Synthesis Technology MOTM-510 The WaveWarper Quick start guide
MOTM-510 The WaveWarper
Assembly Instructions & Owner’s Manual
Synthesis Technology
6625 Quail Ridge Dr.
Fort Worth, TX 76180
(817) 498-3782
www.synthtech.com
June 9, 2006
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MOTM-510 PARTS LIST
Please carefully check that all parts are in your kit. If you have a suspected shortage, please
call or email. If you get free extra stuff, keep it for next time.
Capacitor bag, containing the following 17 parts:
4ea 10mfd, 50V Electrolytic C4, C8, C16, C17
4ea 10mfd, non-polar Electrolytic C1, C3, C5, C13
2ea 1000pf (marked 1N) yellow box cap C12, C15
7ea 0.1mfd (marked 104) ceramic axial C2, C6, C7, C9-11, C14
Resistor bag, containing the following 33 parts:
11ea 10K (brown, black, orange) R4, R5, R7, R11, R12, R14, R18, R19,
R21, R26, R27
7ea 68K (green, gray, orange) R3, R6, R10, R13, R17, R20, R24
6ea 20K (red, black, orange) R1, R2, R8, R9, R15, R16
2ea 12K (brown, red, orange) R30, R31
2ea 1K (brown, black, red) R25, R32
2ea 10 ohm (brown, black, black) R33, R34
1ea 22 ohm (red, red, black) R23
1ea 30K (orange, black, orange) R28
1ea 39K (orange, white, orange) R29
NOTE: R22 is not used.
IC & Semi bag, containing the following 5 parts:
4ea TL072ACP dual opamp U1, U2, U3, U5
1ea AD538 really expensive analog IC U4
1ea 1N4148 diode D1
Misc #1 bag, containing the following 6 parts:
2ea Axial ferrite beads (plain, gray things ) L1, L2
1ea MTA-156 4-pin power connector JP1
1ea MTA-100, 7-pin connector JP2
1ea custom rotary switch assembly plugs into JP2
1ea 18-pin screw machine IC socket for U4
Knobs, containing
7ea TYCO PKES90B1/4 for pots
1ea TYCO AMP2-1437624-0 for rotary switch
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Jacks, containing
8ea Switchcraft 112A
Pots, 7ea containing the following:
1ea 100 ohm Spectrol 148-71101 VR4
3ea 100K Spectrol 149-71104 VR1-3
3ea 100K Bourns conductive plastic VR5-7
Front panel
Mounting bracket
Wire bag, containing the following 12 wires:
5ea RG-174 coax, 4 ½ inches
2ea red/black 22ga. 3in.
2ea orange/gray/white 22ga. 4 ½ in.
1ea orange/white 22ga. 5in.
1ea red/black/white 22ga. 7in.
1ea Power Cable, 20”
Hardware bag, containing:
4ea #8-32 x 3/8 black screws (for mounting module to rack)
4ea #6-32 x 1/2 zinc screws (for attaching pc board to bracket)
4ea 1/4 inch aluminum spacers
6ea #6 KEPS nuts
7ea small tie-wraps
Organic Solder
No-clean Solder
PC Board, MOTM-510
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GENERAL INFORMATION
Thank you for purchasing the MOTM-510 WaveWarper. If you have any issues concerning the
This kit should take the average builder between 3 and 4 hours. The kit contains many
different resistor values and special parts. However, please remember this is NOT a speed
contest; it is an accuracy contest. There is no rule that you have to complete the entire kit in
one day (as long as you wash the flux off!).
Successful kit building relies on having the proper tools. Here is a list of what you will need to
build your MOTM-510:
• Soldering iron, 50W max power
• Needle-nose or chain-nose pliers
• Diagonal cutters
• Allen key set for securing the knobs (1/16” or 1.6mm)
• Magnifying glass: to read the capacitor codes and to inspect solder joints
• Lead bending tool (optional, but makes the job go much faster)
• (optional) oscilloscope (to check the output)
• #1 Philips screwdriver
• Fingernail brush for washing off the organic flux
• Old towel for blotting dry pc board
For more information of tools used and suggestions, see the MOTM FAQ and Catalog pages at
http://www.synthtech.com.
There are no calibrations/trimmer to set for this module.
HOW TO FOLLOW THE DIRECTIONS
Please read the entire instruction before proceeding. There may be valuable information at the
end of the instruction. Each instruction has a check box next to it. After you complete the
instruction, check the box. This way you can keep track of where you are in the process.
VERIFY THE PARTS LIST
Verify that all of the parts are in the kit as shown on the parts list.
A WORD ON SOLDERING
There are 2 very different types of solder used in the kit. Most of the soldering uses ‘Organic
Flux’ solder. This is strictly for use on the pc board, and is NOT to be used on the front
panel wiring!
