Tuesday, 20 June 2017

Multi-Band Distortion - NLC Build notes

These are my build notes for the Nonlinearcircuits Multi Band Distortion module.
It's in Eurorack format.
Andrew has based the layout on a Buchla 194 filter.

This is a fixed 4 channel bandpass from the late 1960's.
He has however added some goodies: Some Fuzz circuits & four Korg 3200 VCAs.
The distorted signal can be mixed with the clean signal . The VCAs use vactrols and allow CV control of the mix.

Andrew's build notes are here:

There are some useful links in the NLC blog:

Some pics of the virgin PCB and faceplate first.

Some NLC words of wisdom:

Jack Smith was born on November 14, 1932 in Columbus, Ohio, USA. He was an actor, known for Flaming Creatures (1963), Chumlum (1964) and Scotch Tape (1963). He died on September 25, 1989 in Manhattan, New York, USA.

Monday, 19 June 2017

Sunday, 18 June 2017

Modular in the (Car)park

So excited about the inaugural Modular in the Car Park.

This will be held on Sunday July 16th, 12noon to 4pm.
The event is open to anyone with a synth.. modular, keyboards, drum machines, etc.
It's undercover so will be held rain, hail, snow or shine.
Please contact me , Andrew, Rory, Claude S,  here, by Facebook or
phone to Prosound & Lighting (02 4226 1177).
Many thanks to Claude Spinelli of Prosound & Lighting for hosting this.

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The address is 16 Flinder's Street Wollongong, 2500

On street carparking & close to North Wollongong Train Station.

The Modular in the Carpark Facebook page is here

Saturday, 17 June 2017

Roland 121 filter & 521

A viewer requested a comparison between the Roland eurorack 521 and the vintage 121.

My understanding is that the  521 filter is not meant to be a clone of the vintage 121m
The docs state it was inspired by both the Roland system 100m and the 700m.
I like the sound of both 521 & 121.
Well done Malekko & Roland.
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The 121 has a lovely bubbly character.
Possibly due to the BA662A OTA (Operational Transconductance Amplifier).
It's actually a VCA chip that Roland also used in the TB303.

The BA662A is long obsolete so I wonder what replacement was used in the 521

 This is from the TB303 service manual.
The OTA is a flexible chip... used in the NLC Dual OTA-VCO
and the Cluster matrix mixer
What the OTA  shares with your common Op-Amp is:
1. a single output.
2. They both have inverting & non-inverting inputs.
3. They both have power lines (V+ & V-)

What makes the OTA different is that it has 2 extra inputs (Ibias & Iabc)
and it's output is a current not a voltage.
So, to put it another way, a OTA is a voltage to current amplifier.

Roland 100m - first pics

Finally .... a Roland 100m.
I loved the Eurorack 521 filter so much I decided to seek out the source.
Many thanks to Mark G.

This is a standard setup ...what Roland refer to as a D-set.
Consists of:

112 Dual VCO, with 3 CV ins, 2 outs, and weak/strong sync
121 Dual VCF, with low-pass and high-pass filters with 24 dB/oct slope
130 Dual VCA with a linear/exponential switch
140 Dual ENV + LFO, (ADSR, invertable, and manual gate button) and LFO (5 waveforms with switchable range: x1, x1/10)
150 Ring Mod, Noise (pink and white), S&H (with lag), and LFO (5 waveforms with switchable range: x1, x1/10)

The 121 VCF is a dual 24 dB Lowpass OTA filter that has Roland's warm, bubbley filter characteristics.

The System 100m offers over 20 modular components to pick and choose to design a custom modular set-up. 

The System 100m has 3 rack sizes, the M-190 holds 3 modules, the M-191 and M-191J hold 5 modules. Each rack provides the necessary 8-pin DIN power connectors and internal CV/gate connections between the modules

This is a 191J  five-module rack with multiple connectors on its base.

Yangon Burma 2016 pics

Yangon served as the capital of Myanmar (Burma) until 2006, when the military government relocated the capital to the purpose-built city of Naypyidaw in central Myanmar. With over 7 million people, Yangon is Myanmar's largest city and is its most important commercial centre.

Yangon boasts the largest number of colonial-era buildings in the region, and has a unique colonial-era urban core that is remarkably intact.

The Sofaer and Co. building in downtown Rangoon was completed by Isaac and Meyer Sofaer in 1906. Both brothers were Baghdad-born.

High tea at the Strand Hotel. Opened in 1901.
It was built by the British entrepreneur John Darwood but later acquired by the Sarkies brothers, who owned a number of luxury hotels in the Far East, including the Raffles Hotel in Singapore and the Eastern & Oriental Hotel in Penang, Malaysia.

