Radio-Flier Electronics Flier Electronics Flier Electronics
Contents
1. 2002 Radio Flier Electronics A Thomas Farrand Page 272. side of the capacitors with the stripe are closest to the copyright message imprinted on the component side of the board The side of C1 and C2 are next to where the ferrite beads will eventually go E If you were expecting more than two electrolytics you are no doubt disappointed as there are only two to be installed You did pee right 2002 Radio Flier Electronics A Thomas Farrand Page 20 RFE 117 VCA Modified on June 10 2002 5 7 Install More Stuff O Install U1 the SSM2018T VCA chip Please note that this chip has a polarity that must be observed Pin 1 of the VCA chip must be inserted into the square pad on the printed circuit board for proper orientation Make certain that all 16 leads protrude through the board before you solder any of the pins TCR1 will mount on top of this chip so there is little point in using a socket for U1 Why would you solder in a resistor on top of a socketed component It can t come out Install the dual opamp OP275 at location U2 If you are using a socket install the socket only at location U2 Please note the orientation for U2 on the component location guide Please note that this chip has a polarity that must be observed Pin 1 of U2 must be inserted into the square pad on the printed circuit board for proper orientation Make certain that all 8 leads protrude through the board before you solder any of the pins Install the dual opamp OPA2134 at location U3 You can also use
3. ORANGE RED BROWN 2002 Radio Flier Electronics A Thomas Farrand Page 19 RFE 117 VCA Modified on June 10 2002 E Installation of the fixed resistors is now complete Do not install TCR1 yet That comes later 5 5 Install The Ceramic Capacitors Ceramic capacitors have no polarity you need be concerned with but the board is easier to inspect if the component values all face the same way You are a real synth junkie if choosing between buying your girlfriend a birthday present and another synth module for yourself is a moral dilemma O Install the 8 0 1 microfarad ceramic capacitors marked with 104 at locations C3 C4 C5 C6 C8 C9 C13 and C14 Install the 82 pf ceramic capacitor marked with 820 at location C10 next to U1 Install the 100 pf ceramic capacitor marked with 101 at location C11 above U1 Install the 2200 pf ceramic capacitor at location C12 near U4 The 2200 pf capacitor will be labeled 222 O Install the 1 0 microfarad ceramic capacitor marked 105 at location C7 5 6 Install The Electrolytic Capacitors Electrolytic capacitors have a polarity that must be observed If installed backwards they will emit smoke and nasty fumes within seconds of power being applied Or they may simply explode Yes this is the voice of experience 0O Install the 2 33 microfarad electrolytic capacitors at locations C1 and C2 They are located just above the location for the MTA 156 power connector The
4. Key 10 0KXBK ND 0 11 1 Yageo 1 1M0 MF 1 4W B_ Res 1 00M 4 watt 1 metal film R13 Digi Key 1 00MXBK ND 0 11 1 Yageo 1 33K2 MF 1 4W B Res 33 2K watt 1 metal film R4 Digi Key 33 2KXBK ND 0 11 2002 Radio Flier Electronics A Thomas Farrand Page 12 RFE 117 VCA Modified on June 10 2002 1 Yageo 2 49K9 MF 1 4W B Res 49 9K 4 watt 1 metal film R9 R16 Digi Key 49 9KXBK ND 0 11 1 Yageo 1 649K MF 1 4W B Res 649K 4 watt 1 metal film R22 Digi Key 649K XBK ND 0 11 1 Yageo 2 1K00 MF 1 4W B Res 1 00K 4 watt 1 metal film R10 R24 Digi Key 1 00KXBK ND 0 11 1 Yageo 1 110K MF 1 4W B Res 110K watt 1 metal film R17 Digi Key 110KXBK ND 0 11 1 Yageo 1 332K MF 1 4W B Res 332K 4 watt 1 metal film R18 Digi Key 332K XBK ND 0 11 1 Yageo 1 374K MF 1 4W B Res 374K 4 watt 1 metal film R19 Digi Key 374K XBK ND 0 11 1 Yageo 1 38K3 MF 1 4W B Res 38 3K 4 watt 1 metal film R23 Digi Key 38 3KXBK ND 0 11 1 1 Precision Resistor Res 1 00K 4 watt 1 metal film TCR1 PRC PT146 1 46 PT146 PT146 3500 PPM C 1 Bourns Trimpot 20K 4 watt Cermet TP1 Digi Key 3006P 203 ND 1 73 3006P 1 203 2 Bourns Pot 100K log taper plastic PC1 PC2 Mouser 652 91 A1A B24 5 37 91A1 B24 D20 conductive panel mount D20 2 Vishay Spectrol Pot 100K linear taper Cermet PC3 PC4 Mouser 594 1
5. Radio Flier Electronics Supplier Name Analog Devices Incorporated Digi Key Corporation Hardware Store Mouser Electronics TTI Precision Resistor Company Inc Stooge Panels Incorporated Larry Hendry amp Dave Bradley Various companies sell the Alco knobs at wildly varying prices Find your best price and stock up A Thomas Farrand Website URL www analog com www digikey com your local Ace or Home Depot www mouser com www precisionresistor com www wiseguysynth com www hotrodmotm com www tycosucks com Page 14 RFE 117 VCA Modified on June 10 2002 5 ASSEMBLY OF THE VCA 5 1 Component Location Guide By Schematic Reference The following is the component location guide by schematic reference See also the component location guide by part value which might be a bit more helpful during construction Gas PCL IN1 PROTO AREA pce JN2 PC3 CTRL Pc4 INI amp fi je e cii Zu _R6 fe e XXXL e Or e s mj jo dat ees OTTA w 8 e e elz e Wi g e XXXI el z je e a jo Ci40 0 coon oje joo o fase Bl caje e a e C4 gu eeoeoceedci3s o le ae C2 Ci C ues ci2 a JBL 33 z Cm n rm i ao uS a 321 J ai al g Eee ee ong J e Z m H xT a x Zuz a R2i e 5 oF2 5 Nw 5 2002 Radio Flier Electronics A Thomas Farrand Page 15 RFE 117 VCA Modified on June 10 2002 5 2 Component Location Gui
