MOTM-480 CS Resonant VCF
Assembly Instructions & Owner’s Manual
Synthesis Technology
6625 Quail Ridge Dr.
Fort Worth, TX 76180
(817) 498-3782
www.synthtech.com
Feb. 11, 2005
MOTM-480 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/Resistor bag, containing the following 14 parts:
2ea 10µfd, 50V Electrolytic
2ea 1nf (0.001µfd) yellow box caps
4ea 3M3 non-polar electrolytic
4ea 1N5 (1500pf) polypropylene caps
2ea 1K 1% 3W Tempco resistor
C28, C29
C3, C6
C8, C15, C21 and C27
C12, C13, C19 and C20
R9, R17 (see text)
A pre-stuffed pc board, containing the following components:
Capacitors
15ea 0.1µfd (marked 104) ceramic axial
2ea 150pf (marked 151) ceramic axial
C1, C2, C4, C5, C7, C9-11, C14,
C16-18, C24-C26
C22, C23
Resistors (NOTE! – 1% resistors may be substituted for 5% parts)
10ea 100K 1%
2ea 221K 1%
4ea 54K9 1%
2ea 562K 1%
2ea 4K99 1%
4ea 51K1 1%
4ea 150K 5%
14ea 10K 5%
8ea 270ohm 5%
6ea 33K 5%
4ea 4M7 5%
6ea 68K 5%
4ea 1K 5%
4ea 6K8 5%
2ea 200K 5%
2ea 1M2 5%
SYNTHESIS TECHNOLOGY
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R1, R2, R4, R5, R10, R12, R13,
R18, R57, R62
R3, R11
R6, R14, R58, R63
R7, R15
R8, R16
R19 – R22
R23-R25, R68
R26, R30, R32, R35, R40, R44,
R46, R49, R70, R71, R73, R74,
R77, R78
R27, R28, R33, R34, R41, R42,
R47, R48
R29, R43, R54, R55, R69, R76
R31, R36, R45, R50
R37, R51, R66, R67, R75, R80
R38, R52, R56, R61
R39, R53, R59, R64
R60, R65
R72, R79
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IC bag, containing the following 18 parts:
7ea TL072ACP dual op amp
4ea BC560C PNP transistor
2ea LT1013 op amp
3ea CA3280 dual OTA
2ea SSM2220P PNP array
U2, U6, U7, U9 – U12
Q3 – Q6
U1, U3
U4, U5, U8
Q1, Q2
Misc #1 bag, containing the following 3 parts:
2ea Axial ferrite beads (plain, gray things)L1, L2
1ea MTA-156 power connector
JP1
Knobs, 8ea, ALCO PKES90B1/4
Jacks, 8ea Switchcraft 112A
Pots, 8ea containing the following:
3ea 100K log Spectrol 148-9609-104
1ea 100K lin Spectrol 149-71104
4ea 100K lin Bourns panel pots
VR1, VR2, VR3
VR4
VR5- VR8
Front panel
Mounting bracket
Wire bag, containing the following 12 wires:
2ea long RG-174 coax
3ea short RG-174 coax
1ea 3-wire set 22ga (white/red/black) long
1ea 2-wire set 22ga (orange/white) long
3ea 3-wire set 22ga. (orange/white/gray) long
1ea 2-wire set, 22ga, 3½” (red/black)
1ea Power Cable, 20”
J5, J6
J4, J7, J8
on VR5
J3
on VR6 – VR8
J1, J2
Hardware bag, containing:
4ea #8-32 x 3/8” black screws (for mounting module to rack)
4ea #6-32 x ½” zinc screws (for attaching pc board to bracket)
4ea ¼” aluminum spacers
6ea #6 KEPS nuts (2 for attaching bracket to front panel, 4 for pc board)
7ea small tie-wraps
Organic Solder AND No-Clean solder (1 bag each type)
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GENERAL INFORMATION
Thank you for purchasing the MOTM-480 VCF. If you have any issues concerning the
building or use of the kit, please contact us at (817) 498-3782 or by email:
synth1@airmail.net.
This kit should take the average builder between 2 to 3 hours. 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-480:
•
•
•
•
•
•
•
•
•
•
Soldering iron, 50W max power. Use 700ºF tip/temperature setting
Small amount of heatsink compound
Needle-nose or chain-nose pliers
Diagonal cutters
Allen key set for securing the knobs (1/16” or 1.58mm)
Magnifying glass: to read the markings and to inspect solder joints
DVM (Digital Volt Meter) or 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 Tutorial pages
at http://www.synthtech.com.
