clean power struggle

[El Heisenberg]

I built a 9v power supply some months ago. I;ve been using it, and with a noise gate its fine, but when I have a few gainy pedals on there's big hum. The noise gate helps this too, but I just wanna get rid of the hum in the first place.

I have 100uf or 220uf caps across + and - in all my pedals. I didn't put one in a tube screamer i built recently. I built it just before I started messing around to try and cure the hum. I disconnected the tube screamers power input and the hum went down (while the TS was off). So i figured putting a 220uf cap in it would solve it. It made the hum louder (even when off). When turned on, the hum just seems amplified by the circuit, but when off, it's still there, unless power is disconnected or not in the chain but still connected to power.

I dunno if the problem is the filtering caps i'm putting in or what. Because4 in amps I've built, filter caps have been the cause of noise for me when placed int he wrong places. Or maybe my power supply just isn't as clean as I could get it. Or maybe it is and I just gotta live with this???

On GGG.com there's a power supply schematic that's supposed to be super clean. It looks jsut like the one I built from Tonepad, except it runs on 24v power and the resistors are fixed and not trim pots. Does all this stuff have to be exact to get rid of the hum? I wanna build another power supply.

[Cliff Schecht]

Sounds like a ground loop problem. The best way to avoid this is to only power ground the first pedal in your chain, all of the other pedals can get their power ground off of the sleeve of the input/output jacks.

[petemoore]

http://geofex.com/Article_Folders/Power-supplies/powersup.htm

 Also see GEO Spyder power supply article.
 Regulated [makes the DC ~ripple free] floating [no ground connection] supplies, supply 'pure' DC and since they're not connected to ground, no chance of ground loops.
  Is the capacitor which increases hum polarized correctly ?

[El Heisenberg]

petemoore, yes it is of course. heh

Cliff, wouldn't that reduce the versatility of my pedals? Oh well, I guess I could always just switch it around. I'll try this.....on al the pedals on my freakin board eeeeaaaaah! thankss hope this works.

[El Heisenberg]

oh wait, petemoore you mean it's NOT that ground loop problem?

[Paul Marossy]

You might have hum coming from your guitar which you normally can't hear. High gain pedals will find that hum and really magnify it. If you have enough EMI going on around you, I have found that even humbucker pickups can pick up a little noise. In my room where I practice, I have at least eight wall warts and a computer with an old CRT monitor all between three and six feet away. My guitars are all well shielded with good humbucking pickups and they all pick up a little hum with a medium gain pedal. A super high gain pedal makes it really pop out.

[StereoKills]

but when I have a few gainy pedals on there's big hum.

I would agree with Paul here. Dirt boxes really amplify any guitar hum, even when it's not noticeable otherwise. I have the same problem sometimes, depending on what electrical stuff I have around me.

[petemoore]

  " You  Hear  Hum? ".
  So do I...and it could be seen on a scope, or your senses can help you find the source of it:
  Turn the guitar so the signal path is grounded...quieter ? then the guitar injects noise.
  Cables too, if you have real-good [which is hard to tell without a scope or another known real-good cable to compare noises with] cable it can pretty much be eliminated as a source of noise that can be improved when worked with.
  There are many points of input for noise:
  Power supplies [anything with a power supply...how good is it ? hopefully none better, kind of like cables but...active and more expensive to make really good. If there's a battery handy which can replace a power supply, the battery makes an excellent 'comparator' by which the finest power supplies can be compared to noise-wise, as close to perfect DC as you can find.
  Antenna, you have one or more in your guitar, anything 'wire' is basically an antenna, if there's not much RF or EMI or what have it getting in there, shielding is of no purpose, otherwise the antenna's may benifit from being bombarded with 'air signals' by adding a grounded shield, shielding may have opposite effect too though.
  Resistor noise, active component noise, once you get all the other noises out of the way, you probably won't notice these sources of noise, or they won't bother you.
 

