Twin & Session - 2 amp hookup- Bad Hum??

[Todd Brown]

Hey guys, I am doing a little experimenting. Since I got both amps I figure I'd try to run them together.

I'm splitting the signal by running out of my Hilton pedal. The 2 amps aren't hooked together in any way, just being fed the signal through the 2 outs on my Hilton.

Problem is I'm getting a loud nasty hum out of both amps. What am I doing wrong? What do I need to do to run these two amps and not get that hum? I shouldn't need a "ground lift" on one of these, do I?

Thanks!

[Jerry Overstreet]

Yes, the hum is caused by the ground loop created when you hook 2 amps together like that.

[James Morehead]

Todd, a simple two prong plug adapter on one of the amps will likely fix you right up.

[Chas. J. Wagner]

Or...if you wanna spend some money...there's the infamous Hum X

[Todd Brown]

Thanks guys!

[James Morehead]

OK. figured that. How do I hook them up with no hum? Possible right?

For reference purposes, how I do it, I use a power strip into the wall, then I plug both amps into the power strip, using a two prong adapter on one of the amp's power chord.

I run two chords from a stereo box like an RV3 or stereo chorus, to each amp's input.

OR if you want, get a small "Y" adapter from Radio Shaack(as pictured). This "Y" works with my Shobud pot pedal(plug it into the "out jack"), since it only has one "out jack". Works with my Twin and Vibrosonic perfect. And ZERO hum.

[Todd Brown]

Thanks, James. Yeah, I didn't see yours and Chas's replies at first.

I'll stop by and get a 2 prong adapter on the way to practice.

Y adapter not needed for the Hilton, right?

I guess it doesn't matter which amp I use the 2 prong adapter on? Just as long as it's on one amp to lift the ground loop?

[James Morehead]

Yes, it doesn't matter which amp you leave grounded. And the "Y" is for us who have the simpler pedals. Enjoy!

[Todd Brown]

Todd, a simple two prong plug adapter on one of the amps will likely fix you right up.

You da man, James. Picked up an adapter at Lowe's for a cost of $.65. Problem solved!! Not a bit of hum.

I think I 'bout melted some faces tonight at practice with Twin and the Session behind me
Lucky for me, I had some earplugs
One hell of a combination, right there!

Thanks to everybody!

[James Morehead]

Cool enough. Glad it's workable for you Todd.

[Lee Baucum]

Lifting the ground on an amplifier just has to be a possible safety issue. The ground is there for a reason.

I prefer to use the Hum X.

[James Morehead]

Leaving a ground loop is the problem, no?

[Lee Baucum]

The ground loop is just an annoyance.

Possible electrocution is the problem!

[James Morehead]

The ground loop is just an annoyance.
Possible electrocution is the problem!

Hummm(no pun intended), never posed a problem as of yet. My understanding, Hum-X is intended for old wiring/magnetic fields in buildings we sometimes have to play gigs at? I'm willing to learn.

[Lee Baucum]

This has been discussed quite a bit in the past.

Do a search of the Forum for ground loop.

Here is one discussion that may be helpful:

Click Here

Brad Sarno and Lynn Oliver make good comments; but, they're all worth reading.

Lee

[Dave Grafe]

Lifting the ground on an amplifier just has to be a possible safety issue

True for a single amp, but with multiple amps it is only necessary for one of them to be grounded to maintain electrical safety.

Ground loops and the hum they induce result from differing resitance of multiple paths to ground. The strings of your guiitar are connected to the shield of your guitar cable, which is connected to the chassis of your amp, and the chassis is connected to the third "safety ground" pin of the electrical plug. When more than one path to ground exists - as with multiple amps connected together by unbalanced cables - and the resistance of these paths varies an electrical potential develops and the infamous "hum" appears. Disconnecting ALL BUT ONE of these paths eliminates the ground loop but maintains the safety of a grounded system, provided of course that the remaining amp ground is secure and the building is properly wired.

[Richard Sinkler]

building is properly wired.

Asking a bit much, aren't we?

[James Morehead]

Dave, That's always been my understanding--you put it in words so well, thankyou.