HOW TO FOLLOW THE DIRECTIONS
Please read the entire instruction before proceeding. There may be valuable information at
next to it. After you
the end of the instruction. Each instruction has a check box
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 washed in the sink. The flux is OSHA approved for flushing down
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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/CAPACITORS ON THE PRE_STUFFED
PC BOARD
The MOTM-480 pc board has most of the resistors and capacitors already inserted, with the
leads bent and cut, ready to be soldered. All of these parts use the organic solder and the
board must be thoroughly washed after soldering.
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. A
SMALL AMOUNT, not a blob!
The rule of soldering: don’t use too much, you can always add more!
After soldering all the pre-stuffed resistors and capacitors, wash and dry the pc board.
PART #2: Soldering the ICs & Misc parts
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.
Locate the MTA-156 power connector. Solder into JP1. Note that the connector has
a “locking tab” on one side. This side is the “inside” facing relative to the pc board.
Note the silkscreen symbol for JP1 has a line on one side, indicating this is the side
where the locking tab goes.
Locate the CA3280 (3). Solder into U4, U5 and U8. Be sure the parts all point in the
same direction: “up”.
Locate the LT1013 (2). Solder into U1 and U3.
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Locate the SSM2220P (2). Solder into Q1 and Q2.
Locate the TL072ACP (7). Solder into U2, U6, U7, U9, U10, U11 and U12.
Apply a small bit of solder to the via holes. These are the small pads (no components
go in them) that allow traces to “change sides” of the pc board. DO NOT SOLDER
PADS FOR THE REMAINING COMPONENTS!! The via holes need a VERY
SMALL AMOUNT of solder.
PART #3: BOARD WASH #2
Wash the board in warm water, gently scrubbing both sides.
Shake the board a couple of times, blot dry with an old towel (the leads will frazzle
a good towel). Let dry at least 15 minutes.
Take another break or set the kit aside for later. You are about 75% finished at this
point: this is a good stopping-point.
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 #4: CAPACITORS/TEMPCO RESISTORS
Locate the CAPACITOR/RESISTOR bag. Set the 2 black TEMPCO resistors aside.
Locate the 1N5 (1500pf) poly caps. (4). They are reddish-brown in color. Solder into
C12 and C13 (by U12), C19 (by U7) and C20 (by U11).
Locate the 3M3 non-polar caps. Solder C8 and C15 (by VR1) and C21 and C27 (by
U11).
Locate the 1nf (1000pf) yellow box caps (2). Solder into C3 and C6 (near U2).
Locate the 10µfd electrolytics (2). Note that there is a stripe on the NEGATIVE
terminal. The pc board has a + on the POSITIVE terminal. Carefully stick the
capacitors into C28 and C29 with the stripe away from the + pad on the board.
Locate the 2 black Tempco resistors. These solder on top of Q1 and Q2. A small
amount of heatsink compound is first applied to the tops of Q1 and Q2, and the
Tempcos are placed so that the DIP packages are in contact with the bottom of the
Tempcos. Be sure the Tempcos are level and flat before soldering.
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PART #5: 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 (4). IMPORTANT: in order for the pc board to properly
align with the front panel, each pot must be absolutely flat on the pc board, with
the shafts pointing away from the pc board. Three of the Spectrol pots have shorter
leads and are marked 148-9609-104. Solder these pots into VR1, VR2 and VR3. The
other Spectrol pot has longer leads and is marked 149-71104. Solder this pot into
VR4.
Locate the WIRE bag. The MOTM-480 has lots of wires: be very careful when
soldering to the pc board in order that the wire colors are correctly into the proper
holes.
The long coax wires solder into J5 and J6. A tie-wrap is used on each wire to secure
the coax flat onto the pc board. Note that the coax wires have one end stripped back
shorter than the other: the short end solders to the pc board. See the photo below for
details (this is a generic photo!)
Solder the 3 short coax cables into locations J4, J7 and J8. Secure with tie-wrap.
Solder the white/black/red wire into VR5. White into 1, Black into 2 and Red into 3.
Solder the orange/white wire into J3. White into 1 and Orange into 2.
