Paia Vocal Zapper 6730 Guide

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Vocal Zapper
Model 6730
Assembly and Using Manual
Whether you want to sing Karaoke to essentially any
recording, practice and improve your vocals or just feel
like a rock star for a few minutes, then the Vocal Zapper
is for you. This low-cost device, when used in conjunc-
tion with any coventional stereo system, removes the
lead vocal from most CDs, records and tapes, and puts
your voice in its place.
There are somewhat more serious uses for the Zapper,
too; for example, with the lead vocal removed, you'll hear
harmony and background parts on records that you've
never heard before. Some aspiring singers have used
the Vocal Zapper to record demo tapes featuring their
voice in place of another singer's. Perhaps best of all,
this is a simple, non-critical circuit that is easy to
construct and use.

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2 Vocal Zapper
ASSEMBLING THE VOCAL ZAPPER
Before beginning assembly, go through the manual.
Look at the drawings. Feel the parts. You’re
naturally eager to plunge right in, but take a few
deep breaths first. Check the parts supplied against
the packing list on the last page of this manual.
In some cases, notes packed with the parts will
be used to call your attention to special situations.
These notes may be in the yellow "MISSING PARTS"
postcard. If parts are missing please notify PAiA at
p405.340.6300, f340.6378, or [email protected] .
Notice that each step in the manual is marked with
a checkoff box like this:
DESIGNATION VALUE COLOR CODE
( ) R27 100 ohm brown-black-brown
Checking off each step as you do it may seem
silly and ritualistic, but it greatly decreases the
chance of omitting a step and also provides
some gratification and reward as each step is
completed.
Numbered figures are printed in the Illustrations
Supplement that serves as a wrapper for this
manual. Remove the wrapper for easy reference
to the illustrations during assembly.
THE CIRCUIT BOARD
The Vocal Zapper is built on a circuit board with solder
masks and plating to help prevent short circuits.
No special preparation or cleaning is necessary
before assembly. The "top" of the board is the side that
is printed with component designations and parts are
mounted from this side. The "bottom" of the board is
also called the solder side.
TOOLS
You’ll need a minimum of tools to assemble the kit
- a small pair of diagonal wire cutters and pliers,
screwdriver, sharp knife, ruler, soldering iron and solder.

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Modern electronic components are small (in case you
hadn’t noticed) and values marked on the part are
often difficult to see. Another handy tool for
your bench will be a good magnifying glass. Also
use the magnifier to examine each solder joint as
it is made to make sure that it doesn’t have any of
the problems described in the SOLDERING section
which follows.
SOLDERING
Select a soldering iron with a small tip and a
power rating not more than 35 watts. Soldering
guns are completely unacceptable for assembling
solid state equipment because the large magnetic
field they generate can damage components.
Use only a high quality 60/40 alloy rosin core solder
(acid core solder is for plumbing, and silver solder is
for jewelry - neither is for electronics work). A proper solder
joint has just enough solder to cover the soldering
pad and about 1/16-inch of lead passing through it.
There are two improper connections to beware of:
Using too little solder will sometimes result in a
connection which appears to be soldered when
actually there is a layer of flux insulating the
component lead from the solder bead. This
situation can be cured by reheating the joint and
applying more solder.
Too much solder may produce a conducting bridge of
excess solder between adjacent pads causing a
short circuit. If WAY too much solder is used it may flow
through the hole and cause bridges between conductors
on the component side of the board or even impede the
action of mechanical components such as trimmer
potentiometers. Accidental bridges can be cleaned off by
holding the board upside down and flowing the excess
solder off onto a clean, hot soldering iron.
Use care when mounting all components. Never force
a component into place.

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4 Vocal Zapper
Solder each of the fixed resistors in place following the parts placement
designators printed on the circuit board and the assembly drawing (figure 1.).
Note that the fixed resistors may be mounted with either of their two leads in
either of the holes provided. Insert both leads in the mounting holes from the
non-foil side of the board, and push the resistor fully against the board. On the
conductor or foil side of the board, bend the leads outward to about a 45
degree angle to help hold the component in place while soldering. AFTER
SOLDERING, clip off each lead end flush with the top of the solder joint. Save
some of these clipped leads for use as wire jumpers in later steps.
DESIGNATION VALUE COLOR CODE A-B-C
( ) R1 1K brown-black-red
( ) R2 1K brown-black-red
( ) R3 2.2K red-red-red
( ) R4 22K red-red-orange
( ) R5 47K yellow-violet-orange
( ) R6 47K yellow-violet-orange
( ) R7 47K yellow-violet-orange
( ) R8 68K blue-grey-orange
( ) R9 100K brown-black-yellow
( ) R10 100K brown-black-yellow
( ) R13 470K yellow-violet-yellow
( ) R14 470K yellow-violet-yellow
( ) R15 470K yellow-violet-yellow
Fig 1. Parts are mounted on the circuit board in the locations shown.