6. VCA The jumper maintains an in phase relationship between the input and output and is the normal configuration The jumper causes a 180 phase difference between the input and output While of marginal value this feature was included as it was free with this VCA core Makes a bullet point on a marketing brochure that is essentially of little to no value Still if this VCA is used to help mangle waveforms in real time a 180 phase difference could actually prove useful 3 2 Audio Output Buffer Section The other half of U2 is used to buffer the audio output signal and is set for unity gain R10 limits output current in a short circuit situation That happens virtually every time one plugs in or removes a patch cord Its inclusion is common sense 2002 Radio Flier Electronics A Thomas Farrand Page 8 RFE 117 VCA Modified on June 10 2002 3 3 VCA Core The VCA core is comprised of U1 and the passive components connected thereto The VCA core is connected exactly as prescribed in the device data sheet The power supply rails are bypassed at the chip by C3 and C4 Capacitor C10 deserves a little explanation The U1 device has a tendency to increase gain at higher frequencies which could lead to oscillation The purpose of C10 is to limit high frequency gain at various VCA gain levels With the value of C10 shown U1 is very stable at all frequencies and gain levels C10 should not be lower than 47 pf nor muc
7. applied control voltage It too develops its output voltage across PC3 at the opposite end to the output of U3A The net result is that PC3 can vary the amplitude of the control voltage and the relative polarity The output of U3 is limited to excursions of 5V for a 5V input 2002 Radio Flier Electronics A Thomas Farrand Page 9 RFE 117 VCA Modified on June 10 2002 3 5 Control Voltage Calibrate Section U4A provides the requisite voltage inversion for the VCA core and level shifting This circuit also includes TP1 which is used to calibrate unity gain The output voltage at pin 1 of U4 ranges from about 4V to 0 5V for normal inputs of 0 to 5V U4 can be most any dual opamp Although the schematic shows a Burr Brown OPA2134 device a TLO72 can be used with the same result An MXL1013CP would be ideal but the cost may not be justified If waveform mangling is your bag use the OPA2134 or the TLO72 An MXL1013CP is a precision but frequency challenged device Frequency challenged Aw shit political correctness is creeping into a mostly technical document Bogus 3 6 Temperature Compensation Section U4B provides the temperature compensation for the VCA The SSM2018T exhibits a 3500 PPM C temperature drift This results in a 7 dB change over a temperature range of 40 C to 85 C Personally I think this is negligible But if you insist on perfection make TCR1 a Precision Resistor Company PT146 1K 1 temperature depend
8. is left unconnected On the other 3 jacks connect the ground braid to both the switched and ground contacts 6 VCA CALIBRATION Before using the VCA for the first time ensure there is a jumper for inverting or non inverting phase through the VCA If there is no jumper there can be no audio VCA calibration is simple but is best done with an oscilloscope Let the VCA warm up at least 2 minutes before calibration That will ensure the VCA chip is at thermal equilibrium Use a VCO to inject a standard 5V P P triangle wave into the IN 1 1 4 jack Set the IN 1 potentiometer to 10 maximum clockwise rotation Set the IN 2 potentiometer to 0 maximum counter clockwise rotation Set the CTRL potentiometer to the centered position white line straight up Lastly set the INI GAIN potentiometer to 10 maximum clockwise rotation 2002 Radio Flier Electronics A Thomas Farrand Page 25 Tee RFE 117 VCA Modified on June 10 2002 Adjust trimpot TP1 such that the output level of the VCA matches the input level TP1 will allow you to get fairly precise if you d want That s it you re done 2002 Radio Flier Electronics A Thomas Farrand Page 26 RFE 117 VCA Modified on June 10 2002 7 USING THE VCA IN A MODULAR SYSTEM As a relative newbie to the modular synth world you probably know better than I how to make use of this module Note that the CTRL and INI GAIN controls interact a
9. that s where the components stay But I do think that a ground plane is essential So rather than wasting time flipping chips around to make it pretty I spent the extra time to lay down a solder plane that nearly covers the entire component side of the PC board Pay attention and you ll have no problems in that regard Pin 1 of all ICs employ a square pad instead of a round donut But do be careful Once a dual opamp is powered with the chip in backwards it is toast Personally I would socket the opamps only and solder U1 directly onto the PC board That way if a better opamp is found for this circuit it can be readily swapped in and out for comparison If you do not like to use sockets then don t use them If you use the suggested PT146 temperature dependant resistor for TCR1 it will require the usual silicone heat sink compound like on a VCO Place a blob between the backside of TCR1 and the top of U1 Make certain the heat sink compound is the last thing you apply to the completed VCA That stuff works great but can make a real mess Use it sparingly The printed circuit board is marked COMPONENT SIDE and SOLDER SIDE The component side of the board has a ground plane that covers a significant portion of the board s surface Obviously the components are inserted into the board from the component side and those components are soldered into place from the solder side of the board I don t mean to insult anyone s intelligence but w