Solder the 3 white/gray/orange wires into VR6, VR7 and VR8. In all cases, the White
goes to 1, the Gray into 2 and the Orange into 3.
Solder the 2 red/black wires into J1 and J2. In both cases, the Red is in 1 and the
Black solders into 2.
YOU ARE NOW FINISHED WITH THE PC BOARD WORK! BREAK TIME.
SYNTHESIS TECHNOLOGY
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PART #6: 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. 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.
Attach the 4 blue Bourns pots to the front panel. The 3 lug terminals point
“downward”, toward the jacks. The lockwasher goes on the inside of the panel, the
flat washer on the outside.
You are now ready to attach the pc board to the bracket and then wire up to the panel.
PART #7: ATTACH PC BOARD TO BRACKET/PANEL
In the HARDWARE bag, locate 4 #6-32 x 3/8
spacers.
screws, 6 #6 KEPS nuts, and 4
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. The #6 KEPS nut attaches on the
bottom of the bracket. Note the bracket has 2 long mounting flanges with a hole
in each. These attach to the 2 threaded studs sticking out of the rear of the panel.
The 4 pots each stick in its panel hole when the bracket is screwed down on the 2
threaded posts.
Attach the pc board to the bracket using the 4 screws, spacers and nuts (the nuts go
on the bottom of the pc board). Do not tighten the nuts all the way, so the pcb can
“slide” in the bracket. Next, attach the bracket/pcb to the 2 threaded studs (tighten
these 2 nuts all the way). With the 4 pcb nuts still partially tightened, put the 4 flat
washers and 4 nuts on VR1-VR4 (on the front of the panel) and tighten. This will
“pull” the pcb up against the panel, resting on the 4 pot nuts. NOW you tighten the 4
nuts on the bottom of the pcb bracket.
SYNTHESIS TECHNOLOGY
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PART #8: 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. You may find, in
some cases, it is easier to first remove a jack from the panel and solder the wires, then
reattach it to the panel.
Solder the red/white/black wire to VR5, FREQ HP. Red on the left lug, Black on the
center, and White wire on the right lug.
Solder the white/gray/orange wire in VR6 to the control RES HP. Orange on the left,
gray on the center and White on the right lug.
Solder the white/gray/orange wire in VR7 to the control FREQ LP. Orange on the
left, gray on the center and White on the right lug.
Solder the white/gray/orange wire in VR8 to the control RES LP. Orange on the left,
gray on the center and White on the right lug.
Now you will solder to the 8 jacks. In all cases, the Top lug is NOT connected. The
BEVELED lug is the Ground connection: the coax braids all solder to this lug. The
wiring is crowded, take your time. Be SURE that you fill the lug’s internal hole
completely with solder. It doesn’t take all that much, but it will secure the wire to
the jack.
Solder the coax in J4 to the BP OUT Jack. The braid is on the BEVELED lug, the
inner conductor is on the LEFT lug. The TOP lug is NOT connected.
Solder the coax in J8 to the LP OUT jack.
Solder the white/orange wire in J3 to the RES CV jack. White wire to the Left lug,
Orange wire to the Beveled lug.
Solder coax in J7 to the IN3 Jack.
Solder the red/black wire in J2 to the FM IN jack. Red on the Left lug, Black on the
Beveled lug.
Solder the coax in J6 to IN2 jack.
Solder red/black wire in J1 to the 1V/OCT jack. Red on the Left, Black on Beveled.
Solder the coax in J5 to the IN1 jack.
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Use the 2 remaining tie-wrap to bundle the wires. Use 1 tie-wrap on VR5-8 wiring
(attach the tie-wrap behind VR7), the other on the jack wiring.
Rotate all of the front panel pots fully counter-clockwise. Locate the KNOBS.
Notice each knob has a white line on it. 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.
************************************************************************************
CONGRATULATIONS! YOU HAVE FINISHED BUILDING THE MOTM-480!
************************************************************************************
All that’s left to do is test it! But before we do, please read the following Theory of
Operation.
THEORY OF OPERATION
The MOTM-480 is based on the circuitry in the Yamaha CS-80 polyphonic synthesizer. The
exact circuit is not copied. Instead, more modern components are used to mimic the overall
architecture of the original design.
