Effects loop hum

[bassman515]

Hello,

I have a pretty bad hum when i am running my effects loop. When i put one of these in the loop

http://store.fplstore.com/hs-hem-331.html

it goes away...my question is, will this affect my tone at all?

Thanks!
Jeremy

[DavidRavenMoon]

It shouldn't effect your tone.

Are some of your effects AC powered? If so, do they have a grounded AC plug on them? You can try lifting the ground on that effect using one of those 3 to 2 pin outlet adapters. None of them should be connected to ground if their jacks are also grounded to their chassis. That's where the ground loop comes from. Your amp is already grounded, so you don't need any of the effects to also be grounded. This is why DI's have ground lift switches.

Another option is to make patch cords with the ground only connected on one end for use between the amp's effects loop and the effects.

Both of these tricks can prevent ground loops and save a bunch of money!

[mozarwasagenius]

Originally Posted by bassman515

Hello,

I have a pretty bad hum when i am running my effects loop. When i put one of these in the loop

http://store.fplstore.com/hs-hem-331.html

it goes away...my question is, will this affect my tone at all?

Thanks!
Jeremy

It appears to be transformer based. Theoretically it shouldn't affect the tone, but audiophile transformers (ala Jensen, Cinemag, etc) are expensive. If they used a good transformer it should work fine. If they used a cheapy then you may lose highs and bass. Based on the price of the unit they likely used a good transformer.

Transformers imho are the best way to eliminate ground loops, which is why I generally prefer passive direct boxes over their active counterparts. Another way is to use only batteries for your effects, but this is a pain.

Let us know how things work out.

[ToneRanger]

I prefer to get rid of ground loops by careful attention to wiring (as David suggests) rather than by adding gadgets.
If you have multiple devices in a rack you may need to insulate them from each other - there are plastic washers designed for this.

[mozarwasagenius]

Originally Posted by ToneRanger

I prefer to get rid of ground loops by careful attention to wiring (as David suggests) rather than by adding gadgets.
If you have multiple devices in a rack you may need to insulate them from each other - there are plastic washers designed for this.

Good point. However, I always find at the end of the day there is a certain amount of hum when connecting to another piece of equipment (ie. a PA). In those situations I still say a good transformer has given me the best results. Your mileage may vary.

[PilbaraBass]

Originally Posted by bassman515

Hello,

I have a pretty bad hum when i am running my effects loop. When i put one of these in the loop

http://store.fplstore.com/hs-hem-331.html

it goes away...my question is, will this affect my tone at all?

Thanks!
Jeremy

It shouldn't affect your tone...what's the specs on the unit?

BTW...I recently made something just like that for about $25...it is really nothing more than an audio transformer...

You can go 5-star and use a Jensen or Lundahl transformer...I found a unit here in australia that's $18 AU and personally, I cannot hear the difference between the unit installed and not installed.

BTW...sometimes you're just at the mercy of the power quality that the venue provides and there's not a lot you can do about it...for instance, your mixing board may be on a different circuit to your stage or you may have stage lights thrown into the mix (dimmer packs are AWEFUL!)

every band should have a few hum eliminating audio transformer boxes available to help out when the buzzing begins to get out of hand.

[PilbaraBass]

Originally Posted by DavidRavenMoon

It shouldn't effect your tone.

Are some of your effects AC powered? If so, do they have a grounded AC plug on them? You can try lifting the ground on that effect using one of those 3 to 2 pin outlet adapters. None of them should be connected to ground if their jacks are also grounded to their chassis. That's where the ground loop comes from. Your amp is already grounded, so you don't need any of the effects to also be grounded. This is why DI's have ground lift switches.

Another option is to make patch cords with the ground only connected on one end for use between the amp's effects loop and the effects.

