If this amp powered by a battery?
A 9V battery, although I plugged a 200 mA 9V AC adapter into it and it
worked also, though I didn't leave it plugged in that long - maybe if
it was in longer it would have fried it. I'm not sure how many mA
would be unsafe for this circuit - I looked up 9V batteries to see
what the current typically is, but it seems this depends on the
circuit. Until I find this out I'll probably just use a 9V "battery
eliminator" AC adapter.
In this configuration, pin 2 is the most sensitive node, and
anything connected to it should be surrounded with shielding.
I think I'll start with this. Thanks for your detailed input! !
On May 30, 6:25 pm, John Popelish wrote:
Mad Scientist Jr wrote:
Did you use shielded wire to connect the controls and jacks?
Thanks for your reply...
No, just normal stranded wire. Is that where the most interference
would be leaking in?
I found shielding paint (see below) - would it help to paint the
inside of the project box with this?
http://www.lessemf.com/paint.html
SUPER SHIELD
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Super Shield A general purpose EMI/RFI shielding in a handy aerosol
spray for use on most substrates. Especially good for RF shielding
plastic electronics enclosures. Consists of a tough, durable acrylic
base pigmented with a high purity nickel flake. One to two mil coating
provides 40dB - 50dB shielding across a frequency range of 5 to
1800MHz. About 1600 inē/can coverage at 1.5 mil. Contains no CFC 'S,
NO HCFC'S, ozone friendly. 340g (12 oz) aerosol can. Dries to a dull
gray color. Click to see MSDS
* Surface Resistivity ~0.7 Ohm/sq
* Dry time: 10 minutes at room temperature
* Recoat time: 5 minutes
* Excellent adhesion to most plastics
* Tested as per IEEE Std. 299-1997
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* NO CFC 'S, NO HCFC'S, Ozone Friendly
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Super Shield (Cat. #A285) ....................................... $24.95
add to cart
It would probably be little help. And if you coat the box
with anything conductive, it won't help much unless you can
make a good electrical connection between the coating and
pin 4 of the chip. If you really want to try this, thin
brass shim stock cut and folded to fit the box, is probably
the best you can get, short of a copper or aluminum box. It
is also easily solderable to make the ground connection.
If this amp powered by a battery?
In this configuration, pin 2 is the most sensitive node, and
anything connected to it should be surrounded with shielding.
Pins 1 and 8 are also somewhat sensitive so if the gain pot
has a metal case, that case should also have a ground wire
run to pin 4 to shield the resistive element.
Pin 7 is less sensitive, and since this circuit connects
nothing to it, it is probably not involved in the noise.