Yusynth VCLFO PCB

YuSynth VCLFO Module Bare PCB

 
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7220-002
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YuSynth VCLFO PCB

Introduction

A bare double sided through hole plated PCB (no need for the wire jumper links shown on the PCB layout) 159x48mm for both the Yusynth VC-LFO 1 and YuSynth VC-LFO 2 modules. These PCBs are manufactured by Soundtronics with a percentage of the sale going to the creator of the YuSynth - Yves Usson. These are early days for the YuSynth Modular Synth at Soundtronics, our plan is to stock PCBs for all of the projects as well as components, kits and front panels. This is going to take time but will eventually be as comprehensive as our MFOS range.

No components are included with the PCB but check out our Synth Components section where you should find what you need. We do suggest visiting the YuSynth  VCLFO project page for detailed information including Yves panel layouts but a summary is shown below.

Introduction

The VC-LFO is an utility module whose goal is to generate slow rate periodic signal that can be used to control/modulate other modules.  The oscillating period can be varied from minutes to ms, that is from subaudio-range (0.01Hz) to low audio range (100Hz).
Yves Usson designed the VC-LFO that can be implemented into two variants. In fact these use the same PCB but some part of it is either used or not. This was lead by his choice of using single width DOTCOM panels for the VC-LFO. Unfortunately, all the features cannot be made accessible on a single width panel, that's why he made two versions of it, each of them giving access to different features.

VC-LFO1 has one FM input and four direct signal ouputs (SAWTOOTH, TRIANGLE, SINEWAVE and SQUARE) and an inverted signal output that can be switched to the following signals : OFF, SINE, TRI, SAW, RAMP and  SQUARE). A toggle switch makes it possible to change the range : up 0.1Hz to 100Hz, down 0.01Hz to 10Hz.

VC-LFO2 has one FM input, a SYNC input and four direct signal ouputs (SAWTOOTH, TRIANGLE, SINEWAVE and SQUARE). A toggle switch makes it possible to change the range : up 0.1Hz to 100Hz, down 0.01Hz to 10Hz.

VC-LF01 Description (see further down page for VC-LFO2)

This module is a very useful utilty module in a modular synthesizer. It provides low frequency signals with different waveshapes that can be used to modulate and control many other modules. Another interesting feature of such a module is that its oscillation rate can be controlled by a CV.
In this version, the frequency can be set with the RATE knob between 0.1Hz (10s repetition rate) and 100Hz (0.01s repetition rate) or between 0.01Hz (100s rate) and 10 Hz, depending on the rate switch.
The frequency can be modulated in an exponential manner using the FM socket, the FM level knob let us control the amount of modulation.

The signals that are available at their own direct output sockets : SAWTOOTH (rising ramp), TRIANGLE, SINE and SQUARE.
Furthermore, the INV OUT socket provides any of the above  but  inverted with reference to the direct outputs. The signal is selected through a 6 position rotary switch : OFF (no signal), SINE, TRIANGLE, SAWTOOTH (rising ramp), RAMP (falling ramp) and SQUARE.

The oscillating heart of the circuit is based on the "design idea" by J. Brice (1976)
. The waveshaper part is based on very basic classical buiilding blocks such as summers, inverters, full-wave rectifier and non-linear waveshaper.

The oscillation rate is indicated by a yellow LED, the brightness of which being linked to the signal at the INV OUT socket.

August 16th, 2006, Yves introduced an enhanced version, as a matter of fact when switching from one timing cap to another, the SAW BIAS setting would change. In order to have perfect waveshapes for both range. Yves modified the schematic and PCB to add a second T2 trimmer (T2b) that allows the adjustment of the waveshapes for both ranges.

Circuit

Click on the schematic thumbnail above for the circuit diagram.

IMPORTANT  : for version 1 make sure to solder a jumper wire i) as a replacement for R5, and ii) where the dashed line

Parts List Version 1

The parts list below is direct from the YuSynth website.

The parts list excludes knobs although we have standardised on the Cliff KM20B but it does include 1/4" jack sockets. All parts are available individually (use the part number in the search box above) or as a components kit that excludes sockets and knobs.

Reference Value Part No. quantity
U1 7555 (CMOS version of the 555) 7212-500 1
U2,U3 TL074 7212-544 2
U4 LM741 or TL071 7212-580 1
Q1 BC557B 7212-402 1
Q3 BC547 7212-401 2
D1,D2,D3*,D4* 1N4148 , * matched for better performance 7212-480 4
R5 must be bypassed with a strap    
R1,R2 10 7163-007 2
R13 820 7163-049 1
R18,R25,R30,R32,R33,R36 1K 7163-051 6
R29 1.5K 7163-055 1
R16 2.7K 7163-061 1
R40 4.7K 7163-067 1
R10 8.2K 7163-073 1
R41,R42 10K 7163-075 2
R8 12K 7163-077 1
R28 15K 7163-079 2
R27 22K 7163-083 1
R12 27K 7163-085 1
R22 50.1K or 49.9K 2000-140 1
R6,R7,R9,R11,R14,R15,R19,R20,R21,
R31,R34,R35,R44
100K 7163-099 13
R24,R26 150K 7163-103 2
R17,R23 200K 7163-106 2
C7 120p 7212-729 1
C8 1n 7212-740 1
C5,C9 10n 7212-746 2
C10,C11,C12 100n 7212-749 3
C6a 1u 7213-210 1
C6b 10uF 7213-212 1
C1,C2 22uF 7213-108 2
T2a,T2b 10K multi-turn 7212-857 2
T1,T3 47K or 50K multi-turn 7212-859 2
P1 10K lin 7300-230 1
P2 47K lin 7300-250 1
LD1 yellow LED 7213-903 1
SW1 DPDT switch 7212-252 1
SW2 rotary switch 6 pos. 1612-024 1
JK1..JK6 jack socket 7212-206 6

Note that R43 is mounted off board.
C6a and C6b, T2a and T2b are switched by the range switch

VC-LF02 Description

This module is a very useful utilty module in a modular synthesizer. It provides low frequency signals with different waveshapes that can be used to modulate and control many other modules. Another interesting feature of such a module is that its oscillation rate can be controlled by a CV.
Furthermore, the oscillation may be synchronized to an external signal. The synchronization is set on the rising edge of the external signal.