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( ) Install 100K trimmer potentiometer R11
and solder in place.
( ) Install 100K trimmer potentiometer R12
and solder in place.
Install the ceramic disc and mylar capacitors. Like resistors, either of the two
leads can go in either of the holes provided. The value of the capacitor will be
marked on the body of the part. Solder in place according to figure 1 and clip
the excess leads.
DESIGNATION VALUE may be marked
( ) C3 .01 mfd. 103
( ) C4 .22 mfd. 224
( ) C5 .22 mfd. 224
Up to this point, all components have been non-polarized (i.e. either lead can
go into either hole). Electrolytic capacitors are polarized; just like a battery they
have a (+) and a (-) end, and like a battery, if installed incorrectly the circuit won't
work. The capacitors supplied will have either the (+) lead or the (-) lead
marked on the body of the part. The (+) lead MUST go through the circuit board
hole which has also been labelled positive (+). In the event that the capacitors
have their negative (-) lead marked, this lead should go through the unmarked
hole in the circuit board. Voltage
rating is a minimum value and parts
supplied may have a higher rating.
DESIGNATION VALUE
( ) C6 1 mfd.
( ) C7 10 mfd.
( ) C8 10 mfd.
Install the 4 PC mount phono jacks on the board in the places designated in
figure 1. Note these will only install in one way so that all the lugs fit into the
board. Press flush against the board, and then solder from the foil side of the
board.
DESIGNATION
( ) J1 phono jack
( ) J2 phono jack
( ) J3 phono jack
( ) J4 phono jack
Longer lead is "+"
Stripe is usually "-"
Mylar
Ca
p
acitor
s
Disk

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6 Vocal Zapper
Install the integrated circuit. Note that the orientation of the IC is keyed by a
notch at one end of the case which aligns with the semicircular key on the
designator printed on the circuit board. Use particular care when installing this
part, like any other semiconductor it is heat sensitive
and should not be exposed to extraordinarily high
soldering temperatures. Make sure that the
orientation is correct before soldering, Once they
are in place they are difficult to remove.
DESIGNATION TYPE NO.
( ) IC1 5532 Dual Low Noise OpAmp
In the following steps wires will be soldered to the circuit board which will, in
later steps, connect to the front panel switches and jack. At each step, prepare
the wire by cutting it to the specified
length and stripping 1/4 inch of
insulation from each end. "Tin" each
end by twisting the exposed strands
tightly together and melting a small
amount of solder into the wire to hold
the strands together.
Using the wire provided, make the following connections to the circuit board.
Use different colored wire for connections to point "M" and "SG" so the origin
can be easily identified after the wires are twisted together in a later step.
PC POINT WIRE LENGTH PC POINT WIRE LENGTH
( ) "M" 4" ( ) "C" 2"
( ) "SG" 4" ( ) "D" 2"
( ) "A" 2" ( ) "E" 2"
( ) "B" 2" ( ) "G" 4"
( ) Solder the black lead from one of the battery clips to the hole marked "V-" on
the circuit board.
( ) Solder the red lead from the other battery clip to the hole marked "V+" on the
circuit board. The remaining leads from the clips will be connected to the
switch in a later step.
Temporarily set the circuit board aside and mount the controls to the panel as
shown in Fig 2.
( ) Using the nuts provided with them, mount DPDT toggle switches S1 and S2
and the Microphone input jack J5 to the front panel. Do not use any washers
supplied with the switches.
pin 1

