piezo problem
Stefan
I have just bought a cheap acoustic (Jack & Danny), mainly to take
down to the beach where I don't want to take a more valuable guitar.
Although not its intended use, I have tried to plug it into an amp. It
has a simple equalizer and what I suppose is a piezo strip below the
saddle. Strangly the d and g strings sound dead when amplified, i.e.
the piezo does not seem to pick anything up there. I will obvliously
return the guitar, but just out of interest: has anyone come across
this problem? Is it common? How does the piezo strip work exactly? I
though it would either work or not, but not for individual strings.
Could it be a problem with the EQ?
Nil
alt.guitar.beginner:
> It has a simple equalizer and what I suppose is a piezo strip
> below the saddle. Strangly the d and g strings sound dead when
> amplified, i.e. the piezo does not seem to pick anything up there.
> I will obvliously return the guitar, but just out of interest: has
> anyone come across this problem?
I had a similar symptom with my acoustic-electric Ovation recently - it
turned out to be the battery. Usually the output just gets weak and
distorted, but this time one of the strings' volume became much lower
than the others.
So, replace the battery, and check to make sure that all wires are
connected to the preamp and pickup.
Lumpy
> ... How does the piezo strip work exactly?
It's a crystal, sandwiched between two pieces
of conductive metal. As the crystal is compressed,
it generates an electrical current. It's much like
a crystal radio. Or like the crystal element in
some cigarette or BBQ lighters. The movement
of your strings moves the saddle which compresses
the piezo element. That generates the electrical
signal and that is amplified and turned into the
audio signal.
If your piezo element is flat in shape, like most
are, here's something to consider -
The bottom of the saddle slot is (hopefully) flat.
Piezo element sits on top of that. Then the bottom
of the saddle is also (hopefully) flat. That saddle
sits on the piezo element.
BUT
When you move the strings, the saddle rocks a tiny
amount fore and aft (toward and away from the neck).
As it does that, it loses a little bit of contact
with the element AND the forward, sharp edge of the
saddle "digs in" to the piezo element.
I have had GREAT success with piezos by very slightly
rounding the bottom of the saddle from front to back.
Then instead of a sharp knife edge at the front of the
saddle, there is a gentle arch or chamfer. Then when
the saddle rocks, it's not digging in, it's maintaining
a more constant contact no matter where it's at in the
rocking movement.
Along the same lines, the tighter the saddle is in the
bridge slot, the better the sound transmission both
acoustic and amplified. Generally, if you remove the
strings and invert the guitar and the saddle falls out,
I think it's too loose.
Lumpy - The Anti Yanni
Stefan
...
> Along the same lines, the tighter the saddle is in the
> bridge slot, the better the sound transmission both
> acoustic and amplified. Generally, if you remove the
> strings and invert the guitar and the saddle falls out,
> I think it's too loose.
> ....
Thanks for the explanation. I have noticed that the "dead strings"
sound a tiny bit, if I hold the saddle down with a bit force, so it
could well be something related to the above. Instead of fiddling with
it, I will return it though, as the guitar is brand new and they will
replace it. It's a pity though, as it plays very well and sounds good
(unplugged).
Stefan
> I had a similar symptom with my acoustic-electric Ovation recently - it
> turned out to be the battery. Usually the output just gets weak and
> distorted, but this time one of the strings' volume became much lower
> than the others.
>
Thanks Nil. Just tried a new battery. Sadly no luck.
Stefan
Tony Done
"Lumpy" <lu...@digitalcartography.com> wrote in message
news:5kr7slF...@mid.individual.net...
I agree with all of that, but I've also had at least one instance where the
saddle has been too tight and caused dead spots. I try to get a friction fit
that will not drop out but can be pulled without resorting to a pair of
pliers. I use brass shim metal in the back or front of the slot to get the
required fit if the saddle is too loose.
It is worth checking that the bottom of the saddle is actually flat, and
fixing it if it isn't.
If the bottom of the saddle slot is uneven it is difficult to repair, but it
can be compensated by making a short shim that goes between the UST and
saddle, just under the dead strings. This worked fine on my Maton, except it
was the two outside strings that were lower output than the middle four.
HTH
Tony D
Lumpy
> ...I use brass shim metal in the back or
> front of the slot to get the required
> fit if the saddle is too loose.
I think it's simpler, and cleaner overall
to simply build a new saddle from wider stock.
> If the bottom of the saddle slot is uneven it is difficult to repair,
> but it can be compensated by making a short shim that goes between
> the UST and saddle, just under the dead strings. This worked fine on
> my Maton, except it was the two outside strings that were lower
> output than the middle four.
Boy, I can't say that I care for that approach.
If the bottom of the saddle slot is not square,
I wouldn't try shimming between the element
and the saddle. I'd simply re-route the slot
and take off a couple .001s to make it flat.
If necessary, fill the slot and reroute for
flatness.
I personally don't consider that difficult to repair,
but you have to have the jigs and Dremel routers to do it.
Another case of having it done for a few dollars or spending a
few hundred dollars for tools to do it yourself.
