MOTM-190 User Manual - Synthesis Technology
Contents
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3. CALIBRATION There are three trim pots on the MOTM 190 a RM carrier null also sets the VCA gain b VCA 1 CV rejection c VCA 2 CV rejection An oscilloscope is ideal for setting these trimmers to optimum setting However you can also set these by ear USING AN OSCILLOSCOPE 1 Apply power Set the upper switch to R RM mode 2 Apply a 5V pk pk audio signal from a VCO at about 1Khz into the IN 1 jack A sine wave is best but any signal will work 3 Set the top knob to RM setting where the LO would be 4 With nothing plugged into the CV 1 jack monitor the OUT 1 signal As you turn TP1 it s a 25 turn trimmer you should see the signal getting smaller and smaller if it gets larger and larger turn the opposite direction You will have to keep switching range scales on the scope to see the signal as it approached the null point The null point is NOT the point where the signal goes completely to zero Rather it is the point where the signal output reaches a minimum amplitude Once you get past this point the signal starts getting larger as you turn the trimmer You want to set the trimmer at the null point To set the 2 CV Reject also called CV Feedthrough trimmers you need a MOTM 800 EG or some other signal that you can use that is 0 to 5V feeding in a bipolar 5V signal will not work If you do not have a MOTM 800 EG or other EG that puts out 0 to 5V then set both trimmers to mid rotat
4. note that the CV input operates over the range OV VCA off to 5V VCA fully on Also the gain from input to output when the CV is 5 0V is not unity rather it s about 0 85 This is a tradeoff in sharing the came current source for the Ring Mod The null point set by TP1 also sets the gain through the VCA In theory the gain should be close to 1 but in reality the gain will be closer to 0 80 0 90 The user has one control BLEND Note that this VCA does not have a CV attenuator so if you want to use this VCA as your final output stage you may first want to use a MOTM 830 Mixer to attenuate the envelope driving CV 1 This will set the overall output volume The BLEND control is a wet dry fade between the original input signal what you have plugged into IN 1 and the VCA output In most cases you will simply set BLEND to the RM position which is for full VCA signal you ll see why it s labeled RM in the next section If you set BLEND counterclockwise more and more of the original signal bleeds through until the VCA is no longer part of the output signal This VCA is AC coupled you cannot use it to modulate DC control voltages VCA 2 will do this however When set to RM mode the input IN 1 changes functions and signal level restrictions The CV 1 input can now accept 5V to 5V signals which is usually an audio sine wave called the modulator signal The IN 1 jack is the carrier another
5. GATE from a keyboard or MIDI CV converter 5 Set the upper switch to V VCA position When you look at the OUT 1 signal while slowly adjusting the CV FEED A trimmer TP2 what you should hear are pops thumps or a clicking buzz as you turn the CV FEED 1 trimmer START WITH THE TRIMMER IN THE MIDDLE OF ROTATION The trimmer is somewhat sensitive be slow and methodical when setting the null point 6 Repeat for the other VCA Set the lower switch to L Linear and monitor OUT 2 while sending the EG stream to the CV 2 jack Adjust the CV FEED B trimmer TP3 for smallest output amplitude 7 If rotating the trimmers doesn t change the output volume then you got a really good CA38280 chip Set the trimmers to mid position SYNTHESIS TECHNOLOGY PAGE 17 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM USE OF THE MOTM 190 VCA RM The two sections of the MOTM 190 operate in different ways Please read the following to familiarize yourself with the different operations of the switches and front panel controls The top section consists of the switch marked V and R and the top panel control BLEND These controls are associated with CV 1 IN 1 OUT 1 jacks The switch sets VCA mode V or Ring Modulation mode CH When set to VCA mode the top section is a standard linear response VCA The audio signal is fed into IN 1 and the control voltage is fed into CV 1 In VCA mode it is important to
