MOTM-120 User Manual
Contents
1. inputs or the outputs from the AND gates What s special about those 4 AND gates Why that s our secret digital ring modulator SYNTHESIS TECHNOLOGY PAGE 15 MOTM 120 ASSEMBLY WWW SYNTHTECH COM If you look at the inputs to each AND gate they are tied to the corresponding sub octave outputs from each counter QA to QA QB to QB etc To show how the lowly AND gate is transformed to a digital ring mod let s first examine the truth table of an AND gate In1 In2 Out 0 0 1 0 0 0 1 1 Hmmmm don t see anything immediately that sheds the light Well let s call In1 a control voltage and In2 our input signal If our CV is 0 nothing comes out If our CV is a 1 HIGH voltage then the input the output If you consider how a VCA works if the CV is maximum then in fact the output signal the input Since we are in the digital world a AND gate is in fact and that s what a ring modulator 1 50 the innocent looking AND gate 1 acting as a ring mod Another way to think about the circuit 1s this the sub octaves generated by IN B gate to the mixer in a binary pattern the IN A sub octaves You will hear this effect if A IN is audio and BIN is a LFO The following chart will help explain this B IN Counter gt gt gt gt Qd Qc Qb Qa A IN Suboctaves Out to mixer 0 0 0 0 none all you get 1s IN 0 0 0 1 Sub 1 0 0 1 0 Sub 2 0 0 1 1 Sub 1 Sub 2 0 1 0 0 Sub 3 0 1 0 1 Sub 3 Sub 1 02. synthesis MOTM 120 Sub Octave Multiplexer Assembly Instructions and User s Guide Synthesis Technology 6625 Quail Ridge Dr Fort Worth TX 76180 817 281 7776 www synthtech com May 1999 MOTM 120 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 1t for next time Capacitor bag containing the following 18 parts 10mfd 50V Electrolytic C3 C4 C6 3ea 220pf ceramic axial C12 C15 C18 lea 0 47 mfd 470N yellow box polycarbonate C7 llea 0 1mfd 104 ceramic axial C1 2 5 C8 11 C13 14 16 C17 Resistor bag containing the following 23 parts 8ea 100K 5 brown black yellow R4 R9 R11 R12 10K 596 brown black orange R1 R2 R3 R16 R17 R21 R22 1 5 brown black red R13 R14 R19 2ea 2M2 5 red red green R18 R23 2ea 4M7 5 yellow violet green R15 R20 lea 33K 5 orange orange orange R10 bag containing the following 8 parts 2ea 74HC161 counter U1 U2 lea 74H C08 quad AND gate U3 lea 74HC157 quad 2 1 mux Ud LM311 comparator U7 U8 lea TLO72 dual amp U6 lea LM78L05 5V voltage regulator U4 Misc 1 bag containing the following 6 parts 2ea Axial ferrite beads plain gray things L1 L2 3ea SPDT toggle switch SW1 SW2 SW3 lea MTA 156 power connector JP1 Knobs ALCO PKES90B1 4 Jacks 3ea Switchcraft 112A SYNTHESIS TECHNOLOGY
3. PAGE 2 MOTM 120 ASSEMBLY WWW SYNTHTECH COM PAGE 2 MOTM 120 PARTS LIST g OU Pots containing the following 4ea 100K linear Spectrol 149 VR1 4 2ea 100K linear Bourns 91 panel mount VR5 amp VR6 Front panel Mounting bracket Wire bag containing the following 10 wires 2ea RG 174 coax 4 1 2 1nches lea RG 174 coax 7 1nches 4ea red black twisted pair lea orange white twisted pair lea yellow 3 inches lea blue wire 2 inches 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 4 inch aluminum spacers 6ea 6 KEPS nuts 2 for attaching bracket to front panel 4 for pc board 6ea small heatshrink tubing bea small tie wraps Organic Solder No clean Solder PC Board MOTM 120 REV A Power cable SYNTHESIS TECHNOLOGY PAGE 3 MOTM 120 ASSEMBLY WWW SYNTHTECH COM GENERAL INFORMATION Thank you for purchasing the 120 Sub Octave Multiplexer If you have any issues concerning the building or use of the kit please contact us at 888 818 MOTM or by email synth airmail net This kit should take the average builder between 2 and 3 hours However please remember this is NOT a speed contest 1t 1 an accuracy contest There 1s no rule that you have to complete the entire kit in one session as long as you wash the flux Successful kit building relies on having the proper tools Here
