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Old 10th December 2012, 10:06 PM   #451
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But at 120Hz it will have less PSRR.
ah, ok
I need to think about this once more

thanks Kean !
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Old 11th December 2012, 08:33 AM   #452
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However, the Kmultiplier isn't better than the chipregs in all ways.
ok, the weird, one of each

now, the question, will they work well together, or against each other

could be done as small seperate modules with small print connectors
that way it would be easy to make changes
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Old 11th December 2012, 08:59 AM   #453
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As far as putting the Kmultiplier before or after, you'll have to tell me which is better. You'll get lots of PSRR either way. The rest is a question of output impedance and transient behavior I think. I'm guessing that you're not worrying about output impedance because you have an RC at the output.
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Old 11th December 2012, 10:06 AM   #454
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I'm guessing that you're not worrying about output impedance because you have an RC at the output.
not sure when low impedance power supply is 'needed'
I thought low impedance was mainly for high current power amps
but I guess also for wide bandwidth

but this is for a bass guitar preamp project
gain stages are often 'simple' designs, and PSRR is probably next to nothing

so, 'the best' power supply could still have positive influence

btw, I thought the series resistors would help protecting the regulator in the power on situation...like a simple softstart
the LED/bleeder I use now also seem to come on quite slowly, as does the voltage on the reg
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Old 11th December 2012, 10:27 AM   #455
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Originally Posted by keantoken View Post
As far as putting the Kmultiplier before or after, you'll have to tell me which is better.
I was mostly thinking of the 'sensitive' output of the IC regs, and thus chose it to drive the Kmultiplier

btw, each single gain stage(or buffer) will all still have their own lytic supply caps
something like a NIC nrsg type 35V/1000uf(12x25mm) will still only be 18mohm(0.018)
but I suppose less will do
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Old 11th December 2012, 05:06 PM   #456
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The Kmultiplier has lower Zout from the treble to several MHz, but below that the chipreg has lower Zout (at least at the currents it was tested in the datasheet). While the chipreg has higher internal feedback, it is also heavily compensated, and may have intermodulation problems with RFI. So it may be best to use the Kmultiplier first to block RFI.

For any audio circuit I would try filtering the PSU to remove RFI and EMI. Zout maybe does not need to be so low. I think the things responsible for sonic improvement from the Kmultipliers are a low bass output impedance, and good PSRR through the ultrasonics to several MHz.

A chipreg will limit inrush current to 1.5A which is no problem. The Kmultiplier also limits inrush, and you can alter this based on the Design Considerations section in my article. So the real danger is of having too much capacitance right after the rectifier, since the regulator limits inrush.
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Old 11th December 2012, 05:13 PM   #457
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Quote:
Originally Posted by keantoken View Post
So it may be best to use the Kmultiplier first to block RFI.
For any audio circuit I would try filtering the PSU to remove RFI and EMI.


Quote:
Originally Posted by keantoken View Post
A chipreg will limit inrush current to 1.5A which is no problem. The Kmultiplier also limits inrush, and you can alter this based on the Design Considerations section in my article.
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Old 11th December 2012, 05:50 PM   #458
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Kmultip as pre filter
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Old 11th December 2012, 06:40 PM   #459
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Originally Posted by keantoken View Post
Here is a nifty way to snub rails. Maybe you could call it the Ksnubber or Kdamper. Maybe I like the letter K too much.
I just ran out a bode plot of the damper -- in comparison with a light resistive load of 13.8mA (1K) on a Jung "improved" regulator, the parallel value of 1K//390R and the damper illustrated in your post -- seems that the effect is pretty slight with the value of the damper primarily arising from the increased load, or decreased output impedance.

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Old 11th December 2012, 08:37 PM   #460
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I'm not sure what you are doing. Do you mean you added the damper, then replaced it with a resistor, and then compared the two?

The damper circuit is for places where it's needed. The only reason I made it is because it's hard to find non-inductive variable resistors that go to 500mR! If I could see the Jung regulator output impedance+phase to 40MHz I could tell whether it would benefit from a snubber.

High-performance amp circuits that have a high UG point can have problems with resonating rails because the very low PSRR at these frequencies causes the rail impedance to become part of the OLG curve, 10MHz spikes and all. In this case local decoupling is the only answer, and sometimes you need a snubber to keep the decoupling from resonating through the rails. I had this problem recently.

The diode circuit allows us to experiment with rail snubbing with resistances that would ordinarily be very inconvenient and time consuming.
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