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SynthCube Fuzzbass TTSH Version 4 Build Manual

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TTSH Version 4 Build Guide
By Fuzzbass, for Synthcube
Version 1.2 September 2019
1

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Summary of Contents for SynthCube Fuzzbass TTSH Version 4

  • Page 1 TTSH Version 4 Build Guide By Fuzzbass, for Synthcube Version 1.2 September 2019...

  • Page 2: Table Of Contents

    Contents About This Guide ............................. 3 Transistor Coupling and Matching ......................4 Part Substitution ............................. 5 New in TTSH V4 ............................6 Known issues in TTSH V4 ......................... 6 Quirks..............................7 Main Board Power System........................7 Planning for Modifications........................8 Construction –...

  • Page 3: About This Guide

    If you purchased the Synthcube kit, you received quantity 8 50mm M3 M-F nylon standoffs. These are intended as stilts to raise the main board from your bench so through hole components can be...

  • Page 4: Transistor Coupling And Matching

    ¼ inch Heat shrink tubing (can be subbed with cable ties) • Cutters • #2 Phillips driver • Nut drivers 5/16 and 1/2 inch. (Synthcube kit includes hex nuts for the 3.5mm jacks) • 2.5M hex key • Fine tip needle nosed pliers •...

  • Page 5: Part Substitution

    All resistors are ¼ watt through hole types and for the sake of consistency are stated as metal foil 1%. Synthcube may pack a few in the kits that are 5%, or 1/8 watt, and this is fine. It is assumed that most of the resistors used in the ARP 2600 were 5% carbon composition types, with probably a small number either higher precision, or hand selected.

  • Page 6: New In Ttsh V4

    All Electrolytic capacitors are polarized, and must have 5mm or less diameter and 2mm lead spacing. For longer life, they should be rated for 105c operation, although only the capacitors on the DC-DC converter sub-board will be exposed to any significant heat. The 47u units should be rated for 25V operation, and the rest may be 25V or 50V.

  • Page 7: Quirks

    Many low value capacitor values are screened with uncommon values. A more conventional value capacitor is included in the BOM / Kit. For example, the footprint indicating “3p” accepts a 3.3p capacitor. See notes in the Synthcube published BOM for more information. Main Board Power System The power rails are distributed to all sections in a middle layer of the main board.

  • Page 8: Planning For Modifications

    You can embark on the build if there are some parts yet to be received, but doing so will increase the risk of an error or omission during the build. If you purchased the Synthcube kit, you will want to report any missing parts as soon as possible.
  • Page 9 4. If you are planning to build with hand-matched transistor pairs, match them now. Recommended matched pairs: a. 2N5087 – four pairs, 4072x4 b. 2N3904 – eight pairs, RMx2, VCAx1, 4012x5 c. 2N3906 – six pairs, RMx2, VCAx2, 4012x1, 4072x1 5.
  • Page 10 Four 1uF box film capacitors are recommend, 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.
  • Page 11 8k87 Capacitors (electrolytic) 30k1 33k2 Active Components 45k3 CA3046 2N3904 61k9 2N3906 2N4125 100k 2N5459 121k 475k Table 1 - 4027-1 VCO Cores BOM 9. Build the PSU sub-board, starting with the SMD LDO Regulator chips. The heavy tab at the top of them needs to be soldered to the large pad footprint.
  • Page 12 Figure 3 - Jumpers on PSU Board Resistors Inductors 240r 100uh Active Components 580-SPM15-150-Q12P-C Trimmers LM2991 500r TL1963A Capacitors (ceramic/film) Locking Headers .156 x 2 220n .156 x 5 Capacitors (electrolytic) Table 2 – PSU BOM 10. Build the 4012 VCF Core. There are five matched transistor pairs (4x 2N3904 and 1x 2N3906). Additionally, there is one thermally coupled NPN-PNP pair.
  • Page 13 820r Capacitors 1k87* 10n (film) 100n 3k32 Active Components 1N4148 23k2 BC558 30k1 LM301 2N3904 100k 2N3906 196k 2N3958 220k Table 3 - 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.

  • Page 14: Construction - Main Board Phase 1

    12. If you plan to install a Gate Booster, build the PCB now. The Fuzzbass Gate Booster is silkscreened with reference designators for parts (ex: R1). The parts list below assumes you are performing the standard install, and does not include optional parts for LED gate indication. Ferrites may be replaced with wire jumpers.
  • Page 15 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.
  • Page 16 VCO1 VCO2 VCO3 Noise S&H Total 84k5 100k 120k 121k 150k 180k 182k 196k 220k 270k 470k 680k 1N4148 8 Table 6 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.
  • Page 17 If you purchased the Synthcube full kit, the 10uF electrolytic capacitors included have a lower profile than other polarized caps. They can be worked in with this batch.
  • Page 18 Set aside the MJE172 and MJE182 transistors for now – as they stand much higher from the board. Note that in the first batch of V4 (Synthcube) boards, the footprint of the 2N3954 in the VCO2 section has pins 5 and 6 reversed. If you are building this main board, be sure to form those pins on the 2N3954 to fix that bug.
  • Page 19 • 2N3904 Matched pairs: RMx2, VCAx1. • 2N3906 Matched pairs: RMx2, VCAx2 • There are complementary pairs (2N3904+2N3906):VCAx1, (2N5172+2N3906): VCO2, that must be thermally coupled before soldering. 14. Repeat the same process to install all remaining electrolytic/polarized capacitors on the main board.