10. 10 2002 The following is a list of all the parts needed to build the RFE 117 VCA module Some items were from my junk box and have no corresponding manufacturer miscellaneous hardware items All of the important items are listed with full part numbers and suppliers Manufacturer and Schematic Vendor Stock Unit Qty Mfgr Part Part Description Reference Vendor Number Cost Number CAPACITORS 2 Panasonic Cap 33 uf 35V radial electrolytic C1 C2 Digi Key P10290 ND 0 46 EEU FC1V330 FC series 8 AVX Cap 0 1 uf 50V radial ceramic C3 C6 C8 Mouser 581 SR205E104M 0 08 SR205E104MAA Z5U 20 C9 C13 C14 BC Components 1 K105M20Z5UFS5T Cap 1 0 uf 50V radial mono C7 Digi Key BC1139CT ND 0 48 H5 BC Components 1 K820J15COGFS5TL Cap 82 pf 50V 5 radial mono C10 Digi Key BC1012CT ND 0 12 2 1 BC Components KIO1JISCOGFSTL Cap 100 pf 50V 5 radial mono Cll Digi Key BC1013CT ND 0 12 2 BC Components 1 K222K15X7RFST Cap 2200 pf 50V 5 radial mono C12 Digi Key BC1074CT ND 0 11 L2 RESISTORS Yageo R1 R3 R7 8 100K MF 1 4W B_ Res 100K watt 1 metal film R8 R14 Digi Key 100K XBK ND 0 11 1 R15 R20 Yageo 2 18K2 MF 1 4W B Res 18 2K watt 1 metal film R5 R6 Digi Key 18 2KXBK ND 0 11 1 Yageo 1 150K MF 1 4W B_ Res 150K watt 1 metal film R11 Digi Key 150K XBK ND 0 11 1 Yageo 2 10K0 MF 1 4W B_ Res 10 0K 4 watt 1 metal film R12 R21 Digi
11. 49 7104 7 88 149 71104 panel mount SEMICONDUCTORS 1 Analog Devices IC SSM2018T VCA Ul Analog SSM2018TP 6 47 SSM2018TP Devices 1 Analog Devices IC OP275 dual opamp U2 Analog OP275GP 2 15 OP275GP Devices 2 Burr Brown IC OPA2134 dual opamp U3 U4 Digi Key OPA2134PA ND 2 63 OPA2134PA MISCELLANEOUS 4 Switchcraft Ys phone jack with closed circuit J1 J2 J3 J4 Mouser 502 112A 1 44 112A Fair Rite Ferrite Bead broadband 43 FB1 FB2 Mouser 623 2743002112 0 12 2743002112 material 1 Molex MTA 156 power entry connector PEC Mouser 571 6404454 0 11 3 Tyco 8 pin IC socket optional U2 U4 Mouser 571 3902612 0 08 1 Berg FCI Berg connector 4 pin JBI Mouser 649 69 192 404 0 23 1 Berg FCI Shunt jumper JB1 Mouser 649 68786 202 0 12 4 Belden 4 length of coaxial audio cable J1 J4 Mouser 566 8216 100 0 18 8216 2002 Radio Flier Electronics A Thomas Farrand Page 13 RFE 117 VCA Modified on June 10 2002 4 6 4 long aluminum spacer HWS 4 6 32 Philips pan head screws 1 HWS 4 6 32 nut HWS 4 6 internal tooth lock washer HWS 4 Tyco Alco Knob with white pointer stripe Various 1 50 PKES 90B 1 4 1 Four potentiometer short stooge SPI bracket 1 RFE 117 MOTM format custom SPI module panel 4 1 Supplier s Index Key Analog Devices Digi Key HWS Mouser PRC SPI Various 2002
12. AN 4 lo Usortert acena n EN A EAN aed gaa alan 5 1 4 Compatibility with Existing Products cccccccccccsseessscesseseseeessecsseeene 6 1 5 Performance and Specifications o ccccccccccsscssssssessssesssssessssessssesssseesssseesssness 6 1 6 Physical GhapaCteristies s 4 4 2 eake inners tttha teecsiniaree See autentaiest 7 1 7 Environmental Requirements 0 cccccccccccssssssssssessssessssseccssseesssesssseesssseessseess 7 2 SCHEMATIC DIAGRAM onic ccccssssssssssssssssssssccccscssssssssonsnsnsnssssesssseesees 7 3 VCA THEORY OF OPERATION wc cccccsssnsssssssnsssssssssesseee 8 3 1 Audio Input Mixer Section sa cescessts cols cuceascatessscrceca italian Sect asanen teed 8 3 2 Audio Output Buffer Section sss 8 3 3 VOA COTE cre ase raa eaten AA A onal nape E E 9 3 4 Control Voltage Polarity Adjust Section wo eecssseesssesennes 9 3 5 Control Voltage Calibrate Section oo cccsccssssssstessseeesseesseesseesseees 10 3 6 Temperature Compensation Section 10 3 7 WC Power Input Section a sxbra hha eatane Maan narcosis eee Act 11 4 REECE PARTS LIS Present cng ecatuanGnewcananaiee 12 4E Suppher SAN Gas os ret cus ctesctes ote Seetia esto tine a A O 14 5 ASSEMBLY OF THE VCA oii ccccsssssssssssssssssssccsscssssssssssssstsnsnssses 15 5 1 Component Location Guide By Schematic Reference 0 000 15 5 2 Component Location Guide By Part Value 16 5 3 Before You Begin Building The VCA 17 5 4 Install The Fixed Resistors ocer es d
13. N BLACK BLACK RED BROWN Install the 1 0M 1 resistor at location R13 next to R12 The color code for resistor R13 is BROWN BLACK BLACK YELLOW BROWN Install the 33 2K 1 resistor at location R4 next to U2 The color code for resistor R4 is ORANGE ORANGE RED RED BROWN Install the 2 49 9K 1 resistors at locations R9 and R16 The color code for these resistors is YELLOW WHITE WHITE RED BROWN Install the 649K 1 resistor at location R22 next to U4 by PC2 The color code for resistor R22 is BLUE YELLOW WHITE ORANGE BROWN Install the 2 1 00K 1 resistors at locations R10 and R24 The color code for these resistors is BROWN BLACK BLACK BROWN BROWN Install the 110K 1 resistor at location R17 next to U4 by PC2 The color code for resistor R17 is BROWN BROWN BLACK ORANGE BROWN Install the 332K 1 resistor at location R18 next to U4 by PC2 The color code for resistor R18 is ORANGE ORANGE RED ORANGE BROWN Install the 374K 1 resistor at location R19 next to U4 by PC2 The color code for resistor R19 is ORANGE VIOLET YELLOW ORANGE BROWN Install the 17 4K 1 resistor at location R21 L H side of TP1 The color code for resistor R21 is BROWN VIOLET YELLOW RED BROWN Install the 38 3K 1 resistor at location R23 next to U4 The color code for resistor R23 is ORANGE GRAY