6. all pressing against the flange Now tighten the 4 KEPS nuts on the bracket The pcb and bracket should be secure with the pc board snugly against the flange Insert the pcb bracket assembly through the 3 pots holes on the rear of the front panel As you press the assembly in place place a washer and hex nut over each pot from the front Using a hollow shaft nut driver tighten each outer hex nut as far as it will go up against the washer The 2 notches in the flange will go around the 2 switch holes Locate the DPDT toggle switch It has 6 solder lugs and goes into the top hole marked V R When viewed from the rear of the panel the solder lugs are 2 across and 3 down The switch is not polarity sensitive just as long as you don t put it in sideways The lockwasher goes on the back side of the panel Tighten the front hex nut making sure the switch is square to the panel not slightly rotated Locate the SPDT switch and attach it to the lower hole marked L E PART 11 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 easier to first remove a jack from the panel and solder the wires then reattaching to the panel SYNTHESIS TECHNOLOGY PAGE 12 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM g The red black wire in J4 goes to the CV 2 jack
7. needed Check solder joints 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 about 15 minutes PART 3 More resistors WS WS US WS YU Locate the 4K7 resistors 2 and solder into R3 below TP1 and R42 below U6 Locate the 12K resistors 2 and solder into R8 below Q2 and R31 above C28 Locate the 220K resistors 2 and solder into R9 above U3 and R10 above Q7 Locate the 1K resistors 2 and solder into R12 below C30 and R32 below C25 Locate the 1M resistors 2 and solder into R13 by VR1 and R28 by J3 Locate the 27K resistors 2 and solder into R17 by SW1A and R30 by C24 PART 4 BOARD WASH 2 g Verify all the resistors are in the correct position g Verify all the resistors are flat on the board Correct if needed Check solder joints SYNTHESIS TECHNOLOGY PAGE 6 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM g Wash the board in warm water gently scrubbing both sides g Shake the board a couple of times blot dry with an old towel the leads will frazzle a good towel Let dry about 15 minutes PART 5 Finish the resistors Locate the 130K resistor and solder into R1 by TP1 Locate the 47K resistor and solder into R2 below C18 Locate the 2K resistor and solder into R5 above C19 Locate the 150K resistor and solder into R6 right of R5 Locate the 100 ohm resistor and so
8. nut driver NOTE when tight not much of the exposed threads of the jack are exposed You are now ready to attach the pc board to the bracket and then wire up to the panel SYNTHESIS TECHNOLOGY PAGE 11 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM PART 10 ATTACH PC BOARD TO BRACKET PANEL 0 0 0 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 Note the bracket has 3 large holes on the flange where the 3 pots stick out The first step is to attach a hex nut without the washer and outer hex nut to each pot Tighten each nut by hand all the way until it touches the face of the pot Then loosen the nut one fourth of a turn Attach the pc board to the bracket You will have to angle the pc board slightly as you insert the 3 pots through the 3 large holes on the flange Place the 4 spacers over the 4 holes and thread the screws in from the TOP side 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 Slide the pcb ALL THE WAY TO THE RIGHT AS FAR AS IT WILL GO so that the 3 pot nuts are
9. orange red lea 75K violet green orange lea 43K yellow orange orange lea 680 ohm blue gray brown g IC bag containing the following 22 parts 4ea TLO72A dual op amp lea CA3280 dual OTA 2ea OP275GP dual op amp lea LM78L05 voltage regulator SYNTHESIS TECHNOLOGY MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM R4 R26 R33 R34 R35 R37 R11 R21 R25 R45 R18 R19 R22 R24 R16 R29 R43 R20 R27 R36 R3 R42 R8 R31 R9 R10 R12 R32 R13 R28 R17 R30 R1 R2 R5 R6 R7 R15 R23 R38 R39 R40 R41 R44 U1 U3 U6 U8 U4 U5 U7 U2 PAGE 2 LI LI OOO Tea 1N4148 diodes D1 D7 4ea BC560C PNP transistors Q1 Q4 3ea BC550C NPN transistors Q5 Q7 Misc 1 bag containing the following 8 parts 2ea Axial ferrite beads plain gray things L1 L2 lea MTA 156 power connector JP1 lea DPDT toggle switch SW1 lea SPDT toggle switch SW2 lea Bourns 3296 10K 25 turn trimmer TP1 2ea Bourns 3386 100K trimmer TP2 3 Knobs 3ea ALCO PKES90B1 4 Jacks 6ea Switchcraft 112A Pots 3ea containing the following 3ea 100K cond plastic Spectrol 148 VR1 3 Front panel Mounting bracket Wire bag containing the following 10 wires 2ea 3 wire set 22ga orange white gray short 4ea RG 174 coax 5 inches 3ea 2 wire set 22ga 3 inches red black lea 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 attac
10. the Bourns multi turn trimmer marked 3296 Solder into TP1 again making sure it is nice and sitting evenly on the pc board Locate the Spectrol pots 3 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 Solder the pots into VR1 VR2 and VR3 Locate the 4 pieces of RG 174 black coax cable Note that one end has longer wires stripped than the other The short ends will go in the pc board in positions J2 J3 J5 and J6 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 STRIPPED ENDS GOES INTO THE PC BOARD There is a trick to attaching the coax to the pc board You pull gently on the braid with a pair of pliers from the underside until the coax is lying flat on the board The inner conductor is at a 90 degree bend in the top hole Then solder the coax 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 When properly done the black outer jacket of the coax is all the way down resting on the pe board SYNTHESIS TECHNOLOGY PAGE 10 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM Here is a photo of properly at