In order for solder to ‘stick’ to the copper, a chemical called ‘flux’ is embedded in the solder. The
flux leaves a residue on the pc board that should be cleaned with warm water. DO NOT USE
SOAP OR OTHER CLEANSERS. Most of the parts in the kits are ‘waterproof’ and can be
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washed in the sink. The flux is OSHA approved for flushing down the drain, so don’t worry
about that! A soft brush is used to gently scrub the board. We recommend a ‘fingernail brush’,
which is about 1” x 2” and can be found for about $1.
The other type of solder is called ‘No Clean Flux’; because as the name implies it does not
require washing. This solder is used for wiring the pots, switches, jacks, etc. This solder is
harder to use on the pc board; because even when melted, it is not very fluid (about the
consistency of toothpaste). We will use it VERY SPARINGLY on the pc board.
OK, let’s get started on the board!
PART #1: SOLDERING THE RESISTORS
Since there are more resistors than anything else, we will start here. If you do not know the
resistor color code, refer to the parts list. Resistors are not polarity sensitive, but the board will
be easier to debug (and look nicer) if you point the first color band in the same direction for all
the parts. The color code is also in the README FIRST document that every customer receives
with his or her first order.
You will start by soldering in ALL of the resistors.
Find the RESISTOR bag.
Find the MOTM-510 blank pc board. There is a copy (larger than actual size) of the
silkscreen which shows where the parts go at the end of this document. It will be useful
if you locate the part on the print first, put the part in the board, then ‘check off’ the
silkscreen. All parts are inserted from the side of the board with the white silkscreen
(the “top” side).
We will stuff the resistors by value to make things easier. The resistors are inserted on
a 0.4 inch spacing. The important thing is to be sure that the part is sitting all the way
down on the board. Push the leads in the holes, push the part on the board, and then
bend the leads on the bottom outwards to a 45 degree angle (roughly!). This is called
‘cinching the leads’: and keeps the part from falling out! From the bottom of the board,
solder (using the organic flux), applying heat to the pad for about a half second first,
then applying just enough solder to make a small puddle that looks like a tiny pyramid.
Enough solder should flow in the hole such that on the top (component) side, a small
amount is on the top pad as well
The rule of soldering: don’t use too much, you can always add more! Cut the leads flush
with the top of the solder joint with your diagonal cutters.
NOTE: later in the assembly, you will need 3 scraps of resistor lead. Be sure to
save some!
ANOTHER NOTE! The AD538 IC is VERY EXPENSIVE to replace ($55). There
is a socket provided, but you MUST BE CAREFUL when inserting the IC into
the socket later in the assembly. Be SURE you solder the socket in the correct
orientation! YOU HAVE BEEN WARNED!
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Locate the 10K 5% resistors (11pcs). Solder the resistors into R4, R5 and R7 (by U1),
R11, R12 and R14 (by U2), R18, R19 and R21 (by U3) and R26 and R27 (left of U5).
Locate the 68K resistors (7) and solder into R3 and R6 (by U1), R10 and R13 (by U2),
R17 and R20 (by U3) and R24 (below C13).
Locate the 20K resistors (6) and solder into R1 and R2 (by U1), R8 and R9 (by U2) and
R15 and R16 (by U3).
Locate the 12K resistors (2) and solder into R30 and R31 (left of C13).
Locate the 1K resistors (2) and solder into R25 (right of J7) and R32 (left of VR4).
Locate the 10 ohm resistors (2) and solder into R33 and R34 (right of VR7).
Locate the 22 ohm resistor and solder into R23 (left of VR3).
Locate the 30K resistor and solder into R28 (left of C16).
Locate the 39K resistor and solder into R29 (below VR7).
NOTE: position R22, to the right of JP2, is NOT USED and should be left OPEN.
PART #2: BOARD WASH #1
Verify all the resistors are in the correct position.
Verify all the resistors are flat on the board. Correct if needed. Check solder joints.
Wash the board in warm water, gently scrubbing both sides. DO NOT USE ANY SOAP!
Just water! Blot dry with old towel and let it sit for at least 15 minutes.
Take a little break! You are about 1/3rd of the way finished.
PART #3: CAPACITORS
Locate the CAPACITOR bag. Note that the ceramic axial caps are bent on 0.300
centers. If you are using the Mouser red plastic bending guide, you will see there is no
‘slot’ for the 0.300 spacing. However, we can use a clever trick! You use the round hole
at the small end. Lay the body of the cap across the hole, and bend the leads over the
sides as before. A perfect 0.300 bend!
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Locate the 2 ‘yellow box’ caps (1000pf, or 1nf) and solder into C12 and C15.