14. RADIO F Lick eLeCrrOoncs RFE 117 EXPONENTIAL VCA USER MANUAL Synopsis This is the user manual for the RFE 117 VCA for application in a high quality modular analog synthesizer All technical documentation relating to that product is disclosed herein The design and all documentation related thereto remain the sole property of Radio Flier Electronics and is copyrighted material SOrTY WORK MA SORNTI STATICn REEI BP VCR a Z Z e CETA 10 hetse TD 117 val pco Silkscreen amp pads L al EypressPCBYRE C My Documents ExpressPC DOCUMENT CONTROL Revision Number 1 0 Revision Date June 10 2002 Principal Author A Thomas Farrand Assisting Author none Document Format Authored in Microsoft Word 2000 distribution via Acrobat PDF Document Status First Release Name of Document RFE117Manual DOC Type of Document PERMANENT Storage Location Author s PC 32 bit Drive C My Documents WORD SYNTH Associated Project Identity 117VCA This document contains information proprietary to Radio Flier Electronics and may not be reproduced disclosed or used in whole or in part without the express written consent of RFE 2002 Radio Flier Electronics RFE 117 VCA Modified on June 10 2002 Table of Contents 1 INTRODUCTION NOTES FROM THE AUTHOR 3 MW 5 SACRO UIN saath scae ce ectastas ce psctaisss i Ciara ta Rpt at ech a E Mie Gan 4 L2 Usable Product Life coda ceca eaei a EAA E
15. a TL072 instead If you are using a socket install the socket only at location U3 Please note the orientation for U3 on the component location guide Please note that this chip has a polarity that must be observed Pin 1 of U3 must be inserted into the square pad on the printed circuit board for proper orientation Make certain that all 8 leads protrude through the board before you solder any of the pins Note pin 1 of both U3 and U2 point at each other This is part of the wild and crazy layout scheme be careful Install the dual opamp OPA2134 at location U4 You can also use a TL072 here too If you are using a socket install the socket only at location U4 Check the orientation for U4 on the component location guide Please note that this chip has a polarity that must be observed Pin 1 of U4 must be inserted into the square pad on the printed circuit board for proper orientation Make certain that all 8 leads protrude through the board before you solder any of the pins Note pin 1 of U4 points towards U1 the VCA chip Next install the two ferrite beads FB1 and FB2 They are located in close proximity to the electrolytic capacitors just installed The PC board is fabricated such that the beads when properly seated do not come in contact with the component side foils on the board itself There is a rectangular notch in the ground plane to accommodate the beads Install TP1 the 20K gain calibration trim pot locat
16. aining a 0 phase shift through the VCA Alternately one could solder a wire in place of the phase jumpers if you are certain you d never want to change this setting 2002 Radio Flier Electronics A Thomas Farrand Page 22 RFE 117 VCA Modified on June 10 2002 5 8 Install The Remaining Board Level Components I would suggest that you wash the board at this point and remove the solder flux It is also a good time to give the board a quick inspection for solder bridges and to make certain the components are in the correct locations and of the proper value If you are older than 16 years I suggest you use a magnifying glass to aid this process Some traces are pretty close Well they look close to this old fart E Install PC1 and PC2 panel controls These pots are the 100K audio log taper units They will become the IN 1 and IN 2 level controls Make certain the pots are flush with the printed circuit board and are aligned flush with the board edge Remove the mounting hardware and save for later For now the hardware just gets in the way Once you have installed these pots the board becomes much more fragile Do exercise care when handling the board once you have begun installing the pots E Install PC3 and PC4 panel controls These pots are the 100K linear taper Cermet units They will become the CTRL and INI GAIN controls Make certain the pots are flush with the printed circuit board and are aligned flush with the board edge Re
17. ant resistor This is the industry standard part used for negating temperature effects of silicon and is very similar to the devices used on many MOTM modules for temperature compensation Otherwise just use a standard 1K 1 4 watt 1 resistor for TCR1 and forget about it I m using them because I have a few If I didn t have them I wouldn t buy any C12 is used to limit noise introduced by the control input The result is there is a noticeable lag in control voltages of about 30 milliseconds if one uses slew limiting values suggested in the data sheet One can eliminate this lag with an attending increase in control voltage noise by eliminating C12 altogether I would suggest using a 2200 pf capacitor for C12 as a reasonable compromise between reduced control voltage noise and the lag introduced The choice is up to the builder of the VCA The control voltage noise is probably more of a spec item issue than something critically important In a synth control voltages vary more widely than in a studio grade mixer for which the SSM2018T was really designed As shown on the schematic the voltage at U1 pin 11 determines VCA gain With a voltage of 3 5V or greater the VCA output is effectively shutoff With a voltage of 0 5V the VCA has an output of greater than 19dBV If your voltage levels on U1 pin 11 are outside this range you have probably installed an incorrect part somewhere in the U3 U4 circuit 2002 Radio Flier Electronics A T
