circuitbenders.co.uk CB55. Construction:
Contents
1. position This will also work but you ll have to check the pinout and rotate the part accordingly The correct DSG pin positions are marked on the board Next install the trimmer pots at VR1 and VR2 the inductor at L1 the LM324 quad opamp and any pin headers you want to use for the off board connections can B TRIG IN2 as z 4 NOISES 6 d 2 A SNARE BODY Dih s RIMSHOT G LL jo CN O 9 BC Phi J ee I elole E JO TA eer K a reas j I i i I I l I Th NN ho 01010 lelte JOLUME TONE Li ey HG D e Ke a 6 pr gt circuitbenders co uk 5 re Fe 9 LTS Le A 5 oli EF 3 zg Nis of Ths SNARE NOISE 1 Power The board is powered by 12v DC On the bottom left of the board you can see a 2x5 pin power connector Only the pins on the right labeled with the larger GND and 12V text are actually used but the 10 pin connector is provided for the standard eurorack format Please note that due to its size this PCB is not designed specifically to be used in a modular system module but we used this connector just in case somebody wanted to try and bodge something together In normal use you can just use the GND and 12V connections with the larger font If you haven t installed the trigger conditioning circuit then you will have left out the 9v regulator In this case you can run the voice circuits from a 9v input instead of 12v if you2. range of adjustment between the noise level being too quiet and it starting to resonate strangely If you need any further support or want to discuss any potential mods for this PCB we have started a dedicated CB55 board on our forum at http www circuitbenders co uk forum index php board 32 0 html l BASS DRUM EIS ane C13 a te paed ia gg U Ga to ete I C11 0 c12 c20 _ Af ae a ae be una2 i az T Jf a AT wr bd Tera k ap ope 000 MSH dr R46 R43 T3 R45 R54 RS2 oof FE C21 f Jha ed ak ie oS ea l AF Paz l Gr C44 f CHAM H 7 C42 LL 2 16 IL l C23 c22 T9 i l l Se SES SS l Q N a ee ee eee er am A T ar merrt a Je T 7 PERE 7 an sls aac a Fi alak d O HTH OE CELTS BE a C1 OS Hd R43 R41 R51 12U GND JAH nE maiji AOSE
3. circuitbenders co uk CB55 The circuitbenders co uk CB55 is an exact clone of the voice board of the Boss DR55 drum machine It features four fully analogue sounds bass drum hat snare and rimshot There is also an overall accent feature that adds a little extra punch to the whole mix when it is triggered The sounds and accent can be triggered using standard trigger pulses or with the optional trigger conditioning circuit you can use gates or trigger pulses longer than 10ms What is the trigger conditioning and do need it The CB55 voices are triggered using standard 5v trigger pulses that last for 10ms Any longer than that and you may experience double triggering and flam sounds any shorter and the sounds decay incorrectly Unfortunately a lot of older drum machines such as the TR707 and TR606 have a fairly random trigger output length and gate signals can be any length so the trigger conditioning circuit takes any 5v trigger pulse of 10ms or more and turns it into a 10ms pulse suitable to trigger the voices If you re using a midi to trigger convertor or a modular system where you know that the triggers are 10ms long then you can use the TRIG_IN2 connector and leave out all the trigger conditioning circuit Components marked in red on the parts list If you don t know how long your triggers are you want to use 5v gate signals or you will be using a mixture of triggers then its probably better to just install the conditioning and trigg
4. electrolytic with a value that small Either an electrolytic or a tantalum will work fine but a tantalum will probably be a lot more difficult to get hold of these days The DR55 uses a 45mH inductor in the Hi Hat These are virtually impossible to get hold of but you can substitute a 47mH or even a 43mH one with no perceptible difference The original part probably had a tolerance of 20 of the stated value anyway so 2mH off in either direction won t make a difference to the sound A Bourns RLB0812 473KL or Murata 22R476C will do the job These links connect the output from each voice circuit to the mix bus They have been provided as links rather than permanent PCB traces to allow for easy modding for individual voice outputs Pieces of cutoff