Hum and Shielding
A properly designed piezo transducer or magnetic pickup should be shielded against electromagnetic
interference (EMI), which causes hum and noise.
When the HZ-10SE is used with a well-shielded pickup,
there is no hum, period
. Too often however, the shielding is inadequate or nonexistent. This is unfortunate,
because a number of rather inexpensive pickups sound quite good except for their lack of shielding. Although
it's possible to use the
LO
band to try to 'notch out' 60 Hz hum, it also ends up removing some bottom end in the
process, and you have a harder time taking advantage of the 'body resonance' technique discussed above.
Here's a quick way to test the shielding on your pickup:
• Set up the HZ-10SE to hear your guitar at normal listening level with the EQ off.
• Put the area of your guitar where the pickup is mounted about 12" from a fluorescent light (an ideal
broadband noise source).
• If the transducer is properly shielded, there should be very little or no hum. If it isn't, you'll know it.
What can you do if it's not properly shielded?
It depends on the type of pickup; if it's a magnetic
pickup or a piezo transducer implanted in the bridge or mounted under the saddle, not much except to try a
different pickup. If it's a stick-on pickup , you can (if
you're adventurous) remove the pickup and try the
following:
• Wrap a single layer of aluminum foil around the pickup, and lead a thin wire from the foil shield to
the ground connection on the pickup's plug or guitar jack. Then, remount the pickup. It's not the
prettiest solution, but it works quite well (and you could use a 'decorative' type of foil).
• A better solution is to apply an black EMI spray coating to the transducer (e.g. Miller-Stephenson RFI
Conductive coating #MS-485 or equivalent, available at your local electronic supplier).
Caution
-
don't try this unless you're willing to suffer the consequences if something goes wrong!
Don't try this if
the piezo crystal and its connections aren't totally encased in an insulated (plastic) housing!
Before
applying the coating, attach the bared end of a thin wire to the transducer. It will act as the ground
contact to the coating applied over it. Apply a few light, even coats, according to the instructions on
the can. When completely dry, it becomes a conductive and will shield against hum and other
interference. Be sure to ground the other end of the embedded wire when you remount the pickup.
We've had excellent results using this technique, making some very inexpensive transducers sound
great.
N ot e: Of t en, h um pr obl ems ca n be t r a ced t o i mpr oper sh i el di ng of t h e connect i on of
t h e pi ckup wi r e a t t h e endpi n ja ck. To r emedy t h i s, sh i el d t h e si gna l pi n wi t h a pi ece of
el ect r i ca l t a pe, a nd cr i mp a pi ece of a l umi num f oi l a r ound t h e a r ea , ma ki ng sur e t h e f oi l
i s gr ounded t o t h e sl eev e of t h e ja ck.
Stereo Effects Interface
The stereo effects interface is designed to make it easy to use all types of two output effects processors.
The signal levels can be set to accommodate everything from the on-the-floor effects boxes you're used to using,
to high-quality rack-mounted signal processors. And its unique switching matrix lets you distinguish between
the two general categories of effects: those that are meant to 'replace' the unprocessed guitar signal, and those
you want to 'mix' with your guitar sound. By using the remote foot switch, you can conveniently keep your
effects back at the rack with the Main Preamp Unit and still have control over them at your playing position.