18. at coincide with the sections of the theory of operation The SSM2018T VCA chip has been factory trimmed for minimization of distortion and control voltage feed through This simplifies circuit implementation as no trimpots need be added for those functions The result is a very high quality VCA function that can be implemented at a very low cost Perhaps discrete designs might beat the specifications of this device but it is not likely that the cost differential is justified That is a statement of opinion not necessarily fact 3 1 Audio Input Mixer Section Referring to the enclosed schematic we start with the audio inputs IN1 and IN2 The audio inputs are summed via R1 and R2 into the inverting input of opamp U2A R3 sets the gain at unity in conjunction with R1 and R2 values of course While this can be a cause of overload if two signals are mixed at full amplitude it was necessary to allow for a single input to cause full output amplitude I strongly recommend the use of the specified OP275 opamp for U2 as that is the device specified in the Analog Devices data sheet for the SSM2018T Besides it is pretty much a staple item in synths these days C7 AC couples the audio signal into the VCA core The value of C7 primarily determines the lower frequency limit for the VCA With a value for C7 of 1 microfarad the low end response is essentially flat to 14 Hz and down less than 3 decibels at 2Hz JB1 provides a selection of overall phase of the
19. ation it is copyrighted by me and produced at no small effort Thank you for your cooperation Analog music synthesizers create sound by means of harmonic rich oscillators and modify that sound through subtractive techniques using filters and other devices to change the timbre of the sounds produced One of the most basic elements of sound modification is an electronic volume control known as a Voltage Controlled Amplifier or simply VCA The term VCA is somewhat of a misnomer as most VCAs have very little gain possible They are more accurately described as a Voltage Controlled Attenuator In typical use however there is an expectation of no output signal when the controlling voltage is zero As the control voltage rises towards a more positive value the attenuation decreases giving rise to an increase in signal amplitude on the output Since that looks like a voltage controlled amplifier the name sticks The RFE 117 is designed to integrate easily within a contemporary analog synthesizer Physically the RFE 117 can be fitted onto a stooge bracket for mechanical stability and then affixed to a custom stooge panel The custom panel already devised is done in a Synthesis Technology MOTM format for size appearance and user interface The RFE 117 VCA has a 2 input mixer in front of the VCA core The primary control input is adjustable for differing level inputs and features a polarity changing mechanism The VCA also feature
20. de By Part Value The following is the component location guide by part value This layout is good for inspecting the board once it is built See also the other location guide for components by schematic reference PLASTIC COMPONENT SIDE PLASTIC CERMET CERMET eon eon eon oon 21 eZI ZI eZI LOG LOG LINEAR LINEAR PCI T PE3 CTRL ae 100 PF ou Z 18 24 w jo o XXXL mE i a i a Hg HE xe i 5 e EKZ XXXI 2 oo ee econ Le as ee g2 O ee PFleje uy JCO e ae C2 Ci 2200 1 THO erie sc aa a gt amp Si J nanon 33 ris 33 Fis J Sag UF UF a Eee 2 OMNA J e za sot 2 ei xT x TE 12 aK i5 GN is C 2002 Radio Flier Electronics A Thomas Farrand Page 16 RFE 117 VCA Modified on June 10 2002 5 3 Before You Begin Building The VCA You already know how to solder The choice of solder is up to you I am probably alone when it comes to solder choice I prefer 0 020 diameter 2 silver solder with a rosin core Kester number SN62PB36AG02 and it costs about 28 for a 1 pound spool Yes the board must be washed with a strong chemical solvent to remove the flux No it does not corrode my solder tips And no the board does not have to be washed right away It can be washed a week after soldering with identical results no hurry to clean up within an hour s time I mention this only in passing and have no desire to start a solder war And
21. e is no magic or anything clever about it It is a very basic VCA with excellent sonic performance Its simplicity is the key to longevity 2002 Radio Flier Electronics A Thomas Farrand Page 4 RFE 117 VCA Modified on June 10 2002 IN1 WZ N AVA INI GAIN Wiz N2 CTRL RADIO FLIER RFE 117 EXP VCA 1 3 User Interface There are 4 controls on this VCA The topmost control knob IN 1 is the input level adjustment for the audio signal input applied to the IN 1 1 4 jack The second control knob IN 2 is the input level adjustment for the audio signal applied to the IN 2 4 jack Together these controls form a 2 input mixer for the VCA audio signal input 2002 Radio Flier Electronics A Thomas Farrand Page 5 RFE 117 VCA Modified on June 10 2002 The CTRL knob serves two purposes First it adjusts the magnitude of the control signal driving the VCA core which is applied via CTRL jack Second it can reverse the polarity of the input control signal to facilitate stereo panning when a pair of RFE 117 VCAs are used at the same time Alternately it can be used to normalize the inverted output of envelope generators or LFOs The INI GAIN knob is a manual volume adjustment for the VCA It sets the initial gain of the VCA when no control signals are present The effect of this control is summed algebraically with the signal applied to the CTRL 4 jack before presentation to t