4. apply any high level signal Set each SUB pot and A IN not B IN to 4 Set B IN to O Let s assume that you have an audio signal into IN A and a LFO to IN B What you should hear is a 16 note pattern that repeats What you are hearing is a binary count of each sub octave generated by A IN being gated to the output by B IN If you increase the frequency of B IN the pattern speeds up SYNTHESIS TECHNOLOGY PAGE 13 MOTM 120 ASSEMBLY WWW SYNTHTECH COM If both IN and B IN are audio signals what you should hear is a giant constantly moving tone this is REAL hard to describe There are WAV files of these sounds at www synthtech com If you feel that this mode is not working proceed to the Troubleshooting Guide ELECTRICAL THEORY OF OPERATION The following discussion explains how the circuit operates and suggests area of possible modification Refer to the schematic and block diagram This is a simplified block diagram of how the MOTM 120 operates CLIPPER INA 4 BIT COUNTER IN B OUT CLIPPER 4 BIT COUNTER The heart of the MOTM 120 are the two 4 bit counters which are 74HC161s U1 and U2 The counters have a clock input pin 2 that causes the 4 outputs to increment 1n a binary fashion from 0 to 15 then repeat The 4 outputs are as follows QA divides the clock input by 2 1st sub octave QB divides the clock input by 4 22 sub octave QC divides the clock input b
5. middle of the pc board The tab is next to the 2 ferrite beads Note the silkscreen symbol for JP1 has a line on one side indicating this is the side where the locking tab goes Locate the IC bag IMPORTANT all of the ICs except U4 point the same way when soldered in the pc board Each IC has a small notch in the end of the plastic body on the top of the part These notches face towards the bottom edge of the pe board Locate the LM311N comparators Solder into U7 and U8 Note that Pin 1 1 the square pad Pin 1 1 the pin near the very small dot in the top of the part Locate the TLO72 op amp Solder into U6 Locate the 2 74HC161 counters Solder into U1 and U2 Locate the 74HC157 quad 2 1 mux Solder into U5 Locate the 78L05 voltage regulator It has a flat side that has the lettering The flat side faces the white U4 on the pc board The center pin is slightly bent forward Press the part in until about 1 8 of lead is still exposed DO NOT try to stuff it all the way down flush with the pc board Solder into U4 Locate the 74HC08 quad AND gate Solder into U3 PART 5 WASH THE BOARD AGAIN g g Verify all the parts are in the correct locations Check C3 C4 amp C6 orientation all of the stripes are pointing the same way up Inspect the solder joints Any solder shorts Too much solder Missing joints SYNTHESIS TECHNOLOGY PAGE 7 MOTM 120 ASSEMBLY WWW SYNTHTECH COM g Wash the board under w
6. pot place the flat washer on the threads then the hex nut Tighten PART 9 FINISH WIRING TO THE PANEL g g Attach and solder the RED wire on SW1 to the bottom terminal of the MODE switch Attach and solder the BLACK wire on SW1 to the middle terminal of the switch There 1s NO wire connected to the top terminal Attach and solder the RED wire on SW3 to the bottom terminal of the MIX B switch Attach and solder the BLACK wire on SW3 to the top terminal of the MIX B switch Attach and solder the ORANGE wire SW2 to the bottom terminal of the MIX A switch Attach and solder the WHITE wire on SW2 to the top terminal of the MIX A switch In the WIRE bag find the single piece of yellow wire Solder carefully to the middle terminal of MIX A switch The other end will go to the IN pot the LEFT terminal Find a piece of small heat shrink tubing Place the tubing over the wire sliding 1t towards the switch Then make a little bend in the yellow wire Insert the wire through the hole 1n the pot lead and solder Leave the heat shrink tubing where 1t is for now Locate the red black twisted wires 1n VR6 They also solder to the IN A pot leads The RED wire goes on the middle lead and the BLACK wire goes on the right lead Before soldering place a small piece of heatshrink on each wire you may have to un twist the wire once or twice As before make SMALL J shaped bend in the wire attach
