amp noise

Bill Tauson · Post by **Bill Tauson** » 3 Oct 1998 6:08 pm

I'm playing my steel through a "Profex II" into an "Evans" amp. If I plug the steel straight into the amp, it's quiet. As soon as I add an effects processor I get a low end noise. The only adjustment which affects this is the reverb on the amp. Since "Evans" amps and the "Profex II" are popular out there, anyone else have this problem? Any ideas? Thanks.

Jack Stoner · Post by **Jack Stoner** » 4 Oct 1998 3:38 am

Two things. First the Profex II tends to be a bit noisy. Second if the output level of the Profex II is set too high you will also tend to get more ambient noise. And it's not your amp - it would do the same thing with any amp.

If the "low end" noise you're referring to is "hum" then it's usually caused by a ground loop. I don't remember if the Profex II power transformer is grounded (third ground wire or rounded ground pin on the AC connector). If it has the third ground wire in it then you can try removing the ground on the amplifier using an adapter AC plug that removes the ground. One caution, only remove one AC power ground, do not remove the AC power ground from all equipment as this is a potentially dangerous situation.

Bill Tauson · Post by **Bill Tauson** » 4 Oct 1998 10:40 am

Jack, I tend to think it is a ground loop problem. I'll try the plug adapter on just the amp and see if it corrects it. Thank you very much for your help.

Bob Cole · Post by **Bob Cole** » 5 Oct 1998 4:01 am

Bill, If the hum can be affected by the Reverb control on the amp, it's the reverb springs picking up the magnetic field from that stupid little video game transformer the ProFex uses. Only solution I ever found was to get that transformer as far away from the amp as possible. One of the reasons I quit using the ProFex is because of that. Also you'll have the same problem if it's any where near your steel unless you have HumBuckers.

Jon Smorada · Post by **Jon Smorada** » 5 Oct 1998 5:38 am

Bill, I tend to agree with Bob as far as the low end noise coming from the transformer. A good way to verify this is to move the transformer around and listen for the hum to change. But I wouldn't lift the ground on your amp. The ProFex transformer, while it has a three-prong plug, delivers low-voltage AC to the unit through two wires, not three. I'm not even sure why that third prong is there. At any rate, the ProFex itself is not grounded. If you lift the ground from your amp then you're putting yourself at risk.

Jack Stoner · Post by **Jack Stoner** » 5 Oct 1998 6:45 am

When I had a Profex II, if I plugged it into the guitar input on my Session 500 it would hum, without lifting the ground. If I plugged it into the guitar input on my Session 400 it would not hum (with the ground connected!).

However, I get ground loop hum from both my Nashville 400 and the Session 400 using my Transtube Fex (which has a grounded AC plug and the power supply built into the unit - like the Profex II should have been). I have to lift the ground on both amps (I'm still grounded through the Transtube Fex).

I know the reverb tank will pick up AC hum fairly easy from almost any unit placed within a couple feet of it, but the ground loops can be a ***** to isolate or even figure out.

Jack

Bill Tauson · Post by **Bill Tauson** » 5 Oct 1998 11:35 am

The noise is not unique to just the "Profex", but instead it does it with differenct effects processors. I'm still working on it, carefully. If I figure it out, I'll let you know. Thanks for everyones imput.

Jack Stoner · Post by **Jack Stoner** » 6 Oct 1998 3:07 am

I still think it's the ground loop problem. Anytime you have two AC powered units and you try to interconnect them there is the potential for the ground loop problem.

Bill Tauson · Post by **Bill Tauson** » 6 Oct 1998 9:27 am

I pulled out the amp's instructions, (when in doubt...), and it's says to remove the ground loop from the effects. I also called "Evans" amps and they explained the same thing. The "Profex II" only has a 2 prong plug, but I have it in a rack with a "Korg" tuner and a power protector. It appears to be a conflict between the amp and the power protector and tuner, not the "Profex II".

Here's the question. If I lift the ground from something in the rack, (as soon as I figure out which combination works best), wil the ground from the amp still be enough to prevent a problems? I would think that the amp has a greater power level and should stay grounded. I would rather loose a $200 tuner than a $1,200 amp. Any CURRENT opinions?

