adjustable ac to dc power supply schematics

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gtzack4

Member
Joined
Sep 1, 2011
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14
So I am just noob here. I have read a few books and I feel I have a pretty good understanding of whats going on when I study a schismatic. So now I feel it is time to get started building something! For my first project I would like build a high quality adjustable ac to dc power supply (for my bench). Id like to be able to use it for mic pres, compressors, eq unit, and guitar/bass amps. Id like to have up to +-25V rails. I think that should be enough for anything I would need for a while. One of my biggest concerns is noise. I really am not sure whats to much noise? What components are critical for noise suppression? How much I should be concerned with the noise introduced by the power supply?

Please help!
 
Well, as far as how concerned you should be, think of it this way...

an amplifier is a modulated power supply, using a small signal to modulate the larger power source. So, your amplifier will only be as clean as your power supply.

Having said that, some amplifier topologies are designed to cancel out noise in the power supply, some are not so great at it. So, to be able to use it for a wide range of designs for testing or experimenting, you should start with a very low noise supply.

To save yourself some headache (or just to get a good look at a good design), check out JLM's ac/dc kit http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=11. They are high quality and kits are available so you don't have to sift through thousands of parts to select ones that will suit the task.

(there are many, many other options around, but this was the one that came to mind first...)
 
you need two power supplies,

1) +/-  0 to 40 DC volts at 5 amps

2) 0 to 400 volts DC with 5 and 6.3 volts AC for tube heaters

you do not need an extra minus 0 to 100 volts for tube grids like the old Heathkits,

had one but never used it once,

now the 0 to 40 volt supply, you do not need continuous variable voltage controls,

you can just have bannana jacks with the more popular voltages,

+/- 5

+/- 9

+/- 12

+/-15

+/-18

and +/-24

this will make it easy to troubleshoot and easy to build.

variable voltage regulators can be ok for a while but if you want something that will never need fixing, go for the solid voltages.

for the above voltages you just use a good multi stage pi filter, no regulators to give you hassles,

power supplies cause 90 percent of all electronic problems, so you want to try and cut it back down to 20 percent.

regulators are fine for studio rack gear but a bench supply gets tortured in ways that can not be mentioned on the air.

not everything you build will be perfect the first time. so if you connect a dead short to a power supply over and over, sometimes the protective circuitry does not like 1000 hits of crowbar testing, get me?

you  need a bunch of transformers or a single transformer with many taps,

the high voltage supply is real fun, have you ever been across 400 volts DC?  :)
you can buy the old Heath high voltage supply for about 50 bucks on evilbay,
then you can rebuild it as a project, much easier than starting from scratch,

here is a site with many DIY projects

check the IP-32 schemo and see why it is better to buy a junker and fix it,

http://www.vintage-radio.info/heathkit/
 
> build a high quality adjustable ac to dc power supply

Build a low-quality supply. Upgrade it WHEN necessary.

I did 30 years of work with an old battery charger, a FWB, and two 2,200uFd 25V caps. +/-18V. Opamps ran clean-enough for breadboarding. Fussy stuff usually wants filtering "near" where the power goes, so on the breadboard or scratch-PCB.
 
...As posted on other threads:
.... May be a meta-thread-post
about how to obtain the power required (Ac to Dc voltages and ampere),
and how to configure the power supply connections,
the 'ideal help ?
 

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