7. the 8 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 1 positions J1 to J3 Look at the pc board Notice that in positions J1 J3 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 SYNTHESIS TECHNOLOGY PAGE 8 MOTM 120 ASSEMBLY WWW SYNTHTECH COM Note there is row of plain holes along the bottom under J1 3 These holes are for threading the small white tie wraps for holding the coax against the pc board The holes are designed so that the coax lies in between the 2 holes The tie wrap enters the left hole from the top comes out the right hole from the bottom and is then secured so that the coax is tightly held against the top of the pc board Note that the tie wraps must thread from the top or there may not be sufficient room between the pc board and the mounting bracket The excess tie wrap 1s cut off Solder then tie wrap the 2 short coax cables J2 amp J3 Trim the excess tie wrap Solder and tie wrap the longer coax into J1 NOTE because of the way the coax 1s made chances are more of the braid will go in the bottom hole than the inner conductor This 1s normal unlike all the other parts and wires The secret 1s to get the coax firmly soldered and tied down YOU ARE NOW FINISHED WITH THE PC BOARD WORK BREAK
8. the two together and solder Now that all 3 leads are on the IN A pot yellow on the left red in the middle black on the right slide each heatshrink tube over the pot leads covering the solder joint Using a heat gun low setting shrink the tubing over the leads You can also place your soldering iron CLOSE BUT NOT TOUCHING the tubing and the radiant heat will shrink it SYNTHESIS TECHNOLOGY PAGE 11 MOTM 120 ASSEMBLY WWW SYNTHTECH COM Find the BLUE wire Solder to switch terminal 2 middle The other end goes to the LEFT terminal of the IN B pot Solder as before slide on the heatshrink attach the wire to the lead Untwist some of the red black VR5 wire Slide on the heatshrink and before solder the RED wire to the MIDDLE terminal of the IN B pot Solder the BLACK wire to the RIGHT terminal Slide the tubing over the pot leads and shrink The last thing to do is to solder the coax cables to the jacks You will start with J3 and work backwards to J1 In this manner you will solder left to right on the jacks Solder the coax on J3 this 18 the OUT Solder the braid to the ground lug beveled edge and the conductor to the left lug The top lug is NOT connected Solder the coax on J2 this is IN middle jack First solder a wire scrap from cut resistor lead from the TOP to the BEVELED lug Then solder the center conductor on the left lug and the braid on the beveled lug Trim
9. the wire scrap so it doesn t get in the way You may want to solder the TOP lug first then insert the coax braid on the beveled lug before soldering This shorts out the IN B when no signal is applied prevents erratic sub octaves from being triggered by the IN A signal Solder the coax J1 this is IN A Braid to beveled and center to left lug Rotate all of the front panel pots fully counter clockwise Locate the KNOBS Notice each knob has a thin 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 and it will peel off kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk CONGRATULATIONS YOU HAVE FINISHED BUILDING THE MOTM 120 SYNTHESIS TECHNOLOGY PAGE 12 MOTM 120 ASSEMBLY WWW SYNTHTECH COM VERIFYING THE UNIT IS FUNCTIONAL You will now verify the MOTM 120 in both SUB and CROSS modes g Apply 15VDC to the unit Power is apples through JP1 15V is on the left the 2 center pins are ground and the right pin is 15V A MOTM 900 supply is highly recommended Set the MIX switches to NORM normal Set all pots to 0 Set the MODE switch to SUB sub octaves Apply an audio frequency of at least 1V pk pk to the A IN jack IMPORTANT NOTE The input circuitry see Theo
