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-   -   Keantoken's CFP cap multiplier (https://www.diyaudio.com/forums/power-supplies/177516-keantokens-cfp-cap-multiplier.html)

maouna 17th August 2017 07:13 PM

Hello.I ordered this 3.3V-12V In / +-15V Out Dual Power Step up converter to power my preamps from USB or batteries. Can i apply the K-multiplier at the output of step up converter?What modifications are needed for low drop K-multiplier supposing max output current wont exceed 100ma per rail?

+15V/-15V Dual Power Supply Module 3W DC-DC Step up Boost Converter 3.3V-12V In | eBay

Destroyer OS 17th August 2017 08:47 PM

Nothing, connect right to it.

But I'd want to put an inductor or some sorta filter in between, personally.

keantoken 18th August 2017 12:50 AM

If you want to add an inductor, most 5uH inductors are pretty good at blocking the upper end of SMPS noise. But they also tend to resonate with your supply lytics in the audio band. IE the same problem as lm317/337 regulators.

RCruz 19th August 2017 01:19 PM

4 Attachment(s)
Can I use KSA 1381 instead of 2SA1930 and KSC 3503 instead of 2SC5171 ?

These KS have 150Mhz Ft and lower Cob around 3pF

RCruz 19th August 2017 01:28 PM

1 Attachment(s)
The Ks are readily available and the 2SA not.

I must decide before ordering the boards because pinouts are reversed.

Also, would you please take a look at the layout.... there are a lot of diodes and I am wondering if it could oscilate.

maouna 19th August 2017 10:19 PM

Quote:

Originally Posted by Destroyer OS (https://www.diyaudio.com/forums/power-supplies/177516-keantokens-cfp-cap-multiplier-post5160158.html#post5160158)
Nothing, connect right to it.

But I'd want to put an inductor or some sorta filter in between, personally.

I was reading the page about K-multiplier The K Multiplier and there is a point that states:

''This regulator exhibits diodic output impedance. This means output impedance decreases with increased loading. The opposite is also true, which is why this circuit should NEVER be used with loads less then 25mA.''

My preamp draws about 18ma per rail.Should the circuit of K-multiplier be modified?

Destroyer OS 20th August 2017 05:15 AM

Two channels, 18x2?

You may need to add a little load if not. A capacitor with leakeage, resistor, something.

maouna 20th August 2017 12:28 PM

Yes just a resistor or a led with a series resistor...Can i replace 2SA1930 /2SC5171 with BD139/BD140 or there will be any degradation?Keep in mind my max current demand wont be above 150ma..

RCruz 21st August 2017 08:10 PM

Quote:

Originally Posted by RCruz (https://www.diyaudio.com/forums/power-supplies/177516-keantokens-cfp-cap-multiplier-post5161688.html#post5161688)
Can I use KSA 1381 instead of 2SA1930 and KSC 3503 instead of 2SC5171 ?

These KS have 150Mhz Ft and lower Cob around 3pF

maybe other alternatives ?

keantoken 23rd August 2017 05:29 PM

Capacitor leakage will usually be far too low to have any effect. Just add a load resistor at the output so that the total current will be over 25mA.

Quote:

Originally Posted by RCruz (https://www.diyaudio.com/forums/power-supplies/177516-keantokens-cfp-cap-multiplier-post5163782.html#post5163782)
maybe other alternatives ?

C29's ground is polluted by C28. C29 ground can be any point before C15 ground, the closer the better. But if C29 ground is after C15 ground, oscillation is much more likely.

The decoupling caps next to your lytics should be around 2.2uF or larger not to reasonate. 5mm caps up to 10uF are available.


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