I want the bottom of the SLOT to be flat and square. I want the
bottom of the SADDLE to be FLAT but with rounded corners front
and back. Something like this ascii drawing, looking at it
from the side (bass toward treble or treb toward bass) -
SADDLE
\
\
|| ||
|| || <-- SLOT
|\___/|
|=====|<-- PICKUP ELEMENT
|_____|
I've known guys to use superglue + filler on the BOTTOM
of the saddle to make a single string pickup spot "hotter".
I don't think that's very precise. I'd much rather address
the slot bottom and saddle bottom mating surfaces, making
sure they are parallel first. And round off those leading
edges to eliminate the sharp contact point.
Lumpy
You were the Tidy Bowl Guy?
Yes. I'm cleaning your bathroom bowl.
www.lumpyvoice.org
Tony Done
> Tony Done wrote:
>> ...I use brass shim metal in the back or
>> front of the slot to get the required
>> fit if the saddle is too loose.
>
> I think it's simpler, and cleaner overall
> to simply build a new saddle from wider stock.
If you can find wider stock in the correct thickness that's fine, but if the
slot is not a standard width you would have to thin down over-wide stock (or
mill out the slot). That isn't especially easy to get neat, unless you have
a milling machine. - I have done it freehand, but it takes experience with
using a file and sanding block. The shim stock is near-invisible if you make
it flush with the bridge and colour it black with fibre tip pen
Well, the shim method works, because I've done it several times. It is
equivalent to the surperglue method you mention but is a good deal more
precise. <g> I stick the shim(s) to the bottom of saddle with saliva to get
it in place. - And there are things I do as a home tinkerer that I would not
recommend for a pro repairer. I do think that chamfering the edges of the
saddle is a good idea, and knocking off the sharp corners is something I do
routinely if installing a new saddle. This helps even in a slot without a
UST, because it avoids contact with the joins between the bottom and sides
of the slot that might have gunk in them or rounded edges.
Tony D
Lumpy
> If you can find wider stock in the correct
> thickness that's fine, but if the slot is
> not a standard width you would have to thin down
> over-wide stock (or mill out the slot)...
I always start with over wide stock.
Adhesive back 3m paper stuck to a flat
piece of 5/16 thick iron welding stock,
then run the bone stock over the sandpaper.
Stop before it is "almost" the right thickness
and allow the polishing to bring it down the
additional .001 or so.
I polish bone out to 12,000 micromesh, then
typically work backwards to take some of the
shine off of it. Maybe to 3,200 grit.
I don't like to have any voids in the mating
surfaces between saddle and bridge.
If the bridge does require re-slotting or
slot widening, it doesn't require a mill.
A dremel router with the appropriate jig
is super precise. Stew Mac and LMII both
have the jig. Clamps on to the guitar without
damaging anything, sets up easily, pretty
foolproof.
Lumpy
You were the "OPERATION" game voice?
Yes. Take out wrenched ankle.
Tony Done
Sounds good. Do use a fairly big piece of steel flat to hold the bone? (I
think that would make it easier to keep the removal uniform.) Or just enough
to use as a handle?
I've read about the slotting jigs, but for the small amount I do, just my
own stuff, I would take it to a pro for that kind of job.
Tony D
Lumpy
> > I always start with over wide stock.
> > Adhesive back 3m paper stuck to a flat
> > piece of 5/16 thick iron welding stock,
> > then run the bone stock over the sandpaper.
> > Stop before it is "almost" the right thickness
> > and allow the polishing to bring it down the
> > additional .001 or so.
Tony:
> Sounds good. Do use a fairly big piece
> of steel flat to hold the bone? (I think
> that would make it easier to keep the removal
> uniform.) Or just enough to use as a handle?
The flat steel lies flat on the table top. My piece
is 4" by 12". The sandpaper sticks to that, abrasive
side facing UP. Then I rub the bone blank on that
by holding it down against the abrasive.
To hold it down, I sometimes use an eraser.
A regular, pink, school type eraser meant for pencil
marks. The rubber "sticks" just enough to be able to
move the bone blank and it keeps my fingers and acrylic
nails out of the way of the abrasive paper.
Typically I don't even use that, just my fingers.
Flip the blank 180 degrees frequently, mark some
pencil witness marks and I find I can get it very
even thickness. I check it from time to time during
sanding with a digital micrometer. If I find it's
a little thick in the middle, I'll apply more pressure
there during sanding. I find that I can easily get
within .005 inch just with finger pressure.
There is a jig that will hold the blank in that
attitude too, but I don't have one. It's a spring loaded
thing that pushes the blank down to the surface of
the abrasive.
I guy that was a Navy machinist taught me about
measuring .001s of an inch. He would put two
feeler blades down on a formica counter top.
One maybe .005 the other .008. Then he'd say
"feel the edge and tell me which one is thicker".
If you do it enough you get to where you can
tell not only which one is thicker, but you can
have someone blindly put down a blade and you
can tell how thick it is. The Navy guy could do
it every time to the thousandth. He'd been doing
it for a gazillion years.
Lumpy
How come you didn't star on Star Trek?
Because Clint Howard beat me for the part of Balok.