Locate the 0.1mfd axial ceramic caps (7) and solder into C2, C6, C7, C9, C10, C11 and
C14.
Locate the 10µfd NON-POLAR electrolytics (4). Note that the caps are labeled NP and
are missing a ‘marking stripe’. Insert these into C1, C3, C5 and C13.
Locate the 10µfd electrolytics (4) which are orange . Note that there is a stripe on the
NEGATIVE terminal. The pc board has a + on the POSITIVE terminal. Carefully stick
the capacitors into C4, C8, C16 and C17 with the stripe away from the + pad on the
board. All 4 capacitors are facing the same direction (stripe ‘up’), so be SURE they are
all in the pc board the same way.
PART #4: MISC and IC STUFF
Almost done with the parts on the pc board! This will finish up the soldering with the organic
flux.
Locate the MISC #1 bag and the IC bag.
Locate the ferrite beads (2). They are axial parts, gray colored with no markings. These
are non-polar, and are soldered into L1 and L2 (by JP1).
Locate the MTA-156 4-pin power connector. Solder into JP1. Note that the connector
has a ‘locking tab’ on one side. The silkscreen symbol for JP1 has a line on one side,
indicating this is the side where the locking tab goes.
Locate the MTA-100 7-pin rotary switch connector. Solder into JP2. Note that the
connector has a ‘locking tab’ on one side. Note the silkscreen symbol for JP2 has a line
on one side, indicating this is the side where the locking tab goes.
Locate the 1N4148 diode. Solder into D1, with the black stripe on the diode facing ‘up’
(matching the while stripe on the silkscreen).
Locate the TL072ACP op amps (4). Solder into U1, U2, U3 and U5. Note that all ICs are
pointing “up” towards the top edge of the pc board. The IC will have a ‘notch’ or
indentation in the top by Pin #1.
Locate the 18-pin IC socket. It solders into the space for U4. See the interesting BE
CAREFUL lettering on the pc board? It’s there for a reason: you need to be careful in
both soldering in the IC socket AND installing U4 (installing is later on). Look at the IC
socket: notice one end has a ‘notch’ in the crossbar. This indicates “pointing up”,
meaning Pin #1 is the UPPER LEFT CORNER on the socket. If you look closely at the
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pc board, Pin 1 is a SQUARE solder pad with the ‘1’ printed above it. The IC outline on
the bard also has a ‘notch’ pointing “up”, which matches the ‘notch’ in the IC socket. So,
solder the IC socket into U4 with the notch UP. The pins are small diameter, so you will
have to hold the socket flat against the pc board while soldering the first 2 or 3 pins. DO
NOT BEND ANY OF THE IC SOCKET PINS OVER ON THE PC BOARD!
Apply a small bit of solder to the via holes. These are the small pads that allow traces to
“change sides” of the pc board. DO NOT SOLDER PADS FOR THE REMAINING
COMPONENTS!! As an example, if you look at VR2, you will see traces, surrounded by
copper, with 2 via holes above VR2 and another via hole to the left of VR2. A ‘hidden’
one (hard to see) is directly above the letter ‘P’ in the “MOTM-510 WAVEWARPER”
lettering near the top edge of the pc board.
PART #5: FINAL BOARD WASH & INSPECTION
Verify all the parts are in the correct locations. Make sure all of the ICs are pointing the
same direction.
Inspect the solder joints. Any solder shorts? Too much solder? Missing joints?
Wash the board under warm water. Scrub gently. Allow to dry for at least 2 hours!
THIS IS A GOOD STOPPING PLACE TO REST OR PUT THE KIT AWAY UNTIL
LATER.
You are now finished with the Organic flux solder. All soldering past this point is
using the No-Clean solder. You do not have to wash the board anymore.
PART #6: FINISHING THE PCB
You will now solder in the remaining parts on the pcb in preparation for wiring to the front
panel. USE THE NO-CLEAN SOLDER. BE CAREFUL!
Locate the Spectrol pots. These have black bodies (the Bourns pots have blue bodies).
Look carefully at the lettering: 3 pots will be marked 149-71104 and 1 pot will be
marked 148-71101. The ‘148’ pot goes into VR4! The 3 ‘149’ pots go into VR1, VR2
and VR3. Insert the leads so that the pot sita all the way down, resting on the pc board
with the shafts facing “outward”. Solder and trim the leads.
Locate the 5 pieces of RG-174 black coax cable. Again, note that one end has
longer wires stripped than the other. The short ends will go in the pc board in
locations J1, J3, J5, J7 and J8. Look at the pc board. Notice that in the coax positions,
there is a large hole pad (lower pad) and a smaller pad (top hole). The braided wire is
soldered into the larger hole. The smaller, inner conductor goes in the top hole. BE
SURE THE SHORTER BRAIDED END GOES INTO THE PC BOARD.
