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27 

 

Positive Probe  Negative Probe  Resistance 
V+ 

“0”

 

 

+15.00 

“0”

 

 

“0”

 

V- 

 

“0”

 

-15.00 

 

V+ 

V- 

 

+15.00 

-15.00 

 

Table 15 - Checking for Shorts 

b.

 

Repeat the resistance checks on the DC-DC converter board outputs.   

c.

 

Set the DMM in voltage mode, connect the negative probe to the center 

“0”

 output pin, 

and the positive probe to the pin (not the test point) 15.00.  Connect the AC 
power supply to power up the DC-DC converter.  You should measure ~+15.75V.  Move 
the probe to the -15.00V pin (not the test point).  You should measure ~-15.75V.   

d.

 

Move the positive probe to the V+ pin.  Adjust the top trimmer to a15.00V.  Move 
the positive probe to the V- pin.  Adjust the bottom trimmer to achieve -15.00V.   

e.

 

Disconnect the external AC adaptor.   

f.

 

Install  the  five-way  jumper  from  the  DC-DC  converter  output  to  the  main  board 
connection.   

g.

 

Reconnect the external AC adaptor.   

h.

 

Repeat step D.  Once the full load is on the PSU, it is usually necessary to adjust the V+ 
and V- voltage trims again.  A good 0V reference point for these measurements is the 

“gnd” pin on the CV header.  Connect a grabber probe there, and use a pointed probe to 

measure the voltages present on the various IDC connectors in the power jumper.   

i.

 

Swap VCF cores to the 4072 and make sure it does not introduce a power issue.  Then 
swap the 4012 back in.   

j.

 

Peek underneath and make sure all slider LEDs and the power LED are lit.  Then disconnect 
power.   

6.

 

Take a Sharpie and sign the main board 

builder’s label.

  You have reached the point of no return! 

7.

 

Proceed to Check Out and Calibration.  It is important to run through all checks and calibration 
before installing the panel.  There is possibility you will encounter problems that need to be fixed 
with the panel off.  There are 81 nuts and 13 screws involved in removing the panel.  Be patient.  

Don’t tie down the 4027

-1 VCO core modules until you have completed calibration of all three 

VCOs.   

CHECK OUT AND CALIBRATION. 

Follow the checks and calibration steps as documented on the ARP 2600 service manual.  You will need 
an oscilloscope and a frequency counter.   

The VCO/VCF pitch and tracking calibration sets the operating range for pitch across a CV scale.  
The builder may position the VCO/VCF base frequency anywhere they prefer on the voltage scale.  
The calibration presented in the ARP 2600 service manual is optimized for use with the ARP 3600 
series keyboard

, and it’s available CV range

.  This may not be optimal for other controllers.  Review 

the Fuzzbass alternative calibration routine for VCOs/VCF presented below, to see if there is a 
calibration more applicable to the controllers you will use, and the way you will be performing.    
This section also deals with internal CV sources such as MIDImplant.   

Summary of Contents for FuzzBass TTSH

Page 1: ...1 TTSH Version 4 Build Guide Covering Synthcube s TTSH V4 release Version 1 10 April 2020 By ...

Page 2: ...n Main Board Finishing Up 25 Check out and Calibration 27 Common Build Issues and Tips 29 Fuzzbass TTSH VCO VCF Pitch Calibration Routine 30 Putting It All Together 35 Modification Add Power Taps for Future Mods 37 Modification AC Coupling on the VCF Audio Mixer Inputs 37 Modification Gate Booster Installation 37 Modification External Control Electronic Switch 39 Modification Adding a MIDImplant 4...

Page 3: ...lled the tailings for these parts are cut to length prior to soldering The benefits of this approach are two fold First cutting after soldering can shock or damage solder joints Second waste material removed and disposed of will not be contaminated with solder This is of particular value if you use solder containing lead Cutting and then soldering necessitates immobilizing components or moving the...

Page 4: ...tors face to face indicate locations for thermally coupled transistor pairs When such transistors are of the same type matching them is highly recommended To thermally couple two transistors place them and add a small amount of thermal paste between them Place a small 3 16 length of inch heat shrink tubing over them and apply heat Do this before soldering Alternatively you can couple them using sm...