Both of these tricks can prevent ground loops and save a bunch of money!

un-balanced patch cords won't work without a ground connection...definitely a good idea to lift the ground for 3-pin XLR...but you can't make a circuit on an unbalanced with one conductor.
On a true effects "loop" to and from your amp, however, you can use an ungrounded connector because the ground is already connected on the "send" side and therefore the circuit will be completed on the "return" side...IMO, however, this won't do a lot to really eliminate a hum problem.


and the ground lift switch on the DI is valid

however...my problem was thus

BASS ==> ZOOM (DI out XLR) ===> House system
ZOOM (line out, unbalanced) ==> Amplifier

The amplifier's ground was putting noise back into the zoom and because nowhere along the balanced chain was there any transformer isolation (not in the zoom, not in the mixing board), there was a ground loop happening...unplug the amp, hum goes away....plug in the amp, hum returns...doesn't matter if the amp was on or off...didn't matter if the Zoom's ground lift was lifted or not...

what I did...

Zoom (line out, unbalanced) ===> Isolation Transformer ==> Amplifier

NOW the amplifier is galvanically isolated from the zoom and house system and no ground loop is possible...hum eliminated...

I'm in the same school as Mozarwasagenius... all bands should have a few transformer isolators lying around for those difficult times.

[DavidRavenMoon]

Originally Posted by PilbaraBass

un-balanced patch cords won't work without a ground connection...definitely a good idea to lift the ground for 3-pin XLR...but you can't make a circuit on an unbalanced with one conductor.
On a true effects "loop" to and from your amp, however, you can use an ungrounded connector because the ground is already connected on the "send" side and therefore the circuit will be completed on the "return" side...IMO, however, this won't do a lot to really eliminate a hum problem.

Right.... since he said it was in his effects loop, I suggested the patch cord with one side grounded. I have used this in situations where running an unbalanced shielded cable between two pieces of audio gear created a ground loop, and eliminating the ground at one side fixed the hum problem.

But I'm still quite sure the issue is that at least one effect is AC powered, and has a 3 pin grounded AC plug.

This is your classic ground loop situation, where the amp is grounded, and an effect is grounded and there is a difference in their potential, so we then have current flowing to the lower potential, and there's your ground loop and hum.

Just lift all the chassis grounded from any AC powered gear, leaving only the amp to establish ground, and the hum should go away.

[mozarwasagenius]

Originally Posted by PilbaraBass

un-balanced patch cords won't work without a ground connection...definitely a good idea to lift the ground for 3-pin XLR...but you can't make a circuit on an unbalanced with one conductor.
On a true effects "loop" to and from your amp, however, you can use an ungrounded connector because the ground is already connected on the "send" side and therefore the circuit will be completed on the "return" side...IMO, however, this won't do a lot to really eliminate a hum problem.


and the ground lift switch on the DI is valid

however...my problem was thus

BASS ==> ZOOM (DI out XLR) ===> House system
ZOOM (line out, unbalanced) ==> Amplifier

The amplifier's ground was putting noise back into the zoom and because nowhere along the balanced chain was there any transformer isolation (not in the zoom, not in the mixing board), there was a ground loop happening...unplug the amp, hum goes away....plug in the amp, hum returns...doesn't matter if the amp was on or off...didn't matter if the Zoom's ground lift was lifted or not...

what I did...

Zoom (line out, unbalanced) ===> Isolation Transformer ==> Amplifier

NOW the amplifier is galvanically isolated from the zoom and house system and no ground loop is possible...hum eliminated...

I'm in the same school as Mozarwasagenius... all bands should have a few transformer isolators lying around for those difficult times.

somebody agreed with me!

[DavidRavenMoon]

Originally Posted by PilbaraBass

I'm in the same school as Mozarwasagenius... all bands should have a few transformer isolators lying around for those difficult times.

I'm going to agree here also!

At the very least it would be the safest thing for each musician to be isolated from the main PA's ground, and have each member's amp grounded correctly.

Nothing sucks more than getting 80+ Volts going between your bass strings and the mic, with you being the conductor! I know this personally.

BTW, I picked that voltage because that's what I measured between my bass and a mic once after I got a good jolt at rehearsal in my basement, of all places!

[PilbaraBass]

Originally Posted by DavidRavenMoon

I'm going to agree here also!

At the very least it would be the safest thing for each musician to be isolated from the main PA's ground, and have each member's amp grounded correctly.

Nothing sucks more than getting 80+ Volts going between your bass strings and the mic, with you being the conductor! I know this personally.