component leg can be used here You should have plenty lying around Troubleshooting and adjustment If you are having problems please check the following e Parts orientation The electrolytic capacitors and the diodes need to be soldered in with the correct orientation The capacitors will have the negative pin marked on their body and the positive pin marked on the board Diodes will have a band on one end of their body This band is marked on the board image e Have you got the power the right way around and are you using the correct GND and 12V connections e Do you have the transistors the right way round Is the FET at Q1 of the correct type e Are your trigger pulses the correct
5. er the sounds via the TRIG_IN1 connector Construction The first thing to do is read through this entire guide and make sure you have all the correct parts Then you should get started by installing all of the resistors as shown below 62 TRIG_IN1 Ol loko OF1O oko a Gi u R09 cards cra aA NG rei aa pg i ee ag pa OF OOOO Aa c ag zi RIG IN2 a Os OO 01010 s RIMSHOT i 40 f IS gt OOO 00 VOLUME TONE ig 6 E e 2 SNARE NOISE HI HAT Next install the diodes and the jumper links The diodes need to be correctly oriented so that the band around one end of the component body is at the same end as the band shown on the board D1 is a larger 1N4001 rectifier diode that provides polarity protection for the power input but all the others can be general purpose small signal diodes such as 1N4148 s or 1N914 s CIN H TRIG IN2 i i CHI Cc O Q 2 x Io H ol LO 49 REG EGt 5 HI HAT C36 C37 SNARE NOISE paroparo TF CWS c ipo A XS Ny S g AAN ACCENT 23 E ECNO T C43 ae lt 3 yo i a a Airy Me e e e e VOLUME TONE circuitbenders co uk The jumper wires at J3 J7 connect the output of each voice circuit to the main mix bus These links are designed as jumpers for easy mods to provide individual outputs but at this point it wou
6. ld probably be better to just install them You can always change things at a later date Next install the non electrolytic capacitors These include the poly film and ceramic caps CHK CWS Pp oO l OCh E c Wii CHT joc Mi bc wg c Beas N4 me a BKO O 5 cz e Co a DOL POV 1 i TA 4 vu AA ta U4 700 am L Ee GS ee Mie e ie e e p2 TRIG_LIN1 831100 c zo LU B es RAHNA aa IY oe gt CHRIS ie c TRI6 IN2 Mel 7 Jele lt RIMNSHOT ca c Ie p 5 O JOLPEBS cm a L RSC r erimid pot C4 Cay 2 CMO 4 A a OO 2 e o1 QIQ FAGIN 3 ommy ANYANAK one Billy F 3 Ma IZ SNARE BODY df 2 vE m re aj i pat to Qo c Wey BD Tee a we ah oe 6825109 fe 20 0 6 NY Me e e e e VOLUME TONE The original DR55 used those green resin dipped film caps that you find in just about everything from that era If you wanted to use them for some reason they will work fine although sound wise they are exactly the same as the box caps we ve used here The 47pF cap at C16 will probably have to be ceramic as alternative types tend to not be available in values that small Next you should install the electrolytic capacitors Be careful you get these the right way round as the polarity is important The positive pin is shown on the board C1 and C3 should be rated for at least 25v
7. length See the start of this guide for details e Check your soldering on any joints that connect to the ground plane on the rear of the board These are often more difficult to solder due to the heatsink effect of the ground plane itself e Have you shorted component legs together This is very easy to do by accident when you are soldering in several adjacent parts at the same time If you have component legs bent across each other to hold parts in place during installation make sure that once you have soldered them in and cut off the excess leg the remaining legs are not in contact with each other See the images below for details Crossed component legs during installation Shorted legs after soldering e VR1 sets the difference between the normal and accented output levels Theres no real right or wrong way to set this although the DR55 service manual does suggest you should adjust it to read 4 5v at the junction between R75 and the VR1 wiper middle pin What we would recommend would be to turn the accent pot to maximum and them play a pattern with accents while adjusting VR1 for best effect Please note that the effect of turning VR1 is delayed so adjustments should be made by moving the trimmer and then leaving the new value to settle for a few seconds before adjusting again e The noise level for the hat and snare sounds is adjusted using VR2 We d recommend using a decent quality trimmer for this as theres sometimes a fairly thin