[El Heisenberg]

ugh so it could be a million things. Back when I had something like 7 pedals all on batteries I didn't have to deal with hum. Just hiss from my high gain pedals. Big Muff introduced a tiny bit of hum. Now I've got eleven pedals daisy chained on my board, with 2 pedals running on batteries: orange squeezer and rangemaster because theyre at the start of my chain and put alot of noise in. The hum really starts when I turn on the RAT or my Big Muff.

My noise gate is the 6th pedal, after my Vox wah. I had to put it there to get my board to function because if it's at the beggining, too much noise gets amplified.

I dunno what to do. It could be any number of things eh?? When I used batteries I didn't have this problem, tho when I used wall wart I had this problem x10. Even when the pedals weren't on, and just plugged in I got HUGE hum. I got this with the One Spot worst. When i built thids power supply that problem went away, but there was still hum when enough pedals were on. Drives me crazy when my buddy comes over and we play Metallica and I gotta turn him up loud enough to play over my drums and the bigg muffs hum causes all sortsa feedback through the mics. It's got soo much bass it's rediculous. He's gotta switch it off when not playing it. This sin't how it should be! GRAAgh!

[JKowalski]

Sounds like a ground loop problem. The best way to avoid this is to only power ground the first pedal in your chain, all of the other pedals can get their power ground off of the sleeve of the input/output jacks.

It would be a good idea to have a ground lift switch by the power jack of all your pedals, now that I think of it. That would save the versatility, and eliminate the hum.

[El Heisenberg]

Sounds like a ground loop problem. The best way to avoid this is to only power ground the first pedal in your chain, all of the other pedals can get their power ground off of the sleeve of the input/output jacks.

It would be a good idea to have a ground lift switch by the power jack of all your pedals, now that I think of it. That would save the versatility, and eliminate the hum.

(!!!!) really??? Do you think it'll help me? I already have SPDT switches next to the power jacks of most of my pedals. They're left over from when they were battery powered. I could just convert em to ground lift switches.....um.....

What do you mean by ground lift switch? Lifting the ground off of the power jack and leaving the ones on the guitar jack rings?? I have 100uf caps across all my pedals power jacks. They're mounted right on the jacks now. It was my first attempt to remedy this.

I dunno much of anything but that sounds weird to just power ground the first pedal. Crazy if it works, but I'll do it!

[El Heisenberg]

I was just under the impression that the hum was comming from the power supply itself since I built ita while ago when I knew less about good layout. Or maybe from the supply because of other things I have plugged in around me. But it doesn't come from any of my guitars that's for sure. And unless there are ways that the cable might be compounding the problem, i don't think the cables are the culprit. When I was on battery power, there was no hum at all. A TINY bit of hum with the big muff, but only a tiny bit even with other pedals on. All I had to deal with was hiss and the noise gate fixed that up good. But every time I've tried to power the set up through the mains I've gotten some sorta hum. With this supply it's the most quiet, but it's still there, and is unacceptable at high playing volumes with my big muff.

I'm gunnna try a new power supply soon. But before that I'll try the ground lift switch. But I'd have to do it to all of them before I know for sure if it's working eh??

[petemoore]