10. 1 1 0 Sub 3 Sub 2 0 1 1 1 Sub 3 Sub 2 Sub l 1 0 0 0 Sub 4 and so on AIN is always added 1n along with IN As you can see if the B IN 1s a slow signal you can here the 74HC157 mux switching the sub octave as the pattern shown in the table If both AIN and B IN are audio frequencies what you will hear 1s a distinctive beating pattern based on this table The mixer U6 adds the outputs of the AND gates with the selected input signals Note that the outputs of the comparators and the AND gates are all 0 to 5 signals If you have the MIX switches set to NORM and you are using a smaller signal say 1V pk pk then the SUB mix will be much louder than the input mix This can of course br compensated for by carefully adjusting the mixer pots Since the digital logic requires 5V supply and MOTM uses 15V there is an on board voltage regulator U4 SYNTHESIS TECHNOLOGY PAGE 16 MOTM 120 ASSEMBLY WWW SYNTHTECH COM USING THE MOTM 120 IN YOUR SETUP In this section we will discuss how the MOTM 120 is used in various applications Of course these are only a few things to try Experiment SUB MODE The SUBoctave mode only requires one input into the A IN jack Note that if you are in SUB mode the B IN jack 1s ignored The B IN pot does nothing For the basic use set the controls as follows e MODE switch to SUB MIX A and MIX B to NORM normal the input is mixed as is with the sub octaves Connect an am
11. HA 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 be found for about 1 SYNTHESIS TECHNOLOGY PAGE 4 MOTM 120 ASSEMBLY WWW SYNTHTECH COM The other type of solder is called No Clean Flux because as the name implies it does not require washing This solder 1 used on 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 GENERAL ASSEMBLY GUIDE document that every customer gets with their first order Find the RESISTOR bag Find the MOTM 120 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 t
12. TIME PART 7 FRONT PANEL PREPERATION 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 g Locate the 3 Switchcraft jacks Notice that from the rear there is a beveled corner This corner is ALWAYS CONNECTED TO GROUND USUALLY WITH THE BRAIDED CONDUCTOR Each jack has a flat washer a lockwasher and a hex nut Remove the nuts and washers from each jack Place aside Keep the lockwasher on the jacks Insert the 3 jacks lockwashers with the beveled corner in the upper right corner into the 3 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 Check to see that each jack has the bevel in the upper right corner and all jacks are neatly lined up g Locate the 3 SPDT toggle switches Note that on one side of the metal plate are the numbers 1 2 3 or ON and ON this will depend on the switch manufacturer We will refer to the switch lugs as top middle and bottom Remove the hex nut keep the lockwasher on stick the switches in the holes with the 1 ON terminal at the top Place the hex nut on the switch and tighten Be s
13. arm water Scrub gently Dry 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 remains parts on the pcb in preparation for wiring to the front panel USE THE NO CLEAN SOLDER BE CAREFUL g Q Locate the Spectrol 149 pots 4 go on the pc board and 2 mount on the front panel NOTE in order for the pc board to properly align into the front panel each pot must be absolutely flat on the pc board with the shafts pointing away from the pe board Solder the pots into 4 Clip the leads off Locate the WIRE bag Note that the pre stripped wires all have a short end and a longer end THE SHORT END GOES IN THE PC BOARD Locate the white orange twisted pair Solder the ORANGE wire into SW2 in the hole marked 1 square pad Solder the WHITE wire short end into SW2 1n the 2 hole Locate one of the red black twisted pairs Solder the RED short end into VR6 into the hole marked 1 round Solder the BLACK short end into VR6 hole marked 2 square Solder red black twisted pair into VR5 red wire in 1 and black wire in 2 Solder a red black twisted pair into SW3 red wire 1 and black wire in 2 Solder red black twisted pair into SW1 red wire 1 and black wire in 2 Locate