11. 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 A SMALL AMOUNT not a blob 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 This pc board has parts very close together It may not be clear where a certain resistor or capacitor is We will try to give you a hint for the parts g Locate the 100K resistors 6 and solder into R4 below U1 R26 by VR3 R33 R35 above J1 and R37 also above J1 SYNTHESIS TECHNOLOGY PAGE 5 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM o Locate the 10K resistors 4 and solder into R11 above Q7 R21 by TP3 R25 right of U7 and R45 below Q7 Locate the 20K resistors 4 and solder into R18 above U4 R19 by C23 and R22 and R24 below TP3 Locate the 15K resistors 3 and solder into R16 left of U4 R29 below Q1 and R43 above U8 Locate the 180 ohm resistors 3 and solder into R20 by TP3 R27 below U8 and R36 above VR2 PART 2 BOARD WASH 1 0 o 0 0 Verify all the resistors are in the correct position Verify all the resistors are flat on the board Correct if
12. 15 C16 C19 21 C24 C26 and C30 Locate the 10ufd electrolytics 4 Note that there is a stripe on the NEGATIVE terminal The pc board has a on the POSITIVE terminal Carefully stick the capacitors into C9 C10 C14 and C17 with the stripe away from the pad on the board Locate the 3M3 electrolytics 2 Note that these are non polar there is no stripe These capacitors are not polarity sensitive Solder into C18 and C23 PART 8 BOARD WASH 4 o 0 o 0 Verify all the capacitors are in the correct position Verify all the axial capacitors are flat on the board Correct if needed Check solder joints Check the orange caps to see all the black stripes are facing the same way towards the top edge of the pc board where TP1 is Wash the board in warm water gently scrubbing both sides Shake the board a couple of times and blot dry You are about 80 finished at this point this is a good stopping point if you have to go do other boring stuff PART 9 MISC and IC STUFF Almost done with the parts on the pc board This will finish up the soldering with the organic flux 0 Locate the MISC 1 bag and the IC bag SYNTHESIS TECHNOLOGY PAGE 8 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM g 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 g Locate the MTA 156 power connector Solder into JP1 Note that the connector has a locking t
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14. RECTIONS Please read the entire instruction before proceeding There may be valuable information at the end of the instruction Each instruction has a check box Cl 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 g 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 the drain so don t SYNTHESIS TECHNOLOGY PAGE 4 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM 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
15. Solder the Black wire to the BEVELED lug and the Red wire to the LEFT lug The TOP lug is not connected g Solder J5 coax to the IN 2 jack The inner wire goes to the Left lug and the braided wire solder to the Beveled lug g Solder J6 coax to the OUT 2 jack The inner wire on the Left lug and the braided wire to the Beveled lug g Solder J1 red black wires to the CV 1 jack Solder the Black wire to the Beveled lug and the Red wire to the Left lug The TOP lug is not connected g Solder the coax in J2 to the IN 1 jack The inner wire solders on the Left lug and the braided wire to the Beveled lug g Solder the coax in J3 to the OUT 1 jack The inner wire solders on the Left lug and the braided wire to the Beveled lug Attach the ty wrap around the wires in a bundle about midway Trim off the excess ty wrap g Solder the red black wires in SW2 to the SPDT switch The Red wire solders to the Top switch lug and the Black wire solders to the Middle switch lug The Bottom switch lug is NOT USED g The 6 wires in SW1A SW1B solder to the DPDT switch Solder the wires in SW1B first The set of lugs nearest the pc board solder to the 3 wires in SW1B The Orange wire solder to the Top lug the Gray wire solders to the Middle lug and the White wire solders to the Bottom lug The second group of wires in SW1A solder to the other set of lugs in the same manner Orange gray then white top to bottom g Rotate all of the front panel pots fully counte