The MOTM-480 has 2 identical multi-mode filters connected in series. The filters are called
state-variable filters (SVF), but not for the reason you may think. It is true that this filter
topology has 3 simultaneous outputs (LP, LP and BP) so it is natural to assume statevariable means….errr…variable outputs. However, the term state-variable is a
mathematical definition. The original paper describing this particular filter topology (in
1967!) was titled “State-Variable Synthesis for Insensitive Integrated Circuit Transfer
Functions”. If you remember solving second-order differential equations, you can substitute
state variables for the differential and integral terms in the equation, and use algebra
(instead of calculus) to solve. I remember like it was yesterday (cough cough).
The 3 outputs of the VCF each have their own equation, and so the mathematical solution
is used to describe the filter, NOT the physical implementation. In fact, the SVF is usually
implemented as a slightly different configuration called a Fleischer-Tow Biquad (whose
output equations are a quadratic equation in the S-domain, but I digress).
Moving right along, the MOTM-480 uses 2 independent SVF filters connected in a certain
way. Internally, there are actually 6 simultaneous outputs, but we elected to only use 2 of
them. I’m sure some industrious person can figure out an expansion panel for all 6 :)
Page 1 of the schematic shows the 2 identical control sections for the 2 filters’ cutoff
frequency. Looking for a moment at the top (HP) section, U3 is just a voltage
summer/inverter for the various panel controls and FM input. Note that the FM input is
coupled to both filters, as is the 1V/OCT input. Each filter does have independent initial
cutoff frequency pots.
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The summed DC voltages are attenuated by divider network R14/R17 to be properly scaled
to 1V/Oct. I elected not to use a trim here because the 54.9K/1K ratio is within 3% of
“correct” and to set a trim more accurate than 3%, an oscilloscope is needed.
The scaled voltage (1V in equals 17.9mv out) feeds the PNP current mirror Q2. The
emitters are fed a reference current of 15V/R15 = 26.7µa which is modulated by the Vbe
voltage. We want a current out because the OTAs we are using (CA3280) need a control
current, not a control voltage.
Now let’s examine Page 2 of the schematic. In the lower-left corner, you will see 2 familiar
circuits: these are almost identical to the circuits on Page 1. Again, 2 voltage
summers/attenuators/PNP current mirrors are used to control the resonance (feedback)
VCA sections of the 2 SVFs). These current mirrors are not quite as “fancy” but they get the
job done.
If you draw an imaginary line across the center of the page, you can see the 2 identical SVF
circuits. The are interconnected by the wire from the top section (U10A, pin 1) to the bottom
section (through R68 and C15, into U7A). We will discuss the top section, because it also
applies to the bottom one as well.
The 3 audio inputs are summed and AC coupled into U10A. Following U10A are 2 cascaded
current-controlled integrators, formed by 1 section of a dual CA3280 OTA (U4) and an opamp/capacitor (U12B/C12 and U6A/C13). The output of the second integrator is fed back
through R55, forming a “closed-loop” system which give the SVF its unique characteristics.
Resonance is achieved by a simple VCA section (U5A) which feeds back a portion of the first
integrator’s output into U10A. The output of the CA3280 is also a current, so R69 is a
simple current-to-voltage converter.
In the SVF, the highpass (HP) response is the output of the summer U10A pin 1, the
bandpass (BP) response is the output of the first integrator stage U12B and the lowpass
(LP) response is the output of the second integrator U6A pin 1. You will see that only the
BP output from the top SVF is brought out to the front panel, after it is amplified by a
factor of 10 (R37/R39) by U6B.
To get that CS-80 sound, two “tricks” need to be used. First, look at the resonance OTA
section U5A. See 150pf capacitor C22 in parallel with 1M2 resistor R72? Normally, there is
no reason for this network to be there. But in the CS-80 it IS there to limit the selfresonance of the SVF. This network induces a phase-shift so that the SVF can go into high
resonance but NOT self-resonance (oscillation). It also imparts a “softness” to the overall
sound which is very “CS-80 like” and so it’s on the MOTM-480 as well.