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Solder each coax cable into the holes. Attach a tie-wrap to secure the coax cable flush to
the board. The tie-wrap goes down, into the left hole and up through the right hole.
Secure and trim off any excess. See the photograph below for proper mounting (this is
generic photo, not specifically using the MOTM-510 pc board).
Locate the 2 red/black twisted wires. These solder into J4 and J6. One end of the wires
has more insulation stripped than the other. We call this the “long end”. The “short end”
is what solders into the pc board. Solder the red wire in the top (#1) hole and the black
wire in the bottom (#2) hole.
Locate the orange/white twisted wire. It solders into J2. Solder the white wire into the
top hole (#1) and the orange wire into the bottom hole (#2).
Locate the red/black/white twisted wire. It solders into VR5. The red wire goes into the
top hole (#3), the black wire goes into the center hole (#2) and the white wire goes into
the bottom (#1) hole.
Locate the 2 orange/gray/white twisted wires. These solder into VR6 and VR7. Solder
the orange wire into the top (#3) hole, the gray wire into the center (#2) hole and the
white wire into the bottom (#1) hole.
Locate the really pretty but painfully expensive IC U4, the AD538. After admiring the
shiny gold top and handsome ceramic body, reflect for a moment that if you mess this
next step up, it’s going to cost you $55 :)
Pin 1 of this IC has a small, white triangle by it. The ‘point’ of the triangle will be
pointing to a thin ‘strip’ of metal. A free Dr. Pepper to the first person who guesses what
this little strip is for. The ‘flat’ side of the little triangle is PIN #1.
If you somehow forgot to install the IC socket, do so now, using no-clean solder.
Soldering U4 into the pc board is, in technical terms, a ‘bad idea’.
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If you discover, with panic, that you soldered the socket in upside down, then DON’T
try to unsolder it. The IC will still go in fine. But no Dr. Pepper for you!
Now, using the utmost caution, carefully insert U4 into the socket with Pin 1
across from C16, where oddly enough I provided this rather large ‘1’ symbol. If you see
that Pin 1 is across from the ‘JP2’ lettering, this, in technical terms, is called “bass
ackwards” or “upside down” or even “about to cost you $55”. You can remove U4 with a
small, flat-bladed screwdriver, prying up under the IC body. Pry the IC a little at a
time, alternating end-to-end (else there is a great chance you will bend the pins).
GENTLY BUT FIRMLY press U4 down in the socket. The IC ‘body’ will NOT touch the
top of the socket. This is because the pins are ‘flared’ at the top, where the pins extend
out from the ceramic body. You may even hear a small ‘click’ as the IC seats in the
socket.
YOU ARE NOW FINISHED WITH THE PC BOARD WORK! BREAK TIME.
PART #7: FRONT PANEL PREPARATION
You will now attach components to the front panel. It is HIGHLY recommended that you use a
set of hollow shaft nut drivers, NOT PLIERS, to tighten the nuts. This prevents scratching.
NOTE: all references to part orientation is from the REAR of the panel.
Locate the 8 Switchcraft jacks. Notice that from the rear, there is a beveled corner.
This corner is ALWAYS CONNECTED TO GROUND, WITH A BRAIDED
CONDUCTOR. Each jack has a flat washer, a lockwasher, and a ½” hex nut. Remove
the nuts and washers from each jack. Place aside. Keep the lockwasher on the jacks.
Insert the 8 jacks/lockwashers, with the beveled corner in the upper right corner, into
the 8 holes. Place the flat washer on the jack, then the hex nut. Hold the jack with one
hand on the backside, keeping it ‘square’. Tighten the hex nut with a nut driver. NOTE:
when tight, not much of the exposed threads of the jack are exposed.
Remember those resistor lead scraps you have been saving? They solder on the OFFSET
X, OFFSET Y and OFFSET Z jacks. Solder the scrap in between the TOP and the
BEVELED lugs. Be sure to leave enough space on the beveled lug to attach the coax braid
(just solder the TOP lug for now).
Locate the 3 blue Bourns 100K pots. These are for the X IN, Y IN and Z IN panel holes.
The pots have a lockwasher that is behind the panel, and a flat washer is on the front
side of the panel. Secure the pots to the panel, with the 3 leads pointing “down”, towards
the jacks. A ½” nut driver is preferred to tighten the panel nut.