16. ab 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 g Locate the TL072 chips 4 Solder into U1 U3 U6 and U8 Be sure the parts all point in the same direction up There is a small circular indention on the top of the IC by pin 1 Note that the solder pad for pin 1 is a square g Solder the CA3280 into U4 The orientation is the same for all the ICs g Locate the OP275 chips 2 Solder into U5 and U7 Be sure the parts all point in the same direction up There is a small circular indention on the top of the IC by pin 1 Note that the solder pad for pin 1 is a square g Solder the LM78L05 into U2 It looks like a transistor but it s really a voltage regulator Match the flat side of the IC to the silkscreen pattern Notice that it points to the right while all the transistors point up g Locate the 1N4148 diodes 7 Notice the diodes have a black band around the part towards one end There is a matching stripe on the pc board s silkscreen they point to the left Solder the 7 diodes into D1 D7 making sure ALL of the diodes point the same way g Locate the 4ea BC560C transistors Solder them into Q1 Q4 matching the flat side of the part to the silkscreen pointing up g Locate the 3ea BC550C transistors Solder them into Q5 Q7 matching the flat s
17. audio signal The circuit multiplies the two signals together creating the sum and difference between the 2 signals and their harmonics The result is often a harsh metallic sound This is a good thing The BLEND control acts slightly differently When fully counterclockwise the IN position the output is the input At the 5 tick mark knob is straight up the output is a 100 AM modulated signal This is the same output as in VCA mode when BLEND is all the way to RM As BLEND is turned to RM the output is a 100 RM also called a 4 quadrant multiplication signal If you are fortunate to have ever played a CS 80 this is the same operation as its RM lever control You will discover many interesting RM sounds by using the BLEND setting The lower VCA is a more traditional VCA similar to the operation of the previous MOTM 110 VCA The switch selects L Linear or E Exponential response In 99 5 of the cases you will want to use L mode This is the usual ON to 5V DC control signal standard VCA The exception is that this VCA is DC coupled you can use it to modulate not just audio but CV as well The E response is for generating extremely tight or percussive outputs In E SYNTHESIS TECHNOLOGY PAGE 18 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM mode the VCA has very low gain say less than 10 when the CV 2 signal is between 0 and 38 5V Over the last 1 5V range of the CV the o
18. hing pc board to bracket 4ea 1 4 inch aluminum spacers 4ea 6 KEPS nuts 5ea small tie wrap Organic Solder No clean Solder PC Board MOTM 190 SYNTHESIS TECHNOLOGY PAGE 3 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM GENERAL INFORMATION Thank you for purchasing the MOTM 190 MicroVCA If you have any issues concerning the building or use of the kit please contact us at 888 818 MOTM 6686 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 190 Soldering iron 50W max power Use 700F tip temperature setting 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 capacitor codes and to inspect solder joints Lead bending tool optional but makes the job go much faster 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 HF FF HF KH HX For more information of tools used and suggestions see the MOTM FAQ and Tutorial pages at http www synthtech com HOW TO FOLLOW THE DI
19. ide of the part to the silkscreen pointing up g 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 pe board DO NOT SOLDER PADS FOR THE REMAINING COMPONENTS The via holes need a VERY SMALL AMOUNT of solder If you rub your finger over a soldered via hole you shouldn t feel a bump An example of a via hole is in between C20 and R13 up in the top right corner by VR1 PART 7 FINAL BOARD WASH amp INSPECTION g Verify all the parts are in the correct locations Make sure all of the ICs are pointing the same direction and all pins are soldered Check the orientation of the diodes SYNTHESIS TECHNOLOGY PAGE 9 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM o 0 Inspect the solder joints Any solder shorts Too much solder Missing joints Wash the board under warm 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 8 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 0 o Locate the 2ea Bourns trimmers marked 3386 the flat ones These solder into TP2 and TP3 Be sure they are flat on the board Locate