BTW, I picked that voltage because that's what I measured between my bass and a mic once after I got a good jolt at rehearsal in my basement, of all places!

80VAC can KILL! OUCH!

another important tool for those who play on the road (I don't, just two or three venues) is one of those devices that checks to see if the power is correct...you know, it checks to see if the hot is on the right pin, the neutral is on the right pin, and that the earth is connected...

unfortunately, your safety often depends on the work of others, and it's not a bad idea (a very good one, in fact) to inspect that work.

[DavidRavenMoon]

A real cheap and effective tool is one of those neon bulb outlet testers.

Hold one end on your strings, and the other on the mic, and if it lights up, so will you!

[improvpwnd]

Originally Posted by DavidRavenMoon

Another option is to make patch cords with the ground only connected on one end for use between the amp's effects loop and the effects.

I just did this and it fixed a hum in my effects loop. I am not too keen on electrical engineering, so I wonder why I had to keep one end of my cable connected to my shield. I mean, if that connection isn't going anywhere could I have just not connected either of the jacks to the shield?

While I was typing this I realized the only reason I am asking this is probably because I made my cable and if I was to have bought one it would be less work to just disconnect one end...right?

[DavidRavenMoon]

Originally Posted by improvpwnd

I just did this and it fixed a hum in my effects loop. I am not too keen on electrical engineering, so I wonder why I had to keep one end of my cable connected to my shield. I mean, if that connection isn't going anywhere could I have just not connected either of the jacks to the shield?

If the shield isn't grounded, it won't be a shield! By grounding one end you keep the wire shielded, but you aren't connecting the ground from one piece of gear to the other. If you don't have the shield grounded you will pick up a lot of hum.

Originally Posted by improvpwnd

While I was typing this I realized the only reason I am asking this is probably because I made my cable and if I was to have bought one it would be less work to just disconnect one end...right?

If you can find a cable you can do that too, than it might be less work, but you still have to do some surgery on one end.

Obviously you can't do it with path cables with molded plugs.

[niftydog]

Originally Posted by DavidRavenMoon

Are some of your effects AC powered? If so, do they have a grounded AC plug on them? You can try lifting the ground on that effect using one of those 3 to 2 pin outlet adapters.

SAFETY WARNING! Disconnecting an AC earth increases the potential for a deadly accident! Your guitar strings are grounded via the connection to all your effects pedals. If the connection to an earth point is compromised and a fault develops in an AC powered device, then you may have a situation where your guitar strings become live with mains voltage! I STRONGLY recommend that you DO NOT disconnect ANY mains earth anywhere, ever!

Those "3 to 2 pin outlet adapters" are illegal in Australia because of the danger they present!

A loop is formed when two different mains outlet earth points are connected via a signal path ground. You must make the distinction between a mains outlet earth point (safety ground) and a signal ground. Never attempt to break a ground loop by disconnecting a safety ground! Break the loop in the signal path, not in the mains power path!

Breaking a ground loop is easy - just pick a signal cable that is part of the connection between the two mains earth points and disconnect the shield. The safety grounds remain intact, but there is no longer a secondary connection between them. This should not upset your signal as the pedals are still referenced to the same point ie; earth.

[JanusZarate]

Hey... has anyone stopped to ask what bassman515 is even using?

Realistically, we can't help you much if all we know is that your effects loop hums when used.

[bongomania]

My GF hums when used... maybe I should try lifting one of her pins...

[niftydog]

Take this simple scenario

                                              AC pedal
     .-----------.      < signal ground >      .----.
     |    AMP    |o---------------------------o|    |o-------o guitar
     '-----------'                             |    |
          |                                    |    |
         --- < safety ground                   '----'
         ///                                     |
                                                --- < safety ground
                                                ///

The ground loop forms because the two safety grounds are connected together back at the switch board. While you could break the loop by disconnecting it anywhere, the safest place to disconnect it is the signal ground path. The two safety grounds remain intact and your guitar remains connected to one of them.

[niftydog]

Originally Posted by bongomania

My GF hums when used... maybe I should try lifting one of her pins...

I'd like to see pics of that mod, Bongo!

[dbcandle]

I've used one of these from time-to-time: http://www.ebtechaudio.com/he-2des.html