8. minimum but the rest don t really matter that much as anything over 10v should be fine Hejtejlej ej e ACCENT 25 90009 8 A irse a 0 24 fe or 00 foie A d gy Sa 4 441 90 d F i Fae O5 G Da FF WU A G 583410 3 oO ey r cen ge CN IS fo Pra wg SSSI R e i a CB s TRIG IN2 L NG Tt 4 o TO Q w _ _ T X SD CW OF LU e C42 1 00000 0 gt BEMA H JOLUME TONE c circuitbenders co uk CB55 E sy Now install the voltage regulators and transistors REG1 is a 78L06 regulator that supplies the 6v power to the voice circuits REG2 is a 78L09 that supplies 9v to the trigger conditioning circuit T1 to T10 are general purpose NPN transistors Roland Boss used 2SC945 s is virtually everything they produced during this era so this is what we ve specified here but you could probably get away with using any number of transistors with similar specs We haven t actually tried it but we would imagine it d also work fine with the common 2N3304 or 2 gt C1815 JARIG IN ace peat A s PAN lt LM324 2 z 00069000 d ca Wee TRIG_IN2 40 k 1 ooo elle VOLUME TONE Q1 in the accent circuit should be a JFET transistor with a DSG pinout A few different types will fit here We ve tried the J201 MPF102 and 2N5457 and they all seem to work okay The DR55 actually uses a 2SK30AY in this
9. trigger converter has a dedicated accent output then make sure you use that for the accent trigger input as it will usually be less prone to midi lag Triggers from a purely analogue system will usually have tighter timing than midi If you are using gate signals to trigger the CB55 instead of trigger pulses the accent will stay activated for as long as the input gate remains high You should only ever use 5v trigger pulses or gate signals Anything higher than 5v will cause unwanted effects and may damage the circuit Parts List Part numbers in RED are not required if you are not installing the trigger conditioning circuitry See the build guide for more details R1 R3 R4 R8 R10 R11 R14 R16 100K All resistors standard 4 watt carbon R2 R9 R15 R22 R46 R61 R72 R73 AK RS R7 R12 R18 R20 R25 2k o R6 R19 R32 R44 R51 R57 R59 10K KEKSZ ET KK la RB RO RT RB 80K a NN R49 a R76 R80 RB n OSS Ra 290K RB 63 RIT RBZ E A RK TT rasa TT RT ek TT ms BRT a a ENNE PSS EN sense mm TT ak 5 8 res RT 01 J201 MPF102 2N5457 Many DSG JFET s work here or ame TRIG_IN 1 TRIG_IN 2 POWER PIN HEADERS You can use standard pin headers in CONNECTIONS OUTPUT any of these connections The DR55 uses a 0 15uF tantalum cap here There doesn t seem to be a particular reason for this choice so we can only assume the original designer wanted to use a polarized cap but couldn t get an
10. wanted to Either will be fine Inputs outputs and pots The wiring diagram for the inputs outputs and pots can be found on the next page The diagram shows all the pots viewed from above The accent amount pot should ideally be an antilog pot commonly known as a C curve pot but a linear B curve pot can be used at a push or a normal A curve log pot if you use the left hand pin and wire it in to operate backwards You can use a 470K pot if you are in Europe and 500K is not readily available Note that the pin assignations for the two TRIG IN connectors are different TRIG IN1 TRIG IN2 C500K PIN1 RIMSHOT PIN1 HAT ie PIN2 BASS PIN2 SNARE ACCENT PIN3 SNARE _ PIN3 RIMSHOT PIN4 HAT PIN4 BASS PINS ACCENT PINS ACCENT wy Teme WAY oY s O li nc Bait BOSD to D mm CIF c Wa oao ogy c Wile c WI hoc WI j d oE ho gi cnp e ain z Fe J E a i h eee em Se pe i i N67 me re Sas fo mi Ari 1 a a eR i mk rer jege lf dul berer 80d haat Sot F a om 1 7 a a H i Hana E ENa a j tarawi DE ia a ia si KA Aig f p n x mar n i ciate J Vat Fi i l k T ai 4 a B af 1 r E A Pi 12V ALL POTS VIEWED FROM TOP ATM Notes For best effect the timing of the accent trigger has to be very tight with the voice triggers If the accent trigger occurs too soon before or too late after the voice triggers you may experience flam or clicking sounds If your midi to
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