20. ion If you do have a MOTM 800 patch the OUT from the 800 to the CV 1 IN of the 190 Set the scope on DC coupling and set the 800 as Attack Decay Release 1 Sustain 10 If you have a 300 310 320 or 890 then use a PULSE output into the GATE input of the 800 setting the PULSE rate to about 30Hz This will send a constant stream of 0 to 5V fast envelopes to the 190 If you do not have a source to drive the EG just use a GATE from a keyboard or MIDI CV converter 5 Set the upper switch to V VCA position When you look at the OUT 1 signal while slowly adjusting the CV FEED A trimmer TP2 what you should see is the envelope leaking to the output Just like the RM Null trimmer you should reach a trim position where the overall amplitude of the output is at a minimum This setting may not be at the point of OV DC out but at a point say 5mv from OV This is OK what we want is for the output not to thump and the thump is when the DC level rapidly jumps The trimmer is somewhat sensitive be slow and methodical when setting the null point 6 Repeat for the other VCA Set the lower switch to L Linear and monitor OUT 2 while sending the EG stream to the CV 2 jack Adjust the CV FEED B trimmer TP3 for smallest output amplitude SYNTHESIS TECHNOLOGY PAGE 16 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM SETTING TRIMMERS BY EAR The most important thing when setting the trimmers b
21. 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 C Find the RESISTOR bag g Find the MOTM 190 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 g We will stuff the resistors by value to make things easier The resistors and other long leaded parts 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
22. ith a resistor to the supply rail Rather we use a constant current source fed by a stable 5V using regulator U2 The stable temperature compensated current source assures that the operating point of the Gilbert multiplier cell the internal circuitry of the CA3280 stays fixed and that any noise on the 15V supply rail is not present on the output any noise on 15V would modulate the diode current which then in turn modulates the output volume level causing IM distortion The RM function is created by switching 2 circuit elements the 5V reference voltage is switched to the CV input summer and the ground side of the 56K resistor R15 you remember the one that converts the OTA s current output into a voltage is switched to the audio input How does this make a Ring Modulator Well first we switch the 0 2 bias used for the VCA to 5V to allow the modulator signal to swing a full 5V to 5V in VCA mode the CV is assumed to be over the range 0 to 5V The second switch is complicated and tricky the simple explanation is that the OTA s current output and a current generated by the input carrier the switched side of R15 performs the RM multiplication function A similar scheme is used in the older MOTM 110 RM circuit In RM mode there has to be a balance between the carrier and the modulator voltages in the OTA This allows the carrier to be nulled out of the output signal Trimme
23. lder into R7 above C18 Locate the 68K resistor and solder into R14 by VR1 Locate the 56K resistor and solder into R15 below U5 Locate the 5K1 resistor and solder into R23 above VR2 Locate the 7K5 resistor and solder into R38 below D5 Locate the 3K3 resistor and solder into R39 above R38 you just soldered Locate the 75K resistor and solder into R40 above R39 you just soldered Locate the 43K resistor and solder into R41 below VR2 BS WS ES WS WS US US US NS US Oo U Locate the 680 ohm resistor and solder into R44 above D7 This completes the resistors PART 6 BOARD WASH 3 g Verify all the resistors are in the correct position g Verify all the resistors are flat on the board Correct if needed Check solder joints g Wash the board in warm water gently scrubbing both sides SYNTHESIS TECHNOLOGY PAGE 7 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM 0 Shake the board a couple of times and blot dry Take another break or set the kit aside for later PART 7 CAPACITORS 0 0 Locate the CAPACITOR bag Remember there is no C1 to C8 on the board I blame the computer Locate the Inf 0 001uf yellow box caps 4 They are marked 1n0 Solder into C13 and C27 29 They are not polarity sensitive Locate the 22pf ceramic axial caps 2 Solder into C22 by VR1 and C25 by U7 Locate the 0 1uf axial caps marked 104 There are 10 of these that you remove from the tape and solder into C11 C12 C