Now comes a tricky part. The rotary switch assembly goes into the
ROOT/UNITY/POWER hole, but it has to be tightened in a specific orientation. If you
look at the rear of the switch, you will see tiny numbers under each lug. In between the
‘7’ and the ‘8’ lugs, you will see a black “support latch”. This black piece, that is in
between the ‘7’ and ‘8’ lugs, must be “straight up” (at the 12 o’clock position) which on
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the other side of the panel is where the UNITY tick mark is. Looking from the rear
(back) of the switch, there will be a red wire on the #7 lug and nothing on #8.
The switch has plastic threads, so be very careful when tightening the nut. You have to
grasp the switch from the rear , making sure it does not rotate from the correct position.
You are now ready to attach the pc board to the bracket and then wire up to the panel.
PART #8: ATTACH PC BOARD TO BRACKET/PANEL
In the HARDWARE bag, locate 4 #6-32 x 3/8 screws, 4 #6 KEPS nuts, and 4 spacers.
Locate the mounting bracket. The pc board attaches to the bracket, with the 4
screws threading from the top of the board, through the spacers, through the
bracket, and then out the bottom of the bracket. If the bracket has a protective plastic
covering, remove it first. The #6 KEPS nuts attach on the bottom of the bracket.
Attach the pc board to the bracket. The flanges will point upwards when the pc board is
sitting on the bracket. Note that the bracket holes for the pc board are
actually oblong. This is to allow adjustment for the pc board to firmly press
up against the back of the panel. As a start, set the 4 screws ALL THE WAY
TO THE LEFT of the oblong holes. Loosely tighten the 4 KEPS nuts on the
bottom.
THIS IS A VERY IMPORTANT STEP, SO PAY ATTENTION AND READ ALL OF
IT BEFORE PROCEEDING!
Note that each of the 4 pots on the pc board have 2 hex nuts and a flat washer.
Remove the first hex nut and the washer. Set aside.
What you will do now is adjust the remaining hex nuts so that when the bracket is
all the way down on the panel’s threaded studs, all the pot hex nuts touch the rear
of the panel.
Screw (by hand) each hex nut on the pots so that it is all the way on (touching
the face of the pot). Now, pick up the pc board/bracket assembly and carefully
slide it over the 2 threaded studs, making sure the pots are aligned in the holes.
Use 2 #6 KEPS nuts and tighten the bracket to the panel.
Loosen the 4 KEPS nuts on the bottom of the bracket. Slide the pcb ALL THE WAY
TO THE RIGHT AS FAR AS IT WILL GO, so that the 4 pot nuts are all pressing
against the panel. By hand, put hex nuts on the outside threads of VR1 and VR4 to
keep the pc board in place. Now, tighten the 4 KEPS nuts on the bracket. The pcb
and bracket should be secure, with no gaps visible between the panel and the pot
nuts. You may need to loosen the nuts on the pots, so that they are touching
the back of the panel. Again, make sure each pot’s nut is touching the back of
the panel (no gaps!). There may be a gap from the edge of the pc board to the panel.
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PART #9: FINISH WIRING TO THE PANEL
Please read the following instructions carefully. In order to neatly attach the many wires to the
front panel components, the wires are soldered in a specific order.
Now you will solder to the 8 jacks. Each jack has 3 lugs from the rear we will refer to
them as LEFT, TOP, and BEVELED. The TOP lug is for the switched contact: this is a
NC (normally closed) contact that is opened when a plug is inserted. The resistor lead
scraps placed between the TOP and the BEVELED lugs purposely shorts unused inputs
to ground. This lowers the noise and the DC offset voltage.
Solder the coax in J8 to the AUDIO OUT jack. The braid goes to the BEVELED lug.
The inner conductor goes to the LEFT lug. This is true of ALL coax wires.
Solder the coax in J7 to FULL OUT.
Solder the coax in J5 to AUDIO Z.
Solder the coax in J3 to AUDIO Y.
Solder the coax in J1 to AUDIO X. This is somewhat of a stretch, but it will reach.
Solder red/black wire in J6 to OFFSET Z. The red wire goes to the LEFT lug, and the
black wire goes to the BEVELED lug.
Solder red/black wire in J4 to the OFFSET Y jack.
Solder the orange/white wire in J2 to the OFFSET X jack. The white wire goes on the
LEFT lug and the orange wire goes on the BEVELED lug
The red/black/white wires in VR5 solder to the Bourns pot X IN. The red wire solders to
the LEFT pot lug (#3), the black wire solders to the center lug (#2) and the white wire
solders to the right lug (#1).
The orange/gray/white wires in VR6 solder to the Y IN Bourns pot. The orange wire
solders to the left lug, the gray wire solders to the center lug and the white wire solder
to the right lug.
The orange/gray/white wires in VR7 solder to the Z IN Bourns pot. The orange wire
solders to the left lug, the gray wire solders to the center lug and the white wire solder
to the right lug.
