Help me locate some power supplies for pedals

[vroom]

Hey everyone.

I have two pedals at this point. One in front of the amp, and one in the effects loop. Because they aren't in the same circuit, using one power supply with a daisy chain could induce ground loop noise.

I'm going to need a separate power supply for each one (wall wart, power brick, transformer, adapter, whichever name you prefer). I don't feel like shelling out $20 a piece at Radio Shack.

If anyone could help me locate a good place to get what I need, that would be great. One pedal calls specifically for a "9V, >100mA, tip-negative" supply and the other requires a "9V, 500mA-1A" supply. I don't know if regulated is required or whatever else isn't mentioned above.

Many thanks in advance.

[Ripper]

I use the Boss adaptor. Lets face it, we spend alot of money on our pedals...Im only going to use what they suggest. If I fry my pedal because of Boss, they will replace it. Radio Shack....ummm no.

[vroom]

Well, one of mine is from eBay and the other was bought from a different forum member. So I'm not in warranty territory I fear.

Besides, am I wrong in my thinking that many people use any old wall wart with matching values? I'm basically looking to buy a couple "old wall warts" since I have none lying around.

[sumgai]

vroom,

Other people may buy and use any old wall wart, but I wouldn't do that, there's too big a chance that they'd arrive broken, or that they'll go TU about 10 minutes after you first plug 'em in. Buy new ones instead, the small difference in price will be what allows you to sleep at night, knowing that the units will work for many months to come.

Old adage: If you don't spend the money on good quality the first time, you're gonna spend it anyway the second time, when you have to replace the crap. 'Struth.

HTH


sumgai

[vroom]

Next question, assuming I have to buy a new, approved supply for each one. Should I buy the factory power supplies for each (I don't think there is a factory one for the iSP Decimator), or prepare for the future and get two One Spots (one for in front of the amp, one for the effects loop)?

[Mini-Strat_Maine]

vroom said:

Next question, assuming I have to buy a new, approved supply for each one. Should I buy the factory power supplies for each (I don't think there is a factory one for the iSP Decimator), or prepare for the future and get two One Spots (one for in front of the amp, one for the effects loop)?

Unless you've got one that is oddball voltage/amp draw/polarity, I'd suggest going with the 1Spots. (They have a convertor plug that changes the polarity, but you may not wanna "go there" in an effects chain.)
See their compatibility chart at www.visualsound.net/docs/1%20SPOT%20Compatibility%20Chart.pdf. They have a huge list of what will (or won't) work off a 1Spot, and which convertor plug (if any) would be needed. I saw some stuff listed that I've never heard of before, but not the Decimator.
And up to twenty pedals per 1Spot, just by adding Multi-Plug 5 Cables? Way cheaper in the long run than individual power supplies.

[RandomHero]

1Spot has a list of pedals that they're compatible with on their website. Check it out, 'cause 1Spots are awesome supplies with a lot of flexibility. I've seen some pretty shabby manuf. ones. (I secretly think they say "Only use Ibanez model BlahdyBlah" in the manual to scare you into buying more of their crap anyway.)

[vroom]

The iSP Decimator is an oddball with tip negative polarity. I'm not sure if 1-Spot's Yamaha Reverse Polarity adapter would work with it or not.

Pricing out two 1-Spots has reminded me how much I could save by getting two cheap wallwarts. Especially since I don't plan to add any more pedals for a while.

Is it guaranteed that I would get ground loop noise if I put both pedals on the same 1-Spot? Keep in mind that one is in front of the amp and one is in the effects loop.

[Mini-Strat_Maine]

vroom said:

The iSP Decimator is an oddball with tip negative polarity. I'm not sure if 1-Spot's Yamaha Reverse Polarity adapter would work with it or not.

Dunno about that, I just know that you should be careful of mixing positive and negative pedals in the same chain. They could each have their proper power supply, but there's another issue of grounding going on. Bad mojo of some kind.
Andreas in Sweden offers this commentary: www.stinkfoot.se/andreas/diy/power/pnppower.htm

Is it guaranteed that I would get ground loop noise if I put both pedals on the same 1-Spot? Keep in mind that one is in front of the amp and one is in the effects loop.

Again, someone else will have more (and better) info about that, but meanwhile, here's a little more from Andreas. Includes more about "negative tip" and "positive tip" plugs. www.stinkfoot.se/andreas/diy/power/psu.htm

Don't do a "smoke test" on your gear!

