Is this a ground loop?????

[akozols]

Hi,

  Just so you know, I did spend some time searching thru previous posts but couldn't find an answer.   I have a 1000ma 9v Boss wallwart that I wired in a bunch of power connectors.  All my effects have the pos on the outside ring(I hate that).  All effects work quietly together( Boss, Danelectro, Morley) until now.  

  I have a Zoom 2020 that uses the same power and same connection.  When I introduce the Zoom into the system, I get a loud hum.  After playing around with some combinations, I found that I only get the hum when the Zoom and Boss  are connected together.  The hum comes in as soon as the power is connected to both EVEN WITHOUT a patch cable between the two.  If I use a separate wallwart for each, the hum goes away.  

  I'm confused because how can it be a ground loop if there is no connection between the two effects(patch cord disconnected).

Thanks,  Al.

[phillip]

I've been looking for one of those 1000mA Boss 9V wall warts...where'd you get yours?

Phillip

[Paul Marossy]

It doesn't sound like a ground loop to me. I think the problem is your Zoom FX unit. I have an older Zoom 9030 half-rack multi-effects unit, and it will hum horribly when I try to use it with a bass guitar. It's pretty noisy in general compared to my ART SGX-2000.

It does seem a little odd to me that you have that problem, those BOSS adapters seem to be pretty decent units, but maybe the Zoom unit doesn't like the shared power supply, for whatever reason. If it were me, I would just use two adapters.

[akozols]

Phillip,  I got the supply with a Boss ME-X.  The ME-X could power 3 addition effects so it needed the power.  

  It's weird that the noise only comes when I power the Zoom and Boss together.  Any other combination works fine.  I guess using two supplies isn't so bad.  I remember that before I learned about electronics, I had a pedalboard with 5 effects and a power strip with an idividual wallwart for each unit.  Then I learned about voltage vs. current and was giddy with excitement.

Al

[jubjub]

'When I introduce the Zoom into the system, I get a loud hum. After playing around with some combinations, I found that I only get the hum when the Zoom and Boss are connected together. The hum comes in as soon as the power is connected to both EVEN WITHOUT a patch cable between the two. If I use a separate wallwart for each, the hum goes away. '


You have'nt mentioned how many units your using or how much current they draw. I find with 1amp supply's that you need to give them some headroom. If I use more than 1/2 an amp you can get all sorts of dramas. Try this. Hook them all up and one by one uncouple the boss units. Start with the delays as they will draw the most power.
I'm also going to go out on a limb here and say that the boss supply could be a bit cleaner for the price they charge. I've seen a couple on the scope, but don't take my word for it.

[akozols]

jubjub,

  I owe you a beer.  As I stated before, I could induce the hum by just hooking up the Zoom and Boss Ds-1.  The Zoom draws 150ma and I think the Boss is only about 50ma.  That's only 200 ma, so I didn't think that was the problem.  

 I assumed that the Boss ps was a good unit since it didn't hum on any other pedal that I have.  We all know what happens when you assume.... :?   I found another Boss ps that was rated at 300ma and quickly soldered in a dual power connector.  Guess what...quietness.  For some reason the 1amp supply has a problem with the Boss and Zoom and the 300ma doesn't.  I did blow the internal fuse inside the 1a suplly a few years ago and replaced the fuse.  It has tons of tape holding it together so it's time for the trash.

Thanks for the replies,

Al

[Paul Marossy]

"I find with 1amp supply's that you need to give them some headroom."

This hasn't been my experience. I have like 12 devices hooked up to my Boss PSA AC adapter via a parallel power cord, and I have never had any problems of any kind.

Just my experience.  

[jubjub]

Glad to help.
My problems were that I used alot of delays which realy draw current. It was fine to start with but I was using the thing 6 nights a week and it would be on for 6 hours straight. Then my tone began to change. Things didn't sound as big. Tried everything else but finaly narrowed it down to supply. I thought that the thing was hot enough to fry an egg on was normal, but apparently not. The quality of your power can make a huge difference to tone. Again this is just my experience, but I had the supply on the scope and as soon as I started to draw more than 600ma from it the voltage began to fluctuate. I'd be interested to hear if anyone else had this problem.

[Paul Marossy]

That's interesting. It really shouldn't do that. Have you also measured the voltage in either case?  Even with 600mA current draw, you should still be getting something that is a little above 9V...

Maybe it is overheating because it's not putting out the amount of current it is rated for? In an overheated state, it could start to do whacky things, I suppose.

[jubjub]

If there's one dodgy supply in a bunch of 20, you can bet I'll be the one walking out of the shop with it. Again, it's just my experience.