14. cket is screwed down on the 2 threaded posts Attach the pc board to the bracket The 2 mounting flanges are located 1n between VR1 amp 2 and in between amp 4 Note that the bracket holes for the pc board are actually oblong Tighten then 4 KEPS nuts on the bottom THIS IS VERY IMPORTANT STEP SO PAY ATTENTION AND READ ALL 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 Make sure the remaining hex nuts on each pot on the pc board is screwed on all the way Tighten by hand each hex nut Now you will see if the pc board needs to be adjusted on the bracket Carefully insert the 4 pot shafts through the front panel sliding the bracket flanges over the 2 threaded studs Slide the bracket all the way forward until the hex screws on the pots are touching the front panel Look at the bracket flanges they should be flush on the panel as well If either the bracket hits first OR the bracket flanges are not yet flush the pc board needs to slide in the bracket either forwards or backwards Loosen the 4 KEPS nuts slightly to adjust the pc board It is VERY important that all 4 hex nuts on the pots AND the 2 bracket flanges are all flush to the front panel NO air gaps SYNTHESIS TECHNOLOGY PAGE 10 MOTM 120 ASSEMBLY WWW SYNTHTECH COM g Now use 2 of the 6 KEPS nuts to tighten the bracket to the panel For each
15. he board with the white silkscreen the top side Solder is applied on the bottom side o We will stuff the resistors by value to make things easier The resistors and other long leaded parts are inserted 0 4 inch spacing The important thing 1 to be sure that the part 1 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 it keeps the part from falling out From the bottom of the board solder with the organic flux applying heat to the pad for about a half second first then applying just enough solder to make a small flat puddle The rule of soldering don t use too much you can always add more Cut the leads flush with the top of the solder Locate the 33K resistor and solder into R10 Locate the 1K resistors and solder into R13 R14 and R19 Locate the 100K resistors and solder into R4 R9 R11 amp R12 Locate the 10K resistors and solder into R1 R2 R3 R16 R17 R21 and R22 UU Locate the 2M2 2 2Meg resistors and solder into R18 and R23 Locate 4M7 4 7Meg resistors and solder into R15 and R20 SYNTHESIS TECHNOLOGY PAGE 5 MOTM 120 ASSEMBLY WWW SYNTHTECH COM That should be all of the resistors And guess what you are about 1 3 of the way done PART 2 BOARD WASH 1 g Verify all the resist
16. is a list of what you will need to build your MOTM 120 Soldering iron 50W max power Needle nose or chain nose pliers Diagonal cutters Wire strippers Philips head screwdriver 5 16 and nut drivers and an Allen key set for securing the knobs Lead bending tool optional but makes the job go much faster Heat gun for heat shrink tubing optional but HIGHLY recommended xo For more information of tools used and suggestions see the FAQ at www synthtech com 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 LJ 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 in the kit as shown 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 1s embedded 1n 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 the kits are waterproof and can be washed in the sink The flux is OS
17. just that with a slow input you can hear the pattern 3 one input 1 noise If you use noise as an input the counter will clock very fast This can create gated feedback types of effects Watch those tweeter levels As you can see the 120 is a truly unique piece of signal processing equipment Just remember to keep your input signal levels above 100mv pk pk SYNTHESIS TECHNOLOGY PAGE 18 MOTM 120 ASSEMBLY WWW SYNTHTECH COM TROUBLESHOOTING GUIDE If your MOTM 120 does not work please verify ALL of the following before contacting us The following reference directions assume that you are looking at the pc board with the panel to the right and the power