Trick #2 is how the 2 sections are interconnected. On the CS-80, and hence the MOTM-480,
the HP output of SVF #1 feeds the audio input of SVF #2. Yamaha could have picked the
BP or the LP outs, but they chose the HP out and so do we. But…..since these filters are in
series, we want to pick the “correct” output from the second SVF to get a “musically useful”
signal, and that’s the LP output (U11A). This allows us to create a variable bandpass
response because we purposely split the controls into the upper section (HP FREQ/HP RES)
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and the lower section (LP FREQ/LP RES). So, you the user can independently set the 2
“corners” of a bandpass filter, each with its own resonance. Sure, the jack is labeled “LP
OUT” and we certainly can get a standard LP output. But in most cases, you will discover
the best-sounding patches use a mixture of HP/LP settings to generate this modified BP
response.
Here are a few graphs off the Audio Precision showing different frequency response plots
for different panel settings. Originals are at www.synthtech.com/files/motm480plots.pdf
A u d io P r e c is io n
A -A F R E Q U E N C Y R E S P O N S E
0 2 /1 4 /0 5 1 9 :3 1 :3 8
+ 10
+8
+6
+4
+2
+0
-2
-4
-6
-8
d
B
V
-1 0
-1 2
-1 4
-1 6
-1 8
-2 0
-2 2
-2 4
-2 6
-2 8
-3 0
20
50
100
200
500
1k
2k
5k
10k
20k
Hz
Sweep
T ra c e
C o lo r
L i n e S ty l e
T h ic k
D a ta
A xi s
1
2
3
1
1
1
M a g e n ta
B lu e
C ya n
S o lid
S o lid
S o lid
3
3
3
A n l r .L e v e l A
A n l r .L e v e l A
A n l r .L e v e l A
L e ft
L e ft
L e ft
Com m ent
M O T M - 4 8 0 B P O U T F r e q u e n c y r e s p o n s e . S e tti n g a r e H P R E S = 0 , a n d H P F R E Q s e tti n g s a t ti c k m a r k s 2 , 5 a n d 8 .
A - A F R E Q R E S P .a t2
A u d io P r e c is io n
A -A F R E Q U E N C Y R E S P O N S E
0 2 /1 4 /0 5 1 9 :3 7 :2 4
+ 20
+ 15
+ 10
+5
+0
d
B
V
-5
-1 0
-1 5
-2 0
-2 5
-3 0
20
50
100
200
500
1k
2k
5k
10k
Hz
Sweep
T ra c e
C o lo r
L i n e S ty l e
T h ic k
D a ta
A xi s
1
2
3
1
1
1
M a g e n ta
B lu e
C ya n
S o lid
S o lid
S o lid
3
3
3
A n l r .L e v e l A
A n l r .L e v e l A
A n l r .L e v e l A
L e ft
L e ft
L e ft
Com m ent
M O T M - 4 8 0 B P O U T F r e q u e n c y r e s p o n s e a t d i ffe r e n t r e s o n a n c e s e tti n g s . H P F R E Q = 5 , H P r e s v a r i e s fr o m 0 to 8 .
A - A F R E Q R E S P .a t2
.
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20k
A u d io P r e c is io n
A -A F R E Q U E N C Y R E S P O N S E
0 2 /1 4 /0 5 1 9 :5 2 :3 7
+0
-2
-4
-6
-8
-1 0
-1 2
-1 4
-1 6
d
B
V
-1 8
-2 0
-2 2
-2 4
-2 6
-2 8
-3 0
-3 2
-3 4
-3 6
-3 8
-4 0
20
50
100
200
500
1k
2k
5k
10k
20k
Hz
Sweep
T ra c e
C o lo r
L i n e S ty l e
T h ic k
D a ta
A xis
1
2
3
1
1
1
M a g e n ta
B lu e
C ya n
S o lid
S o lid
S o lid
3
3
3
A n l r .L e v e l A
A n l r .L e v e l A
A n l r .L e v e l A
L e ft
L e ft
L e ft
Com m ent
M O T M - 4 8 0 L P O U T r e s p o n s e w i th H P F R E Q = 0 , L P F R E Q v a r i e s fr o m 4 to 9 . B o th R E S s e tti n g = 0 .