22. ed to the right of where the MTA 156 power connector will go As a consequence of lead spacing it will only go in the board the correct way Next you ll install TCR1 the 1K temperature compensating resistor If you are using the specified PT146 resistor bend the leads at a 90 right angles about 1 inch apart The goal is to make that resistor span the length of the U1 chip the SSM2018 and fit into the appropriate holes You will notice that I screwed up and made the holes for a PT146 a wee bit too small If you are using a 1 metal film resistor the holes are perfect just plop the resistor on top of U1 and solder away But if you use a PT146 you ll need to enlarge the holes slightly to accommodate the larger 2002 Radio Flier Electronics A Thomas Farrand Page 21 RFE 117 VCA Modified on June 10 2002 diameter wire used on that part I used a dental pick to enlarge the holes a bit and it worked just fine Don t get too carried away they only need to be enlarged very slightly That seems to be the only boo boo I made on the board so you need not search for other documented faults 0O Install the PEC That s the Power Entry Connector and is commonly called an MTA 156 connector Make certain the connector is soldered into place as shown on the assembly diagram E Install connector JB1 That s the VCA phase jumper block and consists of 4 square pins on 0 1 centers Normally the top jumper is used for maint
23. h more than 200 pf If one uses too small of a value for C10 the SSM2018T may oscillate at some gain settings Choosing too large a value for C10 and the high frequency response will suffer The upper frequency end of this device s response is essentially flat to beyond 100 kHz with the part values shown Resistor R11 establishes a class AB operation for the VCA chip This part has been optimized for operation for class AB operation Typically distortion in class AB mode is less than 0 05 which is insignificant in the device application Obtaining distortion levels lower than this is ludicrous as the signals normally processed are very high in distortion Besides the distortion level is well below that of a speaker or headphone Other component values were chosen to match that of the manufacturer s data sheet as there was no compelling reason to deviate from the suggested values The data sheet for the SSM2018T can be obtained from the Internet at www analog com Just do a search on SSM2018 and download the PDF data file You ll want to retain copy for your records 3 4 Control Voltage Polarity Adjust Section The control voltage section is pretty straightforward U3 is configured to provide a normalized or inverted control voltage to the VCA core U3A functions as a non inverting buffer for the applied control voltage at CTRL input The output voltage is developed across PC3 CTRL U3B provides an inverted unity gain buffer for the
24. he VCA core 1 4 Compatibility with Existing Products The audio and control inputs are designed for 5V operation Excursions somewhat beyond that are tolerated without damage but with possibly unexpected results Obviously one cannot apply voltages significantly higher than 5 7V would be about the limit I d want to shove into the module although the VCA chip itself is rated for 13V These voltage limits are very much in keeping with those found on contemporary synthesizers MOTM in particular The current consumption of this module is less than 30 ma per supply rail 1 5 Performance and Specifications The typical performance of this VCA according to manufacturer data is as follows Supply Voltage 15V regulated Supply Current lt 30 ma per rail Dynamic Range 117 dB Maximum attenuation 100 dB Control Feedthrough for a 40 dB gain change 1 mv Gain Bandwidth 700 kHz Common Mode Input Range 13V Total Harmonic Distortion Plus Noise 10dBu input 006 Total Harmonic Distortion Plus Noise other input levels 013 2002 Radio Flier Electronics A Thomas Farrand Page 6 RFE 117 VCA Modified on June 10 2002 1 6 Physical Characteristics The printed circuit board is 5 5 wide by 2 8 deep The mounting holes line up with a standard four potentiometer stooge bracket Potentiometer spacing is MOTM standard of 1 625 between centers The potentiometer holes are spaced to fit Spectrol or Bourns potentiometer
25. homas Farrand Page 10 RFE 117 VCA Modified on June 10 2002 3 7 DC Power Input Section The MTA 156 connector AKA PEC is the standard MOTM style interface used to bring 15V and ground to the module FB1 and FB2 provide a minimum of radio frequency suppression for the power leads Capacitor C1 and C2 provide localized bypassing for the 15V supply rails Unlike MOTM and other manufacturers modules I have selected a low ESR type of capacitor for Cl and C2 These capacitors are more expensive than others typically used but are designed to operate at high temperatures for a long period of time While that isn t specifically needed here long life is certainly wanted That s the side effect in choosing these specific capacitors The most likely fault point in this or most any other module is the failure of C1 or C2 The electrolyte used in electrolytic capacitors is not a solid it is more like a gel Over time and elevated temperatures the electrolyte tends to dry out The result is that the capacitor is much less efficient and will eventually stop working When that happens the module will start to exhibit strange behavior such as oscillating at a high frequency motor boating distorting incoming audio and so on By specifying a very high quality capacitor from the outset one postpones the inevitable failure 2002 Radio Flier Electronics A Thomas Farrand Page 11 RFE 117 VCA 4 RFE 117 PARTS LIST Modified on June
