Monday, 27 November 2017

CEM3340 VCO - NLC - Build notes

These are my build notes for the CEM3340 VCO module. It's a  Nonlinearcircuit eurorack module using the CEM3340.

The CEM3340 is a completely self contained VCO on a single chip.


It featured 4 waveforms : triangle, pulse, square & sawtooth (though they are at different levels). The VCO is extremely stable eliminating the need for a temperature compensation tempco resistor.
The CEM3340 is extremely unusual in that it offers both Hard and Soft Sync inputs (pin 6 and pin 9).

It has featured in many famous synths of yesteryear including Roland's Super Jupiter MKS-80 & SH101, Sequential's Prophet 5.3, The ProOne, the OB-Xa & Prophet T8 and Moog's Memorymoog,

sOME nlc words of wisdom









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There are 3 trimpots:
10k trimpot 10 turn - Tadya A-586
20K single turn - A 2504
100K single turn  A 2506
I only had the 20K on hand so used some non tayda pots for the rest. I'll see how this goes.
Might have to replace them in the future.

There are 10 X B100k linear pots .


 Mount the switch, jacks & posts loosely, then solder after securing into place with the panel
This is what the rear looks like.


Another happy customer.

Links:
* CEM 3340 data sheet
* NLC Build notes 
* Electric Druid - VCO designs
* gear junkies - Update about the new Curtis CEM 3340
* NLC Blog

To be continued.....

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http://djjondent.blogspot.com.au/2015/03/non-linear-circuits-ncl-index.html  

NLC - Envelope follower - build notes


These are my build notes for the NLC - nonlinearcircuit Envelope follower. It's a eurorack module but it's design was based on the Envelope Detector of the Buchla 208 (Music Easel).

The 208 has a a hi/lo switch. Andrew has substituted a gain pot.
The NLC version also has a additional comparator stage to give a gate output.
The NLC build notes are here:
http://www.sdiy.org/pinky/data/ENV%20follower.pdf

The module uses just two op-amps (TL 072)


I mixed the 101 (100pF) and 2M2. - it does not matter as they are in parallel anyway.

The BOM requires:
a S1JL rectifier
Mouser No: 821-S1JL.
There is a long waiting list for this.
A replacement is  Mouser Part No: 583-FM4005-T.
The rectifier is polarized. The cathode end is marked with a band. 
This replacement is slightly too big for the PCB. so i had to solder it on its side.

NLC words of wisdom
I think what I do is positive. in its own way. GG Allin


Jacks, pots, LED

tHE Envelope Follower is ideal for instruments at line level such as guitars, mics and Buchla audio signals.
Synth levels (eg Eurorack) can be a bit hot.
Turning the gain to zero and a input from a VCO seems to trigger the envelope and gate quite well
and doesn't seem to harm the module.
However, I think an additional attenuator in the signal path will give more control over the envelopes produced.

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Sunday, 19 November 2017

Abelton - Using Drum Racks for Instruments, samples and effects

 In Abelton, Drum Racks are very flexible & super useful.
 
 
When I first started using them I just loaded one shot samples.
 

Then I realised they can hold longer loops as well as containing instruments, MIDI and audio effects.
Above, is a drum rack made up of Abeltons Operator & Analog synths.
It's important to remember, that Drum racks by themselves are not instruments. 
They host other instruments.
When you drop a sample onto a pad, an instance of Simpler (Live's basic sampler) is created.
 


Any instrument plug-in can be used to generate sounds in a Drum Rack. 
It can be a instrument which is native to Abelton like Operator, collision, Electric or Analog, or a third party plug-in.
 
 
 
Abelton even has a built instrument rack made up of various  
instruments which is well worth exploring..



























Each rack has macro controls.
You can hide and view this with this button (circled in red)
Macro controls allow you to adjust key parameters within your new drum machine 


To change the range of the control, enter Map mode, and set the min and max values in the Browser area.
 

 The collumn on the left is called the "view collumn".
It holds the corresponding view selectors. 
The actual view selectors available differ depending on whether an Instrument,
Drum or Effect Rack is being used. 

This  button (in yellow) on the left opens/closes the chain list

From here you can set relative levels and pans for individual drum sounds. Selecting any of the channels in the mixer immediately displays the devices in that chain at the bottom of the screen.
 
Press the I:0 button.
This will open another box
Shows the receive & play channels, choke, etc. 