Lee, I'll check out the link you have provided. Thanx, it always pays to be careful.

There ya go, Todd, some fine info here.

[Lee Baucum]

More information---> Click Here

[Todd Brown]

That's real cute, Lee. What's your point with posting on this thread that's almost two months old, with the same link that Ken put on the other thread about 2 Webb amps? Just to prove you're right? So what Do you not have anything else to do?

I've been wrong before and it won't be the last. But obviously I'm not the only one doing it this way. Did all the guys back in day that ran 2 amps go out and buy a Hum-X? I don't think so! I guess no one could run two amps without being electrocuted to death until Hum-X came along? Huh, I've not had a problem with running 2 amps together like this. Got rid of the hum! And NO, I'm not turning around and touching both amps at one time! Didn't Tom Brumley like to run 2 Bassman's. Think he had a Hum-X?

Ken, Brad, Lynn, and everyone else in that camp might be right. And I will not argue with their technical expertise on the subject. But some others tend to lose sight of the "real world" on here in favor of every hypothetical worst case death scenario that they can possibly dream up while sitting behind their computers. Just take a look at the thread discussion that Lee linked to above. Plenty of 'em there. Brad said himself that he does/has used the 3 to 2 adapter method. I do believe he's still with us making great steel products.

I love the posts from guys that say they carry an outlet tester and won't play the gig if their not getting a full 120v out of the wall. Or you won't play if the club/bar doesn't have 3 prong outlets? Gimme a break! Really? "Uh oh, I'm not getting 120 boys, I gotta pack up and go". Come on. I'd like to see your bandmates response to that one. You'd get laughed at and probably run off after you pulled some crap like that, at least where I'm from. Is there really a licensed establishment still operating in the U.S. that hasn't upgraded the electrical to have 3 prong outlets. I doubt it.

While the 3 to 2 adapter may not be the most "recommended" with current gadgets available, it'll get the job done. Like Bo said on that thread, you're probably more likely to die on the WAY to the gig than to suffer the "death blow" from your 2 amps 'cause you ain't running the Hum-X.

Funny, you got folks saying they use the cheap adapter, but then they tell YOU to go buy the $75 box. I'm trying to figure that one out...

[Ken Fox]

I am a member of Local 48, Interational Brotherhood of Electricians for over 30 years. I spent many years in the field, not just "sitting behind a computer". I have dealt with grounding and bonding issues all my life, not just with guitar amps. I have also been knocked on my butt where and when amps were not grounded properly, or house wiring was wrong. You go ahead and do what you want, but spreading unsafe info is not what I will do, period.

Another method used was to lift the cable shield on the interconnection audio cable at the end of the cable from where the signal comes. This is called "telescoping sheiolds". Here is another article that mentions that from the web:

If there is a problem, and one amp's ground becomes hot, that same signal cable ground is ultimately attached to your guitar strings. If whatever building you're in is not absolutely properly wired, and many aren't, you can and will take that current through your body.

The safe way of doing this is to separate the grounds on the amps by lifting the ground connection on the cable that connects both amps. The cable will still be shielded as long as it's grounded on one end, and the signal will reach both amps just fine.

This will absolutely solve ground related hum issues, and is 100% safe. Do not ever lift the ground off of something that should have a ground. The only time "cheater" plugs are safe is when there's a good ground connection available through the outlet screw, which is usually because it is connected to ground through a conduit - which is not ideal from a fire safety standpoint either, but much safer to a person than lifting a ground.

[Todd Brown]

Ken, I obviously wasn't talking about you. No disrespect was directed or intended toward you. No need to go into your resume. I was just trying to pass on info that was given to me. I won't make that mistake again.

[James Morehead]

Ken has the background--his advice is very valuable, and trumps much of this "theory".

Lee, very worthy read that you provided links to, thankyou. I will look at what I do concerning groundloops differently. As I said, I am always willing to learn.

I am not an electrical tech. Though the above method I described might "work" well in some instances, I would advise anyone to research and learn all you can. I would not want to see anyone get hurt. Todd, becareful, my friend. There maybe safer ways to get the same results.