 The Myanmar Port Authority.

The colonial-era commercial core is centred around the Sule Pagoda, which reputed to be over 2,000 years old and contains a hair relic of the Gautama Buddha.

 The city is also home to the gilded Shwedagon Pagoda — Myanmar's most sacred Buddhist pagoda.

The mausoleum of the last Mughal Emperor is located in Yangon, where he had been exiled following the Indian Mutiny of 1857.

Monday, 5 June 2017

Cluster Matrix Mixer - NLC build notes.

These are my build notes for the NonLinearCircuit Cluster Matrix mixer module.
It's 42Hp Eurorack format. The mixer has 8 ins & 4 outs.
Lots and lots of SMD here so be warned. This could take a while to put together :-)

Andrew's build notes are here.

The NLC blog has some pics that might be useful.

Some NLC words of wisdom.

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Back to the build.
My PCB is version 2.
So only two mods need to be made. Check out Andrew's build notes for more details.
A trace needs to be cut where the yellow line is.
I've also circled it in the image below.

There are 32 VCAs

It uses 16 of these  NJM13700M s:
Mouser cart 

The NJM13700M is a Transconductance Amplifier or an OTA (Operational
Transconductance Amplifiers)
It has 3 input pins (V+ & V- like in standard Op amps plus a 3rd input)
 In the above example the pins are respectively, 3, 4, & 1.

The output of an OTA is not a voltage like in a standard opamp. It's a current.
(Now I understand the Tesla vs Edison quote. It's a reference to the AC Vs DC battle). 
The gain of the OTA is controlled by this 3rd input pin.
 It seems that Andrew has used these 16 Dual OTAs to build the 32 VCAs.

If I'm reading this circuit correctly The TL074 acts as the current to voltage converter.
The output of the OTA feeds into the regular Op-amp which has its feedback loop.
This effectively has infinite input impedance.
Since the original input of the OTA is inverting, the final output of the TL074 is non inverted.

 I like to get all the IC's on first.

 Then the rest of the passive components.

 These are the mods needed for rev2 PCBs.

Pots first. These are all B100k.

Jacks next.

The first mod wire broke and removed some of the PCB trace.
So I reattached it further down.

Initally there was a slight hum on the top channel .... channel A.
Andrew suggested checking the channel A 470R resistors are soldered properly to ground, same or any opamp pins that should be going to ground.

I touched up Pins 3 & 4 of the 13700m VCAs. This fixed the hum.

Nice one Andrew.

You can find more NLC builds here.

Wednesday, 24 May 2017

1050 Mixer sequencer - Build notes

This is a Eurorack module inspired by the ARP 2500 mix sequencer.

There are lots of SMD components so it's probably not a good one for beginners.

Here are Andrew's build notes:

Muffs notes:

Some pics of the virgin PCB & Panel

Some NLC words of wisdom

This is great SMD soldering practice.
I like to get those ICs on first. These are SOIC.
The sequencer section uses one CD 4017 (decade counter) , three CD4071s (quad 2-input OR gate) and  one CD 4081 (CMOS Quad 2-input AND gate).

The 4017 decade counter is central to this sequencer.
Sending a pulse to the clock input (pin 14) sends a pulse out from each of the outputs in sequence.

A bit about gates.

CD4071 (quad 2-input OR gate)
 Truth table of the OR gate:

 CD 4081 (CMOS Quad 2-input AND gate).
This is the truth table for the AND gate
I'm using a DG 212.
Here are the mouser details.

You can also use a DG 442. Just make sure it can handle +/-12V.
My DG 212 can handle +/-15V so should be OK.
It's an analogue switch. 4x SPST.

Some earlier versions of the DG442 require a voltage offset on pin12, the spaces for these resistors are on the PCB marked 100k* and 120k*.
New versions do not require these resistors, so check the datasheet for your  IC, if pin 12 is marked ‘NC’ you do not have to install these resistors.

My DG 212 has pin 12 marked as VL. so I will install the resistors.
Data sheet.

Next install the rest of the SMDs.... lots of resistors & caps. These are 0805s
Parts marked "c" are 100K .

Then the through hole stuff.

Install jacks, switches first. Line up with panel.
Then pots. I used B100K.

Don't forget the ground wires for the jacks. I use left overs from caps & resistors.

The PCB looks like this:

Finally the LEDs

LED orientation : The long lead (anode) , (+) goes into the square hole on PCB.

Yah it works. Nice one Andrew.
You can find more NLC builds here.