#1
Will a daisy chain create noise if I do not exceed the current from my power supply?

Basicly, I have 2x power supplies that can give out 1.2 - 24VDC / 1A max. For the info, the power supplies are both linear, with LM317/337 regulators.

I'm also wondering about the reverse polarity adapters and such. If I simply switched the hot and ground wires, wouldn't that work?

Also when people are speaking about isolated outputs, do they mean a seperate transformer/power supply?

I'm looking for a very electrical point of view, as I'm a student in electronics, and feel confortable with doing simple mods like reversing polarities, etc. Although I should probably know the answers, I'm still a student and have never actually messed around with audio, other then repairing power amps.
Quote by MH400
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#2
If you do exceed the power supply's rated current you're gonna blow the transformer on it, so it doesn't matter if it makes noise or not, it has nothing to do with the current being drawn.

I'm very wary of variable output supplies like that when using pedals, unless you fix the Vadj on the reg chips for output to be constantly at 9v, I don't know how it decides how much to put out and I don't wanna even think about blowing my pedals cause of that.

You're right on the reverse polarity, you can just switch them.

You're almost correct there. Isolated outs differ from daisy chains (all parallel connections) in that they all have a separate regulator chip for each output but all use the same rectified DC input at some voltage. So you pretty much have one transformer or rectifier circuit which feeds the voltage regulators which then feed their own outputs. I'm not sure if this is how the voodoo labs thing does it, but that's what I have seen in other contexts. You can add more isolation too if you have transformers providing separated secondary windings giving you two isolated sources to run into a regulator. Etc... So yes you're right in that you could have a separate transformer for every X amount of outs but I'm not sure what the difference would be if you used one transformer and one BR to rectify and then just used that to feed the regulators... So I guess you can isolate it at several steps it's just where you draw the line.
"Experience is not what happens to you. It is what you do with what happens to you." - Aldous Huxley
Last edited by Zamorak at Jul 11, 2010,
#3
Quote by Zamorak
I'm very wary of variable output supplies like that when using pedals, unless you fix the Vadj on the reg chips for output to be constantly at 9v, I don't know how it decides how much to put out and I don't wanna even think about blowing my pedals cause of that.


The way it's done is actually quite simple. For having it fixed at a voltage, you simply add 2 resistors across the regulator(1 resistor between output and reference pin, 1 resistor between the reference pin and the ground). It acts as a basic voltage divider. Say you have 0v at the reference pin, output will be at max(30v). 1v-> 29v output, etc. To make it adjustable, you simply replace the resistors with a pot.

Either way, the best is to use a pot and fix the output with a voltmeter(no charges). After adding a charge, the voltage can only drop, so you don't have to worry about voltage being too high. In the end you can always just fix the voltage once more so it's pure 9v, once all the pedals are plugged.

Either way, I think the supplies I have could be improved with a bridge rectifier per output/regulator. Right now I could get 4x outputs, with 1 bridge per 2 outs. Each output having a max current of 1A. I might aswell just make my custom boards, due to the simplicity of a regulator circuit.

Anyhow thanks for the answers.
Quote by MH400
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You have 2 options.

1. Tits.
2. GTFO.

Last edited by Spike6sic6 at Jul 11, 2010,
#4
NO.

You cannot switch polarity on a daisy chain. You need isolated outputs to pull that off.

In terms of noise ,it depends on what you are running. Some pedals just like isolated outputs, and will complain if their chained. I had lots of noise problems before I switched to an isolated power supply. Then again, I know a lot of people that run some pretty hefty boards off of 1 spots..so it really depends on your specific case.
#5
You can switch the polarities on a daisy chain, you just make sure each plug is right. The only time you get into trouble is if you have a weird pedal that uses a positive internal ground. That has nothing to do with how the plug is wired. You just have to make sure it's right at the pedal's socket.
Daisy chaining will cause noise if you draw too much current for the supply to keep up with but otherwise it shouldn't matter - just make sure your polarity and current draw is ok and you're right to go.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
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#6
Yeah I'm using a separate bridge rectifier with a a bunch of smoothing caps and resistors for each output in the power supply design I'm making, that seems to be the way to go.

Oh and switching polarities is as simple as a wire flip and resoldering, it's not that difficult Denied.
"Experience is not what happens to you. It is what you do with what happens to you." - Aldous Huxley
#7
I just have one thing to say to you Zamarok - LM317T
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#8
Ooo. 80dB ripple protection. Thanks! I don't know how I overlooked these before.
"Experience is not what happens to you. It is what you do with what happens to you." - Aldous Huxley