A - A F R E Q R E S P .a t2
A u d io P r e c is io n
A -A F R E Q U E N C Y R E S P O N S E
0 2 /1 4 /0 5 2 0 :0 3 :0 9
+ 10
+8
+6
+4
+2
-0
-2
-4
d
B
V
-6
-8
-1 0
-1 2
-1 4
-1 6
-1 8
-2 0
-2 2
-2 4
20
50
100
200
500
1k
2k
5k
Hz
Sweep
T ra c e
C o lo r
L i n e S ty l e
T h ic k
D a ta
A xi s
1
2
3
1
1
1
M a g e n ta
B lu e
C ya n
S o lid
S o lid
S o lid
3
3
3
A n l r .L e v e l A
A n l r .L e v e l A
A n l r .L e v e l A
L e ft
L e ft
L e ft
Com m ent
M O T M - 4 8 0 L P O U T w i th L P F R E Q = 8 , H P F R E Q = 1 .5 , L P R E S = 0 . H P R E S i s v a r i e d fr o m 0 to 8 .
A - A F R E Q R E S P .a t2
SYNTHESIS TECHNOLOGY
MOTM-480 ASSEMBLY 2/11/05
WWW.SYNTHTECH.COM
PAGE 13
10k
20k
PRELIMINARY CHECK-OUT & TROUBLESHOOTING/USE
The first thing to remember: this filter will not self-oscillate - Blame Yamaha :)
Checkout is straightforward: use a VCO to input a square or pulse into IN1. Set all panel
pots to “5” and check for audio outputs at LP OUT and BP OUT. Remember, the BP OUT is
only dependent on the top SVF working. If that isn’t functional, then chances are LP OUT
will be dead (unless to have a wiring issue with the coax). Adjust the HP and LP FREQ pots
and listen to the different responses.
One thing to remember: the BP OUT is ONLY affected by the HP controls. The LP OUT is
affected by both HP/LP sets of controls. This can be a little confusing at first.
If there are problems, check the following:
a) No missing solder joints?
b) All of the ICs point in the same direction
c) Check the wiring to the pots. Verify the proper colored wire goes into the proper
hole.
d) Verify the jack wiring.
If you still cannot get the module to perform correctly, please contact us by phone at (817)
498-3782 or by email to synth1@airmail.net
SYNTHESIS TECHNOLOGY
MOTM-480 ASSEMBLY 2/11/05
WWW.SYNTHTECH.COM
PAGE 14
SPECIFICATIONS
MOTM-480 CS-MODE VCF
Audio Input Range
10V pk-pk nom.
Control Voltage Range
-7V/+7V
Output impedance
1000 ohms, nom.
Frequency Range
20Hz – 18Khz nom.
CONTROLS
HP FREQ
sets HPF section initial cutoff
HP RES
sets HPF resonance
LP FREQ
sets LPF section initial cutoff
LP RES
sets LPF resonance
IN1, IN2, IN3
input attenuation of audio inputs
FM
reversing attenuator for both HP/LP
GENERAL
Power Supply
-15VDC @ 28ma
+15VDC @ 28 ma
Size
2U x 5U
3.45 x 8.72
88mm x 221.5mm
Depth behind panel
4.5
SYNTHESIS TECHNOLOGY
MOTM-480 ASSEMBLY 2/11/05
WWW.SYNTHTECH.COM
(114mm)