 
Receive is the MIDI note that plays the pad for that chain. 
Play is the note that gets sent to the instrument on the Chain.
C3 is the default setting. This will play back samples at their original pitch. 
If you are using a Synth, you may need to change this.
 
Choke groups allow you to emulate a feature of the old MPC drum machines. 
Choking is when one sample is triggered to cut off another.
This helps to reduce overlapping of sounds and keeps your drums tight.
 
 
Chain Selector.
This is a great feature.
It allows you to automate the pad tirggering.
Here we have several samples dropped into individual chains.
 

Open the chain select editor, then separate the chains into different zones, so that each chain has its own zone.

You can map this to a macro
 
The zones can be quite large, and individual sounds can have overlapping triggers.

 
 
 At the top of each zone/bar there is a small black line which lets you control fades between each zone. Remember, you can record the macro movements. This can be added to a live performance.
 

 click the Show/Hide Chain List button.
This will display the Chain List editing panel.
 
I've set the midi range for each instrument.
Notice the overlaping between each instrument and how you can fade between each one -- the small balck bar above each of the "blue range bars"
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This automation of Abelton Chains can also be activated with MIDI.
You could map them to a MIDI controller or a MIDI clip.
 
To do that, create a MIDI clip, open the clip envelope box then select Device Selector and add breakpoints.
I'll do this in another blog post.
 
It's good to keep in mind that drum Racks can also contain up to six return chains of audio effects, with independent send levels for each chain in the main Rack. 

Friday, 10 November 2017

EHX "Booster" pedal family

I've recently been exploring some of Electro-harmonix early pedals... The LPB-1, the Screaming Bird & the Mole. They are really simple circuits & fall into the family of Boosters - all using a transistor for amplification.
The component values determine if the circuit boost all frequencies, bass or treble.

The LPB-1 boosts all frequencies, cutting nothing out.
R1 & R2 can be 430K & 43K respectively.
The transistor is a 2N5088 on my vintage example but you could also use a 2N5133 or BC239
if building your own.
 The Screaming Bird boosts treble.

The LPB-1 and the Screaming bird pretty much are the same circuit apart from
two capacitors (C1 & C2). The first part of the circuit (C1 & R2) work like a high pass filter.
Increasing the value of C1 should let in more bass. If you decrease it, more treble should appear.
With 0.1uF, most of the input signal goes through. In the case of the screaming bird, EHX have indeed reduced C1 to introduce more treble.

The Mole has a slightly different design even though one can see a family resemblance to the LPB-1.

EHX added two caps (C3 & C4) and again changed the value of C1 & C2 (the coupling caps).
R2 & C3 form a passive Low Pass RC (Resistor-Cap) filter .
R3 & C4 do the same. We have two LP filters ... before & after amplification.

Links:
+ Electro harmonix time line
+ My LPB-1

Wednesday, 8 November 2017

Linear Power Booster 1 - Electro-Harmonix

This is the "pedal" that started it all for Electro-harmonix.
Note the chicken head knob.
This pedal boosts input signals making the output stand out more. Most of the examples I've seen have a jack at the amp output allowing you to plug this directly into your guitar amp.  You could just sit this one on the floor or use it earlier in your signal chain, between effect pedals rather than at the end. I'm guessing this is from around 1969 to 1971 ??? The pot markings are obscured with solder making this difficult to date.

I've read this sold for about $20USD in 1970 which in today's money (2017) equals $128USD
What a shock. No PCB.

Good Old Eddie

The schematic is uber basic.
Just 4 resistors, 2 caps , a transistor and a pot.

 


R2 = 1M
R3 = 100K
R4 = 10K
R5 = 390R
R6 = A100K (volume pot)

C1 = 100nF/0.1uF
C2 = 100nF/0.1uF

Transistor 2N5088

It's interesting that C2 is ceramic & C1 a polyester.
I think they are just coupling caps to pass the wanted audio (AC) signals, while blocking any DC.

The first part of the circuit (C1 & R3) works a bit like a high pass filter.
Increasing the value of C1 should let in more bass. If you decrease it, more treble should appear.
With 0.1uF, most of the input signal goes through.

R2 & R2 forms a voltage divider. It determines the bias at the base of the transistor
The ratio between R4 (collector resistor) and R3 (emitter resistor) controls the gain of the transistor.

The trannie is a 2N5088. Its a NPN. They are cheap as chips on Ebay.



It's a nice little amplifier circuit. Could easily be used in a modular synth

 

+ Electro-harmonix Timeline