Saturday, 14 November 2015

Master Pulse Divider - CGS 22 - Build notes

These are the build notes for Ken Stone's master clock divider. Cat Girl synth 22
The incoming clock signal is divided into successive clock signals to drive EGs, sequencers, etc ... lots of nice poly rhythms.


Its more than just a simple clock divider though.
There are four outputs each for divisions of 2, 4, 8 and 16.
Altogether there are 16 outputs.
ie : each division had 4 variations that are phase shifted from each other.
The first is a straight division. As far as I can work out, each successive is shifted by 1/2 the frequency of the last. (please let me know if this is BS).
 
HEADERS, Beads, the odd cap & diode .



 Resistors first.



I've followed the suggested values for the resistors:
RA = 1k8
RB = 1k
RL = 2k2 (for the LEDs).



Most of the decoupling capacitors are mounted directly to the solder side of the board. Pads are provided on pin 7 and 14 of each of the 4070 for 100n the decoupling capacitors. 

 I've added heatshrink to the cap legs to avoid shorts.

 Most of the decoupling caps are surface mounted 805s.
Trannies next. These are common BC 547s


There are 4 types of IC used : the TL072,CD4024B, CD 4070B.


 It's a dual op-amp.


The CD 4024 - its a general purpose binary up counter with clock input, reset, and 7 outputs (only 4 of which are used in this circuit - Q1,Q2,Q3,Q4). The binary outputs count up on the negative edge of the clock. It counts out a binary sequence and makes the bits available on the output pins (pins 5,9,11,12).  So we clock this counter (pin 1) and this produces a binary count N bits wide. Hitting the reset (pin2) with a logic signal of 1 resets the counter to 0.

This chip is very useful if you wanna generate square waves from a oscillator.

The 4070 is the logic network which accepts the counter output bits as input.
It's a quad 2-input Exclusive-OR gate. There are 4 of these in this module.


Initial tests indicate that the pulse outputs for the CGS22 are +5v. OK for Eurorack, though my aim is to use this in Buchla land. So looks like I'll have to boost this to 10V to drive the sequencer on my 208.
The Dual Lopass Gates on the 208 do however trigger with the 5V pulses....interesting.


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Update ; The Buchla 208 sequencer can be triggered with 5V pulses from the CGS 22 if you go via the Easel program card. The program card seems to accept much lower trigger voltages.
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The panel is a bit rough around the edges.
The LEDS are mounted straight onto the PCB. I hate wiring things up. Couldn't avoid having to wire the bananas though. Lots and lots of flashing lights. :-)
Gotta love that.

I've wired the bananas according to divisions. The top (left most) four are division2.
The next four are division 4, and so on.... the last being div 16.
It would have been nice to mount the LEDs next to the corresponding banana, but one can't have everything.esp if you decide to mount the LEDs directly onto the PCB.

From top (left in the pic) the LEDs are labelled:
1B - Division 2 Phase 3 (clock XOR Q1)
1D - Division 2 Phase 1 (clock XOR Q1)
1C - Division 16 Phase 4 (Q4)
1A - Division 16 Phase 2 (Q4)
------------
2B - Division 4 Phase 3 (Q1 or Q2)
2D - Division 4 Phase 1 (Q1 or Q2)
2C - Division 2 Phase 4 (Q1)
2A - Division 2 Phase 2 (Q1)
----------------
3B - Division 8 Phase 3 (Q2 XOR Q3)
3D - Division 8 Phase 1 (Q2 XOR Q3)
3C - Division 4 Phase 4 (Q2)
3A - Division 4 Phase 2 (Q2)
-----------------------
4B - Division 16 Phase 3 (Q3 XOR Q4)
4D - Division 16 Phase 1 (Q3 XOR Q4)
4C - Division 8 Phase 4 (Q3)
4A - Division 8 Phase 2 (Q3)

You can see a pattern developing.

 Links:
+ CGS 22 build notes
+ Schematic
 + CGS version 1 
 + MOTM - Richard Brewster 
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For more CGS builds, info, etc click here.

Thursday, 12 November 2015

I only give negative feedback

https://www.youtube.com/watch?v=7FYHt5XviKc
 Learn about opamp circuits

Voltage Processor - CGS 81 - Build notes

These are my build notes for Ken's  Cat Girl Synth 81 - voltage processor.
A very useful module with a super small footprint. It's a classic example of
a two-stage amplifier worthy of breadboarding if you like to examine how op-amps work.

It's very similar to Ken's DC mixer (CGS 04)

First the virgin PCBs.

 You can snap the PCB into 2 if you only need 1 voltage processor.

Resistors, IC headers, first.
I have the diodes (Bat 48 Schottky) on back order. "The BAT48 diodes provide a dead zone in the center of the offset pot's rotation, to allow for easier zeroing". 