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Continue by wiring the front panel parts as shown in Fig 3. Notice that Individual
solder lugs are identified by part number and lug number. For example, S1-2
means the lug labeled “2” of the switch S1.
( ) Use a piece of excess resistor lead to connect S2-6 to S2-3. Solder the
connection at S2-3 but a second wire will connect
to S2-6 later and both wires soldered at that time.
In the following steps, connect wires from the
circuit board to front panel parts as listed.
Solder each connection as it is made.
FROM TO FROM TO
( ) "A" S1-2 ( ) "D" S1-4
( ) "B" S1-1 ( ) "E" S1-3
( ) "C" S1-5 ( ) "G" S2-6 (solder 2 wires)
Loosely twist the wires from points "SG" and "M" together before making these
connections.
FROM TO FROM TO
( ) "SG" J5-S ( ) "M" J5-T
( ) Connect and solder the free RED wire from one of the battery clips to S2-5.
( ) Connect and solder the free BLACK wire from the other battery clip to S2-2.
THE FRONT PANEL MAY NOW BE BOLTED TO THE CIRCUIT BOARD AS
FOLLOWS:
( ) Attach the two "L" brackets to the front panel by passing a 4-40 X 1/4"
machine screw through the holes in the panel and the unthreaded holes in the
"L" brackets. Secure each machine screw with a #4 hex nut. Do not fully tighten
until the front panel is aligned and attached.
( ) Fasten the front panel to the circuit board by passing a 4-40 X 1/4" machine
screw through the corner holes in the circuit board from the solder side and
into the threaded holes in the brackets. Tighten all screws.
( ) Mount the four rubber feet by peeling the protective backing and adhering
them to the corners of the bottom of the circuit board. See figure 2.
THIS COMPLETES ASSEMBLY OF THE VOCAL ZAPPER
Note:Be careful when
soldering the wires to the
switch. Too much heat
can soften the body of
the part causing the
solder lugs to shift
position. If you are using
a 30W or less soldering
iron there is little danger,
but higher power irons
should not be left on the
lugs too long.

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8 Vocal Zapper
Before proceeding with testing and calibration, thoroughly check the bottom of
the circuit board for solder bridges and cold solder joints. Clip off any compo-
nent leads that extend beyond the height of the rubber feet. Recheck parts
placement and values. Once satisfied that all is well, snap two fresh 9v.
transistor radio type batteries into the battery clips with the power off.
By far the easiest way to use the Vocal Zapper is to connect it between a CD
player and amplifier as shown in the illustration below. Alternately, it may be
connected between the preamp and power amp of nonintegrated systems.
The Vocal Zapper can also be connected to a stereo system through the TAPE
OUT and TAPE MONITOR jacks, as shown below. Note that the stereo's TAPE
MON button must be in the IN position to put the Zapper into the stereo signal
path.
After hooking the Zapper into your system, turn on the power switch of the
Zapper and all other components and start playing the program material you
will be working with. With S1 on the Vocal Zapper in the NORMAL mode (right
most position when viewing the panel from the front) you should hear the
program material, but in mono; and you may notice a slight drop in overall
volume level, which can be compensated for with the stereo system's volume
control.
STEREO HIFI AMP
VOCAL ZAPPER
TAPE
OUT
TAPE
MON
L
L
R
R
J1
J2
J3
J4 J5
MIC
Source
Output
Mic In
VOCAL ZAPPER
J1
J2
J3
J4 J5
MIC
CD PLAYER
AMPLIFIER Source
Output
Mic In
Tape monitor
on for Vocal
Zap

021402 Vocal Zapper 9
Now comes the big test. Switch S1 to the Zap mode, and the lead vocal should
drop out as if by magic. If it doesn't, adjust trimpot R12 for the maximum
amount of cancellation (this should occur somewhere near the midpoint of
rotation). Once set, this trimpot need not be changed as you play different
records unless you are altering it for a specific effect.
Now that the lead vocal has been eliminated, it's time to try out the microphone
preamp. Plug a microphone into the J5 with trimpot R11 set full counter-
clockwise and the gain on your stereo tuned all the way down. TO PREVENT
FEEDBACK THE USE OF HEADPHONES IS RECOMMENDED.
Adjust trimpot R11 for the proper blend between microphone and program
material. Note that most people tend to set the mic gain too high at first so that
they can hear themselves well; however, excessively high mic gain settings can
cause distortion. If you experience such distortion, back off on R11 a bit. Now
with the unit in the Zapped mode, you can sing (or howl) along with some of the
world's best backup musicians playing for you. Please note that the Zapper will
not work with mono program material, but stereo tapes, records, or FM with
good separation will work in almost all cases.
PRINCIPLES OF VOCAL CANCELLATION
With most stereo records, certain instruments are traditionally placed in the
center of a stereo mix, such as vocals, bass, and bass drum. Other instru-
ments, such as lead guitar, keyboards, vocal harmonies, and the like are mixed
more towards the right or left side of the stereo spread.
The Vocal Zapper removes the
lead vocal according to the process
shown in the figure. The right and
left channels of a conventional
stereo recording are summed
together in a differential amp (IC1).
As a result, all center channel
material, including the lead vocal,
is cancelled at IC1's output. The
remaining instruments that are
mixed more to the right and left
sides are relatively unaffected.
In order to prevent complete cancellation of the bass and bass drum, C3 only
allows frequencies above approximately 160 Hz to be cancelled. Frequencies
below 160 Hz are not mixed differentially, meaning that bass information
present in the right channel will appear at IC1's output. If you prefer complete
suppression of the center of the stereo field and do not mind losing some
bass, you can change the value of C3. Values between C3's current value of .01
mfd and .22 mfd. will cause greater rejection as the value is increased.
MIC
INPUT
MONO
OUTPUT
STEREO
INPUT
HIGH PASS
FILTER CAP
DIFFERENTIAL
AMP
PREAMP
IC1:A
IC1:B
R
L
_
+