Page 5: ...or is producing units on the old Fairchild fabs and can be considered the reference example The spec sheets for these list gain hFE of minimum 100 and maximum 300 There is a wide variance in there and you will find examples all over the map Every batch they make is different The point being is that you can t ask your supplier to send you transistors more accurately spec ed than this You have to or...

Page 6: ...5 carbon composition types with probably a small number either higher precision or hand selected Generally you can get away with using carbon comp resistors but there are no guarantees and most carbon comp type resistors have a way of soaking up moisture and degrading slowly over time The only resistors dissipating an appreciable amount of wattage are the four 10R units in the Amp section and the ...

Page 7: ...uivalent Part 20p Capacitor MLCC C0G 22p 30p Capacitor MLCC C0G 33p 50p Capacitor MLCC C0G 47p 2n Capacitor MLCC C0G 2n2 20n Capacitor Film 7 5mm LS 22n u1 Capacitor Film 5mm LS 100n Table 1 Marked Capacitors and Their Equivalents In the Voltage Processor Lag Processor section the LM301 op amp location is marked for an alternate TL071 op amp This change is standard and is typically performed on AR...

Page 8: ...00 and 15 00 will typically read on the DMM 15 8v and 15 8v MAIN BOARD POWER SYSTEM The power rails are distributed to all sections in a middle layer of the main board This is hidden from view and cannot be modified This means you cannot drill holes in the main board without risk of permanent damage to the system It also means you cannot selectively power individual sections There are two power di...

Page 9: ...se Improvements for Reverb Adjustment Range LEDs See these sections for installation steps and BOM info CONSTRUCTION GETTING STARTED 1 Whether you purchased a full kit or assembled the BOM components yourself refer to the Master BOM document and verify you have all the required parts on hand There is generally no need to test the components Nonetheless it is a good idea to count them and verify at...

Page 10: ... 1 boards and the VCF PSU boards which are scored Carefully bend and break apart the boards Use sandpaper or a Dremel tool to smooth the edges There are six little riser boards intended for the slide switches on the main PCB next to one of the speaker cutouts You can cut these away with nippers or the Dremel Discard them they won t be used in this build process Lightly clean each PCB with isopropy...

Page 11: ...the required capacitors Four 1uF box film capacitors are recommended and these are included in the Synthcube BOM and full parts kit Figure 2 Locations for trace cuts to implement AC Coupling for VCF Audio Mixer 7 Select a piece of cardboard larger than the main PCB that is flat and without bends or creases Mark the outline of the main PCB on this board and cut it out This will be the backer board ...

Page 12: ... 1k87 tempco are to be thermally coupled using paste Author s preference is to bring the NPN and PNP into contact with some paste between them and then shroud them in heat shrink Later bring the tempco over and with a dab of paste lean it into the side of the pair It s probably better that the two transistors are in direct contact rather than having the tempco in between them Do not install the pi...

Page 13: ... pad and the pad accepts solder If the pad does not heat up sufficiently it won t accept solder When the work cools make sure the chipis bonded to the big pad by pulling upon it Under magnification inspect the smaller pins to make sure they are all soldered and there aren t gobs of solder bridging the pins Then install the remaining PSU parts Install two wire jumpers as shown Trimmed rectifier dio...

Page 14: ... 1 DIP8 socket 1 470r 6 820r 1 Capacitors 1k 1 10p 1 1k8 1 47p 3 1k87 1 10n 4 2k2 1 100n 2 3k32 4 10k 1 Active Components 15k 3 1N4148 4 23k2 1 BC558 1 30k1 4 LM301 1 56k 1 2N3904 14 100k 3 2N3906 4 196k 1 2N3958 1 220k 1 Table 4 4012 VCF Core BOM 11 Build the 4072 VCF Core There are five matched transistor pairs 4x 2N5087 and 1x 2N3906 Additionally there is one thermally coupled NPN PNP pair Ther...

Page 15: ...s may be replaced with wire jumpers 10u electrolytic capacitors may be replaced with 1U 50V types The DIP socket is optional The point of headers and wire housings is to allow disconnect for servicing If you are using a header and wire housing on the main board for the power connection you can directly solder these wires to the power header location on the Booster you only need one disconnect Fuzz...