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The rotary switch white 7-pin connector goes on JP2. If you look at the wires on the
connector, the 2 ‘outside’ wires are red and black. Now look at the pc board: the male
JP2 connector should have the ‘locking tab’ next to the empty R22 position. Place the
rotary switch female connector carefully on JP2, so that the RED WIRE IS ON THE
TOP (NEXT TO VR3) AND THE BLACK WIRE IS ON THE BOTTOM, BY THE
JP2 LETTERING. This will cause the wires to go over the top of U4, away from the
front panel.
BE SURE THAT THE CONNECTOR IS NOT ‘OFFSET’ ON JP2, THAT THE END
PINS ARE BOTH INSERTED.
Rotate all of the front panel pots fully counter-clockwise. Locate the KNOBS. There are
7 “regular” knobs and 1 special ‘pointer’ knob. The pointer knob is for the rotary switch.
This knob goes on first, and it is somewhat tricky to align correctly.
The best way is to loosen the 2hex screws (I have no idea why there are 2 of them),
manually rotate the switch clock-wise until it stops at the POWER position, and attach
the knob. It may take several tries to get the 2 set screws to “balance” the torque on the
knob so that the white line aligns with the 3 tick marks. Well, it’s tough for me, at least
:(
The other 7 knobs go on the 7 pots. Place the knob on the pot shaft,
align the white line to the ‘0’ tick mark, and tighten the hex screw. The silver
part of the knob has a protective clear plastic overlay that can be removed if
desired. Gently rub with your fingernail across it and it will peel off.
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Use the 2 remaining tywraps to bundle the wires to the Bourns pots and most of the
wires to the jacks. Trim off the excess.
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CONGRATULATIONS! YOU HAVE FINISHED BUILDING THE MOTM-510!
************************************************************************************
All that’s left to do is test it! But before we do, please read the following Theory of Operation. A
‘hands-on’ tutorial follows, with several audio demos you can listen to at:
www.synthtech.com/demo/warper
IMPORTANT NOTE:
The ROOT/UNITY/POWER switch is physically disconnecting active signals while the module
is under power. Therefore, the module may output ‘pops’, ‘crackles’ and ‘thumps’ when
switching position. Also, it is possible to apply enough pressure on the knob without turning it
to another position, but will cause this noisy output (the contacts of the switch “bounce” and
this causes noise).
The switch assembly is NOT BAD, nor is the module “bad”.
THEORY OF OPERATION/TUTORIAL
The MOTM-510 is a small, ‘pre-programmed’ analog computer. It is set to perform 1 basic
mathematical calculation, whose end result is a ‘warping’ or distortion of the input(s). The
analog computer is the Analog Devices AD538 IC chip (the gold-plated one), which has
internally many op amps and laser-trimmed resistors set up for the specific calculation.
And what is that calculation, you ask?
To start with, the AD538 is a combination of multipliers and log amps. What’s a log amp? Good
question: it’s a specially designed amplifier whose output is not linear, but goes as the
logarithm of the input. Wait, you groan, as sweat begins to form on your brow….what’s a
logarithm? OK, here’s the quick overview.
A while back, extremely smart people decided that it was easier to add numbers than multiply
them, especially since there were no calculators or slide rules. So, they figured out that if there
could be some way of “cheating”, using say pre-printed tables, so that if you wanted to multiply
X times Y, instead you could add 2 values based on X and Y and still get the right answer, that
would be KEWL! So, these tables were calculated and were called logarithms.
Here’s an example: 2 x 3 = ?
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What you do is find, in the table (let’s not go into how we got the table, OK?), the logarithms
(in this case, these are called the natural logarithms and are abbreviated ln(x), like ln(2). You
may have seen log(x), which are DIFFERENT logarithms and that’s for another day).
So, we find: ln(2) = .6931 and ln(3) = 1.0986. Adding these together, we get 1.7917…Errr…now
what? Well, we perform the inverse logarithm, meaning we look in the table for the ‘answer’ of
1.7917 and see what number has this for it’s logarithm (the choice of the term ‘inverse’ is
sometimes called ‘anti-log’ so that you don’t get confused with the ‘inverse of a number’ which
is 1 divided by that number). Scanning the table, we see that there IS in fact an entry for this
number (1.7917) and by some miracle, that number is 6! So, 2 x 3 = 6. The way inverse
logarithm is written is like this: ln-1.
Now, I’m sure by this point many of you are questioning my sanity why this is even relevant to
the ‘510. The point is: if you want to make an analog multiplier function, then what you can
possibly do is:
a) somehow take the logarithm of the inputs (not obvious)
b) add them together (EASY!!)
c) somehow perform the anti-log and BINGO! (still not obvious)
The solution: the circuitry inside the AD538 does this for us (if you really want to understand
exactly how circuits can perform log/antilog functions, get a copy of the Non-Linear Handbook
from Analog Devices (1-800-262-5643, select option 3). In a manner of speaking, the AD538 IC
calculates, in real time, both log and anti-log functions of input signals. The data sheet for the
AD538 also has more theory, and is contained as a PDF file on the CD-ROM (and also on the
Analog Devices website).
