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Keantoken's CFP cap multiplier
Keantoken's CFP cap multiplier
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Old 17th August 2017, 06:13 PM   #1001
maouna is offline maouna  Greece
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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

Last edited by maouna; 17th August 2017 at 06:41 PM.
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Old 17th August 2017, 07:47 PM   #1002
Destroyer OS is offline Destroyer OS  United States
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Keantoken's CFP cap multiplier
Nothing, connect right to it.

But I'd want to put an inductor or some sorta filter in between, personally.
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Old 17th August 2017, 11:50 PM   #1003
keantoken is offline keantoken  United States
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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.
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Old 19th August 2017, 12:19 PM   #1004
RCruz is offline RCruz  Switzerland
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Keantoken's CFP cap multiplier
Can I use KSA 1381 instead of 2SA1930 and KSC 3503 instead of 2SC5171 ?

These KS have 150Mhz Ft and lower Cob around 3pF
Attached Files
File Type: pdf KSA1381.pdf (249.9 KB, 8 views)
File Type: pdf KSC3503.pdf (245.8 KB, 3 views)
File Type: pdf 2SA1930.pdf (138.3 KB, 3 views)
File Type: pdf 2SC5171.pdf (142.3 KB, 2 views)
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Old 19th August 2017, 12:28 PM   #1005
RCruz is offline RCruz  Switzerland
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Keantoken's CFP cap multiplier
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.
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File Type: png P300 KMult.PNG (126.3 KB, 283 views)
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Old 19th August 2017, 09:19 PM   #1006
maouna is offline maouna  Greece
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Quote:
Originally Posted by Destroyer OS View Post
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?
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Old 20th August 2017, 04:15 AM   #1007
Destroyer OS is offline Destroyer OS  United States
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Keantoken's CFP cap multiplier
Two channels, 18x2?

You may need to add a little load if not. A capacitor with leakeage, resistor, something.
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Old 20th August 2017, 11:28 AM   #1008
maouna is offline maouna  Greece
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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..
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Old 21st August 2017, 07:10 PM   #1009
RCruz is offline RCruz  Switzerland
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Keantoken's CFP cap multiplier
Quote:
Originally Posted by RCruz View Post
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 ?
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Old 23rd August 2017, 04:29 PM   #1010
keantoken is offline keantoken  United States
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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.

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Originally Posted by RCruz View Post
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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