26. ith adequate 2002 Radio Flier Electronics A Thomas Farrand Page 17 RFE 117 VCA Modified on June 10 2002 libation I could make that mistake Hell with a good Cabernet normal speech can be reduced to little more than vowel movements What s brown and sounds like a bell Dung The following assembly guide assumes that you have obtained the requisite components specified in the parts list If you have made substitutions your parts may vary slightly from the descriptions given I will not hold your hand and tell you when it is time to take a break If you need to pee go take care of it Once each component is inserted into the board it is assumed that you will solder it into place and trim off the excess lead length Okay time to get down to brass tacks and build the VCA 2002 Radio Flier Electronics A Thomas Farrand Page 18 RFE 117 VCA Modified on June 10 2002 5 4 Install The Fixed Resistors O O Install the 8 100K 1 resistors at locations R1 R2 R3 R7 R8 R14 R15 and R20 The color code is BROWN BLACK BLACK ORANGE BROWN Install the 2 18 2K 1 resistors at locations R5 and R6 The color code for these resistors is BROWN GRAY RED RED BROWN Install the 150K 1 resistor at location R11 next to Ul The color code for resistor R11 is BROWN GREEN BLACK ORANGE BROWN Install the 10 0K 1 resistor at location R12 next to U3 The color code for resistor R12 is BROW
27. lectronics A Thomas Farrand Page 23 RFE 117 VCA Modified on June 10 2002 5 9 Finishing Construction O Using the 4 screws nuts lock washers and 4 spacers assemble the board onto the requisite 4 pot stainless steel stooge bracket Insert the screws from the component side of the printed circuit board and fit the nuts and lock washers on the blank side of the stooge bracket In all cases the holes should line up quite well You may choose other methods for mounting If you do just be certain that the mounting holes for the printed circuit board do not short out to anything metal O Attach the completed VCA assembly to the custom black stooge panel Use the saved pot hardware to fit everything together Fit the knobs onto the pot shafts and tighten Make certain the alignment of the white line on the knob corresponds appropriately to the legend on the panel 2002 Radio Flier Electronics A Thomas Farrand Page 24 RFE 117 VCA Modified on June 10 2002 O Attach the 4 Switchcraft 4 jacks to the stooge panel using the supplied hardware As you face the rear of the VCA assembly fit the jacks such that the bevel of the jack is in the upper right hand corner when you tighten the mounting nuts It will look something like this a ee a a Se SO e a Switched Ground The OUT jack has only the hot center lead of the coaxial cable and the ground braid connected The switched contact
28. lot In some configurations they seem a bit too sensitive In other configurations they ll seem just right This VCA works quite differently than the MOTM 110 if that s your point of reference You will find this VCA is best at producing natural percussive sounds It is quite a bit perkier sounding than a linear VCA and that is obvious after playing with it for about two minutes This VCA does not replace linear VCAs Rather it is very good at producing some sounds that simply cannot be obtained from a linear VCA But there are sounds that are better produced by a linear VCA than from this VCA It all depends on what sort of sound you seek It is just another tool in the toolbox One last note I would be remiss if I did not point out that this VCA is superb in making the limitations of the MOTM 800 ADSR generator quite obvious Previously I had said the flaws in the 800 didn t really bother me all that much They bother me now When the control voltage from the 800 misbehaves it sticks out like a sore thumb The patch one uses coupled with specific settings of the RFE 117 VCA makes a big difference in the sound and I was able to become annoyed rather easily There is sometimes an extra bounce in the VCA output When the exponential VCA from Synthesis Technology is eventually released there will be many more complaints about the 800 Hmmm Oakley ADSR guts behind MOTM 800 panel That is food for thought Document End
29. move the mounting hardware and save for later E Prepare 4 lengths of small diameter coaxial cable for connections to the 1 4 jacks Each cable should be about 4 in length Tin the wires on each end of the coax Next solder the outside braid of the coax into the large square pads provided at IN 2 IN 1 OUT and CTRL as shown on the component location guide The center conductor of the coax cable goes to the round pads just to the left of the braid connection If you have built any MOTM modules this step should be familiar If not you ll have to use your imagination Using 4 cable ties you got from your local hardware store secure the coax cables to the printed circuit board There are two holes per coax cable located on the extreme right of the printed circuit board provided for this purpose If in doubt look at the photo on the first page of this document for details related to fastening the coax cables At this point the board should be essentially complete Since I don t use solder with a water soluble flux I spot clean the pot and the coax cable connections with my favorite hydrocarbon based cleaner For those of you using H20 do whatever has been working for you so far O If you have included the PT146 temperature compensating resistor at TCR1 now is the time to spread some of that silicone heat sink compound between TCR1 and the VCA chip U1 Use a wooden toothpick to push the compound into place 2002 Radio Flier E