If all the AD538 did was to act as a multiplier, that would be fine but not that exciting (there
are many other analog multiplier ICs out there that don’t cost $55). We already use multipliers
in our synths: these are called ‘Ring Modulators” and “VCAs”. So what’s the big deal with the
AD538 and the WaveWarper?
Well, 2 things. First, the AD538 can also divide. Hmmm…haven’t seen that before in a synth
module! The AD538 does this by another ‘trick’ using logarithms:
ln(X/Y) = ln(X)-ln(Y)
Meaning, that if we subtract the logarithms instead of adding them, we divide! Awesome,
dude! (and people think math is boring). In analog circuits, this is trivial (simple op amp
inverting summer). All of a sudden, the AD538 is looking quite interesting.
But there is one more surprise, and it’s a biggie: using logarithms, it’s also easy to calculate
roots and powers of numbers, too!
This is calculated by using the well-know relationship:
ln(Xy) = y * ln(X)
For example, to calculate 43:
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ln(4) = 1.38629
ln(4) * (3) = 4.15888
ln-1 (4.15888) = 64 <<<taa daa!!!
Of course, step #2 above (the multiply) is done inside the AD538 by adding logarithms (as
before). Personally, I think this is pretty COOL STUFF, being able to multiply, divide AND
raise to powers using only adding circuits. And even cooler, we are able to this is real time,
using voltages as the ‘numbers’ in our little analog computer.
What’s the difference between a root and a power?
In this context, they are the same, but the implication is that a root is <1 (the other use of the
math term ‘root’ means the number that makes an equation equal to zero).
So, a ‘square root’, which is usually written like this: √x
Can also be written as: x.5
The downside of the AD538 (well, a downside for use MOTM users) is that the exponential
factor is NOT a control voltage. Rather, it is designed to be an external trim pot. This is
because the ‘normal’ usage of an AD538 is to generate a specific equation that is application-
dependent. In these circuits, the exponent is a constant that is trimmed. However, the MOTM-
510 ‘abuses’ the AD538: we replace the fixed trim pot with a rotary switch and a front panel
control, so that you can tweak the exponent in real-time.
So, what was the original application(s) of the AD538 (before we started abusing it with audio)?
One widely used application was electric thermometers.
Many of you have heard the term thermocouple. A thermocouple is a temperature probe (there
is one in your oven) made by twisting 2 different metal wires together. This makes a small
(very small!) battery whose voltage output is based on the temperature of the ‘junction’ of the 2
metal wires. Also, you can take certain alloys of metal (usually platinum) that change
resistance to temperature, according to something called the Stainhart-Hart equation:
1/T = a + b + (lnR) + c(lnR)3
where a, b, and c are ‘fudge-factors’ based on the wire used, R is the resistance and T is the
temperature. Note that this “nasty” equation can be ‘solved’ with the AD538 (the ‘ln(R) part
and the c(ln(R)3) part as well). Why is THIS a big deal? Because….this chip was designed in the
pre-microprocessor, pre-ADC world, and the temperature readout was a linear analog meter.
Since the meter has a linear scale, we want a linear relationship between temperature (what
we are measuring) and voltage driving the meter (how we are displaying the temperature).
Think about it for a minute: if I came to you and said: “I need a circuit that uses this equation
to drive a meter over a 0 to +5V scale so that 1V = 100F, 2V = 200F, etc” how would you do it?
Answer: AD538! The details are left to the user, but this part was widely used for this
application. The other application was to “warp” the voltage in radar CRT terminals so that
specific shapes (square, triangles, etc) ‘drawn’ on FAA radar screens (which are NOT flat CRTs,
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but are ‘bowls’) are correctly seen. Hint: to ‘linearize’ a function like XY, you run it through the
inverse function X(1/Y).
AUDIO OUT/FULL OUT (PLEASE READ!)
There are 2 outputs on the MOTM-510, labeled AUDIO OUT and FULL OUT. What’s the
difference, and how do you know which one to use?
The difference is the AUDIO OUT has an AC coupled, 16Khz 2-pole lowpass filter. The FULL
OUT has no filter, and is DC coupled. So??!?
The FULL OUT should ONLY be used for DC control voltages or
LFO outputs.