Page 16: ...e board facing up 2 Lay out parts from the table Main Phase 1 all resistors and 1N4148 diodes Omitted from this list are parts from the LED sections front side of the board sub boards and vertically oriented resistors Stuff all parts as shown in the table When done you should have almost all of the resistors and all diodes in place on the back of the main board Take a minute to double check the or...

Page 17: ...2 13 10 2 6 4 47 Table 7 Main Phase 1 resistors and diodes 3 Place your cardboard backer board over the work and using tape secure the edges While supporting the cardboard in the middle with one hand carefully flip the work over and place it down flat on your work surface pressing down across it to eliminate any gaps between resistor bodies and the main board 4 Working from one side and moving acr...

Page 18: ...337 8 Table 8 LED Sections 8 Flip the board face down cut and solder the LED section parts 9 Remove the four stilts on the front side replace with M3 screws 10 If you elect to omit the DIP8 sockets install the op amps now Otherwise proceed to the next section Install the backer board tape and flip the work Solder all pins at 600f 315c In the following step you will be installing capacitors only 11...

Page 19: ...s on the 2N3954 to fix that bug This dual JFET is used to shape the triangle wave into a sine wave Figure 4 Reversed Pins 2N3954 in VCO2 Note the image shows a different transistor but the reversed pins are as indicated I start with the PNP NPN complementary pairs VCA and VCO2 adding thermal coupling as I install them Then I install the two CAN 6 JFETs VCO2 and S H Next the NPN NPN and PNP PNP mat...

Page 20: ...the backer board and it can be discarded This assumes you have previously installed the 10u capacitors since they stand 7mm tall whereas all of the below are 11mm tall If you have tall 10u capacitors see table 8 add them to this lot Val RM VCO1 VCO2 VCO3 VCF EG VCA MIX Noise VP S H Amp Total 100n 1 1 1u 3 2 2 2 2 5 2 2 5 2 4 31 1u5 1 1 Table 11 Main Phase 1 Electrolytic Capacitors 15 Install reser...

Page 21: ... using M3 nuts Tighten these well since the nuts will not be accessible once the panel is in place 3 Install the Amphenol headers 1x5 156 qty 1 1x2 1 qty 5 and 1x3 1 qty 1 The large five pin header for the power input should be installed reversed from the orientation indicated in the silkscreening This will avoid problems fitting the synth into its case The 1x3 1 header goes onto the 2x3 header pa...

Page 22: ...r in the Preamp section 8 Install the sliders Working in small groups or quadrants of the board place the sliders and then turn the board up 90 degrees to access the back side While holding each slider down to the board and using fine tipped plyers bend one pin at each end of the slider outward This works best if the pins are diagonally opposed Lower the board down and check that each slider is fl...

Page 23: ...ound connection and these are listed below In almost all locations a short will result in either the normalized input the inserted input or the output being shunted to ground This is a problem but it won t result in damage Because some of the locations are inputs with signals from elsewhere on the instrument normalized to them shorts may appear to the operator as faults in the outputs of sections ...

Page 24: ... Right Input this one is BAD Final Mixer Right Output Recommended fix Place these 19 jacks first and bend or remove the part of the jack housing that may come in contact with the signal trace This varies by location Final Mixer Right Input has multiple conflict zones 12 You will need to file or Dremel off some material from the corner of one of the 3 5mm jacks the VCF output jack This is to avoid ...

Page 25: ...e pin While the iron is still on the work reach under and push up on the switch to bring the solder pin back up to flush with the PCB surface not protruding Remove the iron and allow the solder on the one pin to harden Test the switch to make sure it can be moved with your finger Once you are satisfied with the switch placement and elevation solder the remaining pins being sure to fill in the thro...

Page 26: ...a very weak signal and thus is the primary source of noise in the reverb section Minimizing the length and optimized placement can dramatically improve the noise rejection Information on terminating the coax to the plugs is included in back of this manual 3 Install sub boards 4027 1 VCF core start with the 4012 and DC DC converter Only fasten down the DC DC converter If you are installing a gate b...

Page 27: ...wer issue Then swap the 4012 back in j Peek underneath and make sure all slider LEDs and the power LED are lit Then disconnect power 6 Take a Sharpie and sign the main board builder s label You have reached the point of no return 7 Proceed to Check Out and Calibration It is important to run through all checks and calibration before installing the panel There is possibility you will encounter probl...