[Richard Sinkler]

Todd said:

I love the posts from guys that say they carry an outlet tester and won't play the gig if their not getting a full 120v out of the wall. Or you won't play if the club/bar doesn't have 3 prong outlets? Gimme a break! Really? "Uh oh, I'm not getting 120 boys, I gotta pack up and go". Come on. I'd like to see your bandmates response to that one. You'd get laughed at and probably run off after you pulled some crap like that, at least where I'm from. Is there really a licensed establishment still operating in the U.S. that hasn't upgraded the electrical to have 3 prong outlets. I doubt it.

While I and other bandmates don't test for constant voltage, we always test for a proper ground. It's not a real issue with me as I don't have to fear touching a microphone. I have seen my guitar player get lit up from his lips getting too close (we've seen it arc) or touching his mic. No flipping of his ground switches on his amp (even different amps, all Fender tube amps with grounded plugs) did anything. That is a real danger as far as we are concerned. In these cases, we always find no ground in the receptacle. And we have found that there may be a good plug on one side of the stage and a bad one on the other, so we don't assume that all plugs are safe, even if on the same circuit. We will run an extension cord from the good plug to the other side of the stage if we find no ground on our side. Even venues we play at often, we still test because we find that what was once a good socket, now has a problem.

The fact that a venue has 3 prong plugs doesn't guarantee they are grounded. In fact, I myself have replaced outlets in older houses that didn't have a ground wire running through the house for the simple convenience of being able to plug in cords with 3 prongs. That doesn't automatically add a ground to the circuit.

One club I play at sometimes, If the guitar player plugs into the socket on our side of the stage, he gets shocked. Steel player too as he also sings (I don't). So the assumption is a bad outlet on my side of the stage. They all start plugging into the side where the bass and PA plug into. No more shock problem, but I was watching them one night and the Steel amp wait distorting real bad at times (think fuzz box). No one can figure it out. I play the following week with them and I hear every amp breaking up but mine. Since I don't have to worry about getting a shock from a mic, I went ahead and plugged into the outlet by me. So the rest of the band switches to the outlet by me and the problems are all gone, including the shock problem. Don't know really what the problem is, but it is local to that one set of outlets on that side of the stage. All outlets are on the same circuit. It really does pay to check these outlets you use. The owner doesn't care.

As far as the voltage issues, there is a good cause not to play at a place where the voltage drops too much. I played at a place where, when I would really get fat on my C6th, the lights on stage and on the dance floor would go dim. Also happened when the bass player was really cranking down on a song. The pilot lights in mine and the guitars player's Twin Reverbs would also dim and our amps would distort like hell. We bought voltage stabilizing/isolating transformer and the problem vanished. The person who told us about the transformer was an electronics technician, and said that too low of a voltage can damage some equipment and cause amps to break up, although I have no expert knowledge of that, but I'm sure Ken or others here could clarify that. Also had problems at an outdoor venue that had bands playing every weekend. I also played keyboards and had 2 keyboards, 3 rack synths, 2 amps. The guitar player had one of those Roland guitar synths. When we played really hard (not loud), the voltage would drop low enough that our synthesizers would shut down and re-boot. The time I remember the most was in the song "Little Sister" where I was playing piano and the part that goes "duh duh duh duh duh duh duh duh" would always cause the shutdown. After a couple of gigs like this, I decided to dig out my transformer mentioned above, and the problems went away. So, there are many good reasons to check the power at a venue and if it is deemed to be unsafe, you should walk away (and my bands would do it, tell the owner, and possibly report them to the city or whoever is responsible for safe electrical installations if the owner wouldn't address it). I don't know about you, but I and everyone I know, won't risk their life, health or equipment for a gig.

Go ahead and take that chance, it's your health and safety and strictly your business. Nobody really cares, but it is good to have these knowledgeable folks share that info in case someone does care about their safety.

[Lee Baucum]

That's real cute, Lee. What's your point with posting on this thread that's almost two months old, with the same link that Ken put on the other thread about 2 Webb amps? Just to prove you're right?

Todd, I'm not trying to prove anybody right or wrong. I just posted that link for the convenience of anyone that happened to be reading this particular thread.