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+/- 18V Low Noise Fast Transient Supply???
+/- 18V Low Noise Fast Transient Supply???
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Old 11th October 2020, 10:31 AM   #21
safesphere is offline safesphere  United States
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Originally Posted by tubemax View Post
Hi safesphere,

Maybe I'm too late to recommend - but read this DIY Audio link first, I build it twice and it sounds more natural than any other PS for low power pre-amps...

Another look at the LM317 and LM337 regulators
No one is late I want to build and compare several supplies. Thanks so much for sharing!
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Old 11th October 2020, 10:33 AM   #22
tubemax is online now tubemax  Netherlands
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You are welcome!
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Old 11th October 2020, 10:51 AM   #23
safesphere is offline safesphere  United States
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Originally Posted by dreamth View Post
Simple truth is that we don't need that even with the fastest and highest energy eating phono preamps as they are class A.
Thanks for your insight! I had the same thought regarding Class A. In theory, transients shouldn't affect the power supply, but I always test my theories. I plan to build several designs to see if there is any difference in sound for any reason. I also plan to build +5V supplies of the same designs for a USB DAC. Thanks again!
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Old 11th October 2020, 11:21 AM   #24
jan.didden is online now jan.didden  Europe
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One point is the slew rate required from the opamp in a regulator. That slew rate requirement is minuscule. The output of the opamp which drives the pass device will never change more than a few 10's of mV, 100mV tops.
100mV change at 20kHz is a slew rate of 0.026V/us ...

Jan
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Old 11th October 2020, 11:54 AM   #25
dreamth is offline dreamth  Romania
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3 years ago i used to test very expensive, precise(three decimals precision), high power(4kw) smps, around 100khz switching frequency and all the op-amps(about 20 pcs per board ) used there were opa2227 ( around 2V/us slew rate).All the power sources we built (up to 300kV/65 kVA) used the same op-amp and the test for the 300kV/65kVA supplies was to short circuit the output for 300 times, at 100kV, 200kV and 300kV...All power supplies made by that company used a 2.3 V/us op-amp for sensing the currents and voltages change...The capacitors would be the ones to handle all the trouble there, not the op-amps.

Last edited by dreamth; 11th October 2020 at 12:03 PM.
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Old 11th October 2020, 06:20 PM   #26
ferret is offline ferret  South Africa
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@Safesphere - you can try this one too

VRDN: bipolar regulator PCB for line level ckts: 11V to 20V @ 1.5A with "De-Noiser"
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Old 11th October 2020, 06:51 PM   #27
Mark Johnson is offline Mark Johnson  United States
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+/- 18V Low Noise Fast Transient Supply???
Hello safesphere,

I think if I were in your shoes, I might buy a power transformer with 18VAC or even 20VAC secondaries. Then I think I would probably build a cascade of two voltage regulators in series. There's plenty of voltage headroom to do this: 18VAC + Schottky rectifiers gives 24VDC raw. Let the first regulator have 2V in-to-out and let the second regulator have 4V in-to-out. Then: 24V --> reg1 --> 22V --> reg2 --> 18V

The only objective of the first ("upstream") regulator is to reduce ripple and create a much cleaner supply for the second ("downstream") regulator. Now, for the second regulator, you can apply whatever nifty circuits you like, secure in the knowledge that they will operate in a clean(er) environment.

And you get an extra 40-70dB of PSRR at the mains and 2Xmains frequencies.

You can also install RFI filtering and even ferrite bead suppression, before each of the two regulators.

_
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Old 11th October 2020, 07:18 PM   #28
dreamth is offline dreamth  Romania
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A friend of mine is restoring a Sony TA-ax6 amp and its phono preamp supplied with +-16.4 v derived from +-24v derived again from the main +-32 regulator aimed at supplying the first stages of the power amp, and i saw it's power supply idea like an interesting one, especially because you can supply any type of phono preamp with it and very similar idea with this one: Are you really fine with IC voltage regulators ?
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Last edited by dreamth; 11th October 2020 at 07:29 PM.
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Old 11th October 2020, 08:42 PM   #29
safesphere is offline safesphere  United States
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Originally Posted by Mark Johnson View Post
Hello safesphere,

I think if I were in your shoes, I might buy a power transformer with 18VAC or even 20VAC secondaries. Then I think I would probably build a cascade of two voltage regulators in series.
With so much great advice here, I plan to start with building 2 or 3 different designs to see if any of them sounds better. I can use the same transformer/rectifier to compare different regulators. Then I can put them in series like you've suggested and see if this makes any difference in my system. Than you for the idea!
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Old 11th October 2020, 08:47 PM   #30
safesphere is offline safesphere  United States
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Thanks! Is the board available for purchasing?
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