Circuit board and transformer inside the same box --> Hum?

[Morocotopo]

Hi people, I have a question that maybe you can help me with:
I´m making a LHX2 Fender sim and cab sim, the thing needs bipolar power, +/- 9V. I´m using a 12V 500 mA transformer and a bipolar regulated power supply (7809 and 7909)to power it.
I want to put everything into the same aluminum box, with a mains power cable, to avoid having a separate power supply box to lose, forget at home, misplace, etc.
The question is: will I have HUM?
I tried running the transformer and getting close to it with my guitar...hum (pickups "picking up" radiated noise. To be expected)
Then I tried putting the guitar cable near the transformer... NO HUM (I suppose the cable shied "grounds" the noise)
Sooo, maybe if I shield the out and in wires, and maybe the pot´s wires, and/or make a grounded "subdivision " inside the box to put the transformer and regulator´s board in, it will work....
I´d like some opinions before I drill/make the box.

Thanks

Morocotopo

[R.G.]

All of those are good ideas and are steps in the right direction. It is possible. Exactly what is needed is not possible to tell before you build it though, because the exact nature and placement of the transformer will matter.

However, if I may make a suggestion - that's not the only effect you will have is it? If your other effects are near that power line cord leading into the cabinet simulator, they may hum too when they didn't before. If you did not have an AC power cord near your effects before, it's good if you can escape that possibility now. The suggestion is this: measure the actual current drawn from +9V and -9V and see if you can possibly do this with one or more charge pump converters to supply -9V.

[Morocotopo]

Thanks R.G for your advice. I was planning to do a "rehearsal" of parts placement before actually drilling the box to see if it would work without hum (does that make sense?), but I wanted expert opinions.
So, what you mean is that the power cord with AC on it can induce hum into other boxes? Hmmm. Food for thought.
I´m planning to use this -not- in my pedalboard as a stompbox, but as a "standalone" box near my mixer and computer to practice, record, etc.
We´re talking about 28 opamps here!  I don´t think a charge pump will work here. Unfortunately, my DMM doesn´t measure current, never did, it´s a real cheap one... You suggest this to avoid having a separate power supply, right? I investigated the LT1054 chip (100 mA) when doing research for powering the neovibe, but it barely cut it there, so I think it won´t work here. There´s the option of parallelling those, but i´m not sure about how to do it. Besides, I tried to power this LHX2 circuit with a 12V 300 mA transformer, and the thing wouldn´t work, so I guess this thing needs AT LEAST 300 mA...
EDIT: the transformer is a standard one, meaning not a toroidal one.

Thanks again

Morocotopo

[BlueToad]

Well, the lightbulb in the neovibe was probably drawing considerably more power than the opamps will. Looking at the datasheet for the tl084, maximum quiescent current is 2.8 ma, times 28 is 78 ma.  LT1054 can handle this. If you're not driving any sort of load, then the total current draw shouldn't be much more than this. 300ma seems like way overkill; does it work connected to batteries? the problem might be elsewhere...

[Morocotopo]

Blue, thanks for your answer. I tried it with batteries and it worked all right. I don´t know how much current two 9V batts supply...
I don´t understand what you mean when you say "if it´s not driving any sort of load". You mean with no signal applied?
What I don´t get is why it didn´t work with the 300 mA transformer (the voltage regulators put out +8,99 and -0,something when loaded) and it did with the 500 mA one...
Of course the thing, unboxed and connected with alligator clips, oscillates and hums all over the place, could this be cause for more current consumption?

[birt]

i have a big (120VA) transformer inside my talkbox. it's a toroidal transformer and there is no hum wherever i put the circuit in the box.