Page 28: ...ce to the GND pin of the TRIG header in the EG section For VCO2 shapes first set offset and symmetry while observing the triangle output Then set purity and gain while observing the sine output You will not get a pure sine wave but you should be something close and it should be 10V P P with no offset Don t forget to check out the 4072 VCF core and ensure it calibrates Start with it s on board Pihe...

Page 29: ...te All CV inputs disconnected and their sliders down Switch set to KBD Coarse Frequency slider down Fine Frequency slider middle 0V or nothing on KBD CV If you run into a problem calibrating one of your VCOs swap the cores around to see if the problem follows Such problems can come from the core itself or from the CV summing mixer in the VCOs which are on the main board The cores generate a sawtoo...

Page 30: ... connect the reverb unit while power is off One little mistake here will destroy the LM301 in the return amp If your EG outputs don t rise to the full 10V and you did not install a Gate Booster that is probably why The LEDs in the sliders are grouped into six serial groups Like old Christmas tree lights if one LED is not functioning all the LEDs in that group will be out There are brightness setti...

Page 31: ...many of the normalized modulation sources in the TTSH only go into positive voltage For example using the ADSR to modulate the VCF the frequency will only be pushed higher If you don t have adequate headroom in the VCF base frequency you won t have much range for this modulation That being said you can always use the voltage processers to invert a positive going modulation source If you want bass ...

Page 32: ...ransmitting MIDI system exclusive sysex messages MIDIox is a free utility for doing this with a Windows computer Roman Sowa the maker of the MIDImplant suggests you not calibrate the 1V Oct Scale and CV offset of the implant but rather just adjust the base frequency and tracking of your synth to work with whatever the implant is putting out This perfectly valid and easier to do if you plan to use ...

Page 33: ...ale at initialization you must assign the scale to the CV as described in section 6 3 and demonstrated below You must use this command if you want your calibration to stick Make adjustments to the MIDImplant 1V Oct Scale and CV Offset while you have it under load in a powered up TTSH Proper load means all three VCOs are set in audio mode and nothing is plugged into the KBD CV inputs of any VCO or ...

Page 34: ...t power up as described in section 6 3 F0 00 20 7A 01 01 03 00 F7 CV1 Scale assign Select tuned scale Record all your settings and corresponding sysex commands in case you need to apply them again later VCO Pitch and Tracking Calibration This procedure is written to use the base frequency selection C1 MIDI Note 24 0 000v 32 7hz If you have chosen a different base frequency as discussed above adjus...

Page 35: ...y center 2 On the VCF reduce resonance to 0 and bring the Coarse Frequency control all the way up 3 Bring VCO1 up to full in the mixer of the VCF 4 Raise the input of VCO2 on the VCF to 80 5 Play C1 6 Adjust the VCO2 Fine Frequency control to tune with VCO1 eliminate any beating 7 Reduce the input of VCO2 on the VCF to 0 and increase the level of VCO3 to 80 8 Adjust the VCO3 Fine Frequency control...

Page 36: ...small square of lightweight cotton fabric like a handkerchief or bandana and place it between the nut and the driver This will prevent the driver from marring or scratching the panel DO NOT OVERTIGHTEN 8 Remove all stilts from the front and replace with M3 screws 9 Place a pillow towel foam pad or blanket on the work surface to protect the sliders 10 Flip the work over and place GENTLY face down s...

Page 37: ...s located around the synth These can be used down the road to power other modifications such a VCO sync MIDI Devices of the Shapers option MODIFICATION AC COUPLING ON THE VCF AUDIO MIXER INPUTS This modification is commonly applied by most builders and has been applied to large numbers of ARP 2600 units in the field Four of the audio inputs for the VCF audio mixer have film capacitors placed in li...

Page 38: ... event for each new overlapping note This mimics the behavior of an ARP 3600 series keyboard You do not need to connect a trigger CV from the converter just gate The Booster takes care of the rest Note 2 ARP user manuals refer to the Gate and Trigger jacks as outputs This installation converts the function of the Gate jack to an input The Trigger jack still functions as an output for the Booster s...

Page 39: ...ITCH If you install only one mod it should be this one It is utterly simple reversible requires no parts and provides sub oscillator capability This re routes the control input of the electronic switch from the output of the clock to the tip of the External Clock In jack When nothing is connected to that jack the Electronic switch control input is still routed to the clock When an alternate signal...