  • Page 20: Construction - Main Board Phase 2

    Construction – Main Board Phase 2 1. Start by installing the stilts, both sides. 2. 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.
  • Page 21 flush to the main board, it’s tang is upright, and it won’t wiggle or move when touched. Adjust the bending of the pins until all sliders are in place and immobilized. Turn the board over and solder the sliders. 8. Install 12mm standoffs to support the VCF Core (2), Gate Booster (2) and DC-DC converter (3). Fasten on front side of the board using hex nuts.
  • Page 22 Figure 7 - To seat the VCF Output jack, you will need to remove some material from the corner of the jack to relieve conflict with the mounting hardware for the VCF Core sub-board. 13. Once you have the VCF Output jack fit, place all remaining 3.5mm jacks, the momentary push switch in the EG section, and all six slide switches.

  • Page 23: Construction - Main Board Finishing Up

    19. Make sure the power LED is dropped down into position on the panel. Bend the leads out, cut and solder. If your kit includes a flat top LED, drop it just down to flush with the panel front, for improved appearance.
  • Page 24 the return plug on the reverb unit. The return line carries 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.

  • Page 25: Check Out And Calibration

    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. You may follow the VCO calibration presented in the ARP manual, or use the alternate calibration method presented below.

  • Page 26: Fuzzbass Ttsh Vco Pitch Calibration Routine

    Fuzzbass TTSH VCO Pitch Calibration Routine Regardless of what pitch and tracking calibration routine you use, you are not aiming for perfect tracking. You want acceptable tracking. If everything tracked absolutely perfectly, this would not be an analog synth. The point of this alternate calibration routine is to allow the player to set the VCO controls visually, play a concert C, and have a pitch reasonably close to concert C come out of the VCO or VCF.
  • Page 27 Frequency calibration adjusts the set point of the manual frequency control for the VCOs and VCF. The VCOs have a very wide frequency range from 0Hz all the way up to 90kHz(!). 1V/Octave calibration adjusts how each VCO and the VCF respond to pitch modulation CV via the KBD CV bus. Note: If you don’t like the frequency set point used here, you can create your own set point.
  • Page 28 You will need an accurate method of measuring the input CV, and the output audio frequency: • A digital multi meter (DMM) accurate to at least 10mVDC • A frequency counter. Many DMMs have this function. All modern oscilloscopes can count and report frequency.
  • Page 29 The 32.7Hz base set point for the VCF will place the sweet spot of the filter (with no other modulation applied) somewhere to the right of center on the coarse frequency control. This will bias the filter such that more headroom will be afforded to frequency modulation via the KBD CV bus, or the two modulation inputs.

  • Page 30: Putting It All Together

    1. Baseline the VCO tunings (Coarse Frequency=minimum, Fine Frequency=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.

  • Page 31: Modification: Add Power Taps For Future Mods

    Parts to perform this change are included in the Synthcube kit and BOM; 4x 1uf film capacitors. The locations for these are marked in silkscreening on the board, and traces must be cut underneath the...

  • Page 32: Modification: Gate Booster Installation

    capacitors footprints before the capacitors are installed. The location for these trace cuts are also silkscreened. Modification: Gate Booster Installation The purpose of the Gate Booster is twofold; 1. Drive the gate inputs on both the AR and ADSR; 2. Generate the trigger impulse required by the ADSR.

  • Page 33: Modification: External Control - Electronic Switch

    Figure 10 - Standard Gate Booster Installation. On the power jumper here, red=V+ and black = V- Signal Connections: • Gate In > Gate Jack (tip) • Gate Out > Gate Switch (Pin 1) • Trigger Out > Trigger Jack (tip) Modification: External Control –...

  • Page 34: Modification: Adding A Midi-Implant

    External Clock In jack, the Electronic Switch will be controlled by it. To do this, find the two resistors, desolder and lift the lower ends of each, and tie these in common to the tip of the External Clock In jack. Figure 11 - Electronic Switch Mod If you then patch up the Electronic Switch thus: •...

  • Page 35: Modification: Improving Calibration Accuracy

    Bourns makes four-turn trimmers that fit the existing trimmer footprints. They are costly, about $6US at the time of this writing. These are not included in the Synthcube kit or BOM. You may install these in the VCO trimmer locations for Frequency and 1V/Octave calibration, to improve precision. Keep in mind that these merely introduce a gear between the adjustment screw and the resistive element.

  • Page 36: Modification: Reverb Improvements

    The TTSH reverb driver and return amplifier are compatible with any Accutronics (or clone) model whose second and third digit in the model number are “AB”. The Synthcube kit and BOM specify a 1AB2A1B. This is a two spring, medium decay unit in a short pan. The fifth digit “A” specifies a grounding configuration where both input and output have a common ground with the pan.
  • Page 37 another system whose 0V plane is referenced to earth. Another approach, recommend here, is to add a grounding lug connection to the case. It is left to the builder to determine the best way to bond the TTSH to Earth in the studio, so no particular solution is advocated here.
  • Page 38 Figure 12 - Cut and Strip the RG174 as shown 4. Twist the copper conductor, and flare out the shield wiring. Figure 13 – Preparing the cable. 5. Insert the copper conductor and it’s insulated portion into the plug, such that the flared out shield meets the outer part of the plug, and the copper conductor comes out the hole in the tip of the plug.
  • Page 39 Figure 14 - 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.
  • Page 40 Figure 16 - Soldering the Shield Figure 17 - A Finished Plug 9. Repeat three more times. Then, test the cable assemblies for shorts and continuity. 10. If there is excessive solder on the exterior of the tip, clamp the plug and scrape it off with a knife.
  • Page 41 Figure 18 - Mark to ID the Short Return Cable...

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