Hum problem.

[squire5]

I'm using a Zoom 506 along with a Behringer BDI 21.Problem is,using them separately ie one at a time,they're both fine.However,when run together,using a daisy - chain from the wall wart,a loud hum appears.The BDI has a ground lift switch but this has no effect.The annoying thing is that even with the amp volume turned right down,the hum is still there.It's not a buzz,but a HUMMMMM,and the frequency is almost exactly the same as the open 'G' string.However,it does NOT increase in volume when I turn the amp up.Any thoughts,guys and gals?

[Kev]

i had this exact problem with my zoom 506, whenever i had powered from a daisy chain linked with other, especially gain, pedals, there was a loud hum. however if i powered it off a seperate supply, the hum went, so thats what i did, not an ideal solution

id be interested to hear the answer to this one

Edited June 21, 2008 by BassManKev

[obbm]

I had a similar problem with some pedals a few years ago. The problem is that some 9-volt power supplies have a well regulated output and some don't. Some pedals have on-board regulation and some don't. If you use a badly regulated psu with a badly regulated pedal you get hum.

You don't say which Wall-wart you are using.

[Kev]

i tried with several power supplies including well known ones so for me it wasnt the power supply causing the problem, must be the pedal

[Wren and Cuff]

Maybe its the reg/unreg problem as obbm says. But I have a feeling its much simpler than that.

#1 rule as you start to collect more pedals: Daisy chains can make your pedals do screwy stuff. With some pedals, people use them on a daisy forever, and never have a problem. But for many, as you mix vintage and new pedals etc. Weird s*&t happens.

Here is my simple answer.
Those two pedals are trying to suck way too much juice from your wallwart. The hum is your power supply saying "please, I have nothing more I can give!! (if I'm right)" Thats why you get the hum with 2 but not 1 pedal. I believe those are both digital pedals??? Correct me if I'm wrong.

Digi pedals use wayyyyy more power than analog. Some wall warts can't handle 2 digi delays daisy chained.

Try using SEPARATE wall warts for each pedal, wallwarts made for music gear, Boss, Dano, etc. Then see if the hum is still there.

good luck,

matt

[Kev]

already said, when i had it the hum didnt happen with two wallwarts, but it did with the zoom 506 and a boss odb-3 for example. with a regulated 1.3A power supply

[Wren and Cuff]

[quote name='BassManKev' post='223905' date='Jun 21 2008, 04:19 PM']already said, when i had it the hum didnt happen with two wallwarts, but it did with the zoom 506 and a boss odb-3 for example. with a regulated 1.3A power supply[/quote]

yes, but you never described how it may happen, as in the pedals just plain trying to pull too much power from the wall-wart.

[quote name='BassManKev' post='223905' date='Jun 21 2008, 04:19 PM']i had this exact problem with my zoom 506, whenever i had powered from a daisy chain linked with other, especially gain, pedals, there was a loud hum. however if i powered it off a seperate supply, the hum went, so thats what i did, not an ideal solution[/quote]

Although possibly the same solution, this could be a totally different problem than what I described.

[squire5]

Very interesting guys.I'm just in from a gig,but I was only able to use the Behringer on its own.Tomorrow what I'm going to do is:Try the set-up using batteries only,to start with.That way I can pinpoint the problem ie pedals or mains supply.The wall wart is only an Ebay special 300Ma unit which I would have thought could handle 2 pedals.I have some other pedals too(compressor,Eq,flanger)which I will bring into the equation.That may pinpoint the power supply,or maybe one particular pedal which may be causing the problem.We shall see!
PS I'll tell you something tho'.That Behringer BDI 21 is pretty darn good!

[squire5]

OK chaps and chapesses,all tests complete

1.With batteries - all fine.No hum at all.
2.With daisy chain only - with 1 pedal,no hum.Any more than 1-Hum.
3.With 2 wall warts,one feeding each pedal - No hum at all.
Conclusion......The 300ma wall wart with daisy chain is not capable of supporting more than 1 pedal at a time.I've sat here for the past hour swapping patch leads and power input leads and even thought that the bass was at fault at one point.Swapping for another soon dispelled that theory.I also noticed that depending on the order of the pedals,hum was more pronounced in certain combinations than in others.
Looks like a more substantial power supply is the answer.

[Kev]

but that doesnt explain how my 1300ma wall wart still made the pedal hum in a daisy chain, maybe it needs an isolated power supply?? like a seperate wall wart or a dc brick or sumit?