[wolf]

I recommend the Godlyke Power Supply:
www.musiciansfriend.com/product/Guitar/Effects?sku=155051
Yes, it costs $40 but it can power up to 20 effects pedals (if they require 9 volts).
It is transformerless and hum free. I own one and it is well worth it.
Yes I power about 5 effects with this and I have no ground loop hum or whatever.

[sumgai]

vroom,

I've avoided jumping in here for awhile, I wanted to cogitate on that ground loop thing. I think I've got it figured out though.

Most stompboxes isolate their power supply inputs from the signal chain. This lets them use either positive or negative on the shell (or sleeve) with no design problems in relation to "ground". For them, ground is strictly a signal path consideration.

Also on the topic of power...... You don't need to use a 'factory approved' supply, but whatever you use, it should be clearly marked as to what it puts out. Even if you can measure the output with your meter, if the maker didn't take the time (and obey the laws, btw) to mark his unit, then what does that tell you about his faith in his own product? Generic or Over-Hyped (1spot, Godlyke, etc.), it won't matter, so long as you aren't buying a "surprise package".

So let's examine your signal paths. Obviously, the unit connected to the Line Out/Line In is gonna have a ground path, it's the nature of the game (unless you use XLR the whole way). But that unit is self contained, and no other signals are entering or leaving that box, so there should be no "loop", right?

Your "pre" amplifier box is also of the same variety, it is single-ended in that no other signals than your guitar go into it, and the only output is to your amp. I'd say that unless the two boxes touch each other (making possible electrical contact), then the chances of a ground loop are pretty slim. Even then, the signals are fairly isolated from each other, but yes, there is a 0.0000001 percent chance of a ground loop, I have to admit. The obvious answer to that would be, don't let them touch.

HTH!


sumgai

[JohnH]

Ive been thinking on these things too, in relation to my thread next-door.

If you use a single supply for both:

Most transformer based wall-wart type power supplies dont relate the + and - dc output to mains ground. (Im not so sure about the modern type of switching types of power supply.)

Hence there seems minimal chance of the worst type of ground loop, being one that has two elements grounded back to the wall socket, and which is vulnerable to signals generated by the AC mains supply.

However, this arrangement would naturally connect the negative and positive supplies of the two effects units to each other, via the common power supply. Assuming that they both use the '-' power rail for ground, then there is still a loop within the amplifier and effects, since '-' rails in both effects are grounded via their signal wires to the amp, and also they are connected to each other via the common power supply. So I'm thinkingthere is some risk with a single supply, and seperate ones would be better.

John

[sumgai]

John,

Your assumptions would be correct, if the negative power rail of each device were definitely part of the signal path. I can't say with any assurity that this doesn't happen in all boxes ever manufactured. The odds are, it will happen, given the number of boxes ever manufactured with a dizzying array of possible wiring options.

However, the average box available today (and are you considering this in your own soon-to-be-dropped-on-the-world toy?) isolates completely the power and signal paths. This is done mostly to meet safety requirements in various countries, but it does complicate the designer's life, somewhat.

At that point, even if the two units touched, they should not be conducting anything that would be reflected back into the power supply. Unless one or both of them is an older unit, wired to pre-safety era design standards. Then your scenario would operate to maximum disadvantage of the user.

I suppose the only way to be really sure is to try it one way or the other. vroom, if you have only one supply (assuming that both units have the same plug polarity wiring), then you can try it out, listening for objectionable hum. If everything sounds good, you're golden. If not, try using separate supplies, and see what happens. Of course, it shouldn't need to be said (but I'll say it anyway), if you have opposing polarity wiring schemes, then you'll have to use separate wall warts. (Or an expensive supply that can handle both polarities at once, on two different output cables.)


sumgai

[RandomHero]

Or buy a $15 Furman power strip to plug -ALL- your sensitive audio equipment into and eliminate AC hum from your life. =D

[mike]

Since you don't have that many pedals, yet, and no power supplies you may want to consider buying a "Godlyke" or "Onespot" power supply now. Both are about $30 at Musician's Friend and come with a number of adaptors.

Also, "Boss" SINGLE PEDAL power supplies will power Digitech SINGLE PEDALS fine.

There is noise from the power units however, specially when you add more pedals to the line, specially pedals which add a lot of gain. You don't hear it while your playing. I use a Boss Noise surpresser with up to 3 pedals total, and on with my high-gain pedal I put it in line first using a battery and that stops the noise.

I've also found that extending the power supply cord and extending the unit as far away from the pedal board itself keeps the noise down.