Power supply

[served]

Hi to all the readers.

I have been thinking on building a good Power supply for my pedals. But I Would like to build a supply with isolated channels, so that different boxes would not affect each other.
So here is the plan and questions.

I am going to feed it with 24VDC adaptor, its regulated and fixed one, pretty good one. I will start working with that 24V and channel by channel, I will regulate the voltage down to 9V with 7809 and add 2 caps. And I thought I will do so with each channel (3 parts per channel).
Does it actually have any effect to the isolation?
Is it possible that it works or should I buy different transformers and every channel should come straight from 230AC?
24V is good to start from, I can get 12V/18V/24V/9V from it, by just using different regulators.

I did look the schematics from varios sites, but I could not find what I was looking for.

[GibsonGM]

Hi,

What's the benefit of having such isolation?? Seems to me (and this is just opinion, mind you) that you can do just as good a job in feeding your pedals in parallel from a well-filtered and regulated voltage source.  How much current do you anticipate drawing from your PS?  How many pedals?

If you need a variety of voltages, sure, you could parallel regulators to achieve that, but it seems that you might be going into 'overkill' in creating the perfect, and complicated, power supply!  Many, many folks use 1 source to power, say, 10 pedals, with no ill effects such as noise (again, filtering is key).  Sounds like you have a nice transformer there that would do that job nicely!  The 7809 will power quite a few effects nicely on its own...

[served]

Ok thanks for the info. But in this case I cant see the point of building http://www.geofex.com/Article_Folders/Spyder/spyder.htm

Why whouldnt we just use one transformer and filter it.

EDIT: I think I should read the Power Supplies Basics at geofex. I might have a wrong impression about theese things.

[G. Hoffman]

In the scheme you are thinking of, all your pedals will share the same ground, so you will still have a good chance of developing ground loops and the related hum problems.

The point behind a transformer isolated power supply is that you have isolated all the grounds from one another, so the only grounds in common are the signal grounds.  No ground loops, no ground loop hum. 

You don't need separate transformers for each pedal, though, you need a transformer which has enough secondaries for all your pedals.  For most people, the one Weber makes (available from either Weber or Small Bear) will cover their needs.  If you are going to have separate regulators anyway, you may as well spend the extra $20 or so for the Weber transformer and do it right.  Without the transformer, you really aren't gaining anything, and may as well just use one regulator, or at least one regulator for each voltage you need.


Gabriel

[served]

Oh, actually this makes sense. This was what I wanted to hear but could not get to it by my self. Thank you!