connector to the left g Q u g All of the IC are pointing the same way all notches are downwards The flat side of U4 faces the front panel C3 C4 and C6 stripes are both pointing upwards The braided wire on the coax goes to the beveled side of the jacks There is nothing on all 3 jacks on the top switched lug The board has all the right parts in all the right places No solder shorts or missing joints If you still can not get the module to perform correctly please contact us by phone fax at 888 818 6686 or by email to synth1 airmail net Thank you for purchasing the MOTM 120 module SYNTHESIS TECHNOLOGY PAGE 19 MOTM 120 ASSEMBLY WWW SYNTHTECH COM SPECIFICATIONS MOTM 120 SUB OCTAVE MULTIPLEXER Audio Input Output level Input Im
18. o L ELC ETA 9 ZTA MOOT ASZ WOT 9D DOA MOOT MOOT 9AA 6a ASZ ASZ WOT WOT 2 SLLI DHH 9GST NVLNW WT O zd S2 LTO 5 T _ AST SOISLWI EL 25 doze AST AST t I ZO va adawod AAO MOOT SAA HHIM COHWVOH ddO WT O 4 U U gt DDA ca 80O0HVL OT OS 6 TOO 800HVL MOOT MOOT PAA MOOT AE o ans po EAA 55042 IMS ES LSIOHTL 5 MOOT a x MOOT m CHA 2a ae L v MOOT 5 MOOT eds THA WT aca 800HVL AT TOTOHPL TOTOHPL TO 9TA CNC 8TA DDA DDA NTO TTO oH gt VR1 SYNTHESIS TECHNOLOGY MOTM 120 SUBOCTAVE MULTIPLEXER WWW SYNTHTECH COM L2 T _ G 2 4 O J T y 5 va n L1 U3 02 C 5 12 J ws ves C 1 2 R9 d gt R3 R4 ss R5 ve gig RE RR L_ 12 LC A R7 12 14 17 c2C i 52 i ee U8 R11 C R20 Co R14 U6
19. ors are in the correct position Verify all the resistors are flat on the board Correct if needed Wash the board in warm water only gently scrubbing both sides Shake the board a couple of time blot dry with an old towel the leads will frazzle the good towel Let dry about 15 minutes PART 3 CAPACITORS Locate the CAPACITOR bag Locate the 220pf axial ceramic caps marked 221 Solder into C12 C15 and C18 Locate the 0 14 axial ceramic caps These look just like the 220pf caps but are marked 104 Solder into C1 C2 C5 and C8 C11 C13 C14 C16 and C17 Locate the 0 47 yellow box cap It is stamped 474 on the top Solder into C7 Locate the 10mfd electrolytics Note that there is a stripe on the NEGATIVE terminal The pc board has a on the POSITIVE terminal Carefully stick the capacitors into C3 C4 and C6 with the stripe away from the pad on the board SYNTHESIS TECHNOLOGY PAGE 6 MOTM 120 ASSEMBLY WWW SYNTHTECH COM PART 4 MISC STUFF Almost done with the parts on the pc board This will finish up the soldering with the organic flux Q UO U g Locate the MISC 1 bag and the IC bag Locate the ferrite beads 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 towards the
20. pedance Output Impedance GENERAL Power Supply Size Depth behind panel CONTROLS A IN BIN SUB 1 SUB 2 SUB 3 SUB 4 SYNTHESIS TECHNOLOGY MOTM 120 ASSEMBLY WWW SYNTHTECH COM 100mv pk pk minimum 10V pk pk maximum 10V pk pk with A IN BIN both pk pk All pots at 10 50 min 1K typical 15VDC 20 ma maximum 15VDC 20 ma maximum 2U x 5U 3 485 x 8 735 88 5mm x 221 9mm 4 8375 inches 111 1 mm Attenuates either the input signal or the SQUARE version of the input Attenuates either the input signal or the SQUARE version of the input Attenuates the first sub octave into the output mixer SUB mode or the first cross product in the mixer CROSS mode Attenuates the second sub octave into the output mixer SUB mode or the second cross product in the mixer CROSS mode Attenuates the third sub octave into the output mixer SUB mode or the third cross product in the mixer CROSS mode Attenuates the fourth sub octave into the output mixer SUB mode or the fourth cross product in the mixer CROSS mode PAGE 20 499us 866rL azoqueaq4desg ASGUNN HAWVLOOHUQS OCT WLONW STAtTL WLOW 8T8 888 OST9AL XL HLYOM Md ITIIWNO 9299 AOO IONHOHIL SISHHLNAS WI O WI O 22 AST AGT o T E ZLO LL NT gaon iL x S MOOT