  Say you're floating in outer space, and you have a wire in your hand.
  The wire and you are at some voltage potential, but there's really no reference around to compare it to, so you figure that's 0.0Volts.
  As far as you can tell or measure, both ends of the wire are exactly the same voltage, of course they're not, but I think that'd be OT for now.
  You happen to have a battery though, and by connecting the wire across the +/- you have a voltage difference across the wire + a lot of current [fairly short wire.
  That of course is 'electricity' but better stated literally as having created an electromagnetic force.
  You also happen to have more spare batteries, one is in a DMM. Setting the meter to voltage, using the battery to supply a reference voltage by which to compare to the other voltage [the wired battery], measureing it puts a tiny load, this too of course could be measured [but you didn't bring your scope or spectrometer].
  So...ground moved around, go up the wire a bit and notice 0.0v isn't so there, a voltage is measured.
  Connect the guitar to the amp and the shield carries the Gnd.
  Connect the guitar through a buncha boxes with batteries, the shield carries the ground, the batteries are like floating in space, not connected to any grounds anywhere, just a 9v potential there.
  Now put a wire with current going through it to all the boxes, in addition to the shielded wire connected to all the boxes...and hear or see [scope?] a voltage [AC hash] across these two wires.
  Two antenna's work better than one it seems, the shielded wire alone seems able to carry the junk it encounters and still mainly just connect the guitar and amp Grounds, the pickups otoh, well, that's why they're called pickups, they are capable of picking up wide frequency band of signals, some are right in the guitar frequency range too, others well outside.
  Transformer coils are wires floating where they go, having some unknown voltage on them until you assign [connect] it to some voltage.
  Gnd. is a convenient thing to connect to, that's why everything is basically connected to ground in some way, a conductive rod stuck deep in the ground or some suitable alternative like a waterpipe, a thick wire secured with wire clamp.
  As soon as you run a wire and put a load on it the ground could move.
  Floating the grounds...then assign your floating voltage as needed, make a bunch of them [spyder], until you connect that potential to something it is unconnected, floating. Sweet.
  Workarounds include: try this, try that, keep your batteries in your hat.
  I worried that it was the other noise that got into no ground loops before building power supplies and using them. Soon, using the floating DC of 9v from various sources such as power supplies and batteries, I realized that the ground is assigned at the pedal, not here --- through a wire.
  Sometimes it's not needed, I've since almost forgotten about that kind of noise, fortunately I have a VDLPPII and Spyder there to remind me of what a moving AC voltage sounds like when referenced to a solid potential.
  Another way of course is to use balanced lines, a 3rd wire like a mic cable has to carry ground separately from signal, excellent choice for long cable runs.
  The signal potential requires of course the other two wires to carry it, and therefore it is floating, doesn't use ground as one of the signal wires like guitar does. 

[Paul Marossy]

The ground lift switch would be on the signal ground, not the ground at your DC jack. If you break that ground connection at your DC jack, your circuit won't get any power.

[El Heisenberg]

The ground lift switch would be on the signal ground, not the ground at your DC jack. If you break that ground connection at your DC jack, your circuit won't get any power.

Ah, but I thought since the first pedal has the ground connection at the jack, and that circuits ground is connected to signal ground, then if all the signal grounds are connected to every circuit that the pedals would all still get power.


So lift the ground off both signal paths?? so the ground is only supplied through the power jack?? Or lift the ground from the power jack so the ground comes through the signal jacks?

[merlinb]

I built a 9v power supply some months ago.

How are you regulating the voltage (schem) and what's your layout look like?

[Paul Marossy]

I built a 9v power supply some months ago.

How are you regulating the voltage (schem) and what's your layout look like?

Yeah, that would help.

My pedalboard has a well filtered LM317 voltage regulator set at 9.5V, which is what a new 9V battery will typically measure. I can plug any crappy wall wart into it and no worries about hum/buzzing.

There is a difference between hum (60 cycle) that you guitar pickups can amplify and buzz (120 cycle) which is what you get with poorly rectified wall warts and such. It's kind of hard to hear the difference between the two, but if it's more of a buzz, then it's typically your power supply. That is because there is too much ripple in the power supply after rectification. Better filtering can make that go away.

[El Heisenberg]

My noise is sort of a hum. Not really a buzz.

Here ya go: this is what I built. Just a plain regulated supply. I think I'm gunna build another one with a 7809 regulator soon.


http://www.tonepad.com/getFileInfo.asp?id=111


I did it on some cardboard cos I couldn't fit the IC through any of the holes. Also, might have been out of perf board.

[El Heisenberg]

I don't understand tho, if it's noise being amplified by my guitar, why doesn't it occur when I use batteries???

[El Heisenberg]

Hey, it is sort of a buzz too. I think it's both. My noise gate is before my big muff but after a bunch of other pedals. With the noise gate on and big muff on there's a buzz. Turn the noise gate off, there's hum amplified and then buzz.  


I'd like to try the ground lift switch. I'm just not sure which way to do it.