24. ltage is audio and we adjust the bias current that is a basic VCA The bias current is called Iabe and is fed into pin 3 The audio input side is a simple follower U3B Resistors R9 R11 and C18 AC couple the audio into R18 There is a DC offset trimming circuit R19 R20 and TP2 and is later adjusted for reducing thumps in the output caused by DC shifts in the output voltage First we will examine the VCA operation switch SW1 is in the V position Since the output of the CA3280 is a current not a voltage we use a resistor to ground R15 to convert the current into a voltage good old Ohm s law at work The output voltage is AC coupled through C23 into follower U5B in this configuration resistor R14 doesn t do anything It s for the RM operation The output stage U5 is a high end audio op amp the OP275GP VR1 is an interesting control it acts as a wet dry blend between the original audio signal and the VCA output The other half of U5 is just a buffer to drive the output How does the CA3280 get a control current to act as a VCA This is generated by U1A and Q1 This configuration is called a constant current source You will also see this configuration on U1B Q2 we ll get to that in a bit So what make this a constant current and why is that a good thing in this application HI Let s look at U1B and Q2 Ignore for now all the other parts If you look closely you will notice that PNP transisto
25. r Q2 has it s base emitter junction across the op amp s feedback terminals and out Recalling basic transistor theory if Q2 is on there is about a 0 6V drop across the base emitter junction You will also recall this voltage varies about 2mv C which is why VCOs drift and you can buy cheap digital thermometers Diode D2 is used to compensate for the drift and C29 is for stability Gf you don t put it there the small transistor capacitance makes a great 10Mhz oscillator In order to make a current we add resistor R8 Since R8 is tied to the op amp s virtual ground point the current out of the transistor is simply Vin R8 Turning our attention back to U1A this circuit is what converts the control voltage into a control current for the CA3280 SW1A sends a small negative DC offset 0 2V into the summing node to guarantee that with no CV in the VCA is off all the way no audio SYNTHESIS TECHNOLOGY PAGE 14 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM leakage The control voltage is fed through 130K resistor R1 and the resulting current is fed out of Q1 into the Iabc pin of the CA3280 So what is the constant current source doing on pin 1 marked Id Ahhh you really need to read the data sheet and app notes to understand this This is usually just a resistor to the positive supply which biases the 2 internal Gilbert diodes this reduces distortion by a factor of like 10 However since this is MOTM we are not content w
26. r 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 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk CONGRATULATIONS YOU HAVE FINISHED BUILDING THE MOTM 190 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk All that s left to do is test it But before we do please read the following Theory of Operation SYNTHESIS TECHNOLOGY PAGE 13 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM THEORY OF OPERATION The heart of the MOTM0190 VCA Ring mod circuits is the Intersil CA3280 dual OTA operational transconductance amplifier If you wish more detailed information on what these are and how they work visit the Intersil website at www intersil com and download the datasheet and the 3 related application notes listed in the datasheet The MOTM 190 is in two different separate sections The top section is a combination VCA and Ring Modulator RM The bottom section is a linear exponential response VCA TOP SECTION VCA RM The basic VCA core is of CA3280 U4A The OTA s output current is a linear function of the input voltage times a bias current If the input vo
27. r network R3 TP1 is a gain control adjustment This trim sets both the VCA gain it s about 0 85 and the RM nulling simultaneously See the CALIBRATION section for details BOTTOM SECTION LIN EXP VCA Page 2 of the schematics shows the bottom section a straight VCA with switchable linear exponential response You will immediately see identical circuitry form the top section the Id current generator the input follower trimmer network and the output buffer the output buffer does use resistor R41 U7B as the I V converter buffer all in one stage Also the Audio input is DC coupled so that the bottom VCA can modulate not just audio but control voltages as well The portion which is different is in the CV generation section Current source U8B is still there but is fed by the linear expo generator U6A U6B The difference between linear and exponential responses is set by transistor Q5 For a linear response Q5 is not in the circuit When exponential response is needed Q5 is switched in Q5 is biased by R38 R40 to keep it on all the time Diode D5 is again temperature compensation for changes in Vbe over temperature The summed voltage from U6A modulated the base emitter voltage which is an exponential transfer function In exponential mode U6B and the components around it convert the exponential current from Q5 Q6 to a voltage In VCA mode they act as a follower SYNTHESIS TECHNOLOGY PAGE 15 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM
28. synthesis technology MOTM 190 uVCA Assembly Instructions amp Owner s Manual Synthesis Technology 6625 Quail Ridge Dr Fort Worth TX 76180 817 281 7776 www synthtech com Dec 10 2002 MOTM 190 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 g Capacitor bag containing the following 22 parts there is NO C1 C8 4ea 10mfd 50V Electrolytic 2ea 3M3 50V non polar Electrolytic 4ea 1N 0 001uf yellow box cap 10ea 0 1mfd marked 104 ceramic axial 2ea 22pf marked 22P 22J or 220 ceramic C9 C10 C14 C17 C18 C23 C138 C27 C28 C29 C11 C12 C15 C16 C19 21 C24 C26 C30 C22 C25 g Resistor bag containing the following 45 parts all are 5 tolerance 6ea 100K brown black yellow 4ea 10K brown black orange 4ea 20K red black orange 3ea 15K brown green orange 3ea 180 ohm brown gray brown 2ea 4K7 yellow violet red 2ea 12K brown red orange 2ea 220K red red yellow 2ea 1K brown black red 2ea 1M brown black green 2ea 27K red violet orange lea 130K brown orange yellow lea 47K yellow violet orange lea 2K red black red lea 150K brown green yellow lea 100 ohm brown black brown lea 68K blue gray orange R14 lea 56K green blue orange lea 5K1 green brown red lea 7K5 violet green red lea 3K38 orange
29. tached coax leads This photo is also located at http www synthtech com pix coax html Find the 3 red black twisted pairs They go into SW2 J1 and J4 Solder the Red wire into the top hole 1 and the black wire into the bottom hole 2 Be sure that the end with the shorter leads is soldered in the pc board Find the 2 sets of orange white gray wires They go into SW1A and SW1B positions Very carefully clip off the ty wrap The 2 White wires go into the bottom 1 pads the 2 Gray wires into the middle pads 2 and the 2 Orange wires go into the top pads 8 YOU ARE NOW FINISHED WITH THE PC BOARD WORK BREAK TIME PART 9 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 0 Locate the 6 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 hex nut Remove the nuts and washers from each jack Place aside Keep the lockwasher on the jacks Insert the 6 jacks lockwashers with the beveled corner in the upper right corner into the 6 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
30. utput rapidly goes from 10 to 100 unity gain The GAIN control sets the initial gain of the VCA Normally you want to set this to the 0 tick As you increase the GAIN knob you will hear the input signal at the output So one way to think about this control is that it is a DC offset or bias to the CV 2 input The CV MOD is a simple linear attenuator in series with the CV 2 input signal This is handy if VCA 2 is the final output stage of your patch You can use CV MOD to set the overall volume of the audio output Thanks for purchasing and using the MOTM 190 Please email or call if you have any questions regarding its operation SYNTHESIS TECHNOLOGY PAGE 19 MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM Audio Input Level IN 1 and IN 2 Frequency Response Output impedance THD noise Dynamic range CONTROLS BLEND GAIN CV MOD GENERAL Power Supply Size Depth behind panel SYNTHESIS TECHNOLOGY MOTM 190 ASSEMBLY 12 10 02 WWW SYNTHTECH COM SPECIFICATIONS MOTM 190 VCA RM 12V pk pk maximum 20Hz to 35Khz 100 ohms nom 0 025 1Khz at OdBv reference gt 106dB fades between the IN 1 and the VCA RM sets the initial gain for VCA 2 attenuates the CV 2 input 15VDC 38ma 15VDC 38 ma 1U x 5U 1 72 x 8 72 44mm x 221 5mm 4 5 inches 114 8mm PAGE 20
31. y ear is to watch your audio levels Use a mixer to attenuate the 190 OUT signals BEFORE the amplifier Don t complain to me that you blew up your tweeters or power amp Bring the volume up SLOWLY 1 Apply power Set the upper switch to R RM mode 2 Apply a 5V pk pk audio signal from a VCO at about 1Khz into the IN 1 jack A sine wave is best but any signal will work 3 Set the top knob to RM setting where the LO would be 4 With nothing plugged into the CV 1 jack monitor the OUT 1 signal As you turn TP1 it s a 25 turn trimmer the volume will get smaller and smaller as you turn the trimmer if it gets louder and louder turn it the other way When the volume is at the quietest level stop the adjustment To set the 2 CV Reject also called CV Feedthrough trimmers you need a MOTM 800 EG or some other signal that you can use that is 0 to 5V feeding in a bipolar 5V signal will not work If you do not have a MOTM 800 EG or other EG that outputs 0 to 5V then set both trimmers to mid rotation If you do have a MOTM 800 patch the OUT from the 800 to the CV 1 IN of the 190 Set the 800 as Attack Decay Release 1 Sustain 10 If you have a 300 310 320 or 390 then use a PULSE output into the GATE input of the 800 setting the PULSE rate to about 30Hz This will send a constant stream of 0 to 5V fast envelopes to the 190 If you do not have a source to drive the EG just use a
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