In this version, the frequency can be set with the RATE knob between 0.1Hz (10s repetition rate) and 100Hz (0.01s repetition rate) or between 0.01Hz (100s rate) and 10 Hz, depending on the rate switch.
The frequency can be modulated in an exponential manner using the FM socket, the FM level knob controls the amount of modulation.

The signals that are available at their own direct output sockets : SAWTOOTH (rising ramp), TRIANGLE, SINE and SQUARE. The width of the latter signal (SQUARE) can be set with the PULSE WIDTH knob within a 10% to 90% range.

The oscillating heart of the circuit is based on the "design idea" by J. Brice (1976)
. The waveshaper part is based on very basic classical buiilding blocks such as summers, inverters, full-wave rectifier and non-linear waveshaper.

The oscillation rate is indicated by a yellow LED, the brightness of which being linked to the signal at the SQUARE socket.

Circuit

Click on the schematic thumbnail above for the circuit diagram.

Wiring

The wiring schematic image in the above thumbnails show the panel wiring to the pots and sockets etc.

Setting and Trimming

See version 2 below for setting up.

Parts List Version 2

The parts list below is direct from the YuSynth website.

The parts list excludes knobs although we have standardised on the Cliff KM20B but it does include 1/4" jack sockets. All parts are available individually (use the part number in the search box above) or as a components kit that excludes sockets and knobs.

Reference Value Part No. Quantity
U1 7555 (CMOS version of the 555) 7212-500 1
U2,U3 TL074 7212-544 2
U4 LM741 or TL071 7212-580 1
Q1 BC557B 7212-402 1
Q3 BC547 7212-401 2
Q2 BS170 7212-405 1
D1,D2,D3*,D4* 1N4148 , * matched for better performance 7212-480 4
R1,R2 10 7163-007 2
R13 820 7163-049 1
R5,R18,R25,R30,R33,R36 1K 7163-051 6
R29 1.5K 7163-055 1
R16 2.7K 7163-061 1
R40 4.7K 7163-067 1
R10 8.2K 7163-073 1
R3,R41,R42 10K 7163-075 3
R8 12K 7163-077 1
R28,R37,R39 15K 7163-079 3
R27 22K 7163-083 1
R12 27K 7163-085 1
R22 50.1K or 49.9K 2000-140 1
R4,R6,R7,R9,R11,R14,R15,R19,R20,
R21,R34,R35,R44
100K 7163-099 13
R24,R26 150K 7163-103 2
R17,R23 200K 7163-106 2
C7 120p 7212-729 1
C8 1n 7212-740 1
C3,C5,C9 10n 7212-746 3
C4 47n 7212-717 1
C10,C11,C12 100n 7212-749 3
C6a 1u 7213-210 1
C6b 10uF 7213-212 1
C1,C2 22uF 7213-108 2
T2a,T2b 10K multi-turn 7212-857 2
T1,T3 47K or 50K multi-turn 7212-859 2
P1 10K lin 7300-230 2
P2 47K lin 7300-250 1
LD1 yellow LED 7213-903 1
SW1 DPDT switch 7212-252 1
JK1..JK6 jack socket 7212-206 6

Note that R43 is mounted off board.
C6a and C6b, T2a and T2b are switched by the range switch

Wiring

The wiring schematic image in the above thumbnails show the panel wiring to the pots and sockets etc.

Setting and Trimming

  1. Set the FM. MOD. pot to minimum (CCW) and set the RATE pot to maximum (CW)
  2. Set the range switch to x1 (should select C1a 1µF and T2a)
  3. Connect an oscilloscope to the SAWTOOTH output
  4. Check that you have a good linear ramp with an amplitude of 10V, if the ramp is not perfectly linear, check that C1a is not leaking (be sure to use a tantalum cap here!)
  5. Now adjust T2a such as to obtain a linear ramp ranging from -5V to +5V
  6. Connect the oscilloscope to the TRIANGLE ouput
  7. Adjust T2a in order to obtain the best symetrical triangle shape
  8. Then adjust T3 in order to obtain a triangle ranging from -5V to +5V
  9. Connect the oscilloscope to the SINEWAVE output
  10. Adjust T3 in order to obtain the best sinewave shape
  11. Connect the oscilloscope to the PULSE output
  12. Tweak the PULSE WIDH potentiometer and check that the pulse with varies from 20% to 80%
  13. Toggle the range switch to x0.1 (should select C1b 10µF and T2b)
  14. Connect the oscilloscope to the TRIANGLE output
  15. Adjust T2b in order to obtain the best symetrical triangle shape
  16. Set the range switch to x1
  17. Turn the RATE pot to minimum (CCW)
  18. Adjust T1 in order to obtain a RATE of 10s (frequency 0.1Hz)
  19. Check that the LFO is synched when sending a rising pulse to the SYNCH input

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