not solved by the cascode. As they themselves say, it would be caused by the feedback control loop. That stays the way it is, cascode or not. So, not only do they try to solve a non-existing problem, they also try to solve it by the wrong means.

But it may sound quite well. Most reasonably executed supplies sound quite well.

YMMV

Jan Didden
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Old 19th February 2004, 10:40 AM   #3
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The description gave me the impression it was a tracking *post* regulator, i.e. the second reg has a constant voltage drop.

A voltage reg cct makes the load look like a constant-current sink to the raw DC being fed to it. That way, any change in input voltage doesn't make any change in current and therefore any change in output voltage. A cascode reg cct would have a super duper high input impedance and the constant current action would be just that much more constant than a single stage reg. In theory at least it should work way better than a normal single stage series reg.
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Old 19th February 2004, 10:44 AM   #4
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Graham,

I agree, your description is more accurate. But the improvement comes from line rejection, not load or control-noise rejection. And that is what they say is the problem they want to solve by this.

Jan Didden
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