21. plifier to OUTPUT or patch through a mixer better choice IMPORTANT NOTE The MOTM 120 can output voltage levels to 10V pk pk Be careful when connecting power amplifiers directly to the OUTPUT Apply a signal of at least 1V pk pk to the IN A jack Now turn up the pots and you will hear the lowers octave harmonics being added to your input signal Flip the MIX A switch to SQUARE If your input was not a square pulse you should hear the different harmonics in the output NOTE when you are in the SQUARE position the full level 5V signal is applied to the mixer This is NOT the case in the NORM position where the input is routed directly to the mixer Therefore you will probably need to adjust the A IN level control That s all there is to it Any whimpy signal can be fattened up by adding suboctaves You don t have to add ALL of them Sometime a little SUB2 goes a long way Don t think of the MOTM 120 as the last link in your signal processing chain Take the output from a VCO to the MOTM 120 then into your filters SYNTHESIS TECHNOLOGY PAGE 17 MOTM 120 ASSEMBLY WWW SYNTHTECH COM CROSS MODE This mode requires two input signals to function This is the most useful and bizarre mode of the 120 The following are just 3 ways to use the module but there are 100s of others as well 1 both inputs are audio signals If you mix 2 VCOs and they are not in tune you hear a beating effect The beat freq
22. ry of Operation requires that the input signal be greater than 100mv pk pk or the circuitry will not operate This prevents false and erratic triggering with low level noisy signals Therefore use the output of a VCO or other high level source If you synth has HI and LOW outputs use HI Use a non pulse square wave a sine or triangle wave is good or a string patch Connect an amplifier or oscilloscope to the OUTPUT jack WARNING The 120 is designed for use within a modular synthesizer Therefore the output level with all pots at 10 is 10V pk pk Most audio amplifiers are designed to operate with 1 or 2 volts pk pk maximum Be careful when using such an amplifier with full level output signals Slowly turn up the A IN pot You should hear the input signal Now switch the MIX A switch to SQUARE You should hear the different tonal quality The volume may be louder or softer than the input Turn down the A IN pot One at a time turn up the SUB pots You should hear or see on a scope the 4 different sub octaves Each one is 1 octave below the next one If you input signal is too low a frequency the 4 sub octave may be only a clicking sound Increase the pitch of the input If you do not hear the 4 distinct sub octaves proceed to the Troubleshooting Guide Flip the MODE switch to CROSS Apply a second input signal to the B IN If you have a LFO or low frequency lt 10Hz signal this will make testing much easier If not
23. the reference voltage move up and down as the output swings from OV to 5V Hysteresis prevents false switching of the output of the comparator when the input signal is slowly changing like from LFO The effect of R15 causes the trip level of the comparator to be roughly 80mv pk pk If you try to apply a signal lower than 80mv pk pk the comparator ignores it and the counter will not count No output A fair question is why isn t the comparator input tied to ground The answer is because many older synth have tiny levels of noise on the outputs even if no notes are being played This is a noise gate to eliminate the output noisy from triggering the counters Assume we have a strong input and the counters are operational Now what The output of the counter associated with A IN is fed to 2 places the quad AND gate U3 and to the 2 1 multiplexer U5 The 74HC157 mux is a simple switch if the input on pin 1 is LOW lt 5V the signals tied to the A inputs are connected to the outputs If the signal on pin 1 is HIGH 8V then the inputs are connected to outputs Look on pin 1 and you will see that is where the MODE switch on the front panel is connected Pull up resistor R3 keeps the pin tied to HIGH unless it 1s in SUB position Then the pin is shorted to ground or LOW In this manner U5 selects whether the mixer is controlling the sub octaves from the A IN counter they are tied to the A