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10 Vocal Zapper
CAVEATS
There are a couple of fine points. The Vocal Zapper will not work with mono
recordings, since in this case everything is center channel material. Also, any
reverb added to the vocal will tend to remain -- but in most cases, the reverb is
at a low enough level to not be objectionable (and if you're singing along with
the record, it even helps to have little remaining reverb underneath your vocal to
add depth).
It should also be noted that some recordings use vocal processing techniques
where digital delays and other enhancers spread the vocal across both
channels in unequal amounts. Luckily for us, these records are definitely in the
minority; greater than 95% of all pop, rock, and C&W records sampled during
development of the Vocal Zapper had the lead vocals mixed in the center
channel, and were therefore eligible for cancellation.
ABOUT THE CIRCUIT
Referring to the schematic, IC1 is a differential amplifier, built around a 5532 or
equivalent type dual low-noise opamp. The right channel signal couples
through C5 into the (-) input of the opamp; the left channel signal feeds either
the (-) input or (+) input of IC1, depending on the setting of S1. In the normal
mode, the left channel signal feeds the (-) input, and the IC1 acts as a simple
mixer. This produces a mono output that is the sum of the left and right
channels. With S1 in the Zap (or cancel) mode, the left channel signal feeds the
Vocal Zapper Schematic

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(+) input of IC1, thus producing cancellation of common-mode information (i.e.
anything in the center channel above approximately 160 Hz). Note that in the
zap mode, the overall output level may seem slightly lower since the center
channel information is missing. S1b compensates for this effect by slightly
reducing the gain of IC1 in the normal mode. R12 allows the user to adjust the
Vocal Zapper for the maximum amount of lead vocal cancellation. IC1:B's
output couples back into the stereo system through R1 and R2.
IC1:A is a simple mic preamp that accommodates a variety of different micro-
phones, and mixes the microphone signal into IC1:B to replace the lead vocal
with your voice. The mic output goes directly into the (+) input of IC1:A, whose
gain is set by R11. IC1:A's output then couples through C6 and R4 into the (-)
input of IC1. Power for both opamps is provided by a + 9v (bipolar) transistor
radio battery supply. The Vocal Zapper is intended for use with stereo systems
having TAPE OUT and TAPE MON jacks (see INSTALLATION).
IN CASE OF DIFFICULTY
Recheck the wiring according to the instructions given previously in this
manual. Also, make sure the batteries are fresh and functional. Pay special
attention to the orientation of the ICs and to the solder connections. Many kits
are returned for repair having nothing more wrong with them than a bad solder
connection or two. Finally, check for solder bridges, wire bits, or other foreign
matter which may be lodged across conductors on the circuit board.
Should you be unable to determine the source of the difficulty, a repair service
is available. BEFORE sending the unit back, write us for return instructions and
authorization to the addresses on the back cover of this manual or email to
[email protected]. Give as full a description of the malfunction as possible; in
many cases your problem may be diagnosed by mail. If no diagnosis can be
made, you will be supplied with a repair address and shipping instructions.

