Tuesday, 24 November 2015

NLC - 2 x LFOs - Build notes

These are my build notes for the NonLinearCircuits Dual LFO & difference rectifier (Eurorack version).
It's a easy build as all parts are through the hole.

Andrews build notes are here:
and his blog notes are here:
Some pics of the virgin PCBs
And the rear.
There are two op-amps used : a TL074 & a TL072

 Headers first.

Resistors next.

This LFO uses a combination of integrator & schmitt trigger. It's quite a commonly used combo.

This is a simplified version of Andrew's circuit.
The op-amps "A" & "B" are part of the TL 074. "A" is the non inverting schmitt trigger. "B" is the integrator.
The output of the Schmitt trigger is a square wave. This is fed into the integrator. The output of the integrator is a triangular wave, which is fed back to the Schmitt trigger. Thus first stage drives the second, and the second drives the first..... which came first ???? the chicken or the egg ???

The last part of the module is a diference rectifier which is described by Andrew thus:
"This circuit is a hybrid of two basic op amp ‘building blocks’ .....a difference circuit and a rectifier.
 It takes the triangle waves (from the 2 LFOs) and supplies a signal that is the difference between them"

The NLC module uses two standard 1n4148 signal diodes for this rectifier circuit.

"Basically the circuit compares the voltage on the ‘-‘ inputs with the voltages on the ‘+’ inputs. (on the 072 op-amp). The difference between these voltages is fed to the outputs. If the difference is positive  it appears on the ‘+’ output, if the difference is negative it appears on the ‘-‘ output. Again, a great way to mix boring CVs to get something interesting, audio frequency wave - shaping. "

The two electro caps I'm using are rated 25V.
I've used monolithic ceramic capacitors for the two 1uF 105s.
The three 100nF 104s are straight ceramics

I've used 1k 0805 SMDs for the LED resistors. Not really sure of the exact value but they are easy to change if needed.
As it turned out, the 1K resistors seem to work well.

The pots now. I was debating whether to chose two audio 100k pots (for frequency adjustment) and two linear pots for the fine adjustments, but Andrew advised me to use all linear100K pots

I've used scrap resistor wire for the ground connectors

Testing the square & triangle waves.

Lovely !!!

Useful links.
+ Video - VCO using a Schmitt trigger & integrator.
+ Pdx.edu VCO
+ Falstad.com
+ Thomas Henry - The birth of a synth
+ The two amp oscillator
+ Circuits Today
+ What is a schmitt trigger and how it works
+ NLC build notes for the difference rectifier & neuron

Click here to return to the NLC Build Index: 

Monday, 23 November 2015

Ugarit - Syria

Some old travel pics of Syria. These date from 1999.
These are scans of positive prints so my apologies for the quality.
Digital photography didn't exist back then.

This is the entrance to the Royal Palace.

Ugarit is just north of Latakia on the Mediterranean coast & I reached the site via taxi.
Built on a headland, the port city traded extensively with Cyprus and the Mycenaean civilization.
It's also known as Ras Shamra

They had close connections to the Hittite Empire & sent tribute to Egypt at times.
I believe this section of Syria hasn't been overrun by ISIS so I hope these ruins still exist.

Many on these remains are Neolithic. Much dates from around 6000BC

The city was first mentioned in a document of nearby Ebla, ca. 1800 BC. Ugarit later passed into the sphere of influence of Egypt, which deeply influenced its art.

The city was destroyed in the Bronze Age. The exact date isn't know though most historians agree it was during the reign of  the last king of Ugarit, Ammurapi, (circa 1215 to 1180 BC).

 Remarkably, there is a letter preserved from this time from King Ammurapi to the King of Alasiya, where the King of Ugarit pleads for help to fight invading "Sea People". The situation sounds desperate.
"My father, behold, the enemy's ships came (here); my cities(?) were burned, and they did evil things in my country. Does not my father know that all my troops and chariots(?) are in the Land of Hatti, and all my ships are in the Land of Lukka?...Thus, the country is abandoned to itself. May my father know it: the seven ships of the enemy that came here inflicted much damage upon us."[6]
Sounds like Ammurapi never got the help he wanted.
Sadly, history repeats...... today the new enemy is ISIS.

The origins of the mysterious "Sea People" have been lost in time. There is a relief of a battle between the Egyptians & the Sea people in Luxor, Egypt. (The Temple of Medinet Habu)

After its destruction in the early 12th century BC, Ugarit's location was forgotten until 1928 when a peasant accidentally opened an old tomb while ploughing a field. 

Most of the excavations were carried out by the archaeologist Claude Schaeffer from the Musée archéologique in Strasbourg in 1929.
The excavations uncovered a royal palace of ninety rooms laid out around eight enclosed courtyards.

During the excavation many 2 libraries (a palace library, a temple library) of  cuneiform clay tablets were discovered. All dated from the last phase of Ugarit, around 1200 BC. 

This priceless collection of documents was written in Sumerian, Hurrian, Akkadian (the language of diplomacy at this time in the ancient Near East), and Ugaritic (a previously unknown language).
There is ongoing debate as to whether the Phoenician or Ugaritic alphabet is the oldest in the world.

The libraries contained diplomatic, legal, economic, administrative, scholastic, literary and religious texts. 


Sunday, 22 November 2015

CGS 38 - Saw pitch shifter & wave multiplier

These are my build notes for the Cat Girl Synth shifter & wave multiplier.
(CGS 38). A very easy build.

Ken's notes are here:

And the reverse.

IC headers first.

Resistors, caps,  beads next.

I'm waiting on a few components.

Monday, 16 November 2015

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.

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.
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.

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