PAGE 15
J1
J2
1
2
-15V
1
-15V
2
VR7
3 100K
+15V
FREQ LP
1V/OCT
FM IN
FM
3
1
2
VR5
3 100K
+15V
L2
FERRITE
VR4
100K
FREQ HP
MTA-156
JP1
1
2
3
4
L1
FERRITE
51K1
R22
51K1
221K
R3
100K 1%
R2
100K 1%
R18
C28
10M
50V
R19
221K
R11
-15V
+15V
C29
10M
50V
3
2
3
2
U3A
LT1013
1
8
4
U1A
LT1013
1
100K 1%
R1
8
4
100K 1%
R10
7
R6
-15V
R17
1K TEMPCO
54K9
R14
100K 1%
R5
0.1M
C1
5
6
8
4
+15V
U1B
LT1013
0.1M
-15V C2
100K 1%
R9
1K TEMPCO
54K9
562K
7
+15V
U3B
LT1013
0.1M
51K1
8
4
R7
R4
0.1M
C4
5
6
562K
R15
R20
51K1
R21
100K 1%
R13
-15V C5
100K 1%
R12
-15V
8
4
8
4
1
3
+15V
1
|LINK
|M480_2.SCH
2
1
U2A
TL072
Q1A
SSM2220P
3
2
-15V
1N
C3
2
3
+15V
7
U2B
TL072
Q2A
SSM2220P
5
6
-15V
1N
C6
7
ICLP
ICHP
6625 QUAIL RIDGE DR.
FORT WORTH, TX
76180
(817) 281-7776
SYNTHESIS TECHNOLOGY
Q1B
SSM2220P
7
Q2B
SSM2220P
MOTM-480 CS-RESONANT FILTER
Size Document Number
B
M480_1
Date: September
8, 2004 Sheet
1 of
Title
8
6
R8
4K99
8
6
R16
4K99
REV
A
2
J7
J6
J5
200K
R65
LP RES
VR8
100K
+15V
RCV
R62
100K
8
5
6
8
4
-15V
3
RCV
+15V
7
U9B
TL072
1
U9A
4 TL072
100K
200K
68K
R66
R57
2
R67
68K
VR3
100K LOG
VR2
100K LOG
VR1
100K LOG
R60
HP RES
VR6
100K
+15V
J3
RES CV
IN 3
IN 2
IN 1
54K9
R63
54K9
R58
150K
R25
150K
R24
150K
R23
R61
1K
Q5
BC560C
R56
1K
Q3
BC560C
+15V
Q6
BC560C
R64
6K8
Q4
BC560C
0.1M
C14
3
10K
R74
10K
R73
8
4
-15V
33K
R43
33K
LPQ
HPQ
+15V
TL072
1
1
4
V
C
C
U7A
+15V
3
I
B
C
V
E
E
4
-15V
150P
OUT
R54
1
+15V
R72 1M2
HPQ
2
0.1M
8
C22
13
3
U10A
4 TL072
-15V
2
C17
R69
33K
R59
6K8
FBK
+15V
3M3
C15
R68
150K
3M3
C8
0.1M
C10
33K
R29
33K
R55
15
16
68K
R75
-
10K
R40
1
I
D
+
U5A
CA3280_1
10K
R26
R41
270
+15V
R27
270
R42
270
C16
0.1M
+15V
1
I
D
1
4
V
C
C
V
E
E
3
R76
33K
13
R44
10K
OUT
I
B
C
FBK
1
4
V
C
C
4
R30
10K
13
U8A
CA3280_1
4M7
3
I
B
C
OUT
U4A
CA3280_1
R45
V
E
E
-15V
ICHP
0.1M
C18
-
+
1
I
D
+15V
0.1M
C11
-
+
ICLP
15
16
R70
10K
10K
R71
R28
270
15
16
4
-15V
4M7
R31
5
6
+15V
8
4
1M2
+15V
6
I
B
C
7
C24
0.1M
1
1
V
C
C
V
E
E
4
10K
R46
10K
R32
9
10
68K
R80
-
+
+15V
U5B
CA3280_2
8
I
D
U7B
TL072
-15V
150P
OUT
LPQ
12
C19
8
7
U12B
TL072
1N5 ECQP
5
4
-15V
6
C23
R79
C12
1N5 ECQP
R77
10K
10K
R78
R47
270
4M7
R50
R33
270
4M7
R36
9
R48
270
10
9
R34
270
10
-
+
-
+
3M3
1
1
V
C
C
4
V
E
E
C27
+15V
8
I
D
1
1
V
C
C
-15V
3M3
C21
+15V
8
I
D
V
E
E
4
-15V
6K8
R39
R35
10K
12
6
I
B
C
12
6K8
R53
R49
10K
OUT
U8B
CA3280_2
6
I
B
C
OUT
U4B
CA3280_2
3
2
C20
8
4
68K
TL072
5
6
0.1M
C25
3
2
C26
TL072
7
U11B
+15V
1
U11A
TL072
0.1M
TL072
7
U10B
TL072
1
U12A
6625 QUAIL RIDGE DR.
FORT WORTH, TX
76180
(817) 281-7776
REV
A
2
LP OUT
J8
BP OUT
J4
4
8
4
8
SYNTHESIS TECHNOLOGY
1K
R52
1K
R38
6
5
2
3
MOTM-480 CS-RESONANT FILTER
Size Document Number
C
M480_2
Date: September
8, 2004 Sheet
2 of
Title
8
4
68K
R51
8
4
-15V
7
U6B
+15V
1
U6A
TL072
1N5 ECQP
5
6
C9
0.1M
R37
8
4
-15V
0.1M
C7
C13
1N5 ECQP