30. oses ancteen eee recente 19 5 5 Install The Ceramic Capacitors 20 5 6 Install The Electrolytic Capacitors 1110ssssiiissesesiiiissssesirisrrrrs 20 De msall More smi sess spaston sce csihac Gunter tgs NAN 21 5 8 Install The Remaining Board Level Components 00 000 c ccc 23 5 9 SHIPSWIN C O18 MC OM rece acne eet ned ated ae ct eds stan has Aided Rae taal 24 6 VCA CALIBRATION e 0 10 00100000000000so0soesoesoesoesoonoesoesoeseonoostenoeseenoeseenoeseene 25 7 USING THE VCA IN A MODULAR SYSTEM 27 2002 Radio Flier Electronics A Thomas Farrand Page 2 RFE 117 VCA Modified on June 10 2002 1 INTRODUCTION NOTES FROM THE AUTHOR The RFE 117 VCA was designed to be an inexpensive VCA of high quality The control voltage response is exponential and the VCA design is based on an Analog Devices SSM2018T VCA core This VCA core is based on the research of Douglas R Frey and appears in U S patent number 4 471 320 which expired interestingly enough on September 11 2001 Yikes The use of the design documented herein is granted for personal non commercial use I reserve the right to make this design available as a commercial product at any time As of this writing I have no particular commercial interest but might change my position in the future I ask that recipients of this document not disseminate this material on the Internet as if it were in the public domain This is not public domain inform
31. s an initial output level adjustment if manual control is desired 2002 Radio Flier Electronics A Thomas Farrand Page 3 RFE 117 VCA Modified on June 10 2002 1 1 Background This module was designed as an alternative to some other commercial modules The availability of such modules from established vendors is not always to my liking so I rolled my own While the design of such devices is no simple task I am willing to put forth the requisite effort and share the results with others This is probably stupid on my part given the current business climate but this is a hobby to me and I enjoy it I would hope that others would do likewise and share their efforts with me I considered a discrete OTA approach for a VCA which would have provided simultaneous linear and exponential control That approach was abandoned as my personal interest was primarily in exponential control I did not feel like increasing circuit complexity to provide a marginal benefit to me And with the availability of an excellent exponential control response VCA core from Analog Devices there was little point in spending gross amounts of time designing that which already exists 1 2 Usable Product Life The life of this module should be in excess of 20 years with the components specified Of course this will be shortened if the unit is subjected to voltages or temperatures beyond design limits Your mileage may vary as they say This module is very simple Ther
32. s while poking through a custom stooge panel There are a number of uncommitted pads that can be used for adding a small custom circuit on this board There is room for 3 8 pin chips and passives 15V supplies and ground have been brought in close proximity of this proto area I cannot imagine what this are might be used for It is because I cannot imagine the potential use that this kludge area exists in the first place Duh 1 7 Environmental Requirements The operating temperature should be between 0 60 C Humidity must be kept within the range of 15 90 non condensing If you can stand to be in the same room with this module for extended periods of time you will probably not exceed any environmental limit 2 SCHEMATIC DIAGRAM The RFE 117 VCA schematic appears as a single sheet under separate cover 2002 Radio Flier Electronics A Thomas Farrand Page 7 RFE 117 VCA Modified on June 10 2002 3 VCA THEORY OF OPERATION The RFE 117 VCA is nothing more than a glorified implementation of the test circuit provided by Analog Devices in the device specification sheet By implementing the device per manufacturer s recom mendations one should be able to obtain nearly the performance claimed in the specification I ve done nothing bizarre with their basic design Please refer to the schematic diagram when reading the theory of operation for each section The schematic diagram has section identifiers th
33. yes all of my MOTM and Oakley modules were assembled using this solder The RFE 117 VCA does not have a solder mask on either the component or solder side of the board This makes it easier to create solder shorts between adjacent traces To limit solder excursions into unwanted areas use a small piece of masking tape to cover nearby areas that might inadvertently be soldered This technique can also be used to prevent the solder from wicking down a trace that is some distance from the donut pad being soldered As soon as the solder cools remove the tape to prevent depositing glue goo Trimming leads on the PC boards is worth a few words Only those people that are actually reading this paragraph will pickup on this jewel of a tool Get yourself a pair of Klein D 224 4 AC transverse end cutters I have used many cutting trimming tools in my day and most of them suck to varying degrees This tool does not suck I have been using the same pair I got back in 1974 You ll love them I am a big fan of Klein tools Klein manufactures most of the hand tools I use I think they are better quality than Xcelite and the cutting edges stay sharp for a very long time They cost only a bit more than other brands WARNING The PC layout is insane from one point of view the ICs are not inserted uniformly In fact every possible orientation is used save one Sorry I am not fond of laying out PC boards In fact I hate doing it Once a placement seems to work for me
Download Pdf Manuals
Related Search