I'm building this as a processor so there really is no need for trimmers (or diodes).
I've used a 100k for RS and linked the two pads of the SPAN trimmer with some resistor wire offcuts. 
However, I may at a later date add a trimmer or a larger pot (rather than a wire across the SPAN) to one of the processors so I can adjust the level of the inverting output. 


These are two SMD 100nF caps ... optional.
They are placed across the power rails.

The circuit uses just one (dual) Op-Amp - the workhorse TL 072

Check out Ken's schematic in his build notes

Both non-inverting inputs (Pin 5 & pin 3) are connected to ground.
Thus the inverting inputs (pin6 & 2) must also be ground (virtual ground)

The input signal is fed to both inverting inputs (6 & 2). The output from the first opamp (pin 7) is just
the inverted output. This is fed into the inverting input of the second op-amp (pin 2). So they cancel each other out.
"By adjusting the SPAN pot to either side, either the inverting or the non-inverting is increased with respect to the other, the difference being buffered by the second stage and fed to the output."

Such a lovely circuit ... the basic building components are just one TL072, two 47pf caps, one trimmer, two 330R  & three 100k resistors.

To Be Continued.

Links:
1. CGS 81 build notes
2. Serge voltage processor - M module
3. Musings on (Buchla) voltage processors - Buchla Tech
4. Q125 signal processor - Synthesizers.com
5. Moog CP-251 Moogerfooger
6. CGS 70 - Dev-mod Mixer/Inverter block
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Click here for the CGS index

Tuesday, 10 November 2015

Buchla Easel - Krell patch - figure 21

A Krell patch based around the program card.


The temple of Medinet Habu - Luxor Egypt

The Mortuary Temple of Ramesses III at Medinet Habu.
This is very close to the "Valley of the Kings".
This dates from the New Kingdom.

 First Pylon of the Mortuary Temple of Ramesses III
 It's a huge place. Very famous for its decorated wall reliefs -- about 7,000 m2 (75,347 sq ft) of them..

The reliefs depict the defeat of the Sea Peoples during the reign of Ramesses III.


The battle between the Egyptians and the Sea People occurred around  1175BC.
Ramesses III seems to have repulsed an invasion of the Nile delta.
Other sources suggest a date of 1177BC
This period is very important, as it was a time of great upheaval and marked a turning point in civilization
and the end of the Bronze Age.
 1177 BC: The Year Civilization Collapsed (Eric Cline, PhD)

The end of the Bronze age marked the start of a new dark age which lasted till the Renaissance of Greece.






 Ramses harvesting corn

 Lion headed goddess - Sekhmet ??
Sekhmet is the warrior goddess as well as goddess of healing  .... a strange combination !
She is often depicted as a lioness, the fiercest hunter who's breath formed the desert. 



Amun & Maat
Amun - the Father of life who later combined with Ra to become Amun-Ra the all important State God.
Maat is here representing truth, justice, balance and morality. She is the daughter of the Egyptian sun deity Ra and wife of the moon god Thoth.




Horus
God of the sky & Kingship - often depicted as a falcon Horus as the son of Isis and Osiris.

CGS 58 Dual Utility LFO - build notes

I'm finally getting around to building one of Ken's modules.
It's his classic LFO (Cat Girl Synth 58).

First some unpopulated PCB pics.

 And the reverse side.

Headers first.

Resistors, diodes, caps, beads. There are no hard to find parts.
The circuit uses a Schmitt trigger  --> integrator  ----> comparator.
Check out Ken's schematic.
The 1st section, the  Schmitt trigger has a positive feedback applied to the non-inverting input.
In the  integrator , the feedback resistance is replaced with a capacitor and finally the comparator
kicks in  where we have no feedback loop. The comparator generates the square wave.


I've been getting a bit spoilt lately in building modules with surface mounted pots.
So decided to try adapting this.

You need to be careful with polarity of the LEDs too.

It seems to work well.
Now it's time to make the faceplate.


Some useful links:
1. Adding a range switch - Muffs 
2. Bridechamber
3. Adding CV control - electro-music
4.  Serge Audio & CV levels - muffs
5. Ken's own site - CGS
6. Video - youtube


Sunday, 8 November 2015

Prototype Easel program cards

I've been playing around with a few different configurations for the easel patch card.
Its is wonderful way to extend the capabilities of an already incredible instrument.

This is my first version using IC sockets to build the breadboard.

The circuit on the red breadboard is a very simple comparator.


The red breadboard can be removed. It plugs into the IC sockets if more development
space is needed.
This is my second version of the Easel dev board using headers rather than IC scokets.
I found it much cleaner and easier to work on.

A larger breadboard can be added if needed. And the patch cables have resistors embeded into them like the EMS synthi' patch pins.