Page 40: ...ll be available at Jack C on the Electronic Switch If you process this with just a wee little bit of Lag it will be converted into a near triangle wave which can be mixed in post VCF in the VCA s second audio input for Moog Taurus I type sounds MODIFICATION ADDING A MIDIMPLANT Note You should first review the MIDImplant documentation critical info such as programming and pin outs is not duplicated...

Page 41: ...ut it does not work correctly A fix for this is suggested below 2 It is not easy to reliably mount the tiny MIDImplant board directly There are no screw holes and the manufacturer suggests hot melt glue which I find undesirable An alternate mounting is suggested below Improved Routing for KBD CV Bus The KBD CV bus is common to both the tip of the KBD CV Output jack and the CV pin on the header nex...

Page 42: ...nd the CV pin of the header are all isolated and re routed by way of jumpers Two trace cuts are made on the PCB Both solder pins of the jack are removed and replaced with insulated wire jumpers soldered directly inside the jack housing The tip contact jumper passes through the hole in the PCB and is connected to the tip switched pin of the KBD CV jack in VCO1 and thus the KBD CV Bus The tip switch...

Page 43: ...act of the Gate jack Behavior When the Gate Select switch is in the up position the MIDImplant will be the default gate source and may be defeated by introducing an alternate gate signal to the gate jack Either signal will be processed by the Gate Booster Do not connect anything to the Trig header Suggested MIDImplant Mounting My preferred method to support the MIDImplant is to build a small recei...

Page 44: ... A suggested arrangement is to make MIDI CVs and gate trigger signals available on the front panel via the re purposed multiples jacks To do this mount the receiver board on one of the left speaker near the mult jacks mounting points by adding a M F standoff at the site Tap power from the Noise or RingMod section 2x6 header Route the outputs 1 MIDI CV1 to EXT CV header assuming you made the previo...

Page 45: ...per from EXT CV header to tip pin of 1st mult jack 2 MIDImplant CV2 out directly to tip pin of 2nd mult jack 3 Gatebooster Gate out extend from Gate Select Switch pin 1 to tip pin of 3rd mult jack 4 Gatebooster Trigger out extend from Tip pin Trigger jack to tip pin 4th mult jack Figure 15 Suggested Implementation of MIDImplant with Multiples jacks re purposed for outputs ...

Page 46: ...ulated 5V source are needed to complete this quasi thorough function See the MIDImplant documentation or just skip implementing the through port 4 The Learn function using a momentary switch provides some rudimentary programming capability if you don t mind flying blind Sysex is really the way to go with programming however MODIFICATION IMPROVING CALIBRATION ACCURACY Bourns makes four turn trimmer...

Page 47: ... Connect the 0V plane of the synthesizer to a true Earth ground 2 Improve the rejection of noise in the return cable Earth Ground Although not discussed in this guide some builders substitute a linear bipolar power supply for the external brick and DC DC converters In this arrangement there is a strong earth ground brought to the 0V reference in the TTSH This approach yields inherently quieter rev...

Page 48: ...ire specifically engineered for better screening and improved isolation between the shield and the signal wire 2 The connector cables in particular the return wire can be cut to minimum length necessary thus reducing the exposure to noise sources This is how reverb was wired up in old Fender guitar amps The following steps assume the use of the standard steel case 1 Install the reverb unit such th...

Page 49: ...p of the plug Clamp it and support the cable going in so it does not sag Figure 18 Ready for Soldering the Tip 6 Heat your iron to 625f melt a bead of solder onto the iron s tip Bring the iron to the tip of the plug just beneath the opening and the copper wire At same time bring solder to the opening As the work heats up and the solder melts it will be wicked into the inside of the plug Apply a he...

Page 50: ...the Signal Wire 7 Snip off the signal wire protruding from the tip of the plug 8 Push down the shield wire onto the outer part of the plug clamp the work and solder the shield to the outer plug Figure 20 Soldering the Shield ...

Page 51: ... and continuity 10 If there is excessive solder on the exterior of the tip clamp the plug and scrape it off with a knife Don t heat the work again 11 It s a good idea to mark the shorter return wire in some way with red Use either heat shrink tubing or paint Mark both ends I use enamel model paint ...

Page 52: ...52 Figure 22 Mark to ID the Short Return Cable ...

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