24. uency is the difference in Hz between the 2 harmonically related tones This is also called detuning and 1 a popular way to increase the fatness of a sound The MOTM 120 takes this concept to the next level Instead of a 2 tone beat the CROSS mode produces 16 note beat Why Because we are switching in the sub octaves 16 step binary pattern Apply 2 audio signals and hear what we mean Carefully adjust the relative tuning of the inputs and you will hear this effect NOTE the tuning can be real touchy It will greatly depend on the nature of the 2 inputs you use The beauty of the MOTM 120 1s that you do NOT need complex inputs to produce complex outputs Simple sine and sawtooth waves can beat to produce wonderfully complex timbres You can get even MORE complex outputs if you Use white or pink noise see the MOTM 100 an input Use 2 VCOs as inputs and slowly LFO modulate one of them Play with synching the two inputs Use a standard synth patch as one input and a basic waveshape into the other Again use the output of the MOTM 120 and filter ring mod compress and distort 2 one input is audio one input is a LFO You can get sequencer effects if one input is audio and the other is a LFO type signal lt 10Hz This causes the generated suboctave to be sequentially added to the mixer in a 16 step repeating pattern see the table in the Theory section The MOTM 120 always does this in CROSS mode it s
25. ure the switch is straight up and down it is easy to get it slightly off center The numbers letters are on the right side of the switch Place into MIX A MIX B and MODE holes If your switch says ON and ON place the switch in the hole so the ON amp ON side is to the right not that it matters but let s be consistent SYNTHESIS TECHNOLOGY PAGE 9 MOTM 120 ASSEMBLY WWW SYNTHTECH COM Locate the 2 remaining 100K Bourns pots Remove the first hex nut keeping the lockwasher and 2194 nut on Insert the pots one at a time into the IN and B IN holes with the 3 leads pointing down towards the jacks CAREFULLY tighten the hex nut holding the pot with one hand to keep the 3 leads pointing downwards DO NOT OVERTIGHTEN You are now ready to attach the pc board to the bracket and then wire up to the panel See the illustration at the end of the document PART 8 ATTACH PC BOARD TO BRACKET amp PANEL In the HARDWARE bag locate 4 6 32 screws 6 6 KEPS nut 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 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 1n it s panel hole when the bra
26. y 8 8 sub octave QD divides the clock input by 16 4 sub octave Since these counters want the clock signal to go between 0 and 5V a nice sharp manner we have to process our input signal SYNTHESIS TECHNOLOGY PAGE 14 MOTM 120 ASSEMBLY WWW SYNTHTECH COM The inputs are shaped into square pulses of 0 to 5 by a special circuit called comparator Since the 2 inputs use identical circuits we will discuss IN A The LM311 comparator U7 amp U8 is used since we use it with a trick the LM311 has an open collector output with the emitter of the output transistor brought out to a separate pin pin 1 Since we want a 0 5V swing to make the counters happy the emitter is tied to ground and the collector is ties to 5V through a pull up resistor R14 and R19 Why is this such a big deal Because our audio inputs swing and we need to power the LM311 from bipolar supplies and other types of comparators like the LM339 internally tie the emitter of the output transistor to the supply Now we need to use the comparator to square up our inputs The comparator has 2 inputs and Look at U7 On pin 3 input we tie the input signal through a noise filter compromised of R17 and C12 On the input there is a reference voltage derived from R18 and R16 The voltage on this pin is about Vref R16 4 5V R16 R18 28mv However notice feedback resistor R15 is tied in as well This causes hysteresis
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