"Ultra Clean 9VDC Power Supply" questions

[freakazoidas]

I wanted to make this UCPS, but had a few questions before
( http://www.generalguitargadgets.com/projects/24-power-supplies/134-ultra-clean-power-supply )

1. if someone has made it, does it hum because of uninsulated outputs? (i once tried to daisy chain 1Amph walwart but it produced high hum)
2. what kind of transformer i should use (240v to 25v? amperage??) ?
3. how many outputs can i make and how to count amperage of each one? (are 4-5 possible?)



Sorry if the questions sound stupid, i just don't know where else to get the answers.

[Ronan]

1. It is a standard power supply, should not hum.
2. 25VAC is pushing it, you only need around 12VAC to feed that circuit. Output current (amps) should be a minimum of twice what you need. 3 times or four times would be better.
3. The LM317 will supply 1 amp if fitted with a good heatsink. Thats 1000mA. Add up the total current draw of all your pedals. It will only do about 100mA or less without a heatsink, depending on the input voltage from the power transformer.

[Ronan]

I often wonder why commercial sellers sell clean pedal supplies for hundreds of dollars, when DIY supplies can be done for heaps less, and heaps cleaner than the supply schematic linked in the first post. The hifi diy guys have set some remarkable examples that the diy guitar guys could learn from, unless the diy guitar guys have already beaten this subject to death, in which case, both the original poster and I are ignorant of that. Thems the breaks... Hey, let me know if that is the case, pleeeze   

[freakazoidas]

Thanks a lot for the answers! Everything is much clearer now.

and yeah, it's way cheaper, but lackness of motivation, knowledge or just thinking that a brand name made thing is better lets comercial sellers sell these things for hundreds of dollars

[aron]

Is this any better than a one spot which is very cheap???

[freakazoidas]

there are no one spot's in my country 
i have bought a variable voltage power suply of 1A, but it made very high (high frequency? don't know the word) hum, when using daisy chain.
(all pedals with battery - ok,
all pedals with 1 power suply with daisy chain - high squeek,
single pedal with power supply - ok,
all pedals with diffrent power suplies - ok)

So to save space and get rid of the hum, while at the same time not having the ability to buy 1spot, i thought that making UCPS would be the best alternative.

[Ronan]

Aron, I don't know. Here is something I know is pretty good.

[R.G.]

The word "ultra" doesn't mean a lot. Pretty much any IC regulated power supply is that much "ultra". I don't know why that bit of exaggeration nags at me, but it does.

It's as ultra clean as many, many other power supply circuits. Not bad. Nothing wrong with it.

I often wonder why commercial sellers sell clean pedal supplies for hundreds of dollars, when DIY supplies can be done for heaps less,

Because they can.

The greater "you", that being the buying musicians will lay down hundreds of dollars for them. Believe me, if no one bought them, they would not be sold. Beyond that, there are expenses in the price of that pedal that you do not have on a DIY power supply. Like - you don't charge yourself money for the labor you put in to build it. You don't have to pay a safety inspection lab to test it for conformance to safety standards. You don't pay for insurance on the factory, or utilities, licensing, vacations on the Riviera for management, or bribes - er, sorry, campaign contributions - to government officials in countries where that's applicable. You don't have to sell them to distributors and retail stores at reduced prices. You don't have to pay for the store mortgage, utilities, payroll, insurance, taxes, etc, etc. to keep it on the shelf waiting for some musician to wake up and come buy one.

Basically because whatever you buy instead of make, you're paying a little slice of the whole industry for the convenience. Of course they're greedy and want to get your money. If you want to keep all your money for yourself, so are you, in the same manner.

As for me, I work for a company that sells a notably clean, powerful and quiet power supply for pedals for a very reasonable price.

and heaps cleaner than the supply schematic linked in the first post

.
Define "cleaner" and "heaps".

The hifi diy guys have set some remarkable examples that the diy guitar guys could learn from, unless the diy guitar guys have already beaten this subject to death, in which case, both the original poster and I are ignorant of that. Thems the breaks... Hey, let me know if that is the case, pleeeze   

The hifi DIY guys have done good things. They've also swallowed a lot of - well, unhealthy misconceptions is a safe term, I guess.  I did and still do occasionally play in that sand box.

There is a big issue that catches up with you when you're trying to be "ultra" anything. It's called the law of diminishing returns.

[amptramp]

I did design a low-noise ±15 VDC power supply for one military program and I can define "low noise" quite accurately.  We were getting 33 nV/(Hz)^½ for a 180-channel filter amplifier for an infrared scanner.  We had one regulated supply feeding a postregulator stage that used diode switching to start applying power to the regulator diodes (two LM113's in series) through a zener so that when the output came up, the diode switch then sourced regulator current from the output, interposing both the pre-regulator and the postregulator on the current source driivng the LM113's and almost completely eliminating ripple.  The regulator was series pass transistors driven by an LM356 amplifier.  This required external compensation and current limiting as part of the design.

In many cases, the output voltage needs to be quiet but does not need accuracy.  In this case, an LED can be used as a regulator diode without the noise of a zener diode and you can design a discrete regulator stage around it.  Voltage may vary slightly with temperature, but the application may not require an exact voltage or even a repeatable one.  If you have a preregulator (and the diagram from the first post has good ripple rejection), you can add a second regulator stage using discrete components that can achieve better noise performance.  If you want to retain a zener reference, the LM399 is a good choice if you can find it.  Shunt postregulators can be also be used as in:

http://www.wenzel.com/documents/finesse.html

and analyzed here:

http://pstca.com/spice/ripple/ripple.htm

[R.G.]

Yeah, I can define "low noise" pretty succinctly too. But "heaps cleaner"? Very similar to "tastes great and less filling". 

And in many cases, diminishing returns sets in with a vengeance. Opamp circuits can have 40 or more db of power supply rejection easily enough with no special efforts on the supplies. Even transistors with nominally 0db of power supply noise rejection are really sensitive only to ground noise, not the power supply after R-C decoupling. The ground noise issue is more one of wire routing and ground currents than any mystic mojo regulator circuit. No regulator will clean up the buzzy hum caused by putting your input reference ground on the wrong end of the negative side of the rectifier (-) wire.

The original poster knows little of the issues, and is prone to getting very wrong concepts.  A power supply with the term "ultra" in the title has about the same meaning and import as the word "fidelity" and "trust" in a bank name. Or "tastes great and less filling".

[Ronan]

"heaps cleaner" means less background noise and an ability to hear the detail of the sound, and the true sound, without it being compromised by the power supply.

Sorry I never heard of a 1 spot, and sorry I posted at all, looks like I have been taken for a dick head who represents the mass of ill-informed commercial-gear buying people. That could not be further from the truth, I am a diyer as far as possible, it is a hobby, whether it be electronic fuel injection, hifi amps, guitar amps, pedals, or speakers. I did not mean to offend or upset anyone. Especially you R.G. as I have learnt a lot from your  generous writings, and I very much appreciate your sharing of knowledge.

[Ronan]

Whichever way you look at it, for trying to help a clueless kid, I got shafted and laughed at. "No good deed shall go unpunished."

[Jarno]

It's an engineering thing Ronan, it's not meant to take you down. The only thing RG said was that it's important to objectively quantify improvements and avoid hyperbolic statements.
When I saw the title ultra-clean, I thought "are they thinking of using a super-regulator (Walt Jung) for guitar pedals?", that seems overkill. A PSU with a LM317 is easy to build, even on a piece of perf like in the picture you posted, and has adequate performance for a pedal.