Dennis Scoville · Post by **Dennis Scoville** » 6 Oct 1998 10:15 am

Bill,

You also want to make sure that none of your guitar cords are near the Profex transformer. The cords will suck up that noise and feed it right to your amp. -Dennis

Jack Stoner · Post by **Jack Stoner** » 6 Oct 1998 1:20 pm

What you have to do is isolate the chassis on each unit in the rack. What's happening is one of the unit's is causing the ground loop to the others through the metal mounting rails in the rack. You don't necessarily have to "lift the AC ground" on the unit but you do have to insulate each unit so there is no physical metal contact throught the rack for each one.

E-Mail me if this is as clear as mud....

Jack

Chick Donner · Post by **Chick Donner** » 7 Oct 1998 3:28 am

I had a hellacious 60 cycle AC hum using a Korg DTR-1 tuner and an Alesis Quadraverb GT . . . what solved it was mounting EVERYTHING (including the Rack Rider) with "Humfrees" AND using a ground (lift) adapter on the tuner ONLY. That worked. Now all I have to contend with is the little bit of 'hiss' out of the Alesis, which judicious use of the various gain controls (both inside the Alesis and on the amp) which seems to take care of it. But, my BIG problem was the Korg tuner. That was the source of the hum.

John Lacey · Post by **John Lacey** » 7 Oct 1998 1:40 pm

Chick, what's a "Humfrees"?

Jack Stoner · Post by **Jack Stoner** » 7 Oct 1998 1:52 pm

John, Humfrees are small nylon or plastic insulating straps that you wrap around the rackmounting screw holes on equipment. The're supposed to insulate the rack unit from the rack mounting frame and eliminate hum. They used to have them listed in the Musician's Friend catalogs, but I just got a Fall 1998 issue and didn't see them.

Bill Rowlett · Post by **Bill Rowlett** » 7 Oct 1998 2:42 pm

Peavey sells an equivalent device in their accesories blister packs. It's a package of 4 screws and insulating washers. It works well.

Bill

Jay Dee Maness · Post by **Jay Dee Maness** » 11 Oct 1998 10:12 pm

Guys, I to had the hum problem with the Korg DTR tuner, it is most certainly a lot of the problem. I had to take it out of my rack. Of all the years I`ve been playing I`ve never been able to get rid of noise problems, rack or no rack. If you figure this all out, let me know. thanks. JayDee.

Jack Stoner · Post by **Jack Stoner** » 12 Oct 1998 3:30 am

A lot of the "ground loop" problems come from the loop between signal ground and AC ground. I built a rack unit with an AC power supply for several stomp boxes (to eliminate the constant battery replacement) and to do some switching. I had a lot of hum problems in the unit until I isolated (separated) the signal ground from the AC power ground and replaced all the jacks with insulated/isolated ground types from the chassis (the jacks with the black nylon threaded mounting). Usually you can minimize the affects of the hum but it takes a lot of time and sometimes you have to get lucky....

Bill Tauson · Post by **Bill Tauson** » 12 Oct 1998 11:10 pm

I used the "Humfrees" and it took care of the ground problem. Both the "Korg" tuner and the power distribution unit were in conflict with the "Profex II". Now I still have a hiss from the "Profex II", but it's better than it was. If I turn down the gain and increase the volume on the amp, it's not bad. I imagine a compressor might help with the hiss. Honesty, if I were to start over, I'd use the "Profex II, go back to my "Boss TU-12" tuner with the needle which seems more accurate anyway, and worry about my playing skills instead of the gagets.

Thanks for everyone for the help. If anyone needs the "Humfrees" and can't locate them, let me know.

Earnest Bovine · Post by **Earnest Bovine** » 13 Oct 1998 6:54 pm

All the advice here is about how to get rid of hum, not hiss.
There will always be some hiis in audio gera.
Besides getting more expensive gear, there's really only one way to get minimize hiss, and that's to set your levels carefully.
Some people call it manging your gain structure.
You should set the input level control as high as possible without overloading (clipping) the signal. That way the musical signal os louder compared to the fixed level of noise.
If you have more than one effect unit, you have to set all the levels carefully. Even within a single multi-effect box there can be many levels to adjust.

Vic Chaney · Post by **Vic Chaney** » 13 Oct 1998 10:35 pm

I found out why my amp hums---
It doesn't know the words!

Okay, I'll go to my room now.

Vic