WARNING! IF YOU USE THE FULL
OUT AND CONNECT IT TO
AMPLIFIERS/ MIXERS/DIGITAL
RECORDERS/AUDIO
CARDS/WHATEVER, YOU CAN
EASILY DESTROY/BLOW
UP/EXPLODE/FRY/FUBAR/INSERT
BAD THING HERE TO YOUR
EQUIPMENT. YOU HAVE BEEN
WARNED!
The AD538 IC can easily generate large signals with large DC offsets. Also, the wide
bandwidth of the AD538 can generate harmonics up to 400Khz. Yep, I said 400KHz.
So, it’s pretty simple: use AUDIO OUT unless you are warping LFOs (loads of fun!). Then, you
NEED to use the FULL OUT.
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TUTORIAL SECTION
A Ring Modulator is a multiplier: the output can be written as:
Out = X * Y
where X and Y are the 2 input signals (sometimes referred to as the modulator and the
carrier). X and/or Y can be audio or DC signals. The output is simply the voltage X times the
voltage Y. This produces the sum of X and Y (X+Y) and the difference of X and Y (X-
Y)…Instead of the 2 RM inputs, the basic WaveWarper has 3: X, Y and Z. These are audio
inputs. The transfer function is
Out = X * (Y/Z)^m
OK, so let’s plug in some numbers to the MOTM-510 transfer function. If we assume Z and m are
both one then we get
OUT = X * (Y/1)^1
which simplifies to
OUT = X * Y
which the minimally astute reader will recognize as the transfer function for a classic ring
modulator. So if we are understanding things correctly, the following patch should give us
some traditional-sounding RM:
VCO 1 SIN OUT -> 510 AUDIO Y (Y IN = 10, Y WARP = 10)
VCO 2 SIN OUT -> 510 AUDIO X (X IN = 10, X WARP = 10)
510 AUDIO OUT -> amplifier1, power switch = UNITY
Drive the VCO’s however you like, I use the MOTM-101 Sample & Hold module; detuning the
VCO’s shows off the nice RM effect of the patch.
1I take the 510 AUDIO OUT to the MOTM-109 IN and the OUT of the 190 to my mixing desk. This allows me to
attenuate the output going to the desk. The signal in this patch is TOO HOT for my mixer’s inputs, and is probably too
hot for yours, too. Be careful! Also note that the FULL OUT can output up to 400 KHz; at high energy levels, you’re
bound to break something.
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Now try turning down the X WARP knob. At zero, the timbre is quite a bit fuzzier than at 10.
Try the same with the Y WARP knob: same deal, but the Y fuzziness has a different character
It would be cool to automatically modulate the ‘fuzziness’ in and out, me thinks. No problem,
that’s what the OFFSET jacks are for!
In this patch, I use an LFO to sync the S&H speed with the OFFSETs on the ‘510 .Here is a
diagram of the patch:
LFO S&H
VCO
VCO
SQR
510
SIN
SIN
TRI
SIN
OFFSET Y
OFFSET X
AUDIO Y
AUDIO X
AUDIO OUT
X IN = 10 X WARP = 4
Y IN = 10 Y WARP = 6
Z IN = 0 Z WARP = 0
POWER = UNITY
FACTOR = 0
Figure 1: Patch Chart for DEMO #3
Now we’re hearing something pretty interesting with just two sine waves! Play with the X IN,
Y IN, and X and Y WARP knobs and see what it does to the timbre. When you’re done, set
them back as in the patch diagram (that way the next demo will sound close to what you’ll hear
on your system). Now crank the Z WARP knob to 10. Crazy! But what’s going on?
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Pretty simple, really. Refer back to equation (1); by altering Z WARP we are changing the
value of Z in the equation (1). This, of course, alters Out and munges the wave form.
OK, one last demo before moving on to other aspects. This one uses the same patch diagram as
for DEMO #3 except we’ll add another sine wave from a third oscillator to AUDIO Z and tweeze
the knobs a bit. I call this piece “Concerto for Farty Armpit Noises” which is probably not PC.
Oh well.
LFO S&H
VCO
VCO
SQR
510
SIN
SIN
TRI
OFFSET Y
AUDIO Y
AUDIO X
AUDIO OUT
X IN = 0 X WARP = 3
Y IN = 0 Y WARP = 0
Z IN= 10 Z WARP = 5
POWER = ROOT
FACTOR = 10
VCO
SIN
AUDIO Z
Figure 2: Patch Diagram for Demo #5
And finally, here is an extended improvisation using the patch diagrammed in Figure 2. The
only alteration was the addition of an LFO feeding the S&H IN of the MOTM-101 to get a more
regular pattern to play with. All the timbre variations you hear are accomplished by turning
knobs and changing the ROOT/UNITY/POWER switch. This is an amazing amount of
variation coming out of one module! No filters were used and no envelopes:
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