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12 Vocal Zapper
PAiA Electronics, Inc
3200 Teakwood Ln.
Edmond, OK 73013
phn 405-340-6300
fax [phone]
email: [email protected]
Vocal Zapper Packing List
all resistors 5% tolerance 1/4W.
1 22K red-red-orange
2 1K brown-black-red
1 2.2K red-red-red
3 47K yellow-violet-orange
1 68K blue-grey-orange
2 100K brown-black-yellow
3 470K yellow-violet-yellow
variable resistors
2 100K Trimmer Potentiometers
disk and mylar capacitors
1 .01uF Ceramic Disk
2 .22uF Mylar
electrolytic capacitors (minimum voltage specified)
1 1uF/10V
2 10uF/15V
semiconductors
1 5532 Dual Low Noise Op-Amp
hardware and miscellaneous
2 DPDT Toggle Switch
4 PC mounted Phono Jacks
1 1/4" OC Phone Jack
2 18" lengths insulated wire
2 #4 "L" Bracket
4 4-40 X 1/4" Machine screw
2 4-40 Hex Nut
4 Stick-on Rubber Feet
2 9V Battery Snap
1 Circuit Board
1 Front Panel

Vocal Zapper
Model 6730
Ilustrations and Supplemental Infomation
This wrapper page for the Vocal Zapper manual may be removed
for easy access to the illustrations.
BEFORE GOING ANY FURTHER, READ THIS
The Vocal Zapper is most easily used by placing it between a CD
player and CD or Aux inputs of a component amplifier and speaker
system. It can also be easily inserted into the signal path of pack-
aged stereo systems or boom boxes that have "Tape Out" and
"Tape Monitor" jacks. If you have a packaged system that does not
include these features, use of the Vocal Zapper may require some
internal modification to the system.
Also be aware that a filter is included in the Vocal Zapper design to
allow bass lines, which are ordinarily mixed to the center of the
stereo field, to pass without being zapped. This filter may allow
some of the vocal to bleed through but is easily modified for more
complete suppression at the cost of losing some bass. For more on
this see "Principles of Vocal Cancellation" on page 9 of the manual.

13
6
black red
red
black
2
5
4
5
63
42
1
S1 S2
T
S
J5
Fig 2. Show mechanical
assembly. Note different
orientation of switches and
threaded and unthreaded
holes in "L" bracket.
1
2
3
4
5
6
23
1
5
46
S1
S2
J5
attaches to the
threaded bushing.
S
T
The sleeve ("S") lug
Fig 3. Shows panel
wiring. Switch lug
numbers are only on
illustrations and not on
the switch.

More on connecting and testing the 6730 Vocal Zapper
The 6730 Vocal Zapper can easily connect to the external tape
recorder connectors on a stereo receiver. These are specified as
Tape Out and Tape Monitor in the manual for the kit, but basically
they corresespond to line-level outputs and inputs.
The Tape Out is a signal from the receiver that is the selected
'source' (phono, CD, Radio, Auxillary, etc). This set of connectors
may also be called Tape Record, left and right. When the source is
'played' the line-level signal appears at these jacks and to confirm
this, you could connect these 'line outs' to a separate amp/speakers
to hear the selected source.
Tape Monitor may also be labeled Tape In or Tape Playback. It is
a set of line-level inputs that route to the power amp section when
the Tape Monitor switch is asserted. Recorded material on the
external tape recorder is input back to the receiver via these con-
nectors. Normally, this would be the signal from output of a tape
deck, but with the vocal zapper, it is the zapper's outputs. With
only cables connected to these inputs on the receiver (and Tape
Monitor asserted) you should be able to touch the tip of the cable
and hear a buzz or hum through your speakers indicating the inputs
are 'live'. An external CD player could be played through these
jacks. The Vocal Zapper sends the 'zapped' signal in on these jacks.
A quick and simple way to get an idea of whether the Zapper
circuitry is operating or not is to advance the mic gain trim cw and
touch the tip contact of the MIC Input jack to find out if this
introduces a hum or buzz like touching the cables to the Tape
Monitor jacks does. If not, it might be soldering trouble on the
vocal zapper kit. The first check would be of the soldering and
battery condition.
A VOM or multitester can be set to measure 9V DC and the power
to the ICs tested by putting the black probe to the circuit ground/
common while the red probe is put to pin 8 of the IC. Read the

pins by counting up in a ccw direction around the part from the
notch or pin 1 indicator. This should measure +7 to 8V DC. If the
tester is digital readout, it will autopolarize and you can go on and
measure the negative DC on pin 4 for a -7 to 8V DC reading. If it
is analog with a meter movement, put the red on ground/common
and measure with the black so the needle doesn't try to swing the
wrong direction.
The output pins of the op-amp IC (pin1, pin 7) should measure
appoximately 0V DC.