[rmorris]

It's a 'ground loop'. Although the supplies are not 'earthed' there is still a loop : the pedals have a 0V (Ground) connection by means of the power connector AND another 0V connection through the cable screens. External fields will generate currents in the loop. 50Hz fields are all around especially from transformers and this will appear in series with the audio signal. The magnitude of the hum depends on the external fields and area of the loop - you could try rearranging your cables to try and minimise - run the dc power and audio cables together - tape / ty-rap them together ?
Some pedal manufacturesrs take steps against it by resistance in the external power 'ground' connection or similar means which reduces the current.
But the 'proper' way is to have isolated supplies for each unit ( or batteries ).

You could try the 'trick' of breaking the screen of a cable at one end and putting a resistor ( around 100ohm is usual ) between the cable screen and the connector. Not too difficult to do if you have decent size rewireable connectors.
Sometimes it works okay, sometimes not.

Do the common multiple output ' dc bricks ' have a common output ground ? - I don't know as I just use seperate supplies.
I know that a USA company produces a transformer to use to give isolated 9V /18V supplies - single primary with multiple isolated secondaries to give the ac voltages necessary.
But I enquired a while ago and they didn't have a 230Vac version.

Now - does anyone in Brighton know how to fix a Worcester Condensing Combi boiler at this time on a Sunday ?
And yes - I've checked the fuses :-)

[rmorris]

forgot to say the other option is to use a simple 1:1 audio transformer between the fx.

eg the Behringer HD400 like I have which has two channels.
But you'd have to be happy that the sound isn't adversely affected ?
Other brands are available as they say.

[BOD2]

[quote name='squire5' post='224123' date='Jun 22 2008, 01:18 PM']OK chaps and chapesses,all tests complete

1.With batteries - all fine.No hum at all.
2.With daisy chain only - with 1 pedal,no hum.Any more than 1-Hum.
3.With 2 wall warts,one feeding each pedal - No hum at all.
Conclusion......The 300ma wall wart with daisy chain is not capable of supporting more than 1 pedal at a time.I've sat here for the past hour swapping patch leads and power input leads and even thought that the bass was at fault at one point.Swapping for another soon dispelled that theory.I also noticed that depending on the order of the pedals,hum was more pronounced in certain combinations than in others.
Looks like a more substantial power supply is the answer.[/quote]

Check the ratings on the pedals themselves. They will usually quote the current (mAmps) required by the pedal. Add the figures together. If the total is more than 300mA then that power supply is definitely not powerful enough.

[squire5]

A modicum of success has been achieved.By using 3 power supplies(1 x 300ma each for the Zoom and BDI 21,and another 500ma with daisy Chain for the other 3 pedals)and by keeping everything apart from each other ie putting the distribution board on the floor,away from the pedals(which were on a desk),hum has been reduced to an agreeable level.It's still there but nowhere near what it was.Using the Radio system as well, further decoupled everything and reduced the hum yet again.I guess I'm sorta happy now.I'll need to put a board together I think,and make it all a bit more permanent.Now,where did I put that bit of 4 x 2..................?
Bod,the rating of the pedals varies about 20 - 40 Ma each,so the 300 Ma wallwart should have been OK.
Thanx for the input guys.

Edited June 22, 2008 by squire5

[BOD2]

Had a quick look at the specs for the Zoom 506 and BDI 21.

The Zoom manuals says it needs a 300 mA power supply. The Behringer manual says it needs 50 mA or greater.

From that (and your experiments) it sounds to me like the Zoom uses a fair proportion of the 300 mAmps from your original power supply and didn't leave enough to fully power the BDI 21.

Can you borrow a 1200 mAmp power supply from anywhere ? It would interesting to see if that would power everything without any humming - it's a pain to have so many power supplies on the go !

Be aware that power supplies can generate humming that can be picked up by guitar pickups and even through guitar leads, under certain circumstances. You'll have no problems with the actual DC power leads that go to the pedals (hum isn't generated on DC leads) but be careful wher you place the power supplies themselves in relation to other equipment in your chain.

[cheddatom]

I have always had problems getting my zoom units to work daisy chained. I'm pretty sure it's just that they need as much current as they say (300MA+), and the standard pedal board supplies are 300 and 500ma. I have seperate psus for my zoom multi, and for my marshall digi delay. The rest of my pedals are all daisy chained from one fiendish psu.

[squire5]

Right Bod.The whole point is to try and do away with all these power supplies.What about the likes of Pedal Power type units for example?They rate at a total of 450 Ma.With the zoom @300,and the other 4 pedals at 30 - 40 each,would one of that type suffice?I'm not tight with money,but the rest of my rig is budget based,so I'm not going to spend big bucks as you've probably already gathered,but I just want something that is compact,and works,and gets rid of the hum!I'm watching a Pedal Power 450 on the Bay at the mo.What do you think?

[Wren and Cuff]

Any of the voodoo labs p supplies (except the older "AC" version) are great. The keyword here is "isolated". The voodoo labs is basically like having a separate wall-wart for each female jack. I'm oversimplifying here, but you get the idea. It also has a switch for the older boss, arion, and others that require 9V/12V or "ACA" adapters. You can power these on a daisy chain with a regular power supply and a 9VDC pedal, but many times you get weird hum issues. The AC switch on each jack solves that.

That is why the voodoo PS's are more expensive. Many of the cheaper look-alike boxes are basically a daisy-chain in a metal housing, some even have a wall-wart to power them!
The voodoo is just a standard grounded plug.

The new ones have some fancy features that I don't need, so I found a used older model (the "2" I think?) on eBay for $125.00. That was a long time ago and I've beat the hell out of it, and it's never failed me.

no, I don't own stock in voodoo labs...

matt

[rmorris]

[quote name='Wren and Cuff' post='228259' date='Jun 27 2008, 07:52 PM']Any of the voodoo labs p supplies (except the older "AC" version) are great. The keyword here is "isolated". The voodoo labs is basically like having a separate wall-wart for each female jack. I'm oversimplifying here, but you get the idea. It also has a switch for the older boss, arion, and others that require 9V/12V or "ACA" adapters. You can power these on a daisy chain with a regular power supply and a 9VDC pedal, but many times you get weird hum issues. The AC switch on each jack solves that.

That is why the voodoo PS's are more expensive. Many of the cheaper look-alike boxes are basically a daisy-chain in a metal housing, some even have a wall-wart to power them!
The voodoo is just a standard grounded plug.

The new ones have some fancy features that I don't need, so I found a used older model (the "2" I think?) on eBay for $125.00. That was a long time ago and I've beat the hell out of it, and it's never failed me.

no, I don't own stock in voodoo labs...

matt[/quote]

yeah - properly isolated supplies should do it - apart from leakage due to the transformer interwinding capacitance but I'm getting fussy now.
( best solutions would have interwinding shield and appropriate mumetal shielding )

The problem with solutions which seem 'okay' is that it'll probably be okay live / rehearsal where there may be bigger problems wrt noise / ground loop anyway but studio / recording etc can expose a problem.

[squire5]

Right,let me get this right.A power supply has to be able to cater for all the pedals being used with it.In my case thats 1@300ma,1@50ma and another 3 @40ma.Thats 470ma altogether.Bearing in mind that I probably wouldn't be using ALL the pedals at the same time,then a 450 Sound Labs unit would suffice(available for around £25 on the Bay)On the other hand,would something in the 1 amp range be better,in order to have some leeway.I've seen a unit which has 10 outputs,at 1 amp,but which says in the blurb that each output is rated at 100ma.See,this is where I'm confused.At 100ma per output,this would be no use for the Zoom,which needs 300ma.But then I think to myself,is it an overall figure of 1 amp,which would be more than adequate for all the pedals.You know,I'm actually starting to confuse myself now.If anyone can make sense of my inane ramblings please tell me is a 1 amp unit good for what I need?

[cheddatom]

I don't fully understand this, but..... I heard that "star grounded" connectors are better than fully isolated, especially for getting rid of ground loops.

I don't know which way it works, but I have a godlyke powerall that I run at least 18 pedals off, and it's noise free!

[rmorris]

[quote name='cheddatom' post='229531' date='Jun 30 2008, 10:27 AM']I don't fully understand this, but..... I heard that "star grounded" connectors are better than fully isolated, especially for getting rid of ground loops.

I don't know which way it works, but I have a godlyke powerall that I run at least 18 pedals off, and it's noise free![/quote]

well 'Star Grounding' applies to the way the whole system is grounded rather than to a type of connector or a way of wiring it.
Basically all Ground / 0V points are taken back to a 'single point' ( which raises the question of how big is a single point ? ) and loops are avoided.
In the worst case scenario with fx / power supplies this is exactly what you [u]don't[/u] have since the grounds are connected via the screens and the power leads.
Some fx have internal impedances etc to break the loop to some extent at least.
The bigger the loop area the worse the effect all else being equal so minimising inter-effect connection length and not having excess length on the power lead will help.
Those solid jack to jack connectors may be useful.

Ideally we'd have well implemented balanced connections but that doesn't happen at pedal level.
Isolated supplies ( a transformer secondary for each unit ) or transformers in the audio path between units are a solution.

On a slightly different note ( B flat ? ) I've noticed that some of the inexpensive 'six in a bag' type short moulded jack to jack cables ( usually in various colours) have poor shielding at the connectors and pick up loads of noise regardless of the power supply arrangement.

Adam Hall do some good quality inexpensive short patchcords with decent quality re-wireable metal - not 'European' Neutrik quality but look roadworthy none the less - I have a couple.

[wizbat]

+1 for the voodoo